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iamsetsetiam
New member
Hi Sweetbeats. Just wondering if you've worked on, disassembled the Tascam 788. Thanks.
sweetbeats
Reel deep thoughts...
No I haven’t. The only distantly related but likely not helpful experience I have would be working on the Yamaha AW series (2816 and 4416 specifically). If you think you have any follow up questions please start a new thread in an appropriate forum and tag me in a post. This thread is about the analog Tascam 388 Studio 8. Thanks.
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iamsetsetiam
New member
Thanks for replying. I'm new to the forum and somebody recommended you as a Tascam guy and I wasn't sure how to contact you. I may start up that new thread as you mentioned. Thanks again, Set
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johnsonic5000
New member
@sweetbeats - i see you're in the PNW and am hoping you're local to Portland - just got a 388 in good condition that hasn't been used in 20 years, can't record or play back. Would be good to hang - I can't DM folks tho probably because this is my first post. Just putting it out there...
Otherwise reading this entire thread, and diving deeeeeep.
Otherwise reading this entire thread, and diving deeeeeep.
sweetbeats
Reel deep thoughts...
Portland is not terribly far, but I’m not up that way very often, and time to hang with people is not something I have.
1. Are you confident you are setting the machine up correctly to record and play back? How familiar are you with the 388 and how it operates?
2. Are you saying it doesn’t play back what you tried to record, or does it also not play back a known good tape?
3. When you say it doesn’t record, if you want help, you need to post a lot more detail. Walk through the settings of channels to which your inputs are connected, and the settings of the recorder section. Tell me if you have signal on the PGM meters. Tell me if you can’t get signal to tape but it erases the tape.
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johnsonic5000
New member
Hello!
Pretty confident I'm setting it right:
- Plug into channel 1, set routing to 1-2
- Adjust trim
- Make sure L/R is up on all switches
- Arm 1-2, see red light blink.
- Speak into mic - see meter move at the channel
- Master meters are also moving
- Press play then record
- Record for a bit
- Disarm 1-2
- Play it back, no sound
- Tried switching channel to RMX, still very little sound
- Tried switching channel to L/R, still very little sound
The gray 1-8 knobs are also at 3:00 for gain and straight down the middle for L/R
I wish I had a recorded tape so I knew if it was just record that isn't working.
Should also mention I did clean the heads, and also checked all fuses. One was blown so replaced that.
Also - tired different combos of channels and tape tracks, same result. When recording extremely hot on all tracks, and CRANKING it on playback I head the very faintest whisper of a recording.
That's pretty much it! Hopefully something obvious jumps out.
Next step is to inject a tone and start tracing circuits back from the record head with my oscope.
This thread is a goldmine - thank you for documenting your restoration!
Pretty confident I'm setting it right:
- Plug into channel 1, set routing to 1-2
- Adjust trim
- Make sure L/R is up on all switches
- Arm 1-2, see red light blink.
- Speak into mic - see meter move at the channel
- Master meters are also moving
- Press play then record
- Record for a bit
- Disarm 1-2
- Play it back, no sound
- Tried switching channel to RMX, still very little sound
- Tried switching channel to L/R, still very little sound
The gray 1-8 knobs are also at 3:00 for gain and straight down the middle for L/R
I wish I had a recorded tape so I knew if it was just record that isn't working.
Should also mention I did clean the heads, and also checked all fuses. One was blown so replaced that.
Also - tired different combos of channels and tape tracks, same result. When recording extremely hot on all tracks, and CRANKING it on playback I head the very faintest whisper of a recording.
That's pretty much it! Hopefully something obvious jumps out.
Next step is to inject a tone and start tracing circuits back from the record head with my oscope.
This thread is a goldmine - thank you for documenting your restoration!
sweetbeats
Reel deep thoughts...
Whoa there fella…no need to warm up the scope yet.
What if you monitor playback off the TAPE OUT jacks?
