Tascam 388 Story...

  • Thread starter Thread starter sweetbeats
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I have not tried that. I will try when I get home this evening.

In looking at this gut shot it seems the head connections would be the brown/grey bundle coming from the tape area and snaking up to the top of the unit (bottom of the picture). Is that correct?
 
Yes. IIRC you can get to the connectors when you remove the trim that surrounds the headblock assembly...remove the pinch roller and tension arm rollers and then...3 screws?
 
Well that was pretty easy to get in there but unfortunately re-seating the head connectors did not do it.

In reading back my explanation of the PGM and tape outs I was not clear in explaining what's happening.

All tape outs work as they should.

PGM out 1,2,3,4,6,7,8 all work as they should. I can assign any track (including 5) to any PGM output (besides 5) and the fader for that track controls the output level from the assigned PGM output.

When I go from the PGM 5 output I can hear what is recorded on track 5 and it is a weak signal. I can hear this even when track 5 is not assigned to PGM 5, there's no difference in the level if track 5 is assigned to PGM 5 or not. The sound is always present and the track 5 fader does not control the volume. It's almost like a tape out but weak signal. If I assign another track to PGM 5 I can hear it very faintly (even quieter than the constant constant track 5 sound) and the fader for that track will control the level (it's really only audible above the 7-8 mark). When I assign a track to PGM 5 it is louder when the track is panned in the middle (assigned to 5 and 6). If I pan to the left I can still hear it but it's even quieter. This is while only running to the PGM 5 output.

I hope that makes sense. I can make a video if that would be helpful.
 
That was a helpful explanation. Thanks for that.

Just to make sure I understand correctly, NOTHING assigned to PGM 5 is present (i.e. the level is really really low) at the PGM 5 output jack whether the source is an input or a tape track assigned to the PGM 5 buss, correct?
 
sweetbeats said:
That was a helpful explanation. Thanks for that.

Just to make sure I understand correctly, NOTHING assigned to PGM 5 is present (i.e. the level is really really low) at the PGM 5 output jack whether the source is an input or a tape track assigned to the PGM 5 buss, correct?
Click to expand...

I'm 99% sure that's the case. I will double check with a mic and line input source this evening.


Mark7: I'm not actually using the PGM Buss outs for everyday use, this was just part of troubleshooting. The problem is I can not record to track 5, I suspect the PGM 5 problem is related to the track 5 recording problem.
 
Thanks for the reminder...was thinking your problem was just the PGM 5 output jack. Your problem is you can't record to track 5.

Stay tuned.

FYI all I am doing to help troubleshoot is just looking at the block diagram to narrow down the probable problem, then from there going to the schematics. You can look at the block diagram and start with your symptom: no audio to track 5, and just start tracing back on the page to where the signal comes from. You can see where else the signal goes and test if you can get signal there. It's a helpful tool for the high level diagnostic stage.

Can you swap where the PGM L and PGM R master faders plug in and see if the problem migrates? I suspect you will find you now can't record to track 6 but let me know.
 
Vicshat said:
I'm 99% sure that's the case. I will double check with a mic and line input source this evening.
Click to expand...


Okay, confirmed. Mic is quiet from PGM output, the fader does control the level of the mic but it's weak.

I might have a chance to get in there and swap the fader connections later this evening.

I'm fairly comfortable with the block diagram but I need to spend more time with the schematics. I certainly appreciate the help.
 
Okay. So...question: if swapping the faders doesn't effect the problem, is the problem before, or after the PGM master fader? Tell me what you think.
 
hmmm... My initial thought was it must be before. The fader is the last thing before the PGM out so there isn't anything between PGM fader and PGM out to cause a problem.

BUT, I think I've tried swapping everything before the PGM fader, which seems to be just the channel strip.

I think the channel strip from input to buss assign can be ruled out. I've tried swapping channels with no change. PGM 5 input skips all that and it doesn't record.

From PGM master fader it splits to PGM out and to the record function switches (already swapped those, no luck there), to the transport and back to the channel strip via RMX. So I'm thinking the problem must lie somewhere between the transport control and getting back to the input selection, maybe? I guess that would be AFTER the PGM fader but it kind of circles around.
 
It can't be before...if the problem is at or before the fader, that problem would migrate when we (essentially) re-routed the signal by swapping the fader connections. The issue remains at PGM 5 output and track 5.

You say the fader is the last thing before the PGM out...there is a crap ton of opportunity electronics-wise between the fader and the PGM out to cause a problem...Look at the block diagram. You see the triangles before and after the PGM master faders? Those triangles represent amplifiers. We've got active devices, connectors, passive components, etc., etc., etc.

