Peavey Deuce: Power Supply Board Component

[bloodniece]

I'm having trouble identifying a component on a Peavey Deuce power supply board that blew. It's a baby blue cylinder with 2 leads,about 1-1/2 inches long, and is made of pyrex glass. The markings were destroyed mostly but I can make out Corning and FP10. I'm guessing it's a flameproof resistor, but any help is appreciated.

[Gtr_tech]

Got a picture? Sounds like a pigtail fuse to me.....flameproof resistors aren't made of glass. None that I've seen anyway. If you post a pic someone with the layout sheet can ID it.

[oc disorder]

If it connects to the standby switch its a 400 ohm 10 watt.
Bit of guesswork here...

[Enzo]

My thoughts exactly. And if you go looking for one, you might find it easier to look for a 390 ohm since 400 is an odd value. The factory installs 390s often as not too.

And of course if your favorite supplier comes up empty, Peavey sill sell you the exact part.

[bloodniece]

Here's a pic.

http://i42.tinypic.com/161md07.jpg

or

[Enzo]

Looks like the part in oc's photo to me. And that would be the 400 ohm 10 watt resistor. (or 390) PV used a round one, but those common cement rectangular ones would work just fine too.

[bnwitt]

And of course it didn't just burn up for no reason.

[bloodniece]

It burned for a reason along with other components. I'm just replacing things one by one.

Thanks for helping out. We'll see what happens after I replace what fried.

[52 Bill]

It burned for a reason along with other components.

A shorted output tube could cause that resistor to fail or a shorted filter cap, any number of things really. Try reading the resistance to ground on the power supply line where that resistor connects. Be sure to discharge the power supply before doing this.

[bloodniece]

I guess I should supply a story for this amp. Friend dumped this on me and said it didn't work. Its been in my basement for a few years so I decided it's time to either pass it on or fix it. In fact, one of the power tubes was blown. For testing I went to just the inside pair (X,2,3,X) and replaced the resistor with a pair of 200ohm resistors in series and got some sound but the volume is not there. I've used the Mace and know that it works fine with just 2 power output tubes. I need to salvage some 6L6GC tubes to get a full test going. I always short out the power caps to ground before getting in there.

[icefloe01]

I always short out the power caps to ground before getting in there.

It's better to discharge them through a resistor. A straight short to ground stresses the caps and shortens their life and the spark that occurs is simlar to a lightening strike and could also take out other parts in the amp. This is mainly true for the high voltage B+ caps. To discharge them in short order without putting too much stress on them, take the working voltage of the cap and multiply it by 5. Find the closest value 10 to 25 watt resistor and use that across the cap to discharge it. An easy method I can think of is to get some alligator clips that will slide onto the banana plugs of your meter's leads, clip them onto the resistor and use the test lead end to touch the capacitor terminals.

HTH,
Eric.

[bloodniece]

good to know. I'm pretty new to the vacuum tube stuff. I've built lots of pedals, frac rack synth modules, and various solid state DC circuits. Thanks for the help.