mutterd

Tascam 388 - legible schematics anyone?
« on: August 18, 2018, 04:59:53 AM »
Hey guys,

I have a Tascam 388 that i have lugged around for almost 20 years and I cant do it any more.

It was my first tape machine, I loved it, I still kinda do, it worked flawlessly every time I needed it to - the last workshop move sealed its fate, but of course when i got it in the bench to give it a once over before selling it i found that im not able to record to one track.

I swapped the cards around (no easy task, those cards are in there TIGHT) and the fault follows the card, which is a good thing - everything else works as it should (20+ years and its still calibrated!)

So for whatever reason it seems im not getting to the record head - I am able to monitor the program or track input but on playback there is nothing - I was wondering if anyone had:

a: an extra Rec/Repro card for this machine they would be willing to part with...
b: a legible copy of the schematic - I have seen all the ones online and you cant read the component values from any of them..  Id pay for a good copy...

thanks everyone!
Timothy




squarewave

Re: Tascam 388 - legible schematics anyone?
« Reply #2 on: August 18, 2018, 11:45:24 AM »
If you can hear sig in the monitor but nothing gets recorded and the problem follows the card, that does narrow things down quite a bit. In my Tascam 234 the sig splits from the monitor just before the output pot (fader for you) and then goes:

bipolar transistor shunt switch to
level trimmer pot to
single op amp to
test point (TP1) to
bias oscillator trap to
connector to board w/oscillator feeding head

So it's probably similar for your machine and likely to be one of these things. If you can find this stuff use a scope to look for signal. My first guess would be a bad solder joint.

mutterd

Re: Tascam 388 - legible schematics anyone?
« Reply #3 on: August 19, 2018, 01:35:13 AM »
Squarewave,

wow - thanks, thats really helpful - and yeah - thats exactly how it is in this machine as well - I can trace the signal path thru the crappy scans - just cant make out any of the labels, values or part numbers...

here is something else interesting i just discovered - there is a 100Ω series resister in the +18VDC power rail that feeds a discrete dual FET amp stage, followed by an IC repro EQ stage and an IC output amp for the audio from the repro head...

this resister is  getting hot as a pistol. All that is after the resistor are a few decoupling caps, the 2 IC's and the discrete amp stage...

The +18VDC bar seems stable, so its not totally shorted out, but something there is pulling too much current...

Scott - thanks for that  - ebay picks the search category and  it wasnt showing up in my searches.



thanks fella's,
Timothy


here is a link to the available service manual in case it helps.
https://www.manualslib.com/manual/1019712/Tascam-388-Studio-8.html


Whoops

Re: Tascam 388 - legible schematics anyone?
« Reply #4 on: August 20, 2018, 09:15:30 PM »
Can you put that board and a good one side to side, supply them with the right voltages, and comprare the readings?

(Voltages and component reading)

post pics of the pcb


 

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