Mark III Distortion Channel Problem!!

[Tonedefpukeko]

Hey,

I got a problem with the dist. channel of my Mark III (non simul.), it cuts out now and then. Usually not completely, but has also cut out completely. Then after jumping on the foot switches and pulling my hair our it comes back to life with 100% signal. What the f*#K??

The last few session it started happening after 30-40 minutes of playing, but on saturday night (when I had a gig, my stupidity to go a head and use it in this state btw), it was reversed, didn't work at the beginning of the gig, and then worked at the end.

I haven't had time to change the V3 yet, which will be my first task, but if it's the V3 wouldn't it be more consistent? i.e. dead or alive?


Watcha think? Any help would be greatly appreciated!

 

[MrMarkIII]

If the problem happens *only* when using the Lead channel, it very likely is V3.
Are you using the effects loop?
Sometimes the loop jacks lose their connection or go intermittent.
Contact cleaner (not WD-40) or working a plug in-n-out can fix that.
See if the channel works better without the footswitch by using the pull switch on the knob.
That will eliminate the footswitch as a problem.

Mark III FTW!

 

[Tonedefpukeko]

Hey MrMarkIII, thanks for your post,

No, not using the effects loop, just have my effects through the guitar line.

I tried pulling the control knob for Dist., the dist. worked at the time, but I only play for 5 minutes with it so it was possibly not long enough to replicate the problem. Maybe I try this again and perservere for longer.

Anyway I will check the V3 and see how it goes. I have an important gig this weekend that I need a 100% relaible amp for, so I guess I can't take it. ,but I just hope that the amp is not dead in the long run. It's truely a great amp.

 

[mark2boogie]

but I just hope that the amp is not dead in the long run

obviously, it is not ! there is or a bad contact somewhere, or a bad tube. The second option is more easy to find than the 1st one...

A+!

 

[McBarry]

clean/retension FX jacks contacts as first easy job, or replace if inclined.
Primarily, deciding if ONLY on dist ch will decide remainder of troubleshoot path.
Clean/retension V3 socket is easy task too.
Remainder of diagnosing mostly involves working on live chassis, and some of this is simply playing and hoping something shows which U can detect with a DMM/scope etc etc..

Sounds like yr amp is FAR from "deceased", just has a bit of a "head cold" and some TLC and maybe a few "vitamins" will sort it easily... LOL

 

[>Photi G<]

I doubt it's a signal path problem. Something in the switching circuit is acting funny. First, unplug your footswitch, and try using the Pull Lead control on the panel. If there are still problems, something has gone wrong internally, and has to be fixed. If it works without a hitch, the problem is in the footswitch. Try using a different cable for the Lead footswitch. If that doesn't work, try using the R2 footswitch instead. The button could be sticking, which is causing your problem.

 

[Tonedefpukeko]

Cheers,

Had a quick check the other night and noticed that the V3 valve was not glowing as bright as the others, thought this was a bit strange especially as I replaced all the preamp tubes 3 months ago. anyway, i swapped it out with a new valve and it made no difference. So I'm thinking I should give the socket a clean and see if that makes difference.

I already tried changing the lead and footswitch pedal, but this made no difference. It could still be the footswitch input jack that's playing up, but given the low glow in the V3 I guess this is not the problem.

Is it easy to take a preamp socket out to clean, or shall I just leave it where it is?

 

[MrMarkIII]

If the tube is cold or doesn't glow at all, then you will get no sound.
You really can't compare one tube's glow to another.
Be sure to do the test using the pull Lead switch on the knob.
This will eliminate the footswitch as the culprit.

 

[Tonedefpukeko]

Okie Dokie,

Tube does glow, but not as much, but ok, if it vaires then I can't use this as a diagnosis then. Good to know.

Ok, will be sure to check Dist. next with the manual switch.

cheers,

 

[Fronzil]

had this happen to my 60 watt blue stripe. it ended up just being V3. I think the reason it came in and out was because that tube hadn't failed completely yet. I checked a few times, at first the tube appeared fine... later on when the channel started to go in and out, it just wasn't lighting up, and finally i looked when the channel failed all together and the tube had cracked and ****.