The Ghost of FM
Banned
I'm seriously happy for you man! Good job!
+1 !
It seemed a bit desperate near the end with all those phantom problems so very glad to see that Cory persevered and got to the bottom of it!
Cheers!
Tascam 388 Story...
- Thread starter sweetbeats
- Start date
+1 !
It seemed a bit desperate near the end with all those phantom problems so very glad to see that Cory persevered and got to the bottom of it!
Cheers!
cjacek
Analogue Enthusiast
LUNE
...a pieds joints
Some of the wipers in the BUSS MASTER faders had been bent just enough during cleaning to not contact the element anymore.
yes, about those faders, they're different than the others? they seem a little 'sluggish', but in a good way for BUSS MASTER faders to be. was that the intention and is that a common design? I havn't really noticed it on other mixers.
sweetbeats
Reel deep thoughts...
That's a good question.
The reason is because its a bigger fader...the guts I mean. A channel fader is attenuating the level of one channel so there are two wipers (the springy metal contacts that ride on the actual resistive element); one for the dignal and one for ground. Those BUSS MASTER faders are attenuating 4 channels each...4 group channels. The ODD fader manages groups 1, 3, 5, and 7, and the EVEN fader manages groups 2, 4, 6, and 8. So with 4 channels you have 8 wipers. The wipers don't create a lot of friction, but the wipers are mounted to a nylon carriage which is wider to accommodate all those wipers and THAT is where the higher drag comes from...
The reason is because its a bigger fader...the guts I mean. A channel fader is attenuating the level of one channel so there are two wipers (the springy metal contacts that ride on the actual resistive element); one for the dignal and one for ground. Those BUSS MASTER faders are attenuating 4 channels each...4 group channels. The ODD fader manages groups 1, 3, 5, and 7, and the EVEN fader manages groups 2, 4, 6, and 8. So with 4 channels you have 8 wipers. The wipers don't create a lot of friction, but the wipers are mounted to a nylon carriage which is wider to accommodate all those wipers and THAT is where the higher drag comes from...
LUNE
...a pieds joints
Another 388 falls into the hands of the rebel forces!!!
Don't be wary of running the machine and playing with it. I truly think it is mild OCD so my way is definitely not necessarily the "right" way.
yes, in the end my obsessive compulsive "just need to play with it now" disorder got the best of me. the tape transport panel and the side sashes are back on - I pulled it apart enough to slake my curiosity, put some sewing machine oil on the tension arm rollers & pinch roller shafts (this seems to help it run smoother - or else its just that its been warmed up with me playing it after years of sitting.) I did a 'detailing' of the outside without taking out the channel input PCBs - just all the nobs off (would it be considered OCD cleaning all the plastic nobs individually with a toothbrush?) and I'll deal with any cracklies when I get there....
...however, calibration beckons....
sooooo... do we get to see/hear the part about "and they matched input to output -10db at 1, 10 & 15khz happily ever after..."?
(no expectations, really, I've just got calibration on the brain...)oh, and to get mine going I did have to use a bit of temporary ingenuity that i do hope will not be considered heretical or scandalous by our fine and loyal crowd here... (the belt's on the way!)
[with my poor camera you can't see it, but it reads "ROMAINE #4605 PRODUCE OF USA"]
LUNE
...a pieds joints
that IS interesting, so I guess it was just incidental, the drag - still seems appropriate though somehow for the bus faders to be stiffer than the others... but its all on account of the extra 'resistive elements' - (always enjoy broadening my vocabulary, especially when it comes to semi-esoteric jargon with a scientific flair..., and 'resistive element' IS rather more practically descriptive ...if less graphically evocative, than "runway")
I posted some white noise frequency analysis tests on some tape decks including my 388 here:
https://homerecording.com/bbs/showthread.php?t=295904
sweetbeats
Reel deep thoughts...
(would it be considered OCD cleaning all the plastic nobs individually with a toothbrush?)
