Marshall AVT150H - Clean 1 channel volume low

[metaldestiny]

I think I've got a blown part in my AVT150H. I didn't find any obvious issues when I took it apart - no burnt components, no missing traces. Both fans are working fine (I replaced one a few years ago).

The Clean channel 1 volume is very low. I get sound, so I think that the output side is okay. From looking at the schematic, I'm thinking I should replace IC6. I'm suspicious of the ECC83 tube as well, if only because when I turn the amp on, the volume does not swell but stays consistent from the first instant. I don't have a lot of experience with tube electronics, but have made a whole lot of repairs on solid state gear.

Am I on the right track or is there something else I should look at?

[metaldestiny]

Schematic here: http://music-electronics-forum.com/a...avt150-275.pdf

[altazepsta]

MD, I haven't looked lately but I don't think Clean 1, or emulated acoustic, if that is it, goes through the tube pre-amp. maybe someone else knows more on that. Mine is quite low compared to the rest of the channels as well. I seeing alot of this lately in Marshall SS based amps. I can't say for certain if is a flaw or a feature.

[altazepsta]

You may need to clarify for us, since the avt has sim acoustic and Clean on the first channel, which you are referring to. But you know, assuming clean one is sim acoustic, you will see the top right corner is the the stage you are after. check the resistors and caps there, including the VRs to make sure they are giving the correct resistances, etc. (power off and unplugged with multi meter) If a resistor doesn't read correct at first, you might need to desolder one end and check it again. I am no expert by any means on these, so I am watching myself. But it may give you somewhere to start. As I said before, the sim acoustic channel on mine is notably quieter than the rest of the channels. Same issue, ahem feature on my MG100hdfx

[metaldestiny]

Thanks, Yes it's the Sim Acoustic channel. It's always been quieter but not THIS quiet. I'm fairly sure something's up. Will have a go at the components with my meter.

[g1]

page 1 of schem you posted shows the acoustic channel across the top: IC1b, IC9, IC6b. Then through switch IC3d on pg.2 upper right.

[metaldestiny]

So I've traced my problem to IC6b and VR13. Off to source parts!

Thanks

[Sergio1024]

Did you ever fix this mr destiny of metal?