Help! I need to know what type of fuse to buy

[MoFoTWeeTeR]

I have an old 1978 peavey centurion mark III series amp and the original fuse was blown. I went to replace it and noticed it only says 5A on the fuse and has no engraving for voltage. I assumed it was 250 voltage tried two of em and both blew about 5 seconds upon turning the amp on. I tried looking up PDF manuals and forums and found no luck. Any suggestions on the fuse? or is it even a fuse problem? Thanks - Steve

[BogeyBass]

If the fuse keeps blowing then something may be wrong with the amp.

The amp only seems to be about 130 watts so 5amp fuse sounds about right. probably suppose to be a slow blow

[B-string]

Did the original fuse just have a wire inside it? If so it was a fast blow. If it had more than just a piece of wire it was a slo-blow and you need to try a slo-blow 5 amp fuse as the in-rush current could trip a fast blow fuse. If a slo-blow still burns (only use one if the original was one) then the amp has a problem. The voltage only needs to match your line voltage or above (so 250V on a 120V service is fine).

[MoFoTWeeTeR]

Ahh, hope its not the amp. I did get fast blow fuses though, I hope that's the problem. I'm gonna try a slow blow fuse out tonight. Thanks bogeybass

[B-string]

It should say "Slo-Blo" close to the fuse holder if it requires the (time delay) fuse.

[MoFoTWeeTeR]

I'm gonna try a slow blow fuse tonight. Nothing on the back of the head indicates anything about the type of fuse it takes. Just says "fuse" thanks for explaining the voltage too

[B-string]

No problem.

[Calaverasgrande]

I always would rather err on the side of caution. I will much rather use a lower rated fuse than a higher rated one.
A lower amperage rated fuse might blow before you are "in the weeds",
but a higher amperage rated fuse might not blow until you are past the weeds and already in the swamp.

[MoFoTWeeTeR]

I'm assuming its a 5 amp fuse but I really don't know. It was a hand me down header and the guys who I got it from is not even sure himself. I really don't want to put a fuse with a higher rated amp, because that could damage the head. So im gonna stick with what was in there when i got it for now, unless anyone knows what the header really takes. Moment of truth will come in a couple of hours, I hope the slow blow out fuse does the trick.

[BassmanPaul]

I found the manual on Peavey's site but it has no mention of the value.

[Steve Dallman]

I just looked at the 260C schematic. It's a 5A fast blow fuse. A 1978 PV could have a couple problems. The main filter caps, C25 and C27 should be changed. Likely one is shorted...a common problem with old PV's. The are (from memory) 8,000uF/55v caps. Modern caps are smaller, so you could easily up the value and get higher headroom. If you measure those caps with a meter set for resistance, you may find one is shorted.

The next possibility is a bad output transistor or two. Sourcing old PV transistors isn't easy. I don't have the schematic in front of me to see the type of transistors there are. They would have to be removed one by one and tested for shorts.

Those are the most common fuse blowing problems. Google Peavey 260C schematic and there is a DIY forum thread where one guy posted the schematic.

[MoFoTWeeTeR]

No luck with the slow blow fuse... Thanks for the trouble shooting avenues, Steve dallman. I'm gonna have one of my friends venture off into those territories you posted. I'm hands off when it comes to opening equipment and such. Hopefully it's relatively cheap to fix. Thanks again for the help guys

[B-string]

The caps would be cheap enough as would rectifier diodes.Best of luck

[nashvillebill]

Might be a shorted ooutput transistor, but let's hope it's something simple like a wire that had its insulation rubbed off internally.

A Dim Bulb Tester is useful, it limits the input current, rather than blindly plugging in fuses.

If it were on my bench, I'd pop the head open, check for obvious shorts, then if I didn't see anything I'd pull the output transistors and try again on the DBT.

[MoFoTWeeTeR]

So, i had one of my friends look at it, and shes clean as a whistle. no shorts or burns however he thinks it the transformer is the reason why the fuse keeps blowing. 705-16734 Basler electronics, is the transformer on the unit. now im wondering how and where i could get a hold of one these or find one thats the same by a different make etc..

[B-string]

"Thinks" it is the power transformer? It really is easy enough to know and not just think. Peavey can help with specs if not a replacement, but be SURE you need one first.