You really need to get ahold of a known good tape. I don’t care if it’s a 1/4” prerecorded tape of something from the thrift store. Ideally you should have a cal tape. That is what I would use to test. But if you can’t/won’t do that, at least monitor for playback off the TAPE OUT jacks.
An additional thing you should test is connect a mic to any input channel, adjust TRIM and input fader as appropriate, make sure allllllll PGM group assign switches are up/off for all channels, as well as all L-R assign switches *except* for the input channel you are using. So basically the only assign switch that should be latched for all input channels 1~8 is the L-R assign switch on the channel to which the mic is connected. Now over by the headphone level knob in the monitor select section, make sure STEREO is depressed, raise the STEREO master fader, plug in some headphones, turn up the headphone level knob and tell me if you can hear your mic in the headphones.
What if you monitor playback off the TAPE OUT jacks?
You really need to get ahold of a known good tape. I don’t care if it’s a 1/4” prerecorded tape of something from the thrift store. Ideally you should have a cal tape. That is what I would use to test. But if you can’t/won’t do that, at least monitor for playback off the TAPE OUT jacks.
An additional thing you should test is connect a mic to any input channel, adjust TRIM and input fader as appropriate, make sure allllllll PGM group assign switches are up/off for all channels, as well as all L-R assign switches *except* for the input channel you are using. So basically the only assign switch that should be latched for all input channels 1~8 is the L-R assign switch on the channel to which the mic is connected. Now over by the headphone level knob in the monitor select section, make sure STEREO is depressed, raise the STEREO master fader, plug in some headphones, turn up the headphone level knob and tell me if you can hear your mic in the headphones.
flyingace
Active member
Just curious, I have my 388 in storage but was thinking of putting it up for sale. When I bought it, channel 7 VU “glass” was broken but light and meter still work. I came across a working bank of 5-8 VU meters, plug and play for the 388 and wondered how hard is it to replace the VUs? How much disassembly is required?
sweetbeats
Reel deep thoughts...
IIRC, and after refreshing memory by looking at the exploded view in the service manual, it’s not too bad. And consider just replacing the one bad lense rather than replacing the whol bank of meters. I haven’t messed with 388 meters in many, many years…maybe a decade…BUT, I think it goes like this:
1. Remove the cardbay cover.
2. Remove the track 5 & 7 R/P PCB, track 6 & 8 R/P PCB, and track 5, 6, 7 & 8 dbx PCB. You may need to remove the Balance Amp PCB as well. This is so you have clearance to pull the meters away from the meter bridge once they are free.
3. The meters are fastened to the back of the face of the meter bridge in groups of four by a metal bracket for each group. The bracket is fastened to the top lip of the meter panel by screws…screws that are covered up by the cardbay cover when it’s installed. Locate the screws for the channel 5, 6, 7 & 8 meters and remove them.
4. The meters should now be free of the meter bridge. What I can’t recall is if there is enough slack in the wiring that goes between the banks of meter to be able to pull the maters away far enough from the chassis to access and remove the meter lense. If there is not enough slack you may need to also dismount the channel 1, 2, 3 & 4 meters, removing the cards from the first bay of the cardbay like you did for the channel 5, 6, 7 & 8 meters; even may need to remove the STEREO meters and any cards in their way.
5. Once you have access to the meters, the lenses are only held on the to meter by clear tape. Take a sharp razor blade or similar, cut the tape, place a replacement lense, and apply new tape. Installation is the reverse of the above steps.
1. Remove the cardbay cover.
2. Remove the track 5 & 7 R/P PCB, track 6 & 8 R/P PCB, and track 5, 6, 7 & 8 dbx PCB. You may need to remove the Balance Amp PCB as well. This is so you have clearance to pull the meters away from the meter bridge once they are free.
3. The meters are fastened to the back of the face of the meter bridge in groups of four by a metal bracket for each group. The bracket is fastened to the top lip of the meter panel by screws…screws that are covered up by the cardbay cover when it’s installed. Locate the screws for the channel 5, 6, 7 & 8 meters and remove them.
