Help Marshall vs65r

[AL78]

I was just asking I do continuity test with amp off.What I'm saying is this.Before I got continuity between zd1 and ic4 I had the reading -15.5v on zd1 non striped end ok?.Now after I finally got continuity between pin 4 and zd1 I only get -8,77v and the same value I get on zd1.Why zd1 goes down to -8,77v ?that's what I don't understand

[nickb]

I was just asking I do continuity test with amp off.What I'm saying is this.Before I got continuity between zd1 and ic4 I had the reading -15.5v on zd1 non striped end ok?.Now after I finally got continuity between pin 4 and zd1 I only get -8,77v and the same value I get on zd1.Why zd1 goes down to -8,77v ?that's what I don't understand

OK, now I understand - thanks. So, I understand you found a problem and fixed it. but now you have a new problem. Also you switched from continuity with amp off to DC volts with amp on.

The possibilities that occur to me are
(1) The fix wasn't quite done correctly
(2) The path to that point has a higher resistance than it should.
(3) There is another fault that is causing too much current to be drawn through R18. R18 will be running hotter than normal in this case.

I think at this point it probably requires an experienced hand.

[AL78]

Ok I'll give back or I'll throw it away.thanks

[g1]

Sounds like IC4 is bad and is pulling down the -15V line. That is why when you disconnect IC4 connection the voltage goes back to -15V.
Are you able to replace IC4 ?
Unless it is not IC4 in particular but some other IC in the amp.

[AL78]

Any way I can check that component or the others?

[g1]

I would check for one of the IC's feeling hotter than the others.

[J M Fahey]

Just replace the suspect one and remeasure voltage.

[g1]

I'm not sure if it (IC4) was actually suspect or if nickb just suggested it as a convenient point to check for the -15V line.

[J M Fahey]

OK.

The main point is that if expected 15V now shows 8 something V, either some device is eating too much current or dropping vresistor is over value or connection (bad soldering?) is poor.

A hot Op Amp might be the culprit; worst case remove any hot one and check that -15V reappears.

[AL78]

Guys sorry I had some stuff to do.SO now I have -15v on all the place where there's should be -15v but unfortunately still no sound.I tried to connect ma headphone out of my stereo amplifier there only a really low distorted sound very very low.What can I do now?

[52 Bill]

Guys sorry I had some stuff to do.SO now I have -15v on all the place where there's should be -15v but unfortunately still no sound.I tried to connect ma headphone out of my stereo amplifier there only a really low distorted sound very very low.What can I do now?

Rather than make us guess, what did you do to fix the -15 volt power supply?

[AL78]

First thank you.So I was going to check all the IC but before that I had this idea to check non strip end of zd1 again.So I find out the the diode didn't have good connection with the rest of the board so I made some bridge and imediately every ic got its -15v.Unfortunately there is non sound.I will appreciate any help thanks.

[AL78]

Just to clarify I have -15v in all the places I mean on the ICs after zd1 non stripe and ic7 please help me

[nickb]

Glad you are making progress

So to conform you have -15V on every IC pin 4?

If that is OK check every IC for +15V on pin 8.

If that is OK go back to first steps and try the following
a) Plug your guitar into the return jack
b) Plug into the input and connect the line out to a different amplifier
c) What effect, if any, do the controls have?

[AL78]

I don't have a guitar right now I use a cd player I think it's the same right?
So
a)very low sound fx mix control works as a "volume"
b)no sound at all
C)Only fx but only in case a)