Marshall avt 100 problem!!!

[cenizasblancas]

Hi, i have a marshall avt 100 with 2 problem, the amp has much less volume and the distortion sounds pretty ugly. I would like to know what they recommend me to check or possible failures to start checking. I already downloaded the forum scheme and i have changed the tube but it sounds the same.

Thanks for your help!!!

Regards

Juan Motta

[nosaj]

Hi, i have a marshall avt 100 with 2 problem, the amp has much less volume and the distortion sounds pretty ugly. I would like to know what they recommend me to check or possible failures to start checking. I already downloaded the forum scheme and i have changed the tube but it sounds the same.

Thanks for your help!!!

Regards

Juan Motta

Send up the schematic here. Does the amp have a preamp out or a power amp jack? If so plugging the guitar into the power ampjack shopuld give you some sound just lower volume, does it still sound nasty? The idea is to halve the issue between preamp or power amp problem. Divide an conquer.

nosaj

[cenizasblancas]

Thanks for your answer!!! only has an fx return, Here is the shematics:

https://drive.google.com/open?id=1CO...vuGA8QhPyD_mFz

[DrGonz78]

Thanks for your answer!!! only has an fx return, Here is the shematics:

https://drive.google.com/open?id=1CO...vuGA8QhPyD_mFz

It has FX Send and FX return on the schematics, after all if you have one your gonna have the other. Take another look at second document, page 2, quadrant H5. Is it labelled differently on the amp and it says preamp out or something?

[cenizasblancas]

Hi, it took me a long time ... I tried the send in another amplifier and it works fine but the fx return doesn't sound ... I tried it with a direct zoom pedalboard, what could it be?

[The Dude]

Try some headphones. Do they sound normal?

[cenizasblancas]

they sound bad... low volume and the amp speakers sound at the same time.

[J M Fahey]

Best is to scope it to know what´s really happening.
I´ll repost the simplest attenuator possible so a software scope can be used on any PC.

Then you can inject a clean sinewave, raise volume, see when and how it clips and measure real power.

Lacking that, minumum testing is to again inject clean signal, start low and clean, raise volume slooooowly until sound goes from sweet to buzzy, after some practice you can detect clipping onset by ear quite well, I put a Piezo tweeter in parallel with speaker and buzzyness is much easier to hear, and then measure real output power.

Then we know whether we have a real problem or not.

But in any case, "an image is worth 1000 words" .

[cenizasblancas]

Best is to scope it to know what´s really happening.
I´ll repost the simplest attenuator possible so a software scope can be used on any PC.

Then you can inject a clean sinewave, raise volume, see when and how it clips and measure real power.

Lacking that, minumum testing is to again inject clean signal, start low and clean, raise volume slooooowly until sound goes from sweet to buzzy, after some practice you can detect clipping onset by ear quite well, I put a Piezo tweeter in parallel with speaker and buzzyness is much easier to hear, and then measure real output power.

Then we know whether we have a real problem or not.

But in any case, "an image is worth 1000 words" .

Hola tocayo!!! soy Juan Motta de Colonia Uruguay!! la pregunta venia por si el amplificador tenia algún talón de aquiles pero voy a tener que revisar la parte de potencia entonces. gracias saudos

Hi namesake !!! I'm Juan Motta from Colonia Uruguay !! the question came in case the amplifier had any achilles heel but I will have to check the power part then. thanks greetings

[Mick Bailey]

The headphones don't cut off the speakers with this amp - the master volume has to be turned to zero for silent practice. The first thing I do with any amp is to establish that the DC voltages are correct. Not just at the source, but I check them on each board to be sure. It's easy to check the opamps for +/- 15V. The power amp board has a three pin power connection - I can't recall the exact voltage but it's perhaps +/-35v. Don't disconnect this and then reconnect unless you drain the caps first as doing this can damage the power amp IC. Best to check it with everything connected.

There are a few connectors in this amp so make sure they're all pushed on.

[J M Fahey]

Hola tocayo!!! soy Juan Motta de Colonia Uruguay!! la pregunta venia por si el amplificador tenia algún talón de aquiles pero voy a tener que revisar la parte de potencia entonces. gracias saudos

Hi namesake !!! I'm Juan Motta from Colonia Uruguay !! the question came in case the amplifier had any achilles heel but I will have to check the power part then. thanks greetings

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