Tascam 388 detailed list of in and outs

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Instroverb

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that function or not.

Sweetbeats asked me to into more detail. I hope this is enlightening!
Both mic and line imputs:


Track 1 registers input and meter movement but no sound with cue
Track 2 does not register input and meter movement ol light but no sound with cue
Track 3 registers input and meter movement but no sound with cue
Track 4 registers input and meter movement but no sound with cue
Track 5 registers input and meter movement but no sound with cue
Track 6 registers input and meter movement but no sound with cue
Track 7 registers input and meter movement but no sound with cue
Track 8 registers input and meter movement but no sound with cue

there is no stereo meter movement or sound through headphone amps or monitor with all of the above.

Both f/x returns register a signal on the stereo meters and through headphone amp and monitor out

Both stereo ins register a signal on the stereo meters and through headphone amp and monitor out.

All tape outs work

So my guess is something with the cue monitor. What do the tascam gurus think?
 
I'm a little foggy on this without being in front of the unit.

It strikes me that if any channel is "Assigned" to any "Pgm Buss", (white button), and while any track is set "Rec-Enable", (red Rec Function button down), then the "Stereo L/R" button on any channel may NOT be depressed simultaneously as the others, but if done so will cause an "auto-mute" of the internal routing, i.e., the cue monitor. This is an inherent built-in design feature that prevents an internal feedback loop from developing.

As I said, I'm a bit foggy on this one without being in front of the 388.

Check it out/try it. Not sure what else./DA
 
I had all the red stereo buttons in the up position (i had made that mistake way back when I bought the machine without the manual). But thanks for the reply. BTW, I downloaded some of your Ramones and Beatles tracks a few years back and really dig them!
 
Instroverb said:
I had all the red stereo buttons in the up position (i had made that mistake way back when I bought the machine without the manual). But thanks for the reply.
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That must be what I told'ya last time, then.:eek:;)

Instroverb said:
BTW, I downloaded some of your Ramones and Beatles tracks a few years back and really dig them!
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Gosh, thanx! Me too! I've got some newer stuff up since then, heh, heh!:eek:;)
 
So HOW did the feedback loop occur with the 38??? That's where I'm foggy now...you were using the 388 mixer section to mixdown tracks on the 38? And the 38 outs were connected to the LINE inputs on the 388? Just trying to get a grasp on where the feedback loop occurred...
 
Instroverb said:
1 Day Ago

Tascam 388

Hi all,

I was recording and overdubbing with 38 hooked through the patch bay to the 388. I had the outputs of the 38 going through the patchbay into the line ins on the 388. I caused a terrible feedback loop and the next thing I knew there was no sound from the head phones.

Thanks!
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See, I'd missed that earlier!

I can't say what in the way of troubleshooting is the problem, but I'll harken back to many times advising that the 388 could support the 38 as an outboard mixer, but is best configured with something like the M1-B line mixer to provide isolation as "cue" monitor,... lest you inadvertently patch a horrendous feedback loop thru the 388/38 ciruitry.

I know I've recommended that many times over on this board, and this post illustrates why.

To not have been there, the feedback loop goes from the 388's outputs, thru the 38's Rec-Enabled input section & out again, back to the 388's Line-In, where it likely was "assigned" to either a PGM Buss or Stereo L/R Buss, then looped back out to the 38. Instant ear-splitting-component-damaging feedback loop,... at your service! That's one of those "oopses" that you should always try to avoid, hence my rec'mdtion of the M1-B as intermediary. I've patched a few feedback loops in my time, and I know what I speak of.:eek:;)

Sorry if this post is not helpful, beyond the obvious!:eek::eek:;)
 
Sorry,... that was not finger wagging!

Just a real world example of something I'd warned against doing. If you stay on a technical BBS long enough, eventually things (posts, ideas) come full circle.

Okay, but I'd stumbled upon the fact of 38/388 hookup pending the disater a bit late. I'm caught up now.

