Help Marshall vs65r

[nickb]

You need one of these



Did you do anything immediately prior to this happening?
If OK, check the cable to the power amp board to CON1 is securely plugged in.
Unplug the speaker and check the DCV across the speaker terminals - it should be close to zero.
Unplug the cable to CON1 - does it still hum?

[AL78]

So I have 37v DC!!!!
If I disconect the con 1 stil 37dc....

[Dave H]

So I have 37v DC!!!!
If I disconect the con 1 stil 37dc....

I hate this amp too

Measure the +LT and -LT rail voltages.

[AL78]

sorry what is +LT -LT?

[Dave H]

sorry what is +LT -LT?

They are the power supplies to the power amp. T9 collector (or D13 cathode) is +LT, T11 cathode (or D12 anode) is -LT

[AL78]

ok listen I'm gonna report both sides of d 13 and d 12 because I can't recognize(unless you tell me who) which is the cathode and anode ok?
So i have d13 stripe side is 40.8v dc non stripe is 38v dc
d12 stripe side 38v non stripe is -40.8v

[Dave H]

I can't read the schematic but they look like 1N4007, if so the cathode is the end with a white stripe.

[AL78]

Ok I gave you the value before.Maybe I was still editing the post while you answered

[Dave H]

So i have d13 stripe side is 40.8v dc non stripe is 38v dc
d12 stripe side 38v non stripe is -40.8v

That's not good. The power supply rails are OK but the output is at the positive rail which is usually an output transistor failure but it can also take out other components and be tricky to fix. For starters check the emitter resistors (R21, R24) are not open (they should measure 0.33R) and check T9, T11 for shorts C to E.

[nickb]

So I have 37v DC!!!!
If I disconect the con 1 stil 37dc....

Do NOT plug the speaker in until we get this fixed. If it's any consolation this power amp is one of the more simple ones to fix.

[AL78]

Guys I'm done tomorrow I'm gonna put on ebay for auction 10euros and then will see thanks.if you want it let me know I will ship thanks

[nickb]

It's sad to see you give up.

I'd take it, mainly out of curiosity, but I think it would cost way too much to ship.

[AL78]

Yeah I know but i would sell it anyway the owner doesn't want the speaker is not original.I'm tired.About selling to you i wouldn't feel ok I'm not shure it's fixable and reliable there are a lot of jumper made to arrive at this point even in the amp board.Thanks anyway.... I've never asked you what amp you have?

[Enzo]

LT means Low Tension (low voltage)



For diodes, I always remembered it like this. On the drawing, one end has a straight line, the other end is a triangle. To me the triangle looks like the letter A, so A for ANODE. In the real world, the stripe end of a diode is the end with the straight line on the drawing.

I usually do not think in terms of anode and cathode, I just think of the symbol and what it means for current flow. I only use the words anode and cathode in discussions, as they are not ambiguous.

[Dave H]

.... I've never asked you what amp you have?

For the last twenty years or so I've been playing just about the simplest amp you could possibly make. It's very similar to the one below. It doesn't even have a tone control. I must have played hundreds of gigs with it. I just use a small open back cab with V30 speaker.