-SNIP-
sooooo... do we get to see/hear the part about "and they matched input to output -10db at 1, 10 & 15khz happily ever after..."?
oh, and to get mine going I did have to use a bit of temporary ingenuity that i do hope will not be considered heretical or scandalous by our fine and loyal crowd here... (the belt's on the way!)
I don't know if that would be considered OCD or not...probably, but regardless that's what I always do...
Kind of dreading cleaning up the rest of the M-__ knob caps...well over 700 parts to go...
I'll calibrating the 388 after I get my Tentelometer back which will be happening soon. I want to check all the tensions before I line it up.
Don't know how tight that rubber band is but if its snug I wouldn't run it for too long with that on...
Oh, and on your last post, just to be clear the higher drag is because of the wider wiper carriage...yes it is wider because of the greater number of wipers, but the amount of drag from a wiper is negligible. The wider carriage is a different story.
sweetbeats
Reel deep thoughts...
Tracked for the first time today
Just playing around with the kids.
Having a bias issue...related thread here:
https://homerecording.com/bbs/showthread.php?t=296163
The bigger issue is that the L-R buss assign doesn't work. Maybe that's the problem the previous owner was having. He struggled with how to describe it but its making sense now. He thought he was doing something wrong.
On a 388, what you hear in the STEREO buss is coming through the Monitor Mixer until you route a channel to the L-R buss...then the headphones, monitor jacks and STEREO jacks are sourcing straight from those channels assigned to the L-R buss as well as the EFFECT returns 1 & 2 and the STEREO BUSS IN jacks. The monitor mixer is no longer in the picture because you usually use the L-R assign function when its time to mix down...no need for the monitor mixer. Well, when I depress any L-R assign button nothing happens. I know the STEREO OUT jacks are working as is anything else that goes TO the stereo buss and jacks (like the output of the monitor mixer, the STEREO BUSS IN jacks, etc.). So its not the STEREO BUSS...I'm getting better at this part. I studied the schematics for about 10 miinutes this afternoon...the problem is in the transistor switching mechanism that switches the source of the stereo buss from the monitor mixer to those channels assigned to the L-R buss. When you depress a L-R assign switch you are also connecting a third line to ground, the STEREO CONT conductor. This is for the transistor chip that does the switching on the BUSS B board. Yeah...great...the same one for which my spare is missing 7 of the 10 PAN pots otherwise I'd just swap them out. But I will likely confirm that the logic chip is getting proper power, and that the STEREO CONT circuit pulls to ground at the chip when I press a L-R assign switch. There are some resistors in there I can test too. Hopefully I can find it. Can one live without the L-R assign function on a 388? Sure, but mixdowns would then go through redundant summing and buss amps, and the L-R function is neat because it works like a solo-in-place function during tracking and overdubbing. Pretty important.
I'm feeling better now but I was pretty disheartened earlier. Oh well.
On the good side, even though the playback response is whacked at this point and I think my bias is screwey, the response is pretty steady, the transport handles wonderfully, the mixer sounds great and I'm actually impressed with the record quality in spite of it not being properly setup yet.
I have these little home-grown passive 5" monitors (I got the cabs at a thrift shop, the woofers from Parts Express on closeout and the tweeters and passive crossovers from an auto install...I had the cabs plotted and put ports in them). I've had them for 15~20 years. They sound pretty good for what they are, but I haven't used them in a long time so I didn't realize how out-of-tune my ears were to them. Playback sounde so-so but then I listened through my Sennheiser HD280 cans and wow...not to shabby lil 388. 
OH! And another issue: track 1 has even worse on top of bad HF response but I think I've go that figured because if I apply slight upward pressure on the tape edge just before the play head the bad HF response heads to track 8...the head is lightly grooved and with no edge slots I just betcha there is a slight enough tape width difference between the LPR35 I'm using and whatever grooved the head and now the tape rides up out of the groove at the edge by track 1...decreased HF response would result...lift the tape slightly, the bottom settles down into the groove and the top by track 8 pops out of the groove and that's what I'm seeing on the meters...won't worry about it for now...
