Help Marshall vs65r

[nickb]

Thank for your patience.Listen Here in italy is kinda late so I'll do it tomorrow.I kinda new at this for "to ground" do you mean that iI have to touch with my red lead the point you said me and with the black lead the chassis of the amp? I have no idea what's the gate of j111 t 16.Last there is no speaker jack the are faston on the speaker side and the red and black are soldedered on the amp board.

No probs. Had no idea your were from Italy - there might have been a bit of a language issue. It's a good idea to state where you are from in your profile.

Black lead to sleeve of input jack - I don't trust using the chassis in solid state amps as there any many different grounding schemes. I forgot there isn't a speaker jack on this model - use the red speaker lead - take extreme care not to accidentally short the speaker leads together at any time.

Look up a datasheet for a J111 and then the pinout you'll see see which pin is the gate.



HINT: It might be easier to measure the gate voltage at the junction of R34 & R33.

[AL78]

Hi I'm going to do it now.Are you sure that is t 16 and not t 13?cause r 34 &r35 are closer to t 13.Anyway I've done it those are the results meter in volt black on input jacket.
1) Collector of T9 40v
2) Collector of T11 -40v
3) TIP of speaker jack -15,8mv
4) GATE of J111 T16 -26,36v
5) Pin 4 of IC7 0,910v
6) Pin 8 of IC7 0(zero)
I measured Collector of T13 -41v
Thank you

[nickb]

Hi I'm going to do it now.Are you sure that is t 16 and not t 13?cause r 34 &r35 are closer to t 13.Anyway I've done it those are the results meter in volt black on input jacket.
1) Collector of T9 40v
2) Collector of T11 -40v
3) TIP of speaker jack -15,8mv
4) GATE of J111 T16 -26,36v
5) Pin 4 of IC7 0,910v
6) Pin 8 of IC7 0(zero)
I measured Collector of T13 -41v
Thank you

T16, I'm sure.

IC7 has no power:

Check for power on pins 4 & 5 on those connectors too. If close to zero check CON2 & CON 14 for good contact.
Check ground continuity by measuring the resistance between CON12 (black lead to the transformer) and the sleeve of the input jack
Check the voltage on both sides of R17 and R18.

[AL78]

Hi on this board there is nothing on r 17 or R18.Pins 4&5(do you men together right?not against ground right) 33.11 v.About the continuity con 12 sleeve input There is.

[nickb]

Pins 4 & 5 should be measured relative to ground (on sleeve of input jack)
Now check pins 4 then 5 relative to ground on CON12 (black lead)
Check both sides of R17 & R18 - it sounds like you might have check one only one side.






If you have power at pins 4 & 5 and nothing on

[AL78]

Pin 4 against ground is .0910 v
Pin 5 against ground is 34,26 v
pin 4 con 12 0,924
pin 5 con 12 34,26
There is no resistor on the the board at r17&18 only te holes for the resistors and the numbers and the shape no components.Nobody is ever touched this amplifier so It's impossible that someone removed those

[nickb]

Pin 4 against ground is .0910 v
Pin 5 against ground is 34,26 v
pin 4 con 12 0,924
pin 5 con 12 34,26
There is no resistor on the the board at r17&18 only te holes for the resistors and the numbers and the shape no components.Nobody is ever touched this amplifier so It's impossible that someone removed those

Must be a different board rev. What is the part number marked on the board? The schematic I'm looking at is VS65-60-02. Quite often the component reference designators will change between revisions. This is done to make life complicated for everyone. A clear photo of your preamp board might help.


These resistors are big white ones - probably the ones you mentioned right at the start of the topic.
(1) Are they the same value, 330 ohms as the ones on the schematic?

At that time you said they were getting hot, as they should when they are working. That does not tie in with no voltage on IC7. Therefore we need to check the preamp voltage in a few places.


Do you have ZD1 and ZD2 on that board? - Measure the voltage across each of them.
Measure the voltage on both sides of the bog white preamp resistors?

[AL78]

Before we waste time.I count the pin of the ic7 1 it's the bottom left and 8 is the top right is this correct?The board is ma vs65-60-00.Sorry I was looking on wrong place offcourse there'are those big resistors I was looking in the power amp board sorry.
-15v -40v r 18
33,50v 40,04v r17
Both Against ground.
Yes I have zd1 and zd2
ZD1 15,70v
ZD2 399 mv

Here is the reading.Only please clarify me if the reading on the IC7 pins are ok otherwise i'll do it again.I'm not sure about the pin counting thanks you are a trooper
p.s.
I've take pics of the board do I post them here?

[nickb]

Before we waste time.I count the pin of the ic7 1 it's the bottom left and 8 is the top right is this correct?The board is ma vs65-60-00.Sorry I was looking on wrong place offcourse there'are those big resistors I was looking in the power amp board sorry.
-15v -40v r 18
33,50v 40,04v r17
Both Against ground.
Yes I have zd1 and zd2
ZD1 15,70v
ZD2 399 mv

Here is the reading.Only please clarify me if the reading on the IC7 pins are ok otherwise i'll do it again.I'm not sure about the pin counting thanks you are a trooper
p.s.
I've take pics of the board do I post them here?

You have an early rev of the board. We'll have to proceed with some caution. We may not need the pic now. Read on...

IC7:




You have an open between R17 and ZD2. It's probably a bad solder joint on R17.

[AL78]

yeah i noticed that there is some black burn in that area.

[AL78]

I forget t add some info.I've already removed either the resistors and those zd1 and zd2 to check they are ok.I've already changed the caps.What I can do?I've already do the soldering on that area.Is that possible that the burnt brake the board in the area and that's why there's an opening?

[nickb]

It's very obvious that there is no connection between between ZD2 and R17. The 33.5V voltage on R17 is a concern. Rather than speculate you have to pull the board and see what is going on. Use your meter on continuity "beep" test mode so find out exactly where the open is. I've noticed in the past that leads of resistors that have been running very hot can be hard to solder. They need a good scraping to clean off the oxides and a healthy dose of flux can only help.

[AL78]

Hey thank you.Unfortunately all this things are way above my abilities,I'm don't have any idea how to use flux and check any connetions.So I've already put everything back in the enclosure.I think it's the best thing to do thank you for you time at least I've tried.Now it will go back to the friend of mine who gave me.Unfortunately I live in the south and there's nobody who will fix this.They have already told him to trash it so..Thanks

[g1]

If you just ran a jumper wire from R17 to ZD2 it would probably fix it.
No need to trash it.
Anyone who does electronics work should be able to do this if they are told which points to connect. It doesn't have to be an amp repair shop.

[nickb]

Don't bail out just yet. You done all the hard measuring and now it's time to reap your reward Don't sweat the flux - I'm just trying to highlight that those resistors leads sometime need a little extra care.

You can try the wire like G1 said and I might work. If it doesn't, pull the board and have a good hard critical look around the problem area.