Help Marshall vs65r

[nickb]

OK and what about the other questions?

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

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

[AL78]

yes ic 3 ic6 ic7

[nickb]

yes ic 3 ic6 ic7

Yes, those ones plus IC2 and IC4

Now measure the DCV on each of pin 1 and of IC3, IC6 and IC7, and pin 5 of IC2 and IC4.

[AL78]

ic2 pin 4 and ic4 pin 4 -15v
If I understand correctly you want Pin 1 for Ic3 Ic6 IC7
so
Ic6 pin 8= 0 v
Ic3 pin 1= 3,2 mv
Ic6 pin 1= -15v
ic7 pin 1= -3,1 mv
ic2 pin 5= 0 mv
ic4 pin 5= 15v

I checked the scheme and it says that I should have 15v on ic6 but on pin 7 non 8 and i have it

[nickb]

Odd, I replied to this hours ago but it seems to have got lost so here it is again. I forgot a pin...

What we need is
IC3 pin 1 = 3.2mV : GOOD
IC3 pin 7 = ?
IC6 pin 1 = -15V : BAD
IC6 pin 7 = ?
IC7 pin 1 = -3.1mV :GOOD
IC7 pin 7 = ?
IC2 pin 5 = 0mv GOOD
IC4 pin 5 = 15V BAD
IC5 pin 5 = ?


Can you fill in the "?" blanks?

I looks IC6 and IC4 may be bad but we will need to check the input pins to be sure.

[AL78]

Thank you again.
SO
ic3 pin 7 1,8 mv
ic6 pin 7 15 v
ic7 pin 7 14,97 v
ic 5 pin 5 31,7 mv

[nickb]

Thank you again.
SO
ic3 pin 7 1,8 mv
ic6 pin 7 15 v
ic7 pin 7 14,97 v
ic 5 pin 5 31,7 mv

Putting it all together:
IC3 pin 1 = 3.2mV : GOOD
IC3 pin 7 = 14.7: BAD
IC6 pin 1 = -15V : BAD
IC6 pin 7 = 15V : BAD
IC7 pin 1 = -3.1mV :GOOD
IC7 pin 7 = 14.97V: BAD
IC2 pin 5 = 0mv GOOD
IC4 pin 5 = 15V BAD
IC5 pin 5 = 31.7mV : GOOD
All power supply pins have been checked: GOOD

At this point, I would replace these bad ICs. We should also now check IC1 in the reverb path since so many are bad

Check
IC1 pin 1
IC1 pin 7
IC1 pin 8
IC1 pin 14

They should all be within 0.1V of 0.

I expect you'll have to order these in. In this situation I'd be inclined to order a few extra. All these opamp IC may be bad but just not showing it in the DC output levels. Also get IC sockets to fit them is and then it will be easier to change again if need be. You will need to remove the old IC's and take care in doing do else you might damage the PCB. I'm sure if you Google how to do it there will be plenty of advice

While you are waiting for them also resolder all the joints around the zener diodes, ZD1, ZD2, R17 and R18 as they do tend to be troublesome as they run hot.

[AL78]

IC1 pin 1 = -13 mv
IC1 pin 7 = -12,4 mv
IC1 pin 8 = -12,1 mv
IC1 pin 14 = -1,7 mv

do i need to change ic 3 ic 4 ic 6 ic 7 ?

[nickb]

IC1 pin 1 = -13 mv
IC1 pin 7 = -12,4 mv
IC1 pin 8 = -12,1 mv
IC1 pin 14 = -1,7 mv

do i need to change ic 3 ic 4 ic 6 ic 7 ?

That one looks good. Yes you need to replace (at least) IC3, 4, 6, & 7

This is turning into a major repair.

[AL78]

Ok good.question Are those little monster with 8 feet all the same type?

[nickb]

IC1 LM348
IC2,4 NJM2120
IC3,5,6,7 TL072

All DIP (plastic DIL) packages- you have a national source? Don't forget the DIP sockets.

[AL78]

are this ok?

4x TL072CP Amplificatore Operazionale J-FET =NJM072 Dual Operational Amplifier | eBay

2Pcs Jrc2120d Njm2120d Ic Ic's Dip-8Pin New G | eBay

I mean the right one not good or bad quality

[nickb]

are this ok?

4x TL072CP Amplificatore Operazionale J-FET =NJM072 Dual Operational Amplifier | eBay

2Pcs Jrc2120d Njm2120d Ic Ic's Dip-8Pin New G | eBay

I mean the right one not good or bad quality

Yes, that is correct. Edit: I see they are coming from China. I never trust China eBay sources plus it takes a month to arrive.

Don't forget the 8 pin DIP sockets.

[AL78]

Ok Thank you again I think i will wait holiday season so i will have the time do it with clear mind thank you again

http://www.ebay.it/itm/10-pz-zoccoli...0AAOSwv0tVAJZn

[g1]

How about these, from a reliable source:
http://www.mouser.it/ProductDetail/T...09QfBMDDCD%2fE
http://www.mouser.it/ProductDetail/N...AZR66ygeYPQ%3d
http://www.mouser.it/ProductDetail/T...hvVfZZ22CIY%3d