Technics SE-A70 with issues

Banebadboo

Member
2020-02-02 12:29 pm
Hello all,

I have a Technics SE-A70 that I'm restoring. I have restored several other pieces, however this is the first piece that I'm having trouble with. I'm learning as I go.

The issues:

The amp was working(ok) but the main caps were leaking. So I did a complete recap. During the reassembly I somehow didn't install a mica insulator for one of the output transistor... This of course caused major problems. What I have done so far to fix it:

Parts replaced:

TH302
TH301

R364
R363

Q501
Q503
Q338
Q502
Q337

Q328-Q326(paired)
Q325-Q327(paired)

The following were all paired:
Q333
Q329
Q335
Q331
Q334
Q336
Q330
Q332

After all those parts were install I used my DBT to power the amp on. Shortly after power on the R364 resistor burned out again... So I have obviously missed something but what is the question? Any help/ideas on were to look will be greatly appreciated.

I have circled the resistor in the pic(pic was prior to recapping).
 

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Last edited:

U230421

Disabled Account
2017-02-07 1:54 pm
Check again on Q330-332-334-336 and Q326-328.
Raise one of the legs of R366-368-370-372 from the pcb and notice the results.
Either the bias is way to high or extra current runs through R364 from somewhere. There are not so many candidates in that location.
 

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