Mark IV problem - burning smell. HELP!

[badguitarist]

Hi guys. So I've got this Mark IV shorthead this afternoon. I turned it on. Everything was working fine. After 5 mins playing or so I noticed burning smell coming from the amp although the sound was still there. Immediately I turned it off, waiting for 5 mins or so and then turned it back on again. Right after I flipped the standby switch the smell started to flow to my nose. I played for 1 mins and then turned it off. There was still sound. I'm wondering what happened to the amp. Because there were always tones (heaven tones actually I'd say) I guess i'm not burning the transformer right? Please help me. I'm lost now

EDIT: There was no smoke coming from the amp. My setting was full power, pentode, simul-class. Volume at 3

 

[kiff]

you have the right impedance cab right? also, were you playing pretty loud? I've noticed mine can produce a bit of a hot electrical smell when I really crank it up...

 

[Mongo1]

If you are comfortable (and safe) working around amplifier internals, I think a visual inspection would be in order. With the amount of identifiable burning you have already experienced, something cooked should be apparent. If you still can't see a problem, powering it up open might give off a trace trail of smoke.

Remember, safety first.

 

[badguitarist]

you have the right impedance cab right? also, were you playing pretty loud? I've noticed mine can produce a bit of a hot electrical smell when I really crank it up...

Yes I was playing pretty loud as per my settings mentioned above. As far as I recall my old Mark IV combo had no evidence of smell when cranked. I'll probably take a look at the amp's gut. Thanks mate.

If you are comfortable (and safe) working around amplifier internals, I think a visual inspection would be in order. With the amount of identifiable burning you have already experienced, something cooked should be apparent. If you still can't see a problem, powering it up open might give off a trace trail of smoke.

Remember, safety first.

Thanks mate. I'll take a look at the inside and see if I can find any problems.

In the meanwhile any other opinions please?

EDIT: I should've mentioned that the EQ didn't work properly. I couldn't turn it on and off using the footswitch. So I just left it on "ON" mode using the switch on the rear panel.

 

[badguitarist]

I noticed that if the volume is at 2 there was no smell. When it came to 3 the smell appeared very quickly. Anyone has an investigation of what happened?

EDIT: I also noticed that the amp was fine when I wasn't playing. When I started playing the smell began to come out. I actually saw the smoke coming out of the recording out knob in the rear panel.

 

[badguitarist]

Bump... help please!

 

[glawk]

are the power tubes glowing blue? If so or if you hear a PSSHHH sound when switched off then the power tubes are leaking/burning gasses.

 

[badguitarist]

are the power tubes glowing blue? If so or if you hear a PSSHHH sound when switched off then the power tubes are leaking/burning gasses.

All the tubes are glowing blue. I didn't pay attention when the amp was turned off from using. But in the event of the power tubes leaking gas could 'em produce the smoke?

 

[MrMarkIII]

are the power tubes glowing blue? If so or if you hear a PSSHHH sound when switched off then the power tubes are leaking/burning gasses.

All the tubes are glowing blue. I didn't pay attention when the amp was turned off from using. But in the event of the power tubes leaking gas could 'em produce the smoke?

It seems that the interior of the tube is not the only place wherein lies a vacuum... :lol:

 

[badguitarist]

Bump...

 

[stokes]

are the power tubes glowing blue? If so or if you hear a PSSHHH sound when switched off then the power tubes are leaking/burning gasses.

The blue glow is normal.Your power tubes will only "leak" once,then they will stop working,tubes dont "leak" only at certain times,they lose the vacuum and its over.The burning smell is not normal.Take the amp to someone who can fix it before whatever is doing the slow burn takes the rest of the amp with it.Looking inside the chassis will do you no good unless you are able to make the repair,which will include more than just replacing the part that is burning.Quite often someone replaces the burning part only to have the new part burn because they didnt figure out what was causing the part to burn up to begin with.Stop using the amp till its fixed.

 

[badguitarist]

Thanks guys for the advices. I think I found the problem. A power tube was gone bad. I smelled all the tubes after taking them out and the bad boy with the unforgiven smell was easy to be detected. I replaced it with a spare and the burning smell disappeared no matter how long I played at max power possible. Good times.

 

[Anonymous]

Post removed.

 

[badguitarist]

No they're not brand new. Did anybody experience bad tubes burning?