So, work to do yet, but it is a really good sounding package. Can't wait to get the bugaboos taken care of, but it is a fun machine to operate. Just as I thought.
Just playing around with the kids.
Having a bias issue...related thread here:
https://homerecording.com/bbs/showthread.php?t=296163
The bigger issue is that the L-R buss assign doesn't work. Maybe that's the problem the previous owner was having. He struggled with how to describe it but its making sense now. He thought he was doing something wrong.
On a 388, what you hear in the STEREO buss is coming through the Monitor Mixer until you route a channel to the L-R buss...then the headphones, monitor jacks and STEREO jacks are sourcing straight from those channels assigned to the L-R buss as well as the EFFECT returns 1 & 2 and the STEREO BUSS IN jacks. The monitor mixer is no longer in the picture because you usually use the L-R assign function when its time to mix down...no need for the monitor mixer. Well, when I depress any L-R assign button nothing happens. I know the STEREO OUT jacks are working as is anything else that goes TO the stereo buss and jacks (like the output of the monitor mixer, the STEREO BUSS IN jacks, etc.). So its not the STEREO BUSS...I'm getting better at this part. I studied the schematics for about 10 miinutes this afternoon...the problem is in the transistor switching mechanism that switches the source of the stereo buss from the monitor mixer to those channels assigned to the L-R buss. When you depress a L-R assign switch you are also connecting a third line to ground, the STEREO CONT conductor. This is for the transistor chip that does the switching on the BUSS B board. Yeah...great...the same one for which my spare is missing 7 of the 10 PAN pots otherwise I'd just swap them out. But I will likely confirm that the logic chip is getting proper power, and that the STEREO CONT circuit pulls to ground at the chip when I press a L-R assign switch. There are some resistors in there I can test too. Hopefully I can find it. Can one live without the L-R assign function on a 388? Sure, but mixdowns would then go through redundant summing and buss amps, and the L-R function is neat because it works like a solo-in-place function during tracking and overdubbing. Pretty important.
I'm feeling better now but I was pretty disheartened earlier. Oh well.
On the good side, even though the playback response is whacked at this point and I think my bias is screwey, the response is pretty steady, the transport handles wonderfully, the mixer sounds great and I'm actually impressed with the record quality in spite of it not being properly setup yet.
I have these little home-grown passive 5" monitors (I got the cabs at a thrift shop, the woofers from Parts Express on closeout and the tweeters and passive crossovers from an auto install...I had the cabs plotted and put ports in them). I've had them for 15~20 years. They sound pretty good for what they are, but I haven't used them in a long time so I didn't realize how out-of-tune my ears were to them. Playback sounde so-so but then I listened through my Sennheiser HD280 cans and wow...not to shabby lil 388. OH! And another issue: track 1 has even worse on top of bad HF response but I think I've go that figured because if I apply slight upward pressure on the tape edge just before the play head the bad HF response heads to track 8...the head is lightly grooved and with no edge slots I just betcha there is a slight enough tape width difference between the LPR35 I'm using and whatever grooved the head and now the tape rides up out of the groove at the edge by track 1...decreased HF response would result...lift the tape slightly, the bottom settles down into the groove and the top by track 8 pops out of the groove and that's what I'm seeing on the meters...won't worry about it for now...
So, work to do yet, but it is a really good sounding package. Can't wait to get the bugaboos taken care of, but it is a fun machine to operate. Just as I thought.
sweetbeats
Reel deep thoughts...
Sweetbeats 1, IC Logic Circuitry 0
Many of you know I have developed somewhat of a phobia of IC logic circuitry since I killed a bunch of it on the Tascam 58 I used to own (now owned by evm1024 and now fully-functional of course)...So it has been very troubling to me, this problem with the L-R assign function, but today I will hold my victory in my mind for the next time I am beaten by IC logic circuitry and I will remember how I once won.