4. The meters should now be free of the meter bridge. What I can’t recall is if there is enough slack in the wiring that goes between the banks of meter to be able to pull the maters away far enough from the chassis to access and remove the meter lense. If there is not enough slack you may need to also dismount the channel 1, 2, 3 & 4 meters, removing the cards from the first bay of the cardbay like you did for the channel 5, 6, 7 & 8 meters; even may need to remove the STEREO meters and any cards in their way.
5. Once you have access to the meters, the lenses are only held on the to meter by clear tape. Take a sharp razor blade or similar, cut the tape, place a replacement lense, and apply new tape. Installation is the reverse of the above steps.
flyingace
Active member
Thanks Corey! I was hoping I could do it like that. I went back to your first images of this thread and although it wasn’t specific to that removal, I saw a few things that led me to believe what you say. I hope that the cable is long enough to be able to safely work with it and I’ll update you on my progress. 
sweetbeats
Reel deep thoughts...
Well for sure the cabling is long enough to do the lense replacement, I just can’t recall how much of the meter array you have to dismount to get the 5, 6, 7 & 8 meter block out. The wiring for the lamp power and signal to each meter comes from the right end of the meter array as you look at the front of the unit. Of course the signal wiring for each meter goes to each individual meter (as opposed to daisy-chaining), but it’s all bundled together in a trunk, and then what’s even more restricting is the lamp power wiring which does daisy-chain from meter to meter. I’m pretty sure you have to probably dismount the 8 PGM meters, but can maybe get away with leaving the STEREO meters in place. You’ll know for sure when you get in there.Thanks Corey! I was hoping I could do it like that. I went back to your first images of this thread and although it wasn’t specific to that removal, I saw a few things that led me to believe what you say. I hope that the cable is long enough to be able to safely work with it and I’ll update you on my progress.
flyingace
Active member
Here's the replacement unit, hopefully that lead is long enough and I can just simply attach the new "glass"! OR, if it's just these two connectors, I may just be able to do a full swap. We'll see this weekend when I have time to dig into it.
sweetbeats
Reel deep thoughts...
Notice there are cut wires at the left in your pic of the back of the assembly…I circled them in red. So, yes, you have connectorized connections, but there are hard-wired connections too. And I think your replacement assembly is for meters 1, 2, 3 & 4. Notice the vacant solder lands at the other end at the right…I circled in green. These lands are populated with the wires that carry the lamp power to meters 1, 2, 3 & 4 on the 5, 6, 7 & 8 meter bank. They are vacant on the first bank. I don’t see any reason why you won’t be able to just swap lenses…you’ll just likely have to spend a few more minutes dismounting the first bank of meters. Just get in there and get started. It’s not that difficult. You can do it.
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akieffer
New member
Hello All: Long time reader, first time poster.
I recently bought TWO 388s for $100 bucks. Both had been sitting unused for years (at least 10). Both are in great shape cosmetically, all buttons in place, no dents, scratches, and, save for a single UV meter light, seem as good as new. The heads seem unworn with lots of life left in them. I replaced the belts on both, cleaned/lubed pots and faders, cleaned tape path, pinch roller, and did a basic cleaning of knobs etc. I even polished the plexiglass - they look fantastic! Wired it up, slipped in a tape, and, at first, the transport wasn't working on either. I did the reel servo adjustments (tension arm, winding speed, etc) and both came to life - Play, FF, RW, counter, etc. Everything was going well.
I tried my first recording and although I'm sending a strong signal (meters bouncing in channel and main, great sound in headphone/stereo/mon mix) however, the signal I get on playback is muffled and barely audible. And here is the bizarre part - I get exactly the same result on BOTH machines. My first thought was user error - if I'm seeing it on both, then I must be doing something wrong. For three weeks I've been experimenting but I'm stuck in the same position. I'm stumped. Here are few other notes:
-It plays prerecorded tape just fine - so that would rule out the PLAY/RECORD head, no?
