Tascam 388 Story...

[sweetbeats]

I respectfully have to say I don’t follow you a 100% on this one, if I can be more clear, when all the L/R switches on every channels are unpressed the machine switches to monitor sub mix section. This is where the trouble happens with channel 7 and 8. But if L\R switches are engaged (the monitor submix section being bypassed) everything works fine. It’s the gain knob of channel 7 and 8 on the monitor submix that are faulty. Hope it clarifies that.

Right. Okay. So I’m not talking about the L-R assign switches. When the L-R assign switches are all up/unlatched, the source of the monitor mixer is either your PGM groups from the input channels, or the tape tracks. Look again at the chart on page 31 of the manual and you’ll see what I’m talking about. My question is if your problem with channels 7 & 8 of the monitor mixer is the same regardless of whether the source is tape tracks 7 & 8 or PGM groups 7 & 8.

I get that! Gotta be super careful with that kind of things. I was wondering if it would be a good idea to put electrical tape all over the inside of the bottom pannel so that it would prevent any kind of touching to any components/ PCBs. Also just gotta pop the trunk and see if everything is tight in there, nothing loose.

I wouldn’t do that. Teac lined metal surfaces or PCBs with non-conductive plastic film when necessary. They didn’t do that to the 388’s bottom panel. So if something is contacting the bottom panel that something should be rectified rather than band-aid-fix by covering the bottom panel with something non-conductive. No judgment for the idea, that’s just my philosophical approach. And it may not be the bottom panel. Maybe it’s something else. But the point is something is touching something it shouldn’t touch under certain conditions and it should be sussed out and resolved.

 

[Gaspardeden]

Right. Okay. So I’m not talking about the L-R assign switches. When the L-R assign switches are all up/unlatched, the source of the monitor mixer is either your PGM groups from the input channels, or the tape tracks. Look again at the chart on page 31 of the manual and you’ll see what I’m talking about. My question is if your problem with channels 7 & 8 of the monitor mixer is the same regardless of whether the source is tape tracks 7 & 8 or PGM groups 7 & 8.







I wouldn’t do that. Teac lined metal surfaces or PCBs with non-conductive plastic film when necessary. They didn’t do that to the 388’s bottom panel. So if something is contacting the bottom panel that something should be rectified rather than band-aid-fix by covering the bottom panel with something non-conductive. No judgment for the idea, that’s just my philosophical approach. And it may not be the bottom panel. Maybe it’s something else. But the point is something is touching something it shouldn’t touch under certain conditions and it should be sussed out and resolved.

Ok, so I got it.

Sorry for not replying in the last couple of days, it’s been a busy week with the holidays and everything

So.. Yes, it does not matter if its either the pgm groups from the input mixer or the tape tracks going through the monitoring. The problem is the same. After spending more time recording on it I also noticed that it’s not only 7 and 8. Most of the channels are faulty in the way I described before.

I also encountered another issue through my recording sessions. After some time, when I press rewind or RTZ and press PLAY or REC the motor will stop after maybe 3 seconds, just like if I had pressed STOP. Then I just need to hit play or record again and its fine. But as soon as I hit rewind and press play / record again it will stop after 3 seconds. Also, sometimes I would press rewind and the function won’t work, it won’t rewind. Then I need to press play and hit rewind again to « wake it up » (this does not happen often) I noticed and suspect that this happens only when the machine has been turned on for a while and that it’s heating. It’s just annoying when you’re in the process of recording. Visually speaking I can see the right tension arm kinda lose tension and this is what I suspect to make the motor to stop.
If you need a video of the issue I can provide one.

Would it be an issue / failure on the control pcb?
Or maybe a power supply pcb issue and the machine is kind of overheating?


I’m sorry to put some other of my tascam 388 problems on the table. I just want it to work fine once and for all without any kind of issues. You’ve been really helpful to this point.

Happy new year, talk soon

 

[sweetbeats]

…it does not matter if its either the pgm groups from the input mixer or the tape tracks going through the monitoring. The problem is the same. After spending more time recording on it I also noticed that it’s not only 7 and 8. Most of the channels are faulty in the way I described before.

Specifics are important here…”most of the channels are faulty in the way I described…” Which channels specifically? And faulty in precisely the same way as 7 & 8 or are there any differences? You should make a chart listing the channels and a detailed description of the faulty behavior.

I also encountered another issue through my recording sessions. After some time, when I press rewind or RTZ and press PLAY or REC the motor will stop after maybe 3 seconds, just like if I had pressed STOP. Then I just need to hit play or record again and its fine. But as soon as I hit rewind and press play / record again it will stop after 3 seconds. Also, sometimes I would press rewind and the function won’t work, it won’t rewind. Then I need to press play and hit rewind again to « wake it up » (this does not happen often) I noticed and suspect that this happens only when the machine has been turned on for a while and that it’s heating. It’s just annoying when you’re in the process of recording. Visually speaking I can see the right tension arm kinda lose tension and this is what I suspect to make the motor to stop.



If you need a video of the issue I can provide one.

I think a video would be helpful, and one that shows the whole transport in action, and the transport panel so I can follow along with what controls you are activating and observe the behavior of the transport.

Would it be an issue / failure on the control pcb?

Or maybe a power supply pcb issue and the machine is kind of overheating?

There’s just no point in conjecturing at this point. We don’t know enough to form a hypothesis so I don’t want to go stabbing in the dark. I just want to see what it’s doing first.

