#1
Hi there guys. I bought this old Marshall AVT50H from someone for £20 a few months back, and it has been working okay since then. Recently though, it has started giving me a very strange problem. Occasionally the amp will cut out, and no sound from my guitar will come out, although sound from the "CD In" jack will still come out. I'm not sure if this will have something to do with the preamp (I know very little about amplifiers), as the small green and red lights for each channel will not light up when the amp cuts out. It will then function as normal again at any random time.

You can see the channel lights (I don't know their actual name) here: http://imgur.com/a/AFHqA
Any help to figure out what is causing this would be much appreciated!
#2
do you still get sound on the clean channel when it cuts out on the crunch channel?

If you do it maybe the 12ax7 tube in the amp. it is only used on the crunch channel so that would be my first place to check if your experiencing the issues I asked about
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
#3
Quote by Robbgnarly
do you still get sound on the clean channel when it cuts out on the crunch channel?

If you do it maybe the 12ax7 tube in the amp. it is only used on the crunch channel so that would be my first place to check if your experiencing the issues I asked about


Unfortunately, I get no sound from the guitar at all when it cuts out, on either channel. The only thing that will come out of the output is anything in the CD In jack.
#4
I imagine the CD in jack bypasses the 12AX7 and just hits the SS power amp. Robbgnarly, are you sure the tube is only used on the crunch channel? What I've read is that it is used on both the clean and crunch. Marshall doesn't have the amp listed on their site anymore, so all I can go with is MF's "The 2 footswitchable tube preamp channels of the Marshall AVT50H"...

Try getting a new preamp tube and replace it. They're relatively cheap, and you'll probably want a new tube anyway ( you might want to get 2 to have one for backup c: ). Or have a tech test it for you.

SN: The AVT series seems to be somewhat highly regarded for a hybrid amp. Neat.
Last edited by Will Lane at Feb 14, 2015,
#5
Quote by Will Lane
I imagine the CD in jack bypasses the 12AX7 and just hits the SS power amp. Robbgnarly, are you sure the tube is only used on the crunch channel? What I've read is that it is used on both the clean and crunch. Marshall doesn't have the amp listed on their site anymore, so all I can go with is MF's "The 2 footswitchable tube preamp channels of the Marshall AVT50H"...

Try getting a new preamp tube and replace it. They're relatively cheap, and you'll probably want a new tube anyway ( you might want to get 2 to have one for backup c: ). Or have a tech test it for you.

SN: The AVT series seems to be somewhat highly regarded for a hybrid amp. Neat.


I will take it to a tech tomorrow and see what they say, as I am not very confident with messing around with the insides of the amp And yeah, it's a very good sounding amp for it's price range, and I got it pre-owned for £20, so I'm not complaining
#6
Quote by IanSammiches
I will take it to a tech tomorrow and see what they say, as I am not very confident with messing around with the insides of the amp And yeah, it's a very good sounding amp for it's price range, and I got it pre-owned for £20, so I'm not complaining

That's $30 over in US. That's a ridiculous price. You could sell it for parts for more than that.

Just take some money so if he says it is the preamp tube causing the trouble, you can just buy a replacement at the tech's shop. c: Tung Sol, Tube Amp Doctor, and Mullards are good brands.
#7
Quote by Will Lane
That's $30 over in US. That's a ridiculous price. You could sell it for parts for more than that.

Just take some money so if he says it is the preamp tube causing the trouble, you can just buy a replacement at the tech's shop. c: Tung Sol, Tube Amp Doctor, and Mullards are good brands.


Thanks man, I'll be sure do do that
#8
Have you tried a different guitar cable? yours may be bad
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
Krank 1980 Jr 20watt
Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
#9
Quote by Robbgnarly
Have you tried a different guitar cable? yours may be bad


Yes. I've tried over 10. It's the actual amp cutting out. The channel lights turn off.