HELLLLLLP!!!! Serious Amp Woes.

[VoiceX3]

I have a 5150 modded with the integrated quad power tube set (2x6l6, 2xKT88) which has sounded monstrous until the end of my show Friday night. I thought I noticed a change, but had to finish up, then had to break down. Saturday I plugged it in, warmed it up and fired it up. WTF? Now on the lead channel the pre gain is like the volume on the clean channel and the post gain is like a super distortion control. The more you drive it the fuzzier and gets kinda creamy (I can't think of a better adjective) around 8. All the tubes look to be operating normally.

What the hell is going on????

Fortunately, my other guitarist has a backup VHT to loan me until repairs or replacement.

[Inearthed]

If I remember correctly KT-88 + 5150 = Not good.

[VoiceX3]

Well this is the set I bought.

http://www.eurotubes.com/euro-kc.htm

It's been great since May when I did the swap.

[jgcable]

Did you bias the amp??

[VoiceX3]

No, the quad kit didn't require it.

[Inearthed]

Amp techs on the HCAF pretty much were saying that you could damage your amp pretty bad with KT88's

[toejam]

Weird. I've never heard of KT88s being used in those.
I'd use KT66s in it, as they're pretty much a direct replacement for the 6L6s.

[VoiceX3]

I had a lengthy conversation with Bob (from Eurotubes) about this before I bought and installed the set. This set is specifically for within operating specs for the 5150, and like I said, the sound of this thing is monstrous when operating correctly. I checked and they actually went into the amp the last weekend in April and I never had a problem. People from Philly to Arlington Texas have complimented me on my sound/tone and my rig is just the 5150 and 2 4x12 8ohm peavey cabs with loaded with 75watt Celestians.

Granted, this head is old. One of the very first 5150's without the block letters and has seen tons of gigging. So any other problem may be just from regular abuse....I just find these symptoms to be unique and wonderred if anyone ever had an amp do anything like this?

Basically, if it's gonna cost a ton to fix, I promised myself that the next amp I buy will be a Uber and I need to decide what to do before putting out any cash. (not that I'd sell the 5150, it'll go on a shelf to return another day if it's that bad off as it sits right now.)

[MSGfan]

Worse sounding set of new tubes I ever bought were from Eurotubes, Bob told me he knew exactly what I needed for my Mesa Mark IIC+ and they sounded like Dog Sh*t!! One preamp tube died just after I could get a refund or exchange! I tried the 6L6's in one of my Dual Rectos and they sounded like Crap in that amp also. I finally sold the JJ 6L6's on ebay and lost about $30.00 on them. Needless to say I'll Never buy JJ tubes from EuroTubes again!! I only deal with Doug at Dougstubes.com got some great SED's from him and he's a nice guy to chat with also.

[DTP]

I read on Bob's site how he was dissing Roger Crimm of Peavey when he said that it could cause problems, maybe RC was right, if that's what's causing the problems.

J.

[jgcable]

I have never had a problem with Bob from Eurotubes. There are many things that could cause your 5150 to crap out. Filter caps and resistor grids are pretty common. I just dumped $350.00 into my block letter 5150. It was money well spent. Its a GREAT AMP. If you like your 5150 and it sounds good, put the money into it and get it repaired. They really are awesome amps.

[Inearthed]

I had a lengthy conversation with Bob (from Eurotubes) about this before I bought and installed the set. This set is specifically for within operating specs for the 5150, and like I said, the sound of this thing is monstrous when operating correctly. I checked and they actually went into the amp the last weekend in April and I never had a problem. People from Philly to Arlington Texas have complimented me on my sound/tone and my rig is just the 5150 and 2 4x12 8ohm peavey cabs with loaded with 75watt Celestians.

Granted, this head is old. One of the very first 5150's without the block letters and has seen tons of gigging. So any other problem may be just from regular abuse....I just find these symptoms to be unique and wonderred if anyone ever had an amp do anything like this?

Basically, if it's gonna cost a ton to fix, I promised myself that the next amp I buy will be a Uber and I need to decide what to do before putting out any cash. (not that I'd sell the 5150, it'll go on a shelf to return another day if it's that bad off as it sits right now.)

Not to be rude but at the end of the day Bob is still trying to sell you something. I've bought tubes from Bob and been satisfied, but I would definitely NOT buy a mixed tube set like that from him, especially after reading the horror stories and reading amp builders / technicians basically say "Yeah, if you do that you're playing with fire."

I'd call Bob and ask him and see what he says, honestly.

[VoiceX3]

Well, I got the reply to my E-Mail pretty quick:

"Hi Jim-
This is likely a single preamp tube going south, in which case we can most likely warrantee it for you. Although you may simply have a tube that is not seated well and/or not making a good contact in the socket. The first thing to do especially if you did not clean the sockets is to reseat the preamp tubes. If this does not cure the problem then replace the preamp tubes one at a time with your old tubes. If a tube has failed it will most likely be one half of one preamp tube and you will quickly find it.


The failure rate in the field runs right at about .5% so we know that one out of about 150 to 200 of them will fail which we feel is exceptional.



Let us know how this works."

I'm gonna try their suggestion tomorrow. I am pleasantly surprised with how quickly they got back to me and that they were willing to help. So, we'll see. I hope so because I love my sound.