[EDIT] And whatever became of the issue with the shorting or erratic behavior when you press on the wrist rest?

 

[Gaspardeden]

Specifics are important here…”most of the channels are faulty in the way I described…” Which channels specifically? And faulty in precisely the same way as 7 & 8 or are there any differences? You should make a chart listing the channels and a detailed description of the faulty behavior.







I think a video would be helpful, and one that shows the whole transport in action, and the transport panel so I can follow along with what controls you are activating and observe the behavior of the transport.







There’s just no point in conjecturing at this point. We don’t know enough to form a hypothesis so I don’t want to go stabbing in the dark. I just want to see what it’s doing first.

[EDIT] And whatever became of the issue with the shorting or erratic behavior when you press on the wrist rest?

You’re right, so here is a clearer explanation of the monitor section issue

Volume on channel 8 won’t turn off when gain is completely shut down

Intermittent sound signal on channel 1,3,5,7 (especially when the gain knobs are maxed out)

The issue with the wrist rest:
I gently pressed the bottom pannel and noticed that the issue happens only when I pressed underneath the mixer area (somewhere underneath the faders area) I have not opened the bottom pannel yet.


For the video of the motor issue, I tried making the problem happen for 20 minutes of rewind, rtz, play, rewind, play, etc. But it didn’t happen. As soon as the trouble comes back I’ll make a video and show it to you.


Thanks Sweetbeats

 

[sweetbeats]

First and foremost, thanks for the update on what I’ll call the “Wrist Rest Debacle.” Listen…#1 if weird stuff happens when you push on stuff, that should be your top priority to resolve. Maybe your transport is now behaving correctly because you pushed on the bottom panel. Regardless of whether or not that’s true, what you’ve described happens when pressure is applied tells me you’ve got current going where it shouldn’t, it’s not small current, and it affects global systems. This is not good and could be causing damage every time the unit is powered up. So if you know you can make the problem happen by pushing on a certain area of the bottom panel, I’d stop everything else, remove your focus from your other issues, disconnect power, pull the bottom panel and have a look. Is your bottom panel damaged/deformed/dented/distorted or otherwise not right? Repair it if so. Remove that panel and look for pinched wires and such. IIRC the M BUSS PCB should have little foam rectangles adhered to it to prevent the bottom panel from coming in contact. If those are missing, it is easily possibly to push on the bottom panel and deflect it to come in contact with the M BUSS PCB which carries signal, ground and power. Again, this is from memory. I might be thinking of an M-300 series or M-500 series buss PCB. Is your top dress panel for the mixer damaged/deformed/dented/distorted or otherwise not right? If so make it right. Open it up and take a look.

Volume on channel 8 won’t turn off when gain is completely shut down

But does the GAIN control have an effect on the signal level, or no? Does the channel 8 PAN control work appropriately? In other words can you successfully pan the faulty channel 8 signal to the L or R main buss and all points in between?

Intermittent sound signal on channel 1,3,5,7 (especially when the gain knobs are maxed out)

Intermittent throughout the gain range but especially when the gain controls are fully clockwise? Do their respective PAN controls work appropriately? In other words can you successfully pan the faulty channel 1, 3, 5 & 7 signals to the L or R main buss and all points in between?



Did you ever reflow the solder joints to the red 3-pin connector P108 on the BUSS B PCB and inspect the wire that is connected to it and goes to the next board over, the MONITOR PCB?

And just to make sure I understand, is the following a correct statement? Monitor mixer channels 2, 4 & 6 function 100% appropriately. Is that right?

For the video of the motor issue, I tried making the problem happen for 20 minutes of rewind, rtz, play, rewind, play, etc. But it didn’t happen. As soon as the trouble comes back I’ll make a video and show it to you.

Okay. Sounds good. But maybe if you resolve your issues with your bottom panel your transport issue may resolve as well.

 

[Gaspardeden]

First and foremost, thanks for the update on what I’ll call the “Wrist Rest Debacle.” Listen…#1 if weird stuff happens when you push on stuff, that should be your top priority to resolve. Maybe your transport is now behaving correctly because you pushed on the bottom panel. Regardless of whether or not that’s true, what you’ve described happens when pressure is applied tells me you’ve got current going where it shouldn’t, it’s not small current, and it affects global systems. This is not good and could be causing damage every time the unit is powered up. So if you know you can make the problem happen by pushing on a certain area of the bottom panel, I’d stop everything else, remove your focus from your other issues, disconnect power, pull the bottom panel and have a look. Is your bottom panel damaged/deformed/dented/distorted or otherwise not right? Repair it if so. Remove that panel and look for pinched wires and such. IIRC the M BUSS PCB should have little foam rectangles adhered to it to prevent the bottom panel from coming in contact. If those are missing, it is easily possibly to push on the bottom panel and deflect it to come in contact with the M BUSS PCB which carries signal, ground and power. Again, this is from memory. I might be thinking of an M-300 series or M-500 series buss PCB. Is your top dress panel for the mixer damaged/deformed/dented/distorted or otherwise not right? If so make it right. Open it up and take a look.

Okay, I’ll do what you advise me to do regarding the wrist rest debacle. I’ll remove the bottom pannel and inspect it. It might very well be the M BUSS pcb touching the bottom pannel.