Okay. That was corny, but I'm feeling relieved...I fixed it. Here's what I did:
I mentioned in my last post that I used the schematics to narrow down where the problem had to be...Actually I started with the block diagram and then from there went to the schematics. I've taken no classes on how to read these things, its just been trial by fire and a lot of help from others. Ethan has been particularly helpful and I think some of the most valuable times are the couple instances when we've been able to cross paths in-person and look over a schematic...even just listing to him think out loud as he quickly traces his finger around the schematic is helpful. So I had narrowed the problem down to a couple key suspects on the BUSS B PCB.
1. Q105 which is a transistor that (and I know I'm butchering terminology and maybe even function here so take it with a grain of salt) powers the actual logic switching chip U102. When a L-R assign switch is latched, it connects the emitter of Q105 direct to ground which in turn provides ground to pin 14 of U102 and then it does its thing which switches transistors that route the source of the monitor and stereo busses. So if somehow Q105 was bad and wasn't pulling to ground when a L-R assign switch was pressed, none of the other stuff would do its thing.
2. Suspect #2 is U102 itself. If something was cooked/faulty/just plain wore out inside it wouldn't do its thing regardless of receiving ground continuity.
I pulled the BUSS PCB and first did a close visual inspection..anything look cooked? No. Next step. I did a static comparison of continuity from that STEREO CONT circuit that connects Q105 to ground...I checked resistors as well to make sure they were at least functional and reasonable within spec. This is not a sure-fire test mind you because performance can change under load, but I didn't have an easy way to power the board out of the 388 so...anyway, everything seemed good to system ground, STEREO CONT, and to the +/-15V rail connectors. I don't have a transistor tester so at this point it was anybody's guess. BTW I put my spare BUSS B PCB in the 388 (the one missing the PAN knobs for monitor channels 2~7) just to see if the L-R assign function worked and 'lo and behold it did, which reassured me that the problem was indeed on the board. I didn't rest comfortably that it DEFINITELY was on that board, but it working supported my theory so I went with it. So knowing that the spare board worked I swapped Q105...problem still remained when I put the original board back in (with Q105 from the spare board). I started with Q105 because its easier to get replacements of those, less soldering to do the swap, and all around less risky. But, the problem was still there so I bit the bullet and swapped U102. I realize this is a little bit of a hammer-mechanic methodology, but it worked this time. So the 388 is buttoned back up and ready to play today. The above process took about 90 minutes from start to finish so not bad.
Many of you know I have developed somewhat of a phobia of IC logic circuitry since I killed a bunch of it on the Tascam 58 I used to own (now owned by evm1024 and now fully-functional of course)...So it has been very troubling to me, this problem with the L-R assign function, but today I will hold my victory in my mind for the next time I am beaten by IC logic circuitry and I will remember how I once won.
Okay. That was corny, but I'm feeling relieved...I fixed it. Here's what I did:I mentioned in my last post that I used the schematics to narrow down where the problem had to be...Actually I started with the block diagram and then from there went to the schematics. I've taken no classes on how to read these things, its just been trial by fire and a lot of help from others. Ethan has been particularly helpful and I think some of the most valuable times are the couple instances when we've been able to cross paths in-person and look over a schematic...even just listing to him think out loud as he quickly traces his finger around the schematic is helpful. So I had narrowed the problem down to a couple key suspects on the BUSS B PCB.
1. Q105 which is a transistor that (and I know I'm butchering terminology and maybe even function here so take it with a grain of salt) powers the actual logic switching chip U102. When a L-R assign switch is latched, it connects the emitter of Q105 direct to ground which in turn provides ground to pin 14 of U102 and then it does its thing which switches transistors that route the source of the monitor and stereo busses. So if somehow Q105 was bad and wasn't pulling to ground when a L-R assign switch was pressed, none of the other stuff would do its thing.
2. Suspect #2 is U102 itself. If something was cooked/faulty/just plain wore out inside it wouldn't do its thing regardless of receiving ground continuity.
