Help Marshall vs65r

[AL78]

thanks I'get back to you as soon as I have everything

[AL78]

Hi I have a quesiont should r 37 and pin2 ic3 be connected?I'm almost shure but because I have bad joint I want to Know if I read the scheme wrong.Thanks.In case they should be connceted I'll first resold those and then moves on thanks

[Dave H]

should r 37 and pin2 ic3 be connected?

Yes, if it's not connected the amp won't have -ve feedback or a path for its inverting input bias current.

[AL78]

I'm going to reply to all the questions

1)All the led work
2)Since i had to redo the soldering of pin2 ic3 I have measure to vr3.I check twice the pin out to be sure.
So I put a jack in the input(power off)And I got 488 mohm on one sleeve of the input jack and 19,34kohm on the second sleeve.First Sleeve is the one closer to the jack input.
3)Ic3 Pin1 0v
R19 one end is 0 the other is 195v
IC4 pin 1 +15V
IC2 pin 1 +15V
IC5 pin 1 +15V
IC5 pin 5 15,4mv

4)So if I connect something to the input I get very low outcome if I modify the tone the tone change(or at least i get a little bit more volume).If i touch the volume knob I only get some static
If I use the overdrive I get silence the reverb works
And As stated before power amp works with loud volume trought return headphone works with return and of course fxvolume works reverb works with return


https://youtu.be/GANWzblDL5g

https://youtu.be/5Dni9MWlAS4

[nickb]

I think we are making progress, even if rather slowly.

On (2) I asked "Plug something into the input jack and with the amp off, measure the resistance from ground to pin 3 of V3. It will be easier to measure this on R9 but make sure you get the right end i.e the end with the lowest resistance" . I don't see where you did that, or maybe I just don't understand what you wrote. Can you do this again or clarify for me what the result of the test was? Thanks.

The voltages are good but the 195V is higher than I'd expect. It may be OK but I don't have a note of what the should be so we need to do some more checks to find out. So, measure the DC Volts from ground to
(a) R11 (top end)
(b) R20 bottom end
(c) R20 top end.

[AL78]

I used VR3 (as you told me pin3).As ground I used the input sleeve.As You Know the Input jack as two metal leaves that's what I ment I hope this clarify.

http://treestrings.com/wp-content/up...015/02/003.jpg

I did the measurament in both of the sleeves .And pin 3 of Vr3.So I got the 488mohm on the one who is close to the hole and the other value in the second

If the power off test is not clear please tell where to measure r9 bottom or top(considering the direction above)
sorry but some barriers language it's normal :-)

a)r20 one side is 190v(considering bottom the back of amplifier) and top is 350v
b)r11 is 0 top

[nickb]

The voltages on V1 are good. I see I said "pin 3 on V3" when I meant "pin 2 on V1". I'm so sorry, that really confused things! All I am trying to establish is that the mute signal that goes to V1 pin 2 from the switch contact on the input jack is opening when you insert the plug. It's very unlikely to have failed so let's move on.

Since the DC voltages are OK we going to move on to doing some ACV measurements and see if we can establish where the signal is getting lost. First we need a steady known signal to insert at the input. If you don't have a signal generator, you can download a signal generator app for your phone or PC . Maybe you already have something that will work. You set to 1Khz, turn the level up then connect the audio out to the VSR65 input. I haven't used either of these apps so I can't vouch for them.

Then with the amp on and all the controls turned up, we use your meter on the ACV range between ground and measure
IC3 pin 3
IC3 pin 1
IC2 pin 5
IC5 pin 5

Buona fortuna...

[AL78]

Ok thanks again:Listen I think I'm gonna do everything tomorrow.I'll do the Vr1 pin 2 and everything else.Can I do without speaker connect right?I'll put my meter on ac voltage.Listen when you say "turn the level up" you mean the pc or ipod not the amp right?.I think you want to check where the signal die right?So the amp volume it's not important.Thanks again

[nickb]

V1, not VR1

I mean the level on the PC/phone - we want about 500mV rms.

The should be on clean channel and the volume should be up. Speaker not required. If you are disconnecting the speaker take care not to let the leads short out.

[AL78]

Ok I don't know how to measure 500mv for the pc/phone but I'll try

[nickb]

Use the meter on ACV to measure it. It's not critical I just didn't want to too big or too small 100mV to 500mV will be fine.

[AL78]

Thanks Ok I've got this.Listen about the mute system On v1 you told me to check on R9 if I read the scheme ok I have to check the R9 side that is not connect to c5 right?This way I can check if as soon as I connect a jack in the input the circuit close right?

[AL78]

So first thing I did the r9 test and when i plug something I get 500mohm.If i disconnect I disconnect the jack I get 20kohm(more ore less)

so i'm giving 239mv

Ic3 PIn3 235mv
Ic3 Pin1 1,8v
Ic2 pin5 1,8
Ic5 pin5 2mv

[nickb]

so i'm giving 239mv

Ic3 PIn3 235mv
Ic3 Pin1 1,8v
Ic2 pin5 1,8
Ic5 pin5 2mv

Ic3 PIn3 235mVAC =GOOD
Ic3 Pin1 1,8VAC =GOOD
Ic2 pin5 1,8 =GOOD
Ic5 pin5 2mv = BAD

That narrows the problem down quite bit to V1, IC5 or the mute line.

Now the mute line test is not what I expect. When the input jack is unplugged, then V1 pin 3 ( top of R9) should be shorted to ground. When unplugged you should measure 470K ohms to ground. You say when plugged in you get 0.5ohm (?) and >20K when unplugged. That is wrong. There is a contact on the input jack nearest to the front panel that opens when you insert the jack. Take a good look at that general area to see what is going on.

[AL78]

just to be sure for top of the R9 do you mean looking the back of the amp?
when plugged i get 500kohm and 478kohm when unplugged is aroud 20kohm both sides