But does the GAIN control have an effect on the signal level, or no? Does the channel 8 PAN control work appropriately? In other words can you successfully pan the faulty channel 8 signal to the L or R main buss and all points in between?

Gain control does have an effect when it’s fully clockwise. It increases the volume of the track a little bit. Yes, the pan knob works properly.

Intermittent throughout the gain range but especially when the gain controls are fully clockwise? Do their respective PAN controls work appropriately? In other words can you successfully pan the faulty channel 1, 3, 5 & 7 signals to the L or R main buss and all points in between?

Fully clockwise, yes. And yes also, intermittence throughout the gain range. PAN works appropriately.

Did you ever reflow the solder joints to the red 3-pin connector P108 on the BUSS B PCB and inspect the wire that is connected to it and goes to the next board over, the MONITOR PCB?

No, I never did anything of the sort.

And just to make sure I understand, is the following a correct statement? Monitor mixer channels 2, 4 & 6 function 100% appropriately. Is that right?

Yes, 2, 4 and 6 works normally, nothing to signal there.

Okay. Sounds good. But maybe if you resolve your issues with your bottom panel your transport issue may resolve as well.

Let’s hope it resolves it!

Again, thanks for you support.

 

[sweetbeats]

When you have the bottom panel off you may want to manipulate the connector at P108 of the BUSS B PCB and P113 of the MONITOR PCB to see if that has any impact on your monitor mixer channels 1, 3, 5 & 7 issue…like if you manipulate them and can make the intermittent signal happen. This is assuming you can access them. I didn’t look at the PCB layouts to see where those are physically located.

Also, does exercising the MONO/STEREO switch at all help the monitor mixer channels 1, 3, 5 & 7 issue? Like if you rapidly switch the MONO/STEREO switch in and out maybe 25 times, does the problem diminish at all?

For the monitor mixer channel 8 output issue, what your saying is the signal is pretty hot all the time, but the swing to max on the GAIN control does increase the signal a little bit? And is it distorted at all?

 

[Gaspardeden]

When you have the bottom panel off you may want to manipulate the connector at P108 of the BUSS B PCB and P113 of the MONITOR PCB to see if that has any impact on your monitor mixer channels 1, 3, 5 & 7 issue…like if you manipulate them and can make the intermittent signal happen. This is assuming you can access them. I didn’t look at the PCB layouts to see where those are physically located.

Okay, so I manipulated P108 and P113 with the bottom pannel removed but nothing happened, the only way I can make the trouble occure is when I deliberately jiggle the faulty gain knobs. It sounds like a dirty pot or something.

Also, does exercising the MONO/STEREO switch at all help the monitor mixer channels 1, 3, 5 & 7 issue? Like if you rapidly switch the MONO/STEREO switch in and out maybe 25 times, does the problem diminish at all?

I did that but nothing happens

For the monitor mixer channel 8 output issue, what your saying is the signal is pretty hot all the time, but the swing to max on the GAIN control does increase the signal a little bit? And is it distorted at all?

It depends on what you are insinuating by pretty hot. Its just at some normal level, like if it was on the verge of being maxed out except when it’s fully clockwise, which results in volume gain but does not really sound distorted.

Something did happen while I was troubleshooting. I gave a little jiggle to the buss b pcb and some crazy distorted sound happened but did not stay for long. Also, and this is the odd thing, randomly at some point after shaking the buss pcb the sound signal of the channel 3 and 7 (which where the only channels turned on with signal going through) started to sound crazy loud and distorted. I panicked and pushed stop but when I pushed play again it was gone.

As for the bottom pannel problem, I noticed there was some foams missing on the M BUSS pcb.

I also noticed that as the tascam was laying on its side there was a lot less heat emanating from the grids over the power supply pcb. Like none at all.

I am going to the store to purchase some foams that you glue underneath furniture. I’ll put that on the m buss pcb.

I think that my DIY console stand is pushing against the bottom pannel which makes it touch the M Buss pcb. Here is a picture of it, you’ll notice that the way its made makes the weight focused on some areas that can probably bend the bottom pannel a little bit, just enough to touch the m buss pcb. I’ll try to think of a solution to divide the weight proportionally.


EDIT: okay so I did placed some felt protectors all along the M BUSS pcb and gave it a test (so stressful) and it worked. Nothing goes wrong anymore when I push against the bottom pannel. However I would feel safer if you could give me your approbation in doing so and tell me that there is no danger of overheat or any kind of current issue into doing such a treatment. I’m leaving a photo of what I did.

 

[sweetbeats]

Okay, so I manipulated P108 and P113 with the bottom pannel removed but nothing happened, the only way I can make the trouble occure is when I deliberately jiggle the faulty gain knobs. It sounds like a dirty pot or something.

Well, maybe it *is* a dirty pot or something. Although the fact you are experiencing the same behavior with all the odd channels of the monitor mixer is suspicious of something else. Also, I don’t think you responded to my question as to whether or not the faulty behavior of monitor mixer channels 1, 3, 5 & 7 follow their respective PAN controls?

Something did happen while I was troubleshooting. I gave a little jiggle to the buss b pcb and some crazy distorted sound happened but did not stay for long. Also, and this is the odd thing, randomly at some point after shaking the buss pcb the sound signal of the channel 3 and 7 (which where the only channels turned on with signal going through) started to sound crazy loud and distorted. I panicked and pushed stop but when I pushed play again it was gone.