[in a friendly reassuring tone] stop guessing and stabbing wildly. Let's systematically identify the problem. There is no guessing necessary. You've swapped lots of stuff, but not everything. You could have a pinched wire. Let's find the problem.

One more test I want you to do before we drill down to the schematics: record test tone to all 8 tracks. Track 5 is (for all intents and purposes) non-existent, right?

Flip the tape over and reproduce.

Is your problem now on track 3, both tracks 5 & 3, or still just 5?
 
I was looking at the "pictogram" on page 46 of the manual. I thought that was the "block diagram" but I was mistaken. I think I see what is the real block diagram later in the manual but I'm unable to make out what's what on the online version. I'll study my hard copy at home. The pictogram just shows the signal going from PGM fader to the PGM out with nothing in between.

I stopped guessing and stabbing wildly when I came here to ask for help and you told me I was probably making things worse :facepalm:

You asked me my thoughts and I gave them, I just happened to be pretty much completely wrong. :) (btw, I appreciate the opportunity to think about it on my own and be wrong and learn something)

I'm absolutely ready to pinpoint the problem, I am not doing anything besides what you instruct. You know what you are doing and I am hoping to learn what to do.

I'll try the test tone and tape flip this evening and report back.

Again, I truly appreciate the help.
 
Yeah I really can't stand those pictograms of the signal flow...you can actually get *everything* you need to know about operating a device like the 388 *just* from the block diagram...yes you have to study it, but you really learn how the controls and functions are related in the process which I think can make one a better operator...it's the first document I look for when encountering a new piece of gear. And, yes, the online version of the 388 block diagram is impossible to read. :)

I have, and will continue to make many, many more mistakes than experience successes. The mistakes educate and then enable the successes though. I have a friend who's wayyyyyyyyy smarter and more experienced than me and when I go to him periodically with a mess I can always expect he's going to answer my question(s) with (a) question(s)...which I appreciate and enjoy.

Keep in mind I'm just as prone to mistakes and failure as the next guy, and I don't know any more what's wrong with your 388 than you do at this point. We're going to enable it to tell us what's wrong.

We'll need whatever you have for a tone generator, and you'll need a multimeter that can measure AC and DC volts as well as continuity. Your job is to:

1. BE CAREFUL (after all we are working with electricity and millivolts can kill)
2. stay in step with our process
3. realistically expect we may not be able to fix it
4. Ask questions (no such thing as a dumb one, except for the one un-asked)
5. Learn...you WILL have more problems in the future...your 388 is over 30 years old, is a complex electro-mechanical device with unknown history. It will have ongoing problems and if you're committed to partnering with it you'll need to learn in order to keep it fully operational or you'll go crazy.

Lecture over.

"You asked me my thoughts and I gave them..." Yes, and I appreciate them. I hope I didn't say anything that discouraged you from sharing your thoughts. If I did it was unintended and I apologize. You sharing your thoughts helps me help you, and often may include good ideas or reveal clues.
 
Okay I tried the tape flip check. Before I flipped the tape all tracks work except 5, as expected. After flipping there's no playback from 4. PGM out 4 also silent and the same problem I described earlier with PGM 5 out (I can hear the signal faintly even if it's not assigned and the fader does not control the level).

The hardcopy block diagram is MUCH easier to understand. After looking at it for a minute I think that would put the problem somewhere in the triangle after the PGM fader that you mentioned. That's where the signal splits to go to tape (not getting there on 5) and to PGM output (only halfway getting there on 5).


I have a multimeter and a desire to learn how to keep this beast running. :D
 
I don't know why I said track 3. Track 4 makes sense.

Stay tuned.
 
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1. Assign a 1kHz test tone at -10dBv to PGM 5
2. With the bottom cover off of the 388 locate the BUSS B PCB assembly, the one the BUSS master faders plug into
3. Get out your multimeter set to AC volts
4. With the BUSS master fader set to unity, measure the voltage between pins 7 & 9, and then between pins 8 & 9 of the red connector J111, the red one.
5. With the settings set the same, look for the yellow connector that connects to the BUSS A PCB from the BUSS B PCB...measure the voltage between pins 5 & 9.

We are simply looking to verify tone is getting to the fader, is present post-fader, and also present post fader booster amp U381 on the BUSS B PCB.

Report back...let me know if you have questions or need help with the instructions above.
 
Okay I'm about to turn in for the night but I will try that tomorrow.

I just pulled out the schematic and opened up the 388 to see if I have any questions and I think there's an error in the schematic. The white connector is actually the ODD PGM connector. I've triple checked and they're not just installed backwards or anything.

As far as making the actual measurement, pardon my ignorance, but does that mean disconnect the connector and measure against the bare pins and then measure the unattached connector?
 
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