-It records "something" so some signal is getting on the tape, just nothing usable.
-I've tried two kinds of tape (both newly-bought) Quantegy 631, and RMG 975
I'm fairly certain that it's not a playback/RMX issue as I'm getting the same muffled garbage from headphones, mon, aux, stereo outs. It seems that it's just not getting recorded well.
My suspicions are:
-Tape quality (although these are not ultra high quality, I should be getting something beyond a muffled rumble, no?)
-After sitting so long the bios pcb 1 crapped out. Johnsonic5000 mentioned that he had the same issue in #486 and then replied that replacing the pcb fixed it (although today I can not find that response ???) Maybe I pull this and check the capacitance on the components - might have a flat capacitor or three?
-Somehow i've wonked up the tape tension - I don't have (nor have I ever seen in real life) a tentelometer. However, this seems unlikely because prerecorded tapes work fine. Also, the tension arms seem to be hovering in the correct position.
-I've got the tape backwards (oh, it happens). I tried the shiny side and the dull side. Dull side I get the muddy signal, shiny side, I get nothing.
-I'm an idiot and am (repeatedly) doing something stupid.
Sadly, most evidence is pointing to the last one as it seems statistically unlikely that I'm having the exact same failure and result on two entirely distinct machines. However, this is not my first 388 and I've gone over and over the record/playback steps.
I'm baffled. Do we have any suggestions? Anything jump out as an obvious thing to check?
Thank you.
I recently bought TWO 388s for $100 bucks. Both had been sitting unused for years (at least 10). Both are in great shape cosmetically, all buttons in place, no dents, scratches, and, save for a single UV meter light, seem as good as new. The heads seem unworn with lots of life left in them. I replaced the belts on both, cleaned/lubed pots and faders, cleaned tape path, pinch roller, and did a basic cleaning of knobs etc. I even polished the plexiglass - they look fantastic! Wired it up, slipped in a tape, and, at first, the transport wasn't working on either. I did the reel servo adjustments (tension arm, winding speed, etc) and both came to life - Play, FF, RW, counter, etc. Everything was going well.
I tried my first recording and although I'm sending a strong signal (meters bouncing in channel and main, great sound in headphone/stereo/mon mix) however, the signal I get on playback is muffled and barely audible. And here is the bizarre part - I get exactly the same result on BOTH machines. My first thought was user error - if I'm seeing it on both, then I must be doing something wrong. For three weeks I've been experimenting but I'm stuck in the same position. I'm stumped. Here are few other notes:
-It plays prerecorded tape just fine - so that would rule out the PLAY/RECORD head, no?
-It records "something" so some signal is getting on the tape, just nothing usable.
-I've tried two kinds of tape (both newly-bought) Quantegy 631, and RMG 975
I'm fairly certain that it's not a playback/RMX issue as I'm getting the same muffled garbage from headphones, mon, aux, stereo outs. It seems that it's just not getting recorded well.
My suspicions are:
-Tape quality (although these are not ultra high quality, I should be getting something beyond a muffled rumble, no?)
-After sitting so long the bios pcb 1 crapped out. Johnsonic5000 mentioned that he had the same issue in #486 and then replied that replacing the pcb fixed it (although today I can not find that response ???) Maybe I pull this and check the capacitance on the components - might have a flat capacitor or three?
-Somehow i've wonked up the tape tension - I don't have (nor have I ever seen in real life) a tentelometer. However, this seems unlikely because prerecorded tapes work fine. Also, the tension arms seem to be hovering in the correct position.
-I've got the tape backwards (oh, it happens). I tried the shiny side and the dull side. Dull side I get the muddy signal, shiny side, I get nothing.
-I'm an idiot and am (repeatedly) doing something stupid.
Sadly, most evidence is pointing to the last one as it seems statistically unlikely that I'm having the exact same failure and result on two entirely distinct machines. However, this is not my first 388 and I've gone over and over the record/playback steps.
