Marshal AVT150 no output

[sciffer]

So, I got a non working Marshal AVT150 from a friend and decided to take it as a project and fix it.
At the beginning the symptoms where that the only thing that worked is the light on the power switch and I could hear the buzz from the transformator.
Since, I read about it in multiple forums and found out that it is common with this amp that the two resistors(223 & 202) to burn and they got used as if they were some sort of a fuse (I tested those with the multimeter and indeed found they need to be replaced).After replacing them - now I can actually hear the fans and I can choose the channels but there is no output on any of them and the volume does not seems to affect a hum sound (the speaker is connected as expected to internal).

I read about the TDA chips that get burned down a lot and that maybe the tube needs to be replaced, but I'm not sure - how can someone test and verify that this is indeed the issue (they seems perfectly fine) nothing seems or smells as if it was burnt all the components on the board seems to be in perfect condition.

Testing the tube with multimeter I noticed that only 2 legs are shorted together which I believe it is what you should expect(I don't have tube tester).

Anything else I should be looking for?

[stereomonostereo]

You should be able to plug into the back of the amp at the effects loop return to see if your output section is working. That's the first thing i'd check. Your mains fuse didn't blow?

[sciffer]

No the main fuse did not blow - it is totally fine.
I believe that the 2 resistors are burnt once again,Im not sure how come they just keep burning without me even doing anything - just trying to get output through it.
Anything else I should check maybe - I replaced the resistors twice already and I'm kind of had enough with it.

[Jazz P Bass]

No posted schematic.

Sorry, but as I do not work at Marshall, I do not have a clue (or the time) to find R 202 & R 203 on the schematic that I have.

Can you help us out here so that we may have a chance of helping you?

[stereomonostereo]

Did you check your effects loop return to see if you're getting sound from the output section? First you want to centralize the problem.

Those resistors aren't going to burn out unless something is making them burn out. Looking at the schematic you've got a rectifier at L101 and two voltage regulators right afterwards. Have you checked those?

[sciffer]

Did you check your effects loop return to see if you're getting sound from the output section? First you want to centralize the problem.

Those resistors aren't going to burn out unless something is making them burn out. Looking at the schematic you've got a rectifier at L101 and two voltage regulators right afterwards. Have you checked those?

I need to replace the resistors before I can test the effects loop return output, once those resistors are fried there is no electricity to the whole board(even the fans are dead).

I'll try to test the regulators and figure out if they are the source for my issue.

[Jazz P Bass]

Yes, R223 & R 202 are for the low voltage power supply.

Marshall AVT150 & AVT275 Power Supply.pdf

[Enzo]

So check that rectifier bridge for shorts, and the filter cap on either sid as well.

[sciffer]

Tested both rectifiers on L100 + L101 and they both seems fine. Not sure how to locate or test the filter cap though?