I pulled the BUSS PCB and first did a close visual inspection..anything look cooked? No. Next step. I did a static comparison of continuity from that STEREO CONT circuit that connects Q105 to ground...I checked resistors as well to make sure they were at least functional and reasonable within spec. This is not a sure-fire test mind you because performance can change under load, but I didn't have an easy way to power the board out of the 388 so...anyway, everything seemed good to system ground, STEREO CONT, and to the +/-15V rail connectors. I don't have a transistor tester so at this point it was anybody's guess. BTW I put my spare BUSS B PCB in the 388 (the one missing the PAN knobs for monitor channels 2~7) just to see if the L-R assign function worked and 'lo and behold it did, which reassured me that the problem was indeed on the board. I didn't rest comfortably that it DEFINITELY was on that board, but it working supported my theory so I went with it. So knowing that the spare board worked I swapped Q105...problem still remained when I put the original board back in (with Q105 from the spare board). I started with Q105 because its easier to get replacements of those, less soldering to do the swap, and all around less risky. But, the problem was still there so I bit the bullet and swapped U102. I realize this is a little bit of a hammer-mechanic methodology, but it worked this time. So the 388 is buttoned back up and ready to play today. The above process took about 90 minutes from start to finish so not bad.
The Ghost of FM
Banned
Good stuff, Cory!
Cheers!
Cheers!
The Great Cobb
New member
...
Amazing!!!
Amazing!!!
sweetbeats
Reel deep thoughts...
+1 to that...I know I'M amazed...seriously.
sweetbeats
Reel deep thoughts...
AllenM, I always say I know enough to be dangerous. Sometimes I'm operating beyond that (particularly with the mechanical side of things), but on the electronics side I can be a bit of a bull in a china shop.
How did I learn?
Maybe that answers your question, maybe not.
But it was a process of elimination in this case.
I could look at the block diagram (my favorite single document in any mixer manual) and use that to go through and really check which inputs, outputs and routing features were working and which were not. In doing that it really narrowed it down to only a couple of possibilities. Then I figured out on which PCB those controls lived, then you pull the schematic for that PCB and start looking at how stuff works on there. It helps having pulled the 388 totally apart because I can look at the inputs and outputs of a PCB schematic and have a frame of reference in my mind for where those are going and why they are going there and what happens when they get there, and that makes it easier to see how signal flows through the schematic. Once you understand how the stuff works it makes it possible to hone in on something that would stop it from working if that thing was kaput, or if signal wasn't getting to or from the device. So once I've honed in on the device I first check and make sure signal can get to and from the device, then the next reasonable assumption is that the device is shot. That's what happened in this case. In my mind this was not a complex problem and my assumptions were correct. This was the exception. So anyway, like I wrote above I figured it had to be Q105 or U102. I swapped a known entity with Q105 to start because it was easier to swap and I wanted to leave U102 alone if I could. Heat from a soldering iron is never a gentle thing on a component. The Q105 swap didn't work, so I swapped the next suspect and that was it. Button it back up.
But just to be clear, this, in my mind, was a relatively simple problem and I was able to just swap parts. Faulty logic chip, nothing else...and only one at that.
You should look at evm1024's MS-16 Story thread...now THAT would have been absolutely hopeless for me as was my defunct Tascam 58. Ethan has both of those working now and that is amazing to me.
EDIT
And what I've come to learn is that I'm not going to get to that level...would I like to? In a way yes because there is self-sufficiency...I believe as human beings we are wired to try and fend for ourselves. We typically want to take care of it ourselves, but we can't do it all. I've learned in the last several years that some kinds of gear just are not suited for me if I plan on being able to fix it, and also that it isn't fair to keep leaning on people to bail me out and that's part of my attraction to my Ampex MM-1000, because it is a relatively simple system compared to a "modern" recorder. Better chance I can keep it going.
But this 388 is just a wonderful marvel. My goodness it was fun to operate. A very refined package all around and just a joy to use and I'm really surprised at the sound-quality for the relatively narrow format, and not to mention I think my bias and response settings are still whacky at this point. I'll take care of that soon but it was time to play this past weekend and the 388 (once I fixed the L-R assign issue) worked absolutely flawlessly. The first true test. It was powered up for at least 20 hours this last weekend and nothing died, and every control works 100%...no crackly pots or anything. It just...works.
