Marshall TSL-601 - Quiet Volume

[smoothound]

Turned the amp on last night and the level is very, very low.

All the controls seem to work, and the two power valves are glowing. The three 12ax7s never glow, so it's hard to tell.

Is it likely to be a failed pre-amp valve?

What should I be checking?

Thanks,

Griff

EDIT : I should add, that on full volume, you can hear the usual 50hz hum, but the guitar is still quiet. Suggests to me the main amp is OK?

[guitaraid]

It might be one of the pre-amp valves or more likely one of the anode resistors (between +voltage and pins 1 or 6).

[52 Bill]

The first thing to check when an amp has these symptoms, is the FX loop/preamp out/ power amp in jacks.

If your amp has an FX loop, plug a spare guitar cable from the send, directly into the return jack. If this restores your guitar signal, then you need to clean the jack's internal switching contacts. If your amp has the PO/PI jacks, do the same test with these jacks.

[smoothound]

I checked the valves in the dark last night, I can see they're all glowing. And after 10-15 mins they're all pretty warm. So looks like they're fine.

I'll check the other things you both mentioned, then post back !!

Thanks for the advice guys!

Griff

[Enzo]

And another test after that is to plug a cord into the effects send and connect it to another amp. Listen to what comes out of the effects send in that other amp. If it is weak like your amp, then the preamp is at fault. If it is OK, then your power amp has the problem.

And... turn the amp on and the reverb up midway. Tock the amp back and forth to crash the reverb springs. Is it loud reverb crash, or is that real diminished too?

[smoothound]

AH, more good advice !

I like the logic that's going on here !

Cheers !

[smoothound]

If your amp has an FX loop, plug a spare guitar cable from the send, directly into the return jack. If this restores your guitar signal, then you need to clean the jack's internal switching contacts.

No, the signal is still quiet

And another test after that is to plug a cord into the effects send and connect it to another amp. Listen to what comes out of the effects send in that other amp. If it is weak like your amp, then the preamp is at fault. If it is OK, then your power amp has the problem.

The other amp takes the signal. Very loud ! Scared the s*** out of me !

And... turn the amp on and the reverb up midway. Tock the amp back and forth to crash the reverb springs. Is it loud reverb crash, or is that real diminished too?

The reverb is really deminished too.

So, looks to me like the pre-amp is fine, but the main amp is down on power.

The volume knob recently had some service done, so I think I'll check that first. (in fact, I've already asked Marshall for a new PCB and pots)

Any other ideas?

[smoothound]

The volume knob recently had some service done, so I think I'll check that first. (in fact, I've already asked Marshall for a new PCB and pots)

Well, look what I found

Just heating the iron up as we speak...(well, type)