Issue with turning off JCM 2000 TSL 100

[disconeckt]

Hey guys,

I came across your board when looking for any info to a problem I'm having with my JCM and it seemed like a good place that I might get some ideas.

I bought a TSL 100 in 2006 and haven't had any issues with it until now. I decided to sell it and took out the pre amp tubes when taking pictures/cleaning and after replacing them the head makes a slight clicking noise when I flip the power switch off.

The channel lights flicker on real quick when this happens as well. It doesn't seem to be a huge issue, the amp still sounds great, but I don't really want this turning into something major if it causes something else to burn out.

Could it just be the tubes? They're the original set as this hasn't seen much playtime but they still seem to work. I didn't even remove the power tubes.

Any ideas you guys have would be appreciated, thanks!

[Jazz P Bass]

I would remove the preamp tubes & inspect them for misaligned or bent pins.

Does the symptom occur with the preamp tubes removed?

If it doesn't, try to narrow it down to one tube that is causing it.

[disconeckt]

I just tried after removing the three preamp tubes and it still flickers off. Kind of a strange issue really.

[g1]

Are you absolutely 100% positive it did not do this before? It doesn't seem that it's something that would affect the operation of the amp, so could it be you never noticed it til now?

[disconeckt]

Hey, I suppose it's possible and was kind of wondering that myself, but I'm 85% sure this is new.

Even the sound it makes kind of sounds like a short of some kind, almost like a "zzzttt" when it does it. Maybe I loosened some solder joint when I wiggled the preamp tubes out?

I may try to get a video of it tomorrow if that will help.

[Enzo]

or the contacts inside the switch are arcing.

[mikeydee77]

Any liquid involved in the cleaning?

[Mick Bailey]

The channel lights flickering suggests to me that it isn't tube related. Try switching it straight off at the mains and see if the same thing happens. It will probably pop, but just to see if the channel lights are affected.

What's your usual turn-off sequence with the power/standby switches?

[AmpFix]

The channel lights flickering suggests to me that it isn't tube related. Try switching it straight off at the mains and see if the same thing happens. It will probably pop, but just to see if the channel lights are affected.

What's your usual turn-off sequence with the power/standby switches?

Agreed. Seems more like a low +/- 15v rail power supply on the rear board. Do you have a footswitch connected when this happens and does it have an LED? I've also seen this happen with a flaky cable to the footswitch.

[disconeckt]

Hey guys, thank you for the replies!

I didn't use anything but a cloth to clean the inside just to wipe some dust out. Maybe some dust got on a board and is causing the issue?

I think I have another power cable that I'm going to try just to rule out a cabling issue.

And there isn't a footswitch connected when this happens, but I do agree that this probably isn't tube related. It seems like more of an electrical issue.

I've been meaning to get a video but haven't had enough time the past week. I think it might help though so will try to get to it.

Thanks again!

[disconeckt]

Ok, tried the different cord and a different outlet, definitely not that.

Got a video though I'm not sure it helps much. I feel like a crazy person after watching the video, haha, but it's hard to hear the "szt" sound it makes in person.

You can hear me flip the standby first, and then the power which cause the lights to flip on real quick.

Also, when I set the head down after picking it up, there is something that makes a "springy" type noise, but seems like it always did this. Don't know if it's related, but the first time I powered it off today, the noise did seem to be in the same area as that spring.

Who knows. I did talk to a certified Marshall service tech in the area and can get it evaluated for $80, which would cover an hours worth of work and cost of any necessary repairs.

If you guys think it's not a big deal, I may just continue to play it as is. I'm just aware that some of the JCM's can be hard to fix, so wanted to be a little preemptive with it to avoid a more expensive problem in the future.

https://youtu.be/JFqByUV6ahg

[Jazz P Bass]

Isn't the 'springy' noise the reverb tank?

[AmpFix]

LIke I said earlier, check the +/- 15vdc voltages on the rear board. They might be on the edge. There's a simple fix to increase it output, slightly. Depending on component age and tolerances, it can be off by just enough to cause issues. I'd have to go back and check the scheme for the fix.

[disconeckt]

How would I check the voltages? I haven't done a ton of electronics work but could follow a play by play fairly easily. I should have a meter around as well.

[AmpFix]

http://www.lydian.ca/Marshall_DSL_fi..._RearBoard.pdf

The power supply that is involved in switching the relays (and make the leds flicker), is the 24vdc rail. That's the one you need to look at, not the +/- 15vdc.

BUT... Because this is happening on power down, the relays are just going back to their normal state. I would not worry about it too much. The caps are just draining out and the relays switch out to their normal state.

Leave all the channel select buttons out and plug no footswitch in. What does the amp do?