Marshall AVT50 Valvestate 200 Combo blowing main fuse

[loudnproud]

Marshall Parts

Thanks. I'll give it another try. I've been all over the Marshall site. The only authorized repair center within 300 miles of where I live went out of business because of guitar center. I know there are parts somewhere. I'm new to this. I'm thinking about replacing all the boards and be done with it.

Someone wrote that the AVT150 was a lemon? I don't know. It was the only tube combo in the store and it was a demo. But 3 years for an $1100 amp hurts. Maybe fix it and trade it?

Thanks for the help,
LnP

[52 Bill]

Thanks. I'll give it another try. I've been all over the Marshall site....I'm thinking about replacing all the boards and be done with it.

I doubt than anyone will have all of the boards for your amp available.

I suggest that you start a new thread for your amp and see what help you can get to fix your problems. This thread is mainly regarding blown output chips and replacement output boards.

If your amp is working, but only making some noise and stuff the problem is probably in the preamp.

[Enzo]

Marshallparts is not the MArshall AMplification web site, it is a completely different company. They are an independent company that sells Marshall parts, they are not the parts department at Marshall amps. The link I posted comes out looking funny, so here, I will edit it to look right.

www.marshallparts.com

if you are looking for entire circuit boards, good luck, but if you want the little boards with power amp chips on them, as many guys do, they can get them. And anyone who sells Marshall products can order the parts for you as well.

Meanwhile, this is going to require soldering parts. Are you up to that?

For the price of a complete set of boards, even if they were available, you could just buy a used amp.

[loudnproud]

Marshall amp

I haven't looked inside yet; but, I can imagine 4 to 6 little boards and perhaps one larger one. But, I don't do amps. Never studied them to any depth. I'm an electronics tech but it is all digital stuff that I work on. I can solder quite well, though.

I've thought about a used one; but, talking my wife into another amp to add to my collection is impossible any time soon, new or used. I paid $1100 for this one 3.5 years ago. I really need to get this one going.

In a way, this was used. It was the demo and the last one in the store. They dropped $100 because it was a demo. But the web sites that sell amps and the store I bought it from didn't say anything about being discontinued. Used tastes bad to me now.

I did find an authorized repair center. I'm sure they will be glad to take my money even though they can't fix it due to part not availiable. So, I'm kind of undecided on what I want to do at this point.

Thanks for the info everyone and best wishes,
LnP

[Enzo]

What part is not available? I said it is not likely you will find the entire main circuit board, but in amp service we do not replace entire boards, we repair them. But all the electronic components are readily available.

[brassriot]

Whats the part # on that Jaycar kit, unparalleled? Plus does anyone know if I could swap out just one TDA7293 (in an AVT50) for something like this with two- HP ENTERPRISE different kinds of Chinese Commodities. ?

[dobrota]

Hi Music Man, here it is !
It was very easy some years ago. Marshall's sent You any schematic You asked for without problem. It isn't possible now...
Please can you make a some photos of main PCB inside AVT50 (preamp, PSU, valve etc..) for me ?

Thanks, Fr.

[unparalleled]

Jaycar KC5150.
Personally I would not use the amp on your link, the valve stage would put me off.

[Hanger-18]

Need to know the wiring you used for the module.

I had the same instability problem with AVT50.
Marshall seem to have built a lemon in this model. They used minimum supporting components for the power amp chip. I tried everything I could think of to no avail.
There does not seem to be many of this type of amp around so perhaps Marshall stopped producing them because of the instability?
The amp I worked on was only just out of warranty and had lots of problems from new.
I eventually gave up in disgust and fitted a kit amp module with a decent heatsink for good measure.
Schematic:

Hey I bought an AVT 50h in a box of broken parts. It's just a chassis but the previous owner took out the power amp board. A new board is $65 and I was considering using a $9 generic one from ebay. Problem is the generic one has 2 inputs, 2 output, and power inputs. The Marshall one has a multitude of connections and a 3 pin connector. I'm wondering which connections you used for this board? How did you modify it and did it work well?

[Hanger-18]

Anyone got a power amp board for this amp laying around. Mine came missing (someone else tried to fix and took out). Got it as parts. Really dont care if it works, just want it for the cable connections.

[Enzo]

Which power board? is this the discrete component version, or do you mean the board with a TDA7293 15-leg IC? I have a couple of the IC boards with the IC removed.

[Hanger-18]

Yes I need the power amp .

[Hanger-18]

Basically this one with or without TDA7293 Chip. Mine is just a chassis with the fan and heatsink( piece of cheap bent aluminum)

Marshall Amplification M KITS 00003 Amp Module PCB for AVT150H | Full Compass

Without the $65 price tag.

[Enzo]

I have an empty board of that sort. I only have one, so if you need two, you need to keep looking. You'd have to add your own TDA7293 IC. This board was a pull, though it is not burnt or any other damage. Just a bad IC was removed. A three pin plus an 8 pin. (I also have several of the other style, a 15 pin connector) If you want it, postage is a bit under $7, and add a dollar or two for me. PM me if you are interested. This does not come with cables.

[Hanger-18]

9158d1272896393-avt50_1.pdf

Enzo this is the only way I could show you the schematic for the AVT50 in regards to the Reverb circuit. Thanks. Here's a document that has the AVT reverb circuit in the examples a couple pages Dow.

reverb_tank.pdf