#1
So my 6505+ Combo has a very strange problem. At first I thought all the symptoms were pointing to a bad standby switch. But then while the amp was on and I bumped it, i could hear the reverb tank! So with the amp on, you can bang it and hear reverb. But no matter what channel it is on, there is no signal. No amp noise at all! No hiss, nothing. I have reseated ALL of the tubes, and have used known cables and different speaker cabinets with no success. Whats could possibly be causing this?
#2
First thing to try is replacing a preamp tube, Buy one (I recommend a JJ ECC83S) and try it in every position,
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#3
Check that all the preamp tubes are lighting up. If they're not, you probably have overheated rectifier diodes. This is a known issue with the 6505+ combo and the fix is very simple.

Take the amp out of the chassis and check for any burnt areas around the rectifier diodes. If you're confident with working on electronics safely (you MUST discharge all the large caps on the amp as the charge they hold can potentially kill you if they discharge through your body) then it's a simple matter of taking the old burnt out diodes and replacing them. Being careful to check that the diodes are being soldered in with the correct polarity.

If you're not confident with doing the repair yourself, take the amp to a tech. But it doesn't harm anything to take the amp out of the chassis and checking for any burnt areas on the circuit board. As long as you don't start poking your fingers anywhere on it.
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Quote by Axelfox
Reeeeeeeeeeeeeeee
#5
Thanks for the responses everyone. I did change all the tubes and the front ones are not lighting up. The PI and Power tubes are just fine. So guess it's probably those diodes that (after researching all day) I see is somewhat of a common problem. I found an older thread on this forum that sounds like my exact issue so time to study up on how to discharge those caps safely. Looks like a a resistor and an aligator clip to the chasis is the way to go from a quick read but going to study more. 

On a side note - Can you recomend where/what to order for those DIODES? I dont have any electronic stores close to me so I am going to have to order them. What/where should I order? I am not going to break it open until I have the diodes to replace (just in case it is indeed them). Also what fuses are in there?

Thanks in advance,

Jerry

old thread i found that seems to be very helpful - https://www.ultimate-guitar.com/forum/showthread.php?t=1669373&page=2#70
Last edited by surjer at Jul 16, 2017,
#6
Quote by surjer

On a side note - Can you recomend where/what to order for those DIODES? I dont have any electronic stores close to me so I am going to have to order them. What/where should I order? I am not going to break it open until I have the diodes to replace (just in case it is indeed them). Also what fuses are in there?

Thanks in advance,

The schematic tells you everything. Read the bill of materials below.

http://www.thetubestore.com/lib/thetubestore/schematics/Peavey/Peavey-6505PLUS-112-Schematic.pdf

It's pointless ordering anything if you don't know what has blown. Take the amp chassis out of the cabinet. It's child's play as long as you don't be dumb and stick your fingers anywhere on the PCB without discharging the caps first.

Parts are available just about everywhere in the magical land of google.
Roses are red
Violets are blue
Omae wa mou
Shindeiru



Quote by Axelfox
Reeeeeeeeeeeeeeee
#9
Got the board out. Since the burn marks are around D24, D23, D18, D19 and C83, would you agree that is where I should start with replacing? Found an electronics store about an hour and a half away and I will be picking up the parts tomorrow. (Anything else I should grab while I am there?)