Technically,... sight unseen,... I'd throw an educated guess that if you were using the 388's inputs, assigning them to PGM Busses, then patched out to the 38? Then, to monitor the outgoing busses, you'd have to be listening thru the 388 (cue) Monitor section? Then, when flipping to listening back to tracks, using the Line-Ins,... as long as you Never switch to Line when the channel is assigned to any PGM Buss with any of it's associated 38 Tracks set Rec-Enable. Of course, it's easy to say "just avoid that pitfall", but it's a quick, inadvertent move that gets you there in a hurry when you momentarily forget.

Based on this basic scenario, or regardless of whether you used Assign-Busses or the Stereo L/R subsystem,... because the Monitor and Stereo L/R busses share the same circuitry,... I believe you might have fried the pair of output transistors for the Stereo L/R & Monitor shared output section.

You're definitely looking at Tech Time for this matter. I'd start looking at the Output transistors, and then look for the signal going backwards. If that seems too convoluted, other techs might work from the known signal point (input) and go forward. No matter, some may half-split in troublshooting signal trace, but it's likely to me you just fried the stereo pair of transistors. Sight unseen, I could only say that and it's up to others to diagnose. Are you near Tascam in LA? That's the best bet IMO.

Best of luck!

It's something shared by all input-Pgm-Busses and Stereo, so is the shared circuitry of the basic L/R Stereo signal chain.
 
Thanks, Dave

that is exactly how I had it set up and that is exactly what I did. I switched from repro to input on the 38 an viola: feedback!!:eek: I thought I caught in time, but didn't. I am not technically inclined to fix it myself. I am in CO and have been looking for someone who might fix it. All of the original authorized Tascam repair sites here no longer work on analog equipment. But there is a guy who says he fixes anything. We'll see!

But at least you gave me a place to start. I have the original manual that came with my 2nd 388 (hope I don't end up with as many as you; or do I?)if he needs it. Thanks again for all your help.
 
Oh,... he'll need it!

I'd say provide him with scanned & printed pages of the technical maintenance sections, parts diagrams, schematics, etc., as much as possible in copy format! I'd not give him my only manual, even temporarily. There's a scanned version of the 388 manual on the web, if you search this forum.:eek:;)
 
is replacing the transistors easy to do?
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  1. Find out which ones are bad
  2. buy replacements
  3. pull the PCB's upon which they are mounted
  4. desolder said transistors
  5. solder in the new ones
  6. test

That gives you an idea if I'm not also stating the obvious. The hardest part is isolating what cooked. Then ya gotta be comfortable pulling things apart (to access the parts that need replaced), and ya gotta be handy enough with a soldering iron to remove and resolder relatively small components (like, compared to building cables for instance).
 
Thanks guys,

is the a particular pcb card I should look for. And (bear with me) what do the transistors look like. I am a total newbie at the techinal side of things (but have been using analog for over 20 years). I am willing to learn, though.
 
Flash!

Check the fuses right off the bat, before sending to a tech or going in deep! No book in front of me, but the voltage rail for the output section could be fused! Try it!:eek:;)
 
The transistors...

All the power transistors in the 388 are (AFAIK) in the rear on the "transistor deck",... the large rear mounted heat sink assembly. The manual should be checked, though.:eek:;)
 
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I been reading

up on transistors and the symbols used to represent them in schematic diagrams. If I'm not mistaken, the 388 uses bipolar instead of FET transistors. I'm still hazy though on which pcb to find the stereo transistor that Reel mentioned. I have removed the panel on the back and the top where the meters and fuses are. Do the pcb's pull out easily ( for example, I have a Revox half track that I did this with)? Any help to the small detail would not be an insult and would be greatly appreciated.
 
Are the fuses

you are talking about the ones above the power supply? What exactly am I looking for?
 
Those are the fuses Reel is talking about; the ones you see on the top right when you remove the top cover...and he's right...check them first. Take your multimeter and set it to test for continuity and measure accross each fuse...don't trust if the filament looks intact...use the meter.

I wish I could point you to someplace in the manual for finding the transistors, but my 388 manual is low-res...can't even read all the symbols on the schematic, much less the fine print... :(
 
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