Tube Amp Gurus, need some help

[FX4 SAPPER]

I have a Peavey 6505+ head running through some vintage Fender cabs. Ive been playing with this setup for about 9 months now with no issues. Running at 4 ohms since im running two 8 ohm cabinets. Recently ive been having an issue with my lead channel on my head, to where after the amp has been on for a couple of minutes the channel loses volume/gain, almost like the volume knob on the guitar is down. Its not the guitar or cables and its only on the lead channel. I have contacted Peavey but they are closed for the holiday. Im leaning towards a bad tube possibly but it doesnt sound normal that its only happening after its been on instead of being immediately after i power on. The bias is still on its factory setting with the original tubes. Possible tube failure? resistor failure? This is a my first Tube amp and im a Tube Noob for sure. I know they can go at any time but yeah. Thanks

 

[trendkilllx]

tube amp

check to make sure tubes are all the way in the sockets. I have had a bad 6l6 but power was low all the time so may not be the tubes. Sounds like you already checked but make sure it is not the guitar or guitar cable. Also a dirty volume can do this but thinking your amp is probably kind of new. Thinking of getting a 6505+, currently using a older high gain crate 3500.

 

[cobracide]

Resistance is four ohms for two eight ohm cabinets in parallel, correct. You are running them in parallel, right? Anyhow, it does sound like one of your tubes is going. Really it could be anything amp related almost and it's just a guess until a tech tears it apart and starts debugging the issue. Do NOT mess with it yourself as tube amplifiers send a LOT of amps through the circuits. Find a very competent tech or send it to Peavey. The only other thing to suggest would be to just start replacing tubes and maybe you'll get lucky but that can be expensive too. Good suggestions above with checking the cord and other basic things.

 

[FX4 SAPPER]

check to make sure tubes are all the way in the sockets. I have had a bad 6l6 but power was low all the time so may not be the tubes. Sounds like you already checked but make sure it is not the guitar or guitar cable. Also a dirty volume can do this but thinking your amp is probably kind of new. Thinking of getting a 6505+, currently using a older high gain crate 3500.

Even with this issue i dont regret buying a 6505+ at all. I play out regularly with my band and it has allowed me to basically rid myself of my Boss eq/metal zone pedals. I actually dont even use any effects at all anymore lol i dont like molesting the amps sound. This amp sounds well even on the clean channel which a lot of people gripe about.

Resistance is four ohms for two eight ohm cabinets in parallel, correct. You are running them in parallel, right. Anyhow, it does sound like one of your tubes is going. Really it could be anything amp related almost and it's just a guess until a tech tears it apart and starts debugging the issue. Do NOT mess with it yourself as tube amplifiers send a LOT of amps through the circuits. Find a very competent tech or send it to Peavey. TH only other thing to suggest would be to just start replacing tubes and maybe you'll get lucky but that can be expensive too. Good suggestions above with checking the cord and other basic things.

Yeah that was my next thing, ive never messed with tubes but i do know a bit about the high amperage running through them, I have 6 12AX7 Preamp tubes and 4 6L6GC power amp tubes. I would assume that it would be best to start out with the Preamp tubes as its only happening on one channel?

also, i can switch between clean and crunch and those channels are fine so its isolated in the lead channel circuit.

 

[cobracide]

I have 6 12AX7 Preamp tubes and 4 6L6GC power amp tubes. I would assume that it would be best to start out with the Preamp tubes as its only happening on one channel?

Correct, start at the preamp. Besides, the tubes there will be cheaper. The tube models you listed are very common so you should have no issue finding them.

 

[FX4 SAPPER]

Correct, start at the preamp. Besides, the tubes there will be cheaper. The tube models you listed are very common so you should have no issue finding them.

Excellent. Thanks. Would you recommend a certain brand or just stick with the brands i have. its a combination of Ruby and Sovtek

 

[cobracide]

Heard good things about these guys but never bought from them. Talk to them, they seem like they can steer you right. Let me know.

Eurotubes

 

[cobracide]

As far as mixing - I wouldn't.

 

[trendkilllx]

I just picked up a boss gt10 used and although it has a bunch of pre-amp models I ended up only using the effects (chorus, delay, wah, tremlo). Took a bit of work to make sure overall tone of the amp was not being changed. I also heard some people complain about the clean sounds on the peavey, but sounds like some people like it, will have to try one out.

 

[FX4 SAPPER]

Heard good things about these guys but never bought from them. Talk to them, they seem like they can steer you right. Let me know.

Eurotubes

Looks like they have a fairly large selection of retube kits for alot of options for this amp. Thanks man :beer:

 

[cobracide]

No problem, good luck!

 

[cobracide]

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Approximately 22 miles away

 

[08 Z06 Dude]

As far as mixing - I wouldn't.

Because the 6505 uses preamp tubes for power inversion and buffering the effects loop, as well as the fact some players prefer a different chime from the clean channel, mixing preamp tubes is very popular with this amp.

I suggest checking this thread out as a starting point and good luck.

UG Community @ Ultimate-Guitar.Com - Help! The 6505+ Preamp Tube Layout...

 

[Mayo5]

Sounds like your transformer is gone, or on the way out, or one of the pre's died. Which slot is the pre for the lead assigned to? V2/V3? Check those tubes.

Cleaning and checking the input jacks is easy, as well as testing the tubes. Does that amp have external bias adjustment? If it's internal, and you don't know what you are doing, then TAKE IT TO A TECH!! You CAN be killed by messing with the amps.

Mixing pre's is fine, but power is not. I have a single channel 50w head, that I run different NOS pre's, and I run two 50's KT66 power tubes, and an NOS 5ar4 rect.

It could also be a number of internal things as well. If you still have warranty then take it in, and let them do it.

 

[FX4 SAPPER]

Cobracide thanks for the link to Eurotubes, i went over to my dads house, he has some older Fischer and Marantz stereo equipment and had a spare 6L6 laying around and low and behold, the V3 tube was bad. It was process of elimination, and i also found a bad solder joint as well so went ahead and fixed that. I never use the efects loop and thats where the bad solder joint was. I went ahead and got a matching 6L6GC and im back in action, also Peavey tech was awesome, they emailed a schematic, a lot of people said that certain manufacturers are reluctant to give out their Schematics for fear of copying, but they helped me out. if anyone needs or wants a copy for a 5150-II/6505-+ Amps let me know.

 

[FX4 SAPPER]

Sounds like your transformer is gone, or on the way out, or one of the pre's died. Which slot is the pre for the lead assigned to? V2/V3? Check those tubes.

Cleaning and checking the input jacks is easy, as well as testing the tubes. Does that amp have external bias adjustment? If it's internal, and you don't know what you are doing, then TAKE IT TO A TECH!! You CAN be killed by messing with the amps.

Mixing pre's is fine, but power is not. I have a single channel 50w head, that I run different NOS pre's, and I run two 50's KT66 power tubes, and an NOS 5ar4 rect.

It could also be a number of internal things as well. If you still have warranty then take it in, and let them do it.

Everything else checked out good, and the amp has an external bias. I bought the amp used from an older guy who said he only played it a few times, he had a collection of 5150 amps and judging by his music room a big EVH fan. He actually kept the amp in the plastic bag and box that it came in, and i got it for a steal basically brand new in mint shape, Tolex was pristine, no scratches on the finish or input jacks for $650.