I'm baffled. Do we have any suggestions? Anything jump out as an obvious thing to check?
Thank you.
J
johnsonic5000
New member
Weird - I was going to post an update here (and hadn't yet) and @akieffer mentioned I fixed it by replacing the PCB. I was able to confirm that all tracks were recording by swapping the rec/play cards around - the channels not playing back moved with the cards. Bought two replacement cards off ebay and I am up and running! On to calibration!
I hope you get it figured out akieffer!
Another question - if I were to make a test harness - anyone have an idea on the pin connectors I should be using? Looked up the part number and couldn't find anything. I know they are about a 3mm pitch but there are other connectors on mouser damn close to 3mm and wanted to make sure I'm getting the right ones.
I hope you get it figured out akieffer!
Another question - if I were to make a test harness - anyone have an idea on the pin connectors I should be using? Looked up the part number and couldn't find anything. I know they are about a 3mm pitch but there are other connectors on mouser damn close to 3mm and wanted to make sure I'm getting the right ones.
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akieffer
New member
Thanks Johnsonic5000. So sorry but I think I inadvertently referenced your post when I meant to reference post 284 by Rikard (and his resolution - post 291). It seems he had the same problem that I did - recording problems across all 8 tracks. He resolved it by replacing the BIOS PCB1 card. I'll admit - I by the time I'd posted I had consumed all 25 pages of this thread and my head was spinning - sorry for the confusion and hope you get some satisfaction on your test harness query. cheers.
sweetbeats
Reel deep thoughts...
Does it erase? IOW put all 8 tracks into record on a tape with pre-recorded signal on all 8 tracks, but record nothing. Is the pre-recorded signal erased?
More later.
More later.
sweetbeats
Reel deep thoughts...
Now that’s a disgustingly commendable deal…
Maybe the slight manipulation of the plug-in card mitigated oxidized connections.
Have you reseated the cards in the cardbay and treated the connections with something appropriate like DeoxIT D5?
If the units were in storage and it was damp at all, that’s the problem with tin-plated connections…they don’t last and they oxidize. I’ve come to really appreciate gold-plated contacts in vintage equipment.
Well, that may be the case…sure…but you don’t know that, and the opposite could be equally true because the units are of similar vintage and we’re stored in the same location for a similar or identical amount of time.
Don’t get distracted by assumptions. Troubleshoot it using a methodical and reasonable process.
Is the recorded signal muffled off the TAPE OUT jacks as well?
I’m going to repeat my question/suggestion regarding reseating/treating the plug-in cards if you haven’t done that.
Correct. Good deduction. Since the same coils are used for recording and reproduction, if it can reproduce properly, your problem is not related to the head coils or head wiring.
Right, but take the unknown out of it and verify what’s coming straight off the reproduce amps and monitor straight off the TAPE OUT jacks. That bypasses the mixing section and monitor section. And on the other side of it, verify that what is going into the record amp is clean…route signal to the PGM groups and monitor off the BUSS OUT jacks. Is the signal clean and strong?
I should think so. Though keep in mind it is likely the bias level is set too high for the tapes you are using…overbias conditions typically result in a diminished HF response and record level. Which to some can sound muffled. It might be worth uploading a sound clip of your issue somewhere and posting a link.
Also, and I’m pretty certain this has nothing to do with it, but you tried recording with dbx engaged and with it disengaged, yes? No significant difference except maybe a little less muffled with it disengaged.
First, note that it is “bias” not “bios”. Maybe there is an issue with your bias system, sure. The bias system is what accomplishes erasure and applies bias signal to tape during recording to minimize distortion and improve HF response. That’s why I’m asking if it erases. If it won’t erase, the bias system is not working.
Did I mention it’s a good idea to reseat the plug-in cards and treat the connections?