How did I learn?
- Aptitude is part of it I'm sure
- Exposure (I grew up around lots of electronics thanks to my brother)
- Desire (gotta get this stuff working)
- LOTS of questions
- LOTS of reading and studying
- LOTS of errors
- MORE questions
- MORE reading and studying
- A TON more exposure
- A CRAP TON more mistakes
- And most of all, a number of really nice patient people that were willing to give of their time to answer questions and bail me out when I screwed stuff up.
- It also helps that I have always loved taking stuff apart and seeing how it works, and I love taking something that doesn't work and has been cast aside and making it work, especially when I can get it cheap and its a really cool device and make it work. Very satisfying. I guess that goes under aptitude...I distinctly remember taking apart my Kenner Star Wars X-Wing Fighter toy at age 9 simply because I wanted to know how pushing down on R2-D2's head would make the "wings" pop open into the "X" configuration.
Maybe that answers your question, maybe not.
But it was a process of elimination in this case.
I could look at the block diagram (my favorite single document in any mixer manual) and use that to go through and really check which inputs, outputs and routing features were working and which were not. In doing that it really narrowed it down to only a couple of possibilities. Then I figured out on which PCB those controls lived, then you pull the schematic for that PCB and start looking at how stuff works on there. It helps having pulled the 388 totally apart because I can look at the inputs and outputs of a PCB schematic and have a frame of reference in my mind for where those are going and why they are going there and what happens when they get there, and that makes it easier to see how signal flows through the schematic. Once you understand how the stuff works it makes it possible to hone in on something that would stop it from working if that thing was kaput, or if signal wasn't getting to or from the device. So once I've honed in on the device I first check and make sure signal can get to and from the device, then the next reasonable assumption is that the device is shot. That's what happened in this case. In my mind this was not a complex problem and my assumptions were correct. This was the exception. So anyway, like I wrote above I figured it had to be Q105 or U102. I swapped a known entity with Q105 to start because it was easier to swap and I wanted to leave U102 alone if I could. Heat from a soldering iron is never a gentle thing on a component. The Q105 swap didn't work, so I swapped the next suspect and that was it. Button it back up.
But just to be clear, this, in my mind, was a relatively simple problem and I was able to just swap parts. Faulty logic chip, nothing else...and only one at that.
You should look at evm1024's MS-16 Story thread...now THAT would have been absolutely hopeless for me as was my defunct Tascam 58. Ethan has both of those working now and that is amazing to me.
EDIT
And what I've come to learn is that I'm not going to get to that level...would I like to? In a way yes because there is self-sufficiency...I believe as human beings we are wired to try and fend for ourselves. We typically want to take care of it ourselves, but we can't do it all. I've learned in the last several years that some kinds of gear just are not suited for me if I plan on being able to fix it, and also that it isn't fair to keep leaning on people to bail me out and that's part of my attraction to my Ampex MM-1000, because it is a relatively simple system compared to a "modern" recorder. Better chance I can keep it going.
But this 388 is just a wonderful marvel. My goodness it was fun to operate. A very refined package all around and just a joy to use and I'm really surprised at the sound-quality for the relatively narrow format, and not to mention I think my bias and response settings are still whacky at this point. I'll take care of that soon but it was time to play this past weekend and the 388 (once I fixed the L-R assign issue) worked absolutely flawlessly. The first true test. It was powered up for at least 20 hours this last weekend and nothing died, and every control works 100%...no crackly pots or anything. It just...works.