If you can make faulty behavior occur just my manipulating the BUSS B PCB you have one or more bad solder joints, traces, or plug-in connections. I suggest you carefully and methodically manipulate each connection to see if you can identify a specific connector or connectors that cause the behavior, and then work toward resolving that.

As for the bottom pannel problem, I noticed there was some foams missing on the M BUSS pcb.



I am going to the store to purchase some foams that you glue underneath furniture. I’ll put that on the m buss pcb.



I think that my DIY console stand is pushing against the bottom pannel which makes it touch the M Buss pcb. Here is a picture of it, you’ll notice that the way its made makes the weight focused on some areas that can probably bend the bottom pannel a little bit, just enough to touch the m buss pcb. I’ll try to think of a solution to divide the weight proportionally

Good observation and idea with the missing foam. What you did looks fine, but are those pads the same thickness as the factory pads? I would just make sure the bottom panel isn’t now pressing on the M BUSS PCB all the time. Under normal conditions the M BUSS PCB and it’s foam pads should not be touching the bottom panel. Those foam pads are there just in case there is an unfortunate temporary deflection of the bottom panel and to avoid short circuiting. So…you don’t need a whole bunch of them. Look at where the factory pads are placed and follow Teac’s example. Remember, you just stuck sticky things all over the PCB and if you ever have to repair the PCB you’ll have to remove them.

There’s no heat in the PCB unless there’s a series problem with the 388.



How wide is your stand? The 388 should ONLY be sitting on its feet on the bottom. That bottom panel is not designed to bear the weight of the machine. It’s a cover, not a load-bearing surface. The 388 can be in a stand as long as the surfaces of the stand align with either the extreme front and rear surfaces of the bottom, or the extreme right and left surfaces; basically where the feet are located.

I also noticed that as the tascam was laying on its side there was a lot less heat emanating from the grids over the power supply pcb. Like none at all.

That is what I would expect. Heat rises. If you tip the machine on its side, heat will rise to the opposite side. It’s not going to continue emanating through the cooling slots in the cardbay cover.

 

[Gaspardeden]

Well, maybe it *is* a dirty pot or something. Although the fact you are experiencing the same behavior with all the odd channels of the monitor mixer is suspicious of something else. Also, I don’t think you responded to my question as to whether or not the faulty behavior of monitor mixer channels 1, 3, 5 & 7 follow their respective PAN controls?

Yes, pan controls works fine.

If you can make faulty behavior occur just my manipulating the BUSS B PCB you have one or more bad solder joints, traces, or plug-in connections. I suggest you carefully and methodically manipulate each connection to see if you can identify a specific connector or connectors that cause the behavior, and then work toward resolving that.

Will do!

Good observation and idea with the missing foam. What you did looks fine, but are those pads the same thickness as the factory pads? I would just make sure the bottom panel isn’t now pressing on the M BUSS PCB all the time. Under normal conditions the M BUSS PCB and it’s foam pads should not be touching the bottom panel. Those foam pads are there just in case there is an unfortunate temporary deflection of the bottom panel and to avoid short circuiting. So…you don’t need a whole bunch of them. Look at where the factory pads are placed and follow Teac’s example. Remember, you just stuck sticky things all over the PCB and if you ever have to repair the PCB you’ll have to remove them.

The felt protectors are a little bit thicker than the original pads, but They are not pushing against the pcbs or if they are, it’s probably very minimal

There’s no heat in the PCB unless there’s a series problem with the 388.



How wide is your stand? The 388 should ONLY be sitting on its feet on the bottom. That bottom panel is not designed to bear the weight of the machine. It’s a cover, not a load-bearing surface. The 388 can be in a stand as long as the surfaces of the stand align with either the extreme front and rear surfaces of the bottom, or the extreme right and left surfaces; basically where the feet are located.

I came to the conclusion that my stand, which is a fifties scholar desk with the top removed, is not wide enough to support the weight of the tascam and yes the weight was supported by the bottom pannel which is a silly mistake on my side. The tascam bottom dimension is about 23 inches wide, I just screwed back the 22 inches top of the table to prevent any kind of catastrophies and now the support is much improved. I just liked the way it looked without the top, which looked like if the stand was part of the tascam. Anyways, now the weight is correctly supported.

That is what I would expect. Heat rises. If you tip the machine on its side, heat will rise to the opposite side. It’s not going to continue emanating through the cooling slots in the cardbay cover.

Thanks. That’s logical.. makes sense!

I will leave the tascam like this for a while. It’s been through a lot; even if the monitor section is not perfectly behaving, it’s still usable.

I was wondering if flipping the tascam on its side and moving it around could affect the recording / playback calibrations.

Thanks again for your support and your teachings

 

[sweetbeats]

@Gaspardeden

I was wondering if flipping the tascam on its side and moving it around could affect the recording / playback calibrations

No, not likely. I think things that have a greater effect are vibrations, temperature changes, and time. Like a mobile recording truck is a relatively brutal place as far as stable calibration goes. But every machine drifts a little with time, and warming up and cooling down, etc. The pro studios typically lined up their tape machines every morning or before each session…standard operating procedure. This would be a thankless task for the tech in a working studio with any two head machine like the 388. Actually forget the 388…how about the MSR24. Just shoot me. Anyway, depending on how often you are transporting your 388 and whether or not your recording space temperature varies widely, if you are just using the machine periodically, you might check the calibration every few months or even longer intervals. Certainly if you switch tape types you’ll probably want to do a full calibration, or if you are going to share recording projects with another 388 owner, you’d both want to “line up” your machines before sharing tapes. That’s one reason the pro studios did it so often…it was always possible a 2” 24-track master tape (for instance) might be partially tracked in one studio and finished in another…everybody needed to know what “0VU” meant with a given set of test tones so the engineer wasn’t chasing their tail when mixing. But if it’s just you and your machine doing periodic project work, it’s of lesser consequence. Hope that helps.