Also, I don’t know where the idea comes from that capacitors are the possible culprit of such a wide variety of issues. Yes they can go bad like anything else, but in a system like this the typical symptoms of bad caps are complete signal loss for a completely roached cap, but most typically higher noise floor, possible hum if a primary filter cap is bad, increased “skritchies” when actuating switches and potentiometers (due to less effective DC blocking), and improper timing of certain processes since caps are also used that way, as signal timing delays, like control signals…I wouldn’t expect a bad cap or caps to cause the kind of symptom you are talking about…first time for everything I suppose. But if you’re having issues like described above, then it is likely time for a recap.
Let’s go with that last thing you said. Again, that’s a good reasonable deduction. The transport is operating the same way during record and reproduce. It’s only the status of the bias system and record/reproduce amplification systems that are different between those two modes. So if it reproduces a known good recording fine, it’s not the transport.
sweetbeats
Reel deep thoughts...
I’ve always called them mini Molex connectors. I think they are made by Molex. I’ve never had to purchase anything for that because I have so many connectors and plugs and headers around here from units I’ve parted out. But you don’t have to get the exact same connector style. Anything that has the same style (square) pins of the same size, and the same pitch will work. If you have a dial caliper you can measure all this with reasonable accuracy and narrow down your search on Mouser or Digikey or whatever. And maybe try narrowing the search by Molex. I might be wrong, but if I’m right that should help.
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akieffer
New member
Thank you, sweetbeats. Your guidance is invaluable. I followed your lead and did the following:
-Tried to record over a (properly functioning) pre-recorded tape. It successfully deleted / inserted a silent section.
-Loaded the tape with the muffled sound. Monitored the tape outs (thus bypassing the mixing and monitoring circuitry) and experienced the same (poor) quality
-You suggested monitoring the BUSS out - I don't know exactly what you mean there. I attached mic, routed signal to program groups, and then monitored the MONITOR, STEREO (RCAs, not the balanced jacks), and TAPE outs. I have NOT monitored the AUX or EFFECTS outs (but certainly could).
-I tried recording with DBX on - same muffled effect (hard to discern any effect as the signal is so quiet and uneven).
-With high hopes and expectations, I removed BIAS PCB (1) and BIAS PCB (2) (not BIOS - too much time with computers
). Applied some Deoxit, reinstalled. Sadly, no change.
-Regarding CAPs - Thank you very much for describing what they do and what symptoms a bad one would display. I just recapped the power supply on my vintage receiver (for probably no good reason) and was feeling very pleased with myself. Since it's a thing I now know how to do, I was hoping that the problem could be here - "For a man with a hammer, every problem is a nail." I did peek at the caps on those two boards and there were no leaks, stains, or bulges - for what it's worth.
So, still nothing. I certainly have no plans of giving up but I'm not sure which direction I should head next.
-Tried to record over a (properly functioning) pre-recorded tape. It successfully deleted / inserted a silent section.
-Loaded the tape with the muffled sound. Monitored the tape outs (thus bypassing the mixing and monitoring circuitry) and experienced the same (poor) quality
-You suggested monitoring the BUSS out - I don't know exactly what you mean there. I attached mic, routed signal to program groups, and then monitored the MONITOR, STEREO (RCAs, not the balanced jacks), and TAPE outs. I have NOT monitored the AUX or EFFECTS outs (but certainly could).
-I tried recording with DBX on - same muffled effect (hard to discern any effect as the signal is so quiet and uneven).
-With high hopes and expectations, I removed BIAS PCB (1) and BIAS PCB (2) (not BIOS - too much time with computers
). Applied some Deoxit, reinstalled. Sadly, no change. -Regarding CAPs - Thank you very much for describing what they do and what symptoms a bad one would display. I just recapped the power supply on my vintage receiver (for probably no good reason) and was feeling very pleased with myself. Since it's a thing I now know how to do, I was hoping that the problem could be here - "For a man with a hammer, every problem is a nail." I did peek at the caps on those two boards and there were no leaks, stains, or bulges - for what it's worth.
So, still nothing. I certainly have no plans of giving up but I'm not sure which direction I should head next.