LUNE
...a pieds joints
U102 or U104?
so i'm following along here with manual and Buss B PCB (as mine just so happens to be available out of machine for other reasons...
https://homerecording.com/bbs/showthread.php?t=296452) ...did you mean U104 (not U102)? it was the IC chip you switched out that saved the day right? my manual page 3-23 lists U102 as another transistor ("SI.TR.2SA1346" - whats the 'SI' stand for anyway?) and just next to it U104 as the IC ("IC,MC14049B"). on my BUSS B PCB this is confirmed, though they are right next to each other and one could almost read U102 for the IC.
as a general aside for all this, does anyone know what goes bad more often generally : a transistor or an IC?
still haven't reverse engineered your logic following the schematics, but maybe I'll have a go. (I fear I'll be having to do some similar sleuthing over here soon...)
so i'm following along here with manual and Buss B PCB (as mine just so happens to be available out of machine for other reasons...
https://homerecording.com/bbs/showthread.php?t=296452) ...did you mean U104 (not U102)? it was the IC chip you switched out that saved the day right? my manual page 3-23 lists U102 as another transistor ("SI.TR.2SA1346" - whats the 'SI' stand for anyway?) and just next to it U104 as the IC ("IC,MC14049B"). on my BUSS B PCB this is confirmed, though they are right next to each other and one could almost read U102 for the IC.as a general aside for all this, does anyone know what goes bad more often generally : a transistor or an IC?
still haven't reverse engineered your logic following the schematics, but maybe I'll have a go. (I fear I'll be having to do some similar sleuthing over here soon...
)
LUNE
...a pieds joints
Tentelometer Tantrums
OK, I did all this last week before pulling my PCB's out, but I thought I'd wait to post til you might have your tentelometer back....
in any case feel free to ignore all this until you get around to tentelometering, but I’ll be curious what you find whenever that is.
What I find on my machine:
When I set R112 & R212 by eye to where I think looks right (according to manual), I can get hardly any reading at all with my Tentelometer (model T2-H2O-1, same as recommended in Manual) even with R103 & R203 full tilt. If I compromise and ride the tension arms (what to me looks) a little high, I can get a slightly bouncy reading under 20g for left (supposed to be 40g +-5g) and under 30g for right (supposed to be 50g +-5g). I can get the correct reading on the left by tweaking R112 & R103, but the Tension Roller rides almost equal with the inertia roller. Takeup tension is harder to get anywhere in the realm of 50g, (when I have the back tension set to an unnatural 40g) it basically keeps bouncing around 20-25 unless it falls to nothing which it does when it hits fully clockwise or (more to be expected) when too far counterclockwise – also when it (the takeup tension roller) is outside of its ‘eyeball’ range, it bounces rather more when passing tape – I can get it running pretty even without much movement otherwise.
An initial guess is that perhaps the springs on these that keep the tension rollers down are a bit lax by now after all these years, Is it worth it to see if tascam has replacement springs in case that is the reason for the discrepancies?
And (if we’re compromising) do we want to have the tentelometer readings closer to correct readings, or the tension rollers to ‘look right’ & ‘feel more comfortable’?
I haven’t ruled out a mis calibrated teltelometer, but it does reed past 60g on the left when I crank everything – it SEEMS as if its working, though I’m not sure what to test it on to be 100% sure and haven’t used it for anything else.
...Curious what your machine reads.
OK, I did all this last week before pulling my PCB's out, but I thought I'd wait to post til you might have your tentelometer back....
in any case feel free to ignore all this until you get around to tentelometering, but I’ll be curious what you find whenever that is.
What I find on my machine:
When I set R112 & R212 by eye to where I think looks right (according to manual), I can get hardly any reading at all with my Tentelometer (model T2-H2O-1, same as recommended in Manual) even with R103 & R203 full tilt. If I compromise and ride the tension arms (what to me looks) a little high, I can get a slightly bouncy reading under 20g for left (supposed to be 40g +-5g) and under 30g for right (supposed to be 50g +-5g). I can get the correct reading on the left by tweaking R112 & R103, but the Tension Roller rides almost equal with the inertia roller. Takeup tension is harder to get anywhere in the realm of 50g, (when I have the back tension set to an unnatural 40g) it basically keeps bouncing around 20-25 unless it falls to nothing which it does when it hits fully clockwise or (more to be expected) when too far counterclockwise – also when it (the takeup tension roller) is outside of its ‘eyeball’ range, it bounces rather more when passing tape – I can get it running pretty even without much movement otherwise.