The other reason some studios calibrated their machines so frequently is some machines were notorious for going out of alignment pretty easily, so it was just better to do it every day. An experienced tech could bias and line up a 24-track machine in a matter of minutes. Also it was one thing for a studio that was supplying a known tape type and there was consistency there, but if a studio was allowing the talent to supply the tape? Well they’d need to at least set bias and maybe do a playback EQ tweak, and maybe then a record EQ tweak, and if you’re going to do that then you really have to do the whole shebang.

 

[Gaspardeden]

@Gaspardeden



No, not likely. I think things that have a greater effect are vibrations, temperature changes, and time. Like a mobile recording truck is a relatively brutal place as far as stable calibration goes. But every machine drifts a little with time, and warming up and cooling down, etc. The pro studios typically lined up their tape machines every morning or before each session…standard operating procedure. This would be a thankless task for the tech in a working studio with any two head machine like the 388. Actually forget the 388…how about the MSR24. Just shoot me. Anyway, depending on how often you are transporting your 388 and whether or not your recording space temperature varies widely, if you are just using the machine periodically, you might check the calibration every few months or even longer intervals. Certainly if you switch tape types you’ll probably want to do a full calibration, or if you are going to share recording projects with another 388 owner, you’d both want to “line up” your machines before sharing tapes. That’s one reason the pro studios did it so often…it was always possible a 2” 24-track master tape (for instance) might be partially tracked in one studio and finished in another…everybody needed to know what “0VU” meant with a given set of test tones so the engineer wasn’t chasing their tail when mixing. But if it’s just you and your machine doing periodic project work, it’s of lesser consequence. Hope that helps.

The other reason some studios calibrated their machines so frequently is some machines were notorious for going out of alignment pretty easily, so it was just better to do it every day. An experienced tech could bias and line up a 24-track machine in a matter of minutes. Also it was one thing for a studio that was supplying a known tape type and there was consistency there, but if a studio was allowing the talent to supply the tape? Well they’d need to at least set bias and maybe do a playback EQ tweak, and maybe then a record EQ tweak, and if you’re going to do that then you really have to do the whole shebang.

Thanks for your insight in this matter.

The struggle continues..

I had a session tonight and out of the blue channel 7 just *stopped* recording at a normal level. Playback was SUPER quiet. I had proper signal at line input, everything is fine but as soon as I recorded and played it back it was almost like the information just wasnt recorded. I could hear a glimpse, a shadow of what I recorded. VU meters also indicated that the signal had not been recorded as it was at line input, I almost had nothing on my VU meter. Note that this issue was ONLY on channel 7.

I removed the bottom pannel once again, started playing around with the connectors on the stereo master pcb, buss a pcb, m buss pcb… and the channel came back. I just don’t know where it came from or which connector was faulty.

 

[sweetbeats]

Well, I guess just keep us posted. Seems you have yourself a finicky 388. There’s no way for me to know the cause of the latest issue…could be all sorts of things and intermittent issues are the worst to troubleshoot. If something is dead it’s dead and you can start to suss it out. If it comes and goes you often chase your tail trying to find the cause.

 

[sweetbeats]

But it does seem, in general, you have issues around the connections between the M BUSS PCB and master section boards (BUSS A, BUSS B and MONITOR PCB assemblies), and/or connectorized wiring between these boards.

 

[Gaspardeden]

But it does seem, in general, you have issues around the connections between the M BUSS PCB and master section boards (BUSS A, BUSS B and MONITOR PCB assemblies), and/or connectorized wiring between these boards.

Hey sweetbeats.

So…

*Regarding the problem of channel 7 not recording*

- I reflowed connectors solder joints on M BUSS pcb and monitor pcb to see if it would help with the issue of the channel 7 not recording. I removed some extra felt I’ve put on the M BUSS PCB to avoid the bottom pannel from exercising extra unwanted pressure on the PCB.

Result:
when the tascam was laying on its side, track 7 recorded correctly; I also gave a little shake to all the connectors in the monitor pcb area but nothing happened, no intermittent signal of any sort. as soon as I put the pannel back and lay the tascam on its bottom the problem reappears. I trouble shooted by gently lifting the tascam from different angles while recording and when I lifted the back the channel reappeared. it seems that there is something underneath that exercises pressure and "bypass" some connector that prevents the channel 7 from recording correctly. Very odd. So when I reached a sweet spot with the channel 7 still recording I very gently laid down the tascam again and at the moment channel 7 records but its very finicky. It’s kind of hard to troubleshoot this problem since I can’t see anything.


*Regarding the problem of gain knobs being faulty on the BUSS pcb (monitor section)*

- I reflowed all connectors solder joint on the BUSS pcb and also on the faulty gain knobs

-I noticed that I did not replace the electrolytic capacitors on the pcb, so I did.

