new tascam 388 problem-any ideas?

W

williambslack

New member
I've followed the 388 enthusiasts on here for a while (bought a 388 years ago not knowing what it was). Usually you 388 fans answer questions without me having to ask, but now i've got a specific one:

When i turn on the 388 (which has worked great for a long time), about half the time the right channel won't play back, and it's not due to a heaphone/speaker connection issue. When it's acting like this, the right-panned even channels WILL still record, just no playback.

when the right channel is out, i can switch the unit to MONO, and I get signal in both speakers, so again, it must have something to do with the repro head, no?

here's a weird thing: when it's acting up, i found that a loud source panned to the right (a mic input, or simply panning all recorded tracks right and cranking them up) will eventually "wake up" the right playback, almost as if that side needs to be warmed up. after that, the right side more or less functions until the 388 is turned off, though sometimes at a lower level than it should.

What could this be due to? fuses? am i hurting the unit further with my "warm up" method. any ideas would be appreciated.
 
It could be a whole host of things...

Are you lacjing the R channel in both sets of stereo out jacks AND the headphones AND the monitor out jacks?

Check to see if the tape deck is outputting from all tracks at the TAPE OUT jacks.

Can you hear both channels outt he monitor and stereo jacks if you input a source at the sub in L and R jacks?
 
I haven't tried the unbalanced stereo outs, but all the others lack the R track when intermittent. Actually, to be more specific: When lacking the R track, it's still actually there, just extremely quiet and crackly (you can only hear it when you pan to the right). But, as mentioned before, the channel jumps to life and loses all crackling when a loud signal is sent through it.

I'll check the tape outs now.

sub in L and R jacks? is that the stereo bus in jacks? sorry for being so amateur, i have never even used those jacks. I'll try them out.
 
well, all above mentioned jacks seem to be working fine. Any other ideas? I guess it's pretty hard to get to the bottom of an intermittent problem like this. Thanks a lot for helping.
 
Sub in jacks means stereo buss in. sorry...my bad. that's what I get for trying to remember the labeling from memory. :o

Let us know about the result of checking the tape out jacks. You can do this by setting the PGM/CUE switch in the down/latched position which is PGM, and then patching the tape out jacks to one or more of the LINE IN jacks, setting the input select switch to LINE and just routing the channel(s) you have then patched to to the L-R buss...listen in the headphones or whatever...we donzt care about hearing it in the R channel we just want to confirm that the head and play electronics for each track are working.

The crackling symptom and being able to get it to work sounds like possibly a bad capacitor. Doing the tests as far as how things work through the different jacks will help to hone in on where the issue might be.

If you have any DeoxIT FaderLube you might try squirting that down in the buss master and stereo master faders and exercising them, though if you can't mak the condition change by working the faders that probably isn't it...
 
Ah...so you tested the tape out jacks and all tape tracks are outputting audio yes? That's good. I didn't think that was the problem but its good to confirm.
 
oh, i see the logic in trying the tape out. cool.

so the repro head is working fine, does that narrow it down much? Can I assume that the capacitor (or whatever the problem is) is in a particular part of the mixer near the stereo bus out?

any suggestions on locating bad capacitors?

thanks.
 
What was the result of using the stereo buss in jacks?

And is there any difference whether you are in PGM vs. CUE mode?
 
So when you connected a stereo source to the STEREO BUSS IN L and R jacks you had normal stereophonic sound in your headphones or on your monitor speakers? No crackle, no need to kick start the sound?? This is important...
 
But it IS telling that the STEREO BUSS IN jacks work normal...we are honing in on the culprit.

Now try the EFF BUSS and AUX BUSS IN jacks...plug a mono source into them one at a time and use the EFF and AUX master gain and pan knobs to see if there is any R channel signal loss or crackling, etc.

Its like a game of CLUE okay? I take the info you provide and that narrows the possibilites down using the block diagram and then we zoom in to the schematic level.
 
Also,

Test the PGM OUT 1~8 jacks like you did the TAPE OUT jacks (i.e. set the PGM/CUE switch in the UP position which is the CUE position, make sure all the REC FUNCTION switches are in the up/off position, playback a tape and check to see if audio passes from all the PGM OUT jacks)

Test to see if an input at the EFFECT RTN 1 and EFFECT RTN 2 jacks can be heard normally (i.e. panned R and L and sound good)

Another question: what happens if you assign a mic just to the L-R buss? Can you hear it normal in the headphones and/or monitor speakers or is it messed up?

So:

1. check to see if an input sounds normal at the AUX BUSS and EFF BUSS IN jacks
2. check the PGM OUT 1~8 jacks
3. check the EFFECT RTN 1&2 jacks
4. tell me what happens if an input on one of the channel strips is routed to the L-R buss...
 
one year later

That's right, i've been limping the 388 along for a YEAR, but i'm ready (forced to) revisit this problem in search of a solution.

-I have run the tape outs to other channel line ins--this works great
-Tape outs to stereo bus mix in--works great
-PGM bus IN and OUT seem to function properly, both with through signal, and PGM OUT from the recorded tape.
-EFFECT RTN 1 & 2 both seem to function properly
-AUX BUS and EFX BUS IN sound normal

so...any ideas. The good news is I now understand the board a lot better. The bad news is that a track played back through the L/R send or monitor section will still frequently become weak to nonexistant in the right channel. This also occasionally affects recording on even (bus'd right) channels in the same way. I have worked around it for some time, but I have got to figure this out.

THANKS!
 
further development

I ran some recorded material out of the PGM OUTS and into a seperate mixer to listen to the mix and see if that worked. Intermittent problems are a pain in the ass!

seemed great, but then various tracks would crackle and fade out, even tracks on odd (left panned) channels! I'll have to retry the tape outs, but i'm still feeling clueless.
 
ok, I ran recorded material out of the TAPE OUTS and into a mixer for a while, so I think i can safely say that the TAPE OUTS worked--all channels came through clearly with no problems. So, if I understand the signal path of the board, signal comes off the tape playback head and goes to the TAPE OUTS (this all works)--it seperately goes to the channel input, EQ, assign/pan, fader, and master fader, and something in the second path is causing the problem, it seems. So, I'm closing in, but I'm not sure what to do next. I might try cleaning all the faders and pots with deoxit, but that's the only plan i have. ANYONE have any ideas?

THANKS.
 
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