Jvc rx-9v reciever

[bigdrums925]

I have the "daughter board" unsoldered so I could work on it. Soldered necessary voltage wires +/- 64 volts, & ground out to it.
Now when I check the +/- 2.35 volt terminals (pins 11,10 & 6,7) they are all +63 volts. Not even having the right polarity. 11 & 6 should be -

Here's a pic of the daughter board

Yes the board shows heat discoloring but I have yet to find any bad components.

[bigdrums925]

Pretty much stuck not knowing what to check next. Can anyone explain why the +/- 2.35 voltages are 63 volts?

[Jazz P Bass]

That board that you disconnected is the "driver" board for the output section .
You cannot disconnect it & expect the voltages to be proper.

[bigdrums925]

OK, but if I put it back in its inaccessible. When it was in I could only get to the 12 terminals and though the +/- 64 volts were present, the +/- 2.35 were not.
What about if I have all 12 terminals connected with wire? Say 12" or so?

I have put the "driver board" back in and now 1/2 of the 2.35 volts are there. But pins 7&6 are +0.9 volts.

[Jazz P Bass]

Then concentrate on that.

There should not be any positive voltage on that circuit.
It is the negative driver.

Go with the schematic & find where the + voltage appears.

All of this assumes that you know how to test an in circuit transistor.

[bigdrums925]

Looking closely at the 12 pins on the schematic there are voltages listed for some of them. I assume you saw them?

PINS:

12 - 0
11 - -2.35
10 - +2.37
9 - +64.3
8 - -64.4
7 - +2.37
6 - -2.35
5 - 0
4 - 0
3 - 0
2 - 0
1 - 0

So I don't know what you mean there should be not be any positive voltage on that circuit.?

[Jazz P Bass]

Thought it was obvious that I meant Pin #6.

Relist the voltages that you do have now.

Q707 & 709

Q708 & 710

That is where the 2.3 + and - voltages are derived.

[bigdrums925]

I took me awhile to remove the driver board again this time feeding all 12 terminals back to the amp board in order to measure the voltages requested
Q707 Q709 Q708 Q710
base 63.9 61.4 64.1 61.1
collector 53.6 0 53.6 0
emitter 64.0 53.8 63.9 53.5


Having trouble making the chart readable, it is when I type it but once posted it jams all together

[bigdrums925]

I got the voltages back to normal by resoldering the driver board, but seems every time I turn it on they change
Even the +/- 64 sometimes are at 46?

[g1]

What ground are you connecting your meter probe to?
Any chance you have a bad ground connection somewhere?

[bigdrums925]

Well after much frustration I was able to get the proper voltages and it works! another dead unit brought back to life with the fantastic help here.
Thank you all once again!