Result:
For some reason, probably the capacitors replacement, the section sounds more "clear" and clean but the problem persists. I came to think that this is indeed a problem of faulty potentiometers. If you happen to know where I can purchase the proper ones please do let me know. I had to change one in the past on one of the input pcb and it was a challenge. These potentiometers are 20 kOhms Reverse with a D shaft, and it’s hard to find. I had to order one with a longer shaft that I had to cut and shim it so it could take the D shape but it’s kind of sketchy and it does not give a clean result similar to the originals.


*Regarding the transport problem of PLAY sometimes stopping after 3 seconds*

- I disconnected the CONTROL pcb and inspected the soldering joints I had to do around the digital chip I replaced a couple of months ago (some traces lifted in this very tiny area, it was a real pain to recreate the paths to ensure the proper connectivity of all the components AND make sure that there is no short circuits between paths but I did) I reflowed the solder joints

- I did not change the electrolytic capacitors on this one too so I did

Result:

This is a very capricious area of the tascam to work with. A LOT of connectors goes into that pcb and it’s really hard to even remove the pcb from there to work on it. I had to be very careful and meticulous to not create more problems than resolving some. when I reconnected everything properly and gave it a spin the transport worked fine, nothing went wrong of any sort. Since it’s a problem that only occurs after a certain amount of time while the tascam is running, I can’t tell yet if my procedure solved this case. I guess I’ll know in my next recording sessions. I had the opportunity to capture a video of the trouble in real time a couple of days ago which I will include in this link here for you to view:



(Note that everytime it stops without me rewinding it right after it stops, THIS is when the trouble happens. You can see the right tension arm losing its tension)

Again, thanks for your insight and your patience / time.

 

[sweetbeats]

Quick set of questions: how long have you owned this 388? Do you know if any trauma or damage inflicted on the unit prior to or after you took ownership? If anything happened under your watch, it would be EXTREMELY helpful for you to share…no judgment…if done some regrettable things or sometimes accidents just happen, but I’ve spent hours and hours helping somebody on my own time chasing gremlins only to find the whole time they knew they dropped something heavy onto the control surface or whatever and we could have just started there. I’m not saying that’s what’s happening here, but I want to rule it out because every post you put up has a blossoming set of issues and at some point, and we’re getting close, it will be too much for me to be able to assist.

More to follow later.

 

[RFR]

That’s a very valid point to bring up.

What happened BEFORE it became troublesome.

While it is a fact that sometimes things just wear out, so often a failure is caused by some catalyst. Something happened to create the current situation.

Think of a broken toe or toes. They didn’t just up and beak themselves. What happened right before?
Well....... I dropped my hammer on them.

 

[Gaspardeden]

Quick set of questions: how long have you owned this 388?

I’ve owned it for almost two years now

Do you know if any trauma or damage inflicted on the unit prior to or after you took ownership?
The past owner told me that nothing wrong ever happened to it, it was actually supposed to be in good working condition as his add said. but when I turned it it was in poor condition.. got naive. connectors were rusty, a lot of gremlins sounds popping out of nowhere, intermittent problems on channel six, a LOT of bleed between track 6 and 7, the tape machine poorly calibrated, etc.

I had a tech looking into it at the time. He fixed the issue of channel six being intermittent. He also cleaned thoroughly all the pcbs by putting each one of them in an ultrasound bath which was pretty conclusive.


But then we came to the point, me and my tech, that we needed to calibrate the machine and when we went through the procedure to make the mechanical calibrations (setting up the tape tension arms with a tentelometer) we realized we were not even close of being in specs even with the trim pots screwed to their maximum capacity.

he realised that a lot of capacitors needed replacement and invited me to do a full recap of the machine in order to get proper results.

Many things happened while I worked on it. As I said, I am not an engineer and my sheer will to make my machine work without having to pay thousands of dollars and my love for the sound / workflow of tape recording drove me to try to repair it by myself. But I did mistakes, that I tried to correct the best I could.

Something went wrong at some point with the reel servo pcb; it was the first pcb I worked on and I murdered it. Bad traces and everything. . This is when things got nasty for a while. A short circuit happened because the reel servo pcb pcb was loose as I was testing it and touched the metal frame. Smoke came out. I think the machine didnt like it. This is when I started having logic transport problems. I can’t perfectly recall how it was behaving with the ancient pcb but I know at first the motors were just spinning WAY too fast. At some point it just stopped working. When I installed the new one, the transport went back to normal on play function, but as I described in another post the rewind and FF modes were acting all messed up because of a digital chip that was not behaving like it’s supposed to on the control pcb.

So after many months of troubleshooting we finally pinned down which one it was and I ordered it and installed it. I have to say that when I installed the digital chip, some traces lifted and went bad. It’s been a real pain to work on it to recreate the paths because it is a really tinny area with many many traces.. but when I replugged everything, it worked.


I had to buy three NOS tascam 388 pcbs, all bought from audioproz.com. One was a new reel servo pcb. Then I also bought a new power supply pcb because one fragile connector on the original one broke as I tried to plug it in. Same thing happened with one of the bias pcb which I had to replace.

I did a full recap, being extra careful of installing every capacitors with the right values.

