A 388 with a problem and maybe some mods?

  • Thread starter Thread starter j.harv
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j.harv

j.harv

@#$%
I just scored another Tascam 388.I got it for the nice low price of $150.Cosmetically it's fantastic.
I bought it knowing it wasn't functioning properly,and I figured I could use it for a parts donor for my working 388 if anything were to go wrong.But this thing is cosmetically nicer than my original and the heads are in good shape.
I also noticed something different I have never seen before.
But first the problem.
The machine powers on,the rewind and FF work.It passes audio very cleanly through every channel.Vu meters register etc....The only thing is the capstan isn't spinning.I put all new fuses in,the belt is fine.
I located on the mother PCB (2) a burnt out resistor.Its made of metal.Its labeled r4 on the schematics.I noticed in my working 388 the same resistor is a regular carbon kind.I bought the same kind and tried it and it started to smoke.So I guess I need one of these steel ones.It traces back to the capstan servo PCB on the schem.So im guessing this is the problem.I'll include a pic of this.Does anyone know where I can get this steel kind of resistor?
The electronics store I went to have tons of the carbon ones but no steel ones.Im hoping this will remedy the situation because everything else seems to be working fine.The pic of the steel resistor is how it looks after I removed it and gave it a light brushing with a wire brush before reinstalling it.

Now for the so called mods I think I have located.
All of my rec/play PCBs have additional wiring,caps,resistors and transistors soldered to the opposite side of the populated side.I dont know if this is factory or if some else did this.There isnt anything like this on my other 388 or on my junk parts 388.I have included pics.Let me know what you think.

One last thing....When I opened this 388 up a shit load of 1/4 inch tape pieces fell out of this thing.It was everywhere.In the bottom of the card bay,underneath when I took off the bottom and pieces stuffed in the headblock!!! It looked like a tape bomb went off.I'll include a pick of this too.

So,Im hoping someone can lead me to one of these steel resistors and hopefully that will get the capstan spinning.
Any help would be greatly aprreciated.

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Are you completely sure your replacement R4 had the right power rating? The schematics warn that it must be able to handle at least 3W or it will go up in smoke...
 
Im note too sure.I probably got it wrong.I realised it supposed to be a nf (non flaming) resistor.This was a regular one.
But even before I put the new one in,I grabbed the one from my junk 388 and that smoldered too.But that one wasn't made of metal.So I guess some 388 are different in this area.Would you know what exact resistor I would need?
I guess its a 47 k ohm (Nf) 3w.?
I just dont want to keep installing these and keep seeing smoke.
Thanks for the reply.
 
Sadly, I don't. And it's always possible that the reason the old one was burned was because something has faulted and caused more than 3W to be running through that circuit...
 
What interests me primarily are the mods. I've done plenty of amp mods but haven't fooled with my 388. Since the caps are incorporated on the record/play amp PCB, I'm wondering if they haven't been used to stiffen the amp somewhat and tighten up and/or buffer the bottom end. I'd like to do a side by side (if that were even feasible) with a good pair of headphones and see if there was any audible difference in the LF response.

As far as the resistor goes, the main purpose is to limit the voltage and turn the rest into heat, so I'd suspect you'd need to install one with a higher value. I wanna know how this problem is finally rectified. Here's a good link discussing resistor types: http://www.aikenamps.com/ResistorNoise.htm

Fine looking deck, BTW. Excellent score.
 
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Just an update.
Got a replacement resistor. Now it works great.
I can't believe I got another one of these machines in such good shape and for a fairly cheap price.
As for the "mods",I posted a question over at tape op, and a member said they had something similar on their 388.
So it could most likely be factory. Even though none of these extra parts are listed in the schematics.???
 
Okay, so it was just a matter of the safety-critical resistor being too low rated? Cool.
 
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