Tascam 38 issues - newbie

leitrim_lad

New member
Hi folks, i just purchased a tascam 38 secondhand on ebay, its my first tape machine and the seller told me it had been brought to a tech and everything was ok with it. However when the machine arrived there was loads of issues. I have gotten through most of the mechanical issues (belt change, washer at the back of the flywheel gone to mush etc)

however im stuck with as issue where it keeps blowing fuses 503 and 504.

It was playing back audio on the repro head but there was an issue with it not playing back audio on 3 channels when in sync so i took out one of the cards with an issue (channel 2) and tried resoldering where the connectors meet the card. When i put the card back in no channels would play audio from repro/sync or input. When i removed that card and left it out the rest of the cards would play audio on repro again.

Tried this a second time and now the fuses seem to keep blowing and no audio will play or UV meters dont show any activity on any channels

Any help would be greatly appreciated

Thanks
 

RRuskin

Rick Ruskin
The power supply needs work if you keep blowing the same fuses over and over. Your bad card might be dragging all the others down when it's in place. Have it checked out. It's also possible that the motherboard is iffy and having all card in it messes with a cracked trace. FYI - the repro head is for ease of alignment. Once properly setup, all work is meant to be done from the record/sync head.
 
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leitrim_lad

New member
The power supply needs work if you keep blowing the same fuses over and over. Your bad card might be dragging all the others down when it's in place. Have it checked out. It's also possible that the motherboard is iffy and having all card in it messes with a cracked trace. FYI - the repro head is for ease of alignment. Once properly setup, all work is meant to be done from the record/sync head.
Thanks so much for getting back to me, ive unplugged P171 off the main board and the fuses still go so im taking it ive a problem with my 15v + and - on the power supply?
Ive checked my main board for shorts etc and it seems good..
Any advice would be greatly appreciated.. thanks a million
 

RRuskin

Rick Ruskin
Thanks so much for getting back to me, ive unplugged P171 off the main board and the fuses still go so im taking it ive a problem with my 15v + and - on the power supply?
Ive checked my main board for shorts etc and it seems good..
Any advice would be greatly appreciated.. thanks a million
Other than suggest what subsystem might be at fault I can't help with specifics. Someone else might be able to chime in on that. From what you posted, you seem to have 2 different problems. 1 is in the power supply while the other is somewhere in the repro/sync electronics. Perhaps the 1 card or the motherboard. I would repair or have them repaired in that order.
 

sweetbeats

Reel deep thoughts...
I’m not sure what P171 is, but the first step is to determine if you have a problem with the power supply. That’s always step 1 unless you have conclusive reason to believe you know what the problem is and it is elsewhere. In order to determine e if you have a problem with the power supply you have to completely isolate the supply, which means all outputs from the supply *must* be disconnected. All of them, whether by connector or hard-wire connections. So unplug, desolder, do whatever you have to do to isolate the supply, put in new fuses, power it up and see if they blow again. If they do, then, yes, you have a problem with your power supply. This does not mean you don’t have problems elsewhere as well, but you’re never going to get anything working right if the headwaters are at fault. So that’s step 1...isolate the power supply and test for correct operation. If the fuses don’t blow, I would then check the outputs with an oscilloscope making sure the voltage is correct on each rail and that there are no AC artifacts on the DC rails. If that’s all good then the last step is to load test each rail, make sure the fuses don’t blow, and also check for correct voltage and for absence of AC artifacts on the DC rails under load.
 

leitrim_lad

New member
Thanks for all the help.. So I sourced 2 diodes and changed them d812/d813 and my issue with the blowing fuses has now stopped. However everything seems to be going well until the capstan motor suddenly stopped.. It spun for a second and then completely stopped.. I looked at the power supply and now R829 seems to have blown.. Please see attached picture. Any help would be greatly appreciated.
Thanks

https://drive.google.com/file/d/14qtvBLq-V89YfETI1GCIT3NsPLK3VQIC/view?usp=sharing
 

wkrbee

Member
Your fuses started blowing after you resoldered, plugged, and unplugged R.P. cards? Go back over your work looking for solder bridges/ splashes, bent/misaligned pins on the R/P cards, pinched wires shorting to the chassis, screws shorting something to the chassis etc. Very easy to chase down the problem. Find which voltage is shorted using a VOM and work forward or backwards circuit wise to isolate the problem.
 

Transducer67

New member
Hi,
This is very typical of machines purchased on eBay, most sellers lie about bringing machines to a tech since it sells the machine at a higher price. You should request some sort of refund or return the machine to the seller. Though being that its been tampered can make it more difficult.
We service and sell 38's all the time. If your located near the NYC area, we can service the machine for you.
Feel free to contact me at 800.404.5520 or email Funktionaltech@gmail.com

Best regards,
Andrew
funktionaltech.com
 
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