Then one last goof happened when I’ve reassembled it all together, I inadvertently switched two connectors in the stereo master pcb and the buss pcbs area. I freaked out when I pushed the rec functions; all vu meters went into red peaks instantly and smoke came out of the machine. But then when I fogured out which connectors I switched and fixed it, the machine worked properly. It may have damaged something else though.

So.. the rest is me calibrating the machine. Getting decent results. Fixing my last problems through your assistance.

I went silent for a while because I did not want to bother anymore with all these issues. I am currently recording my album on it and after all the work I’ve put on it I just wanted a moment of actually using it for whats its supposed to be used for.

But now I can’t keep working like this, the issues just kills my workflow because of these three issues that drives me crazy:

- when the tascam runs for a while, especially when I operate a lot of Play / rewind / play rec / rewind / play rec and so on, the transport will eventually end up having some kind of failure. At first it took maybe one hour but now it takes like 15 minutes. I hit play and it spins for three seconds, then the right tension arm looses tension and it stops. But when I hit play right after, it works. Then as soon as I hit rewind or fast forward and hit play, the same problem happens again. Let me tell you it gets pretty annoying in the process of tracking..

- Second problem is that very weird phenomenon that happens on track 1 and track 7 when I record or playback with the DBX on. If I record a loud source in track 2 and record track one at the same time (let’s say two microphones from a drum kit for exemple) , a HUGE feedback occurs on track one and it just won’t stop. Its like a high pitched frequency. Same thing happens on track 7 if I record through track 8 while track 7 is on playback mode with the DBX mode. None of this happens if the DBX are off. I tried troubleshooting it a little bit, removed the dbx boards and did the same manoeuver with the DBX buttons on but it happens anyways so I know the problem doesnt come from the dbx pcbs.

Third super annoying problem is that when I try collapsing /ping pong tracks as described in the manual the same high pitched frequency happens on each track that are setup in recording mode. Its like the audio disappears and whats left is that super strident high pitched sound that makes everything peaks. And the sound gets recorded to tape. This happens even if DBX are off.

I wonder if I should buy a new stereo master pcb and or a new control pcb or not..

I hope it gives you some insight regarding the background on my tascam. If you got any questions I will do my best to provide.

I’m sorry to lay down other issues on the table; at least the last issues we talked about are fine for now. Track 7 records and also no more weird pressure problem with the vu meters peaking.

If anything happened under your watch, it would be EXTREMELY helpful for you to share…no judgment…if done some regrettable things or sometimes accidents just happen, but I’ve spent hours and hours helping somebody on my own time chasing gremlins only to find the whole time they knew they dropped something heavy onto the control surface or whatever and we could have just started there. I’m not saying that’s what’s happening here, but I want to rule it out because every post you put up has a blossoming set of issues and at some point, and we’re getting close, it will be too much for me to be able to assist.

More to follow later.

I understand that and I don’t want to bother or anything. What you can provide I’ll take.

Thank you!

 

[sweetbeats]

I appreciate your honesty.

The past owner told me that nothing wrong ever happened to it, it was actually supposed to be in good working condition as his add said. but when I turned it it was in poor condition.. got naive. connectors were rusty, a lot of gremlins sounds popping out of nowhere, intermittent problems on channel six, a LOT of bleed between track 6 and 7, the tape machine poorly calibrated, etc.

So your machine was damaged goods from the start…not maintained or cared for properly, and if connections were actually rusty that’s really not good. The 388 is a finicky machine if not cared for or maintained properly and part of the reason is how the different power rails propagate throughout the machine. You have to know what can and what cannot be isolated for testing, etc. For instance you don’t want to turn it on with certain cards uninstalled. I had an issue where I had one of the cards out of the cardbay to access one of the bias amp PCBs and within 30 seconds or so of powering it up I could smell a hot electrical smell…something was overheating on the bias amp PCBs…I shut it down quick. It made no sense why it would do that, but looking at the interdependence of how power goes through the motherboards and through cards, that means certain pathways for power or ground are interrupted if certain things aren’t installed, and power always looks for the easiest path to ground. I determined at that point to never power it up without all the cards installed, and to make extender cables in order to service the different cards…changed my view of the machine from one with modular plug-in cards to one whole system that needed to be all installed when powered. The only card that can be isolated is the power supply, and that’s only if you have a custom extender cable set and can leave the output connector disconnected. Having cards with rusty or heavily oxidized connections could create a situation similar to not having the card installed at all.

Speaking of connectors…those card edge connectors…again, the 388 is relatively fragile. I always inspect the connector housings to make sure they are straight, and the two small clips are in place that keep the connector housing fastened to the card. Those clips often crack or break, so I like to put a small bead of superglue between the connector housing and the card to keep it in place. And then reflow the solder joints. And then it’s also often important to inspect the corresponding pins on the motherboard because it’s easy for them to get bent. People don’t take care when installing or removing the cards, or realize how fragile they can be. The card guides by design are poor or non-existent, so the operator has to be careful the connectors on the cards are aligned with the pins before seating. And people don’t do this. Or the connector housing clips are snapped and the connector is cockeyed and it’s not going on right, so instead of doing the right thing, removing the cards, inspecting and remediating anything that’s not right, they just shove harder. Not kidding. I’ve straightened a fair amount of pins and repaired a fair amount of connectors on machines I’ve gotten because of those kinds of negative practices. So you might need to look at some of those things and be careful to have all cards installed when powering the machine.