An initial guess is that perhaps the springs on these that keep the tension rollers down are a bit lax by now after all these years, Is it worth it to see if tascam has replacement springs in case that is the reason for the discrepancies?
And (if we’re compromising) do we want to have the tentelometer readings closer to correct readings, or the tension rollers to ‘look right’ & ‘feel more comfortable’?
I haven’t ruled out a mis calibrated teltelometer, but it does reed past 60g on the left when I crank everything – it SEEMS as if its working, though I’m not sure what to test it on to be 100% sure and haven’t used it for anything else.
...Curious what your machine reads.
sweetbeats
Reel deep thoughts...
Yes, my bad...Good catch LUNE...the chip in question was indeed U104.
Thanks!
BTW, tell us about the calibration procedure you put your Tentelometer through before checking tensions on the 388 with it? It is critical to the process...
LUNE
...a pieds joints
AHA! my ignorance is now aware of itself!
though made right by the great videos you made that i just found...
...and the tentelometer manual i also found hiding behind the foam in the case...
well, now's the time for me to feel stupid and remember when next I'm rushing into things I don't understand... and I feel bad about the torture i must have put on her tweaking all the tensions...
I should have guessed I needed to calibrate the tools i was using to calibrate the machine I plan to use to calibrate my existence... now, if i can just find the instructions on how to calibrate that allen wrench and that weight I'll be set!...
but actually, even now that i (somewhat more) know what i'm doing, i don't have a totally clear path. it turns out while calibrating the tentelometer I'm maxing out the range (going clockwise to the very end) and only getting close to 3/4 ounce. (its old and rusty in spots) this does give me a much better range for guessing though. I guess what i'm 'supposed' to do now is send my tentelometer back to tentelom-central for 'repair'. but i did try to make an educated guess for the tension, trying to eyeball down in a nonlinear fashion like the gauge. would this be just compounding my stupidity, leaving it at an 'educated guess'? it seems to be running smooth by looks. i'll make some recording tests to see if i can hear any differences, though i'm not expecting to.
though made right by the great videos you made that i just found...
...and the tentelometer manual i also found hiding behind the foam in the case...
well, now's the time for me to feel stupid and remember when next I'm rushing into things I don't understand... and I feel bad about the torture i must have put on her tweaking all the tensions...
I should have guessed I needed to calibrate the tools i was using to calibrate the machine I plan to use to calibrate my existence... now, if i can just find the instructions on how to calibrate that allen wrench and that weight I'll be set!
...but actually, even now that i (somewhat more) know what i'm doing, i don't have a totally clear path. it turns out while calibrating the tentelometer I'm maxing out the range (going clockwise to the very end) and only getting close to 3/4 ounce. (its old and rusty in spots) this does give me a much better range for guessing though. I guess what i'm 'supposed' to do now is send my tentelometer back to tentelom-central for 'repair'. but i did try to make an educated guess for the tension, trying to eyeball down in a nonlinear fashion like the gauge. would this be just compounding my stupidity, leaving it at an 'educated guess'? it seems to be running smooth by looks. i'll make some recording tests to see if i can hear any differences, though i'm not expecting to.
sweetbeats
Reel deep thoughts...
Which videos?
Where is your Tentelometer rusty?
You are using the same tape when calibrating the Tentelometer as you are using on the 388 right?
And when calibrating it you are holding the meter so the prongs are horizontal and oriented so that when you pull the tape upward (with the weight attached) it is passing through the prongs in the same direction that the tape travels through the prongs when in PLAY mode on the transport?
Are you sure the weight is 1oz?
Where is your Tentelometer rusty?
You are using the same tape when calibrating the Tentelometer as you are using on the 388 right?
And when calibrating it you are holding the meter so the prongs are horizontal and oriented so that when you pull the tape upward (with the weight attached) it is passing through the prongs in the same direction that the tape travels through the prongs when in PLAY mode on the transport?
Are you sure the weight is 1oz?