my mark III stopped working, what should i do?

[caf]

i turned the standby on and there was a loud crackling sound like when you push the input jack into a guitar when the amp is turned on and then the amp stopped, i tried to switch it back on and there was no power.

would it just be a blown fuse?
i was planning on replacing all the tubes as i thought they were getting old so i'm hoping at worst this is the problem.

thanks in advance for any help & advice.

 

[Tuna141]

Probably (hopefully) just a blown fuse. Check/replace the fuse - Radio Shack sells them. If it blows again, you probably have a bad power amp tube. Try running Class A so only one pair of tubes are on. If the fuse blows again, swap the inner pair with the outer pair. If the fuse blows again, I'd open the amp up and look for a blown resistor or other component. Good luck.

BTW -My Mark III died a couple weeks ago while I was pushing it hard at rehearsal. I replaced the fuse and it has been fine ever since. Fuses can get fatigued over time. If the fuse does blow again, I'm going to throw in some new power tubes, because the ones I have in there are pretty old.

 

[acorkos]

or you can save yourself a bunch of fuses by putting in one new fuse and taking out your power tubes...then power on. if the fuse blows, you know it was something more than just tubes. if the fuse holds with the power tubes out, then get some new tubes because your old set was bad.

 

[caf]

i replaced the fuse today, turned the power on, warmed it up then turned on standby and started playing and within 10 seconds the amp stopped again.
i'm waiting on some new tubes so i think i will try again when they arrive.

 

[MrMarkIII]

Take it to a tech before you spend all your money "fixing" it yourself.

 

[6L6C]

Take it to a tech before you spend all your money "fixing" it yourself.

+ 1
Probably is just tubes but take it to a tech and let them go over it, less stress and less of a chance you doing something else if you are not sure of yourself.

 

[acorkos]

"...spend all your money 'fixing' it yourself."

you mean all of $.50 for a fuse?

don't listen to them. go for the gusto and try the tube swap yourself. there's a 90% (or greater) chance that it is a bad power tube. tubes go bad...that's why they're on sockets.

like i said in the earlier post, you can usually confirm it's a bad tube by putting in a new fuse and pulling th power tubes out of the amp. if the amp holds the fuse when you switch the standby to operate, you probably have a bad power tube.

go for it!

 

[acorkos]

and besides, if it is just a bad power tube, you'll feel like an idiot when you have to shell out $200 to a tech just for new power tubes (including parts markup and installation costs). now, for just power tubes, that IS a waste of money.

 

[caf]

well i replaced all the tubes today and no problems at all! fingers crossed that it was just a bad power tube.
sounded really good too!
i really appreciate everyones advice
thanks!

 

[6L6C]

Cool!

Glad to hear that was only problem. And nothing like a fresh set of tubes to make you fall in love again with your amp.