I have an older guitar amp.
Long story short. I used the pre of this amp into the power section of another.
However, I did not know what I was doing and did not use a dummy load.
The amp I used the power section from was fine. But now the amp I used the pre from is not working.
It turns on, but i dont get anything out of the speakers.
Anyone know what I did? Maybe I need a new transistor or something.
I dont know anything about amp repairs please help.
Long story short. I used the pre of this amp into the power section of another.
However, I did not know what I was doing and did not use a dummy load.
The amp I used the power section from was fine. But now the amp I used the pre from is not working.
It turns on, but i dont get anything out of the speakers.
Anyone know what I did? Maybe I need a new transistor or something.
I dont know anything about amp repairs please help.
If the one which has blown was a valve amp then you may have damaged the output transformer. I'm afraid this may be expensive!
Running a valve amp at high level with no output load causes high voltages to develop which can break down the transformer insulation. The result is shorted turns in the primary winding.
Running a valve amp at high level with no output load causes high voltages to develop which can break down the transformer insulation. The result is shorted turns in the primary winding.
Fuse 3 1A is the HT fuse.
This should be your first check!
Please be carefull Tube amps hold voltage at 400V and can kill you if you touch a live part!
If you are very lucky it's the fuse, just hope someone has not fitted an incorrect rating!
Fuse 3 is on the last schematic on page 2 of the PDF. It is in line with the HT to the Output transformer. This is not the mains fuse!
I guess its on the circuit board! Remember take care!
Regards
M. Gregg
This should be your first check!
Please be carefull Tube amps hold voltage at 400V and can kill you if you touch a live part!
If you are very lucky it's the fuse, just hope someone has not fitted an incorrect rating!
Fuse 3 is on the last schematic on page 2 of the PDF. It is in line with the HT to the Output transformer. This is not the mains fuse!
I guess its on the circuit board! Remember take care!
Regards
M. Gregg
Last edited:
Thanks for that thread M
sound similar.
Only it didnt cut out.
I actually fried my amp on my own doing. just not sure what went bad.
Thought maybe a couple of gurus here could point me in the right direction.
Truth be told i have another amp I use. This Crate is just sitting in my garage and either fix or trash scenario.
It would probably cost more to have a tech even look at it than id be willing to spend.
sound similar.
Only it didnt cut out.
I actually fried my amp on my own doing. just not sure what went bad.
Thought maybe a couple of gurus here could point me in the right direction.
Truth be told i have another amp I use. This Crate is just sitting in my garage and either fix or trash scenario.
It would probably cost more to have a tech even look at it than id be willing to spend.
Was the older amp you used the preamp from a valve (tube) or transistor output stage? (mostly the tube ones have ventilation grills you can peer through and see things like jamjars glowing inside, and will produce a lot of heat. Or tell us what model of amp it is.)
Stage amps using transistors should not get upset about driving open circuits (= nothing plugged into the output), so the problem is most likely signal not getting where it's supposed to be. The reason tube amps get unhappy is the output transformers, which tend to ring on transients when undamped.( a bit like one of the joke hand held electroshockers). As this can produce fifteen or twenty thousand volts on bits of circuitry designed to take four hundred and fifty, octal bases can arc over, transformer windings fry, output tubes produce their own light shows; not the best first job for a neophyte repair experience.
However, the indicator light comes on, and the preamp stage was still working as long as you tried it, so you've not blown the mains fuse, and probably not the HT, which most of the more extreme damage would have done. Good sign. and I assume it wasn't making any fizzy, crackley noises from inside the electronics, or smelling of burnt bakelite, or you'd have mentioned that.
What do you have available as test gear? Even a nasty little multimeter would be a help.
What
Stage amps using transistors should not get upset about driving open circuits (= nothing plugged into the output), so the problem is most likely signal not getting where it's supposed to be. The reason tube amps get unhappy is the output transformers, which tend to ring on transients when undamped.( a bit like one of the joke hand held electroshockers). As this can produce fifteen or twenty thousand volts on bits of circuitry designed to take four hundred and fifty, octal bases can arc over, transformer windings fry, output tubes produce their own light shows; not the best first job for a neophyte repair experience.
However, the indicator light comes on, and the preamp stage was still working as long as you tried it, so you've not blown the mains fuse, and probably not the HT, which most of the more extreme damage would have done. Good sign. and I assume it wasn't making any fizzy, crackley noises from inside the electronics, or smelling of burnt bakelite, or you'd have mentioned that.
What do you have available as test gear? Even a nasty little multimeter would be a help.
What
The subject amp is a Crate Stealth 100w.
I took the PRE from the crate into Power of Peavey 6505+ 120W
Did not use dummy load. Fried the Crate but the Peavey was fine.
There was a little flubber if you will at first from the crate. Like you could barely barely hear guitar notes coming from the amp its self not the speaker cab.
Nothing at all coming out of speaker cab.
Amp turns on fine power indicators are good. Just no sound.
I have an OHMeter?? lol
I took the PRE from the crate into Power of Peavey 6505+ 120W
Did not use dummy load. Fried the Crate but the Peavey was fine.
There was a little flubber if you will at first from the crate. Like you could barely barely hear guitar notes coming from the amp its self not the speaker cab.
Nothing at all coming out of speaker cab.
Amp turns on fine power indicators are good. Just no sound.
I have an OHMeter?? lol
From what you have described as sounds coming from the Crate amp and not the speaker itself, an output transformer will "sing" if you will, with no load (speaker) connected to it, so its quite possible you fried the output transformer. As noted above, A short occured in a winding from having no load.
How did you hook this up? Did you unplug the speaker from the Crate in order to use its pre-out? If so, then yeah, your output tranny is probaly smoked. It's probably $50 (+-50%) to replace -- if you can find out the specs, and do the work yourself.
Don't trash the amp though! Hell, send it me. I'll pay for shipping (unless it's really heavy).
..Todd
Don't trash the amp though! Hell, send it me. I'll pay for shipping (unless it's really heavy).
..Todd
Oh, I was thinking the crate was a combo - built-in speaker. Just a head makes more sense.
..Todd
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