To anyone who's ever had fuse problems...

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JohnBJohn

Tard
I have an AC30 that just eats through fuses. I swapped the output tubes but that didn't seem to do much. Takes about 2 minuets for a fuse to blow(the one right on the ac in) and the specs on the fuses all check out. Wondering if anyone has had a similar problem or know of a fix?
 
There is almost certainly a short somewhere. One possibility is the "ground" cap (also known as the Death Cap). Could be an intermittent short there. If you still have your Death Cap, you should have it cut out just on general principle, but if that is where the problem is it might do the trick. Of course, if it's one of the newer amps, it might not even have a Death Cap.

Whatever it is, if you aren't familiar with the guts of a tube amp, you should take it to a good tech.


Light

"Cowards can never be moral."
M.K. Gandhi
 
Make is: CC2, 2006 - not sure bout the death cap. Hopefully the short theory has some merit because it is needed for two shows this week.
 
I'm fairly sure that a CC2 will not have a death cap. Actually, I'm reasonably sure they are illegal these days.


Light

"Cowards can never be moral."
M.K. Gandhi
 
JohnBJohn said:
Make is: CC2, 2006 - not sure bout the death cap. Hopefully the short theory has some merit because it is needed for two shows this week.
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Unless you're a fairly decent tech or have one that will immediately tear it down, you'd possibly better have an alternative amp available.
By short, Light isn't necessarily talking about two wires that you can just spot. It's more likely you have a component that's gone bad and shorted. And a problem that doesn't blow a fuse for a couple of minutes can be devilishly hard to find unfortunately.
I really wish you luck because I know what a pain it is to not have your regular amp but I really think you might need to prepare for that possibility. It would suck to get 2 minutes into your gig and have the amp go down.
 
Slow blow fuses

:confused:Hi,
That is a very frustrating situation. There are different types of fuses available for the same ampere rating. make sure it is exactly identical. I had a problem years ago where I replaced the fuse with a fast blow fuse and it would continually blow fuse after fuse before I realized it was suppose to be a slow blow fuse. If the fuse reads T500ma it is a slow blow fuse. The T stands for time delay. So make sure your fuse starts with the T prefix before the correct ampere rating. I hope this helps.:eek:
Victory Pete
 
Victory Pete said:
:confused:Hi,
I replaced the fuse with a fast blow fuse and it would continually blow fuse after fuse before I realized it was suppose to be a slow blow fuse. If the fuse reads T500ma it is a slow blow fuse. The T stands for time delay. So make sure your fuse starts with the T prefix before the correct ampere rating. I hope this helps.:eek:
Victory Pete
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good point.
I've seen this too.

"at 2minutes fuses blow" is a good data-point for troubleshooting.

Questions I'd ask is, do the fuses blow if you aren't playing. Just let the amp sit there, no volume?

if its in the power supply, I'll assume a SolidState power supply... look for any "pregnant capacitors". Any visuals.

but definately try the fuses first. there's more to them than amperage values, as Pete said.

If your ok with electronics, unplug the power supply from the circuit, and this will partition your area, for example if the fuse blows with only the power supply ON, the problem is most likely the power supply and you can change that out.
What we often do on the partitioning is isolate the power supply, and add each circuit to the power supply one by one, and often the "bad circuit" will blow a fuse when connected to the power supply.

good luck....

you can always sell it on EBay...........(bad joke, but I'm laughing...:p)
 
Fuses were all slow blow. I'll swap the rectifier and hope for the best so I don't have to bring out the old fender.
 
Just wrap the blown fuse in aluminum foil and stick it back in. Problem solved. :D














It's a JOKE. Don't do that unless you want to torch your house for the insurance.
 
OK, don't quote me on this, but I believe there is a design flaw with the output stage. This did happen to me. I went through a plethora of EL84s, but would have your problem. Rectifier tubes didn't alleviate the problem, either. So one day while taking a chance and playing the amplifier on stage, I decide it's OK to look like a self-absorbed wanker and stare into the vent right above the output tubes. Before the fuse blew (again), I noticed the EL84's on one side would glow a nice orangey-red color :eek:. Of course any service shop cannot find any problem while the amplifier is under warranty. After the warranty period is over, I am on my own, and almost excited about the challange. So I put my thinking cap on, and did this; I measured the Plate current. It's too high for the EL84's at the AC30 voltages. Don't ask; I don't remember. Anyway, I also notice they use two 100-ohm resistors in parallel to bias the output stage :confused:. I pulled them out, and instead used two 125-ohm resistors. Don't ask where I got them from, I don't remember. Anyway, the meat and potatoes of the story is thet my problem mysteriously went away, and the amplifier played happily ever after. This is not an anecdotal rambling, but my own personal experience. A coincidence? I dunno. Maybe there was a parasitic oscillation causing excessive current drain. I dunno. But you can certainly see (or ask your personal technician to do it) if you have the two 100-ohm resistors for the Cathode bias scheme. If so, remember the ramblings of a man mixing his medications.
 
ranjam said:
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While that is all a possibility, there are so many different possibilities that it is a bad idea to give any advice this specific without seeing the amp in person. As Lt. Bob said, you should plan on using another amp, and if you're not good with high voltage electronics you should take it to a good tech.



Light

"Cowards can never be moral."
M.K. Gandhi
 
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