Something went wrong at some point with the reel servo pcb; it was the first pcb I worked on and I murdered it. Bad traces and everything. . This is when things got nasty for a while. A short circuit happened because the reel servo pcb pcb was loose as I was testing it and touched the metal frame. Smoke came out. I think the machine didnt like it. This is when I started having logic transport problems. I can’t perfectly recall how it was behaving with the ancient pcb but I know at first the motors were just spinning WAY too fast. At some point it just stopped working. When I installed the new one, the transport went back to normal on play function, but as I described in another post the rewind and FF modes were acting all messed up because of a digital chip that was not behaving like it’s supposed to on the control pcb.

So after many months of troubleshooting we finally pinned down which one it was and I ordered it and installed it. I have to say that when I installed the digital chip, some traces lifted and went bad. It’s been a real pain to work on it to recreate the paths because it is a really tinny area with many many traces.. but when I replugged everything, it worked.

I had to buy three NOS tascam 388 pcbs, all bought from audioproz.com. One was a new reel servo pcb. Then I also bought a new power supply pcb because one fragile connector on the original one broke as I tried to plug it in. Same thing happened with one of the bias pcb which I had to replace.

So, yes…see my comments above about the connectors.

And soldering…you mention several times traces lifting. No offense…you need to work on you soldering skills, or change your iron or the tip type or devote some more attention to prepping the tool or the work surface…probably a combination of all of those. As I’ve mentioned many times over the years, the phenolic resin PCBs used in the 388 and many, many other devices, or more fragile and require more skill to work on than an equivalent assembly using a glass fiber board. They don’t take the heat well and traces do lift and break…it can be a real PITA. But, truly, with the right equipment, and properly maintained equipment, and good technique, you can avoid all of those maladies and preserve the integrity of your PCB assemblies while doing the work. The more work you do without the right skill or equipment is only inviting more and more problems. You should only have to apply the tip for a second or two at the most when removing or applying solder. And a tip temp of 700F is sufficient. Oh and prepping and maintaining your tip and the work surface is critical…that greatly reduces the chances of having to keep the tip on the work for too long. So I don’t know where you’re at with all of that, and, again, I’m not meaning to offend, but if you’re having trouble with traces lifting then there is room for improvement with your soldering skills and equipment.

Then one last goof happened when I’ve reassembled it all together, I inadvertently switched two connectors in the stereo master pcb and the buss pcbs area. I freaked out when I pushed the rec functions; all vu meters went into red peaks instantly and smoke came out of the machine. But then when I fogured out which connectors I switched and fixed it, the machine worked properly. It may have damaged something else though.

What connections did you erroneously swap? Use the number designation on the boards or post a pic of the ones you swapped.

Smoke is bad. It always means failed components, and or pathways. Once there’s smoke you can’t ever expect it to work right until you get to the bottom of what failed, WHY it failed, and repair every bit of the damage. You can’t just swap connections so they are correct, turn it back on and expect it to work. You can actually damage it further by doing that. So what connections did you swap?

So.. the rest is me calibrating the machine. Getting decent results. Fixing my last problems through your assistance.

I went silent for a while because I did not want to bother anymore with all these issues. I am currently recording my album on it and after all the work I’ve put on it I just wanted a moment of actually using it for whats its supposed to be used for.

But now I can’t keep working like this, the issues just kills my workflow because of these three issues that drives me crazy:

…

I don’t honestly know how much help I can provide. Your machine started off very compromised, not all of which may be resolved, and there are new issues that have occurred along the way, some maybe the result of compounding pre-existing issues with new problems and you couldn’t have known what was going on, and some the result of unintended errors on your part. Again, no judgement at all. I’ve swapped connections, forgot connections, accidentally touched a metal tool tip where it shouldn’t go, put caps in reverse polarity even after triple-checking…years ago I killed my mint condition 58-OB because I installed an amp card offset by one pin…one pin! Great, great care must be taken, slow planful process and procedure when working. If you don’t, the risk factor for unintended consequences increases many-fold. I’ve done plenty of hasty work and been lucky, but I always have in my mind I might deeply regret it as I proceed hastily. That’s the reality. And the 388 is:

Complex, and…

Fragile (relatively speaking)

You’re not going to like this, but I think if it was me I’d be considering saving up to buy a known working 388 that’s been maintained and use the current one as a parts donor. You still have complicated problems occurring across multiple systems. It is going to be very difficult at best to sort them out, and because of the poor condition the machine was in when you purchased it, it’s hard to say when the next issue will rise up…black rain cloud I know…but from personal experience, with a machine like your 388, it is likely you will never be on top of all its problems, at least not long term…it is likely to always have some issue or issues.

 

[BMG123]

Good morning Sweetbeats! This has been a really interesting thread as I'm bringing my 388 back to life.
After all your help on the power supply recapping suggestions I was hooking things up to the outputs and have uncovered another issue.

1. RCA stereo outs to an adcom preamp to amplifier to ns-10s = perfect, no noise
2. RCA monitor outs to tascam MH-40 headphone amp = perfect, no noise
3. when both RCA stereo and RCA monitor outs are connected im getting a loud buzz/hum from the monitor outs through the headphone amp.

as soon as I unplug either L/R of monitor or stereo outs the noise stops.

It seems like there is a connection between the rca outs of the main stereo and monitor outs that aren't playing nice together.

Any thoughts on something to check?

As always, my deepest gratitude is sent your way in advance.
Brian