Peavey Deuce VT

[memoryman]

Keep in mind that the previous owner had a home made attenuator between the amp and the speaker which I removed.He said it would blow fuses.I had the power tubes(6l6) tested and they are fine.  The area under the flameproof resistor (R1 400 10 watt) board was scorched so I scraped and cleaned the area and coated it with high temp epoxy. I replaced the flameproof resistor (R1 400 10 watt) and the power transformer because the metal looked like it had gotten really hot. Tried to power it up in the standby mode. In a couple of milliseconds the power indicicator came on and went out and the fuse blew. I did not replace any of the electrolytic filter capacitors, so I probably will be doing those next.I'm obviously a newbie so any help would be great.

[phatt]

You need one of these little devices.
http://www.ssguitar.com/index.php?topic=2093.0

meantime maybe pull the valves and see if it still blows fuses?
If so you will have to find out why,, plenty good minds here will be able to help.
Phil.

[Roly]

Hi and welcome @memoryman.

Like Phil says, you'll need a limiting lamp.

Also, please find and post the circuit/schematic here (or link) so we are all talking about the same thing.

You don't say why you replaced the power transformer (or do you mean the output transformer, valves to speakers?).

A way to approach this is to disconnect the primary of the power transformer and see if you can apply power without problems.

Then reconnect power transformer primary while disconnecting the secondary (at least the high voltage winding) and see if that will power up okay.

You proceed progressively like this, bringing up a section at a time until the problem appears; the limiting lamp saving you from blowing lots of fuses.

Something to have an initial look at though is the main HT rectifier, which looks like that bunch of four diodes being cooked by that power resistor.  You will need to lift one end of each for a certain test (and be sure the main HT line is fully discharged first, lest you "shake hands with beef" stored in the filter caps), and you will need to test all four.

It's fairly unusual for filter caps to lead to fuse blowing without first going through a long period of degeneration, increasing hum and so on, but a boofed rectifier will do it for sure.

[Enzo]

I preach and believe in a systematic approach, but when fuses blow right away, check a few basic things first.  Are any of the high voltage rectifier diodes shorted?   Are the secondary fuses the right type?  Hell, is the mains fuse the right type?   And there are two diodes on the power tube socket board, is either shorted.  here is a simple way to check them.  Power off of course, measure resistance to ground from pin 3 of the power tube sockets.  Is either shorted to ground or low resistance to ground?

Phatt's suggestion of trying it without the tubes is of course good.

[memoryman]

I tried replacing the fuse (5 amp slo blo) pulling the tubes and achieved the same result.

[Enzo]

And the other things I asked about?

[DrGonz78]

Trust and follow all the advice Enzo and Roly give you here!!  That advice is right on the money... Build the Light bulb limiter before anything else that you do... Unless you like blowing fuses... Read all the posts have been sent and follow up before you move forward...

Edit: There are many others here that give great advice too!! Just named Roly and Enzo as a starting point. There are many others here too and you need follow their advice to the T to get the most out of your repair process.

[memoryman]

I tested the rectifier diodes and sure enough one of them was shot so I replaced all four of them.While I was in there I replaced the filter caps(old amp so I already planned on that). Amp is functioning fine but kind of noisy.There is a hiss when the volume is down but it is not affected by volume adjustment. There is also a short buzz when the standby switch is flipped from run to standby. Thank you as I have leaned what a rectifier diode is and how to test them from this repair.

[Roly]

I tested the rectifier diodes and sure enough one of them was shot so I replaced all four of them.While I was in there I replaced the filter caps(old amp so I already planned on that). Amp is functioning fine but kind of noisy.There is a hiss when the volume is down but it is not affected by volume adjustment. There is also a short buzz when the standby switch is flipped from run to standby. Thank you as I have leaned what a rectifier diode is and how to test them from this repair.

Pardon my astonishment - not.    This sort of failure is quite common, and it was a good idea to renew all the diodes while you were at it.

A short buzz coming off standby is pretty normal - it's all the discharged capacitors down the HT/B+ supply line recharging.

There is a hiss when the volume is down but it is not affected by volume adjustment.

The hiss requires a few tests to try and isolate where it is coming from.

Plug a lead into Power Amp In and short it.  If this stops the hiss then it is coming from earlier in the amp, the preamp, if not it's arising in the power amp stages.

[Enzo]

Yes^^^^

There is no "the" volume control, each channel has its own post gain and pre gain controls.   Does turning ALL control to zero affect the noise in ANY way?   level or tone or anything?  Or does it remain untouched.   ANy control that affects the sound of a noise is after its source.


If the hiss does go away with ALL controls at zero, bring up ONE of the post controls.  ANy hiss?  urn it back down.  Now bring up the other one.  Hiss?  Back down.  Turn up the reverb control.  Hiss?

[Roly]

Or you could try tempting it with a mouse.

  Yessssssssssssss?


{I once found a valve amp in an old timber mill powder magazine, but when I tried to move it I found that it had a resident Diamond Python.}

[memoryman]

Please no ex wife pics, I'm under enough stress just trying to learn about this stuff. Allow me to be more articulate. This hum/hiss occurs when the standby switch is set to "on", with or without an instrument or cable connected to any of the four inputs.This sound is not affected by changes in the pre gain, post gain, or tone controls. By saying "Plug a lead into Power Amp In and short it." do you mean a guitar cord or what?

[Enzo]

Yes.

What he meant was plug something into the power amp in jack, a guitar cord will do, then short the tip to ground. A simple way is to touch the tip of the cord free end to the shell of the end plugged into the jack.  What I usually do is just plug a guitar into the jack and zero the guitar's volume control.  What all that does is first disconnect the signal (noise or otherwise) coming from the preamp, and also grounds the signal path at that point.   If the result still has noise, then the source is obviously after that jack, and so mostly must be the power amp.   If that stops the noise, then the noise must be coming from before that jack, ie. the preamp.

[Roly]

Yup.

Please no ex wife pics

I had one of these fellas co-habit with me for about the same length of time as my first wife, but not concurrently, and I thought they were both pretty good looking actually, 'tho Pi was a much better mouser.  Pythons are the gentle giants of the snake world and for all the years Pi would curl up on top of my monitor and watch me working he never once had a go at me, but after lights out he was awful mean to the mice.  The are many others I would not tolerate, such as Tiger snakes who are stroppy little buggers, are seriously venomous, and suffer from short snake syndrome and will chase you around the kitchen if the mood takes them.

[memoryman]

I shorted the lead by plugging my guitar in and turning the guitar volume down...same noise no change so it must be in the power section. How do you think I should proceed at this point?