Amp not turning on, HELP!!!

[my_shadow22]

I have this old tube PA head made that I'm use as a guitar amp. Well I bought a Celestion Blue recently and using the head with it is awesome. One of the best sounding od's I've ever heard. Well anyways, yesterday I turned it on to let it warm up. Came back in 15 mins and it was off. I tried the switch a few times and finally it turned on and was fine. Later on that night I unplugged it to take to a jam and went to turn it on an nothing. I shook it a few times tried it again, it turns on. While I'm playing it shuts off and now it won't turn on at all. I opened it up and saw that the ground was not connected to the input jack. I resoldered it and still won't turn on. Does anyone have an idea what could be wrong?

I'm a beginner when it comes to working on amps but I am starting to learn. I would really like to try to fix this myself but I have no troubleshooting skills. I just got a multimeter and was wondering if I could use that to see if any the parts are bad?

Thanks in advance for any help!!!

 

[PaulC]

Does it not light up (tube heatres and pilot light) when you turn it on? If so I'd look at the ac mains/fuse/pwr switch first. The switch could be going bad, or there could be a cold solder connection somewhere in that area. Fuse holders can make loose connections to the fuse also. If you are getting the heaters to light up then it's going to be a problem after the pwr tranny. If it was the pwr tranny you'd be popping a bunch of fuses. But just BE SURE TO UNPLUG! PaulC

 

[my_shadow22]

Thanks for the reply Paul, the amp doesn't turn on at all. I'm going to solder in a new switch and see if that works. Thanks again!

 

[Chambers]

hey my_shadow, you like tool?

 

[my_shadow22]

Chambers:

You're the first person to get that! Most people think I play a Cu22. Tool is probably my all time favorite band.


PaulC:

I tried installing a new switch and it still doesn't work. Any other ideas?

 

[PaulC]

If you've got an ohm meter try this:

Take your AC cord and connect the meter across the hot and neutral lugs. With the pwr switch off you should read an open circuit with your meter. Turn the switch on and you should see almost a dead short - just a few ohms. That's showing you that the hot and neutral lines are making it to the transformer. If you're not reading anything find where the pwr tranny primary wires connect to the ac mains. Meter there. If still open then you've got a break in the tranny primary.

If you do read a few ohms then trace back. Check all the connections all the way back to ac cord plug. The fact that you don't have any pwr (B+/heaters/pilot light), yet you don't pop fuses really makes me think you've got an open circuit somewhere in the mains. This could be the fuse holder, any solder connections, a break in the ac cord, even a bad ac plug. But unless this is something from mars you'll see what looks like a short from hot to neutral with the pwr switch on. Start there. You can email me if you like about this. Or call me at work (It's fine - this is what I do!) It's 615-832-8250. The place is Tusculum Music in Nashville. Later - PaulC

 

[my_shadow22]

Hey Paul, thank you very much for the help!!! I'm going to try out your suggestion and I'll let you know what happens.

 

[Chambers]

damn straight man, tool is up there on my top 3, there freakin amazing