Should I continue to put money in this amp?

[GoldenVulture]

I thought that too, but the bias will hold at the 18ma recommend by Lee Jackson. The tubes just started changing color last night. I just want to believe it's tubes. I've seen the same thing before.

At what point did you measure the bias ?

Is there  a model name/number  other than " Crate Stealth 50w head " ?

I was trying to find a schematic for it but couldn't find anything with Stealth in the name. I did find a big repository of crate stuff.

[Oinkus]

The Prosonic has the best distortion ever put into an amp , just had some odd flaws built into it by Fender. The power tubes and rectifier tubes had large patches of silver on the inside of the glass too. I imagine it is one of the million caps in it. Swapped out every preamp tube one at a time. There are not any decent amp techs around here for one and zero dollars will never get any work done. I had a guy that fixed my Trace Elliot but he is a tool , he felt he shouldn't have to pay my standard fee for a setup because he worked on my amp. Then he got all bent out of shape wanting the action lowered more when it was down as far as the really worn frets would allow without buzzing all over the fretboard ? He also thinks the pickups should be actually touching the strings to get "the most" sound out of the guitar? Not trying to be harsh but the guy was clutching the guitar to himself like it was a life buoy , never seen so much pressure applied to the body of a guitar with an elbow it looked painful. BTW it was a Mex Tele with a maple board which I don't care for at all but played it for well over an hour because it played really well. Get a stick and beat me to death please?

[GoldenVulture]

The power tubes and rectifier tubes had large patches of silver on the inside of the glass too

That tube is fine and a common thing on most if not all RCA 6L6GC tubes.

And many other tubes. It's usually the result of the manufacturing process.

What are the amps problems/symptoms ?


Note: Swapping tubes around or replacing them is not going to solve a lot of amp problems. It's a methodology purported at SD and it is not particularly logical or practical one. It can also be an expensive one. Tubes don't die very easily unless they're being used constantly. Even then you should get years out of most of them. It's usually something peripheral to the valves that affects their performance or the performance of the amp.
EG: redplating is usually your bias up the creek. Internal damage and shorting will produce red plating too but that's usuall a result of shock/vibration damage to the valve. [ the amp got dropped ] A dying valve won't start redplating, it'll just start sounding pissy and soft.

[karpathion]

At what point did you measure the bias ?

Is there  a model name/number  other than " Crate Stealth 50w head " ?

I was trying to find a schematic for it but couldn't find anything with Stealth in the name. I did find a big repository of crate stuff.

The model is GT50. As far as bias goes, I'm just testing the negative bias. I checked it yesterday after the screw up.

This morning, I pulled all the tubes, and cleaned all the sockets with contact cleaner. I pulled the tubes in and out a few times for each, changed their positions.

I'm not noticing any drop in power, power tubes don't appear to be so dark today. I've been playing it at about 40% volume for over an hour now. Everything seems fine ATM.

[Oinkus]

The silver was not on the tubes when I put them in the amp or when I swapped out a couple preamp tubes a year or more ago. It was making popping sputtering sounds with no headroom on the clean channel distorting. Opening it up and looking at it there is nothing that is apparently blown up but it now has very low volume and none of the other sounds.

[karpathion]

I've seen that before, inside the tubes. I had a Peavey Ranger that did that within an hour of putting new tubes in it. The fuse would pop, and 1 or 2 of the tubes would look like that. I never figured out. Ended up throwing that amp in a dumpster.

[GoldenVulture]

OinkusThe silver was not on the tubes when I put them in the amp or when I swapped out a couple preamp tubes a year or more ago. It was making popping sputtering sounds with no headroom on the clean channel distorting. Opening it up and looking at it there is nothing that is apparently blown up but it now has very low volume and none of the other sounds.

Seems a bit like they're getting too much HT [ Plate voltage ] Do they get very hot , hotter than usual ?

Spots appearing after use is common too. It's something to do with a gas they put in them to absorb anything leftover from the vacuum process. it solidifies on the glass. If it's just black and seems rather a lot it's probably fucking out.

The lack of volume is indicative of dying  valves as is the frypan popping [ if that's what it sounded like? ]
Excessive blackening suggests components other than the valve is causing it to fuck out.

There's a relationship between the bias voltage and the HT. either going astray can cause redplating.

[Oinkus]

This amp has always run pretty hot as far as actual heat radiating from the back of it. Not going to throw away an amp I paid $1400 for 21 years ago for any reason. Most I have ever spent in my life on a single piece of gear. Oh yeah and $42 bucks for a cover because it was pouring buckets when I got it. I would automatically assume it was a cap issue because I had that problem before and a hack worked on it. I am not sure if he even knew how to bias an amplifier. The actual bis adjust was turned on its side because the newer caps were much bigger then the old blown ones. Looks like he put a couple resistors in it too. I tried taking pics but my camera sux they are on the photobucket page http://s1195.photobucket.com/user/KenoMa...t=3&page=1

[GoldenVulture]

This amp has always run pretty hot as far as actual heat radiating from the back of it. Not going to throw away an amp I paid $1400 for 21 years ago for any reason. Most I have ever spent in my life on a single piece of gear. Oh yeah and $42 bucks for a cover because it was pouring buckets when I got it. I would automatically assume it was a cap issue because I had that problem before and a hack worked on it. I am not sure if he even knew how to bias an amplifier. The actual bis adjust was turned on its side because the newer caps were much bigger then the old blown ones. Looks like he put a couple resistors in it too. I tried taking pics but my camera sux they are on the photobucket page http://s1195.photobucket.com/user/KenoMa...t=3&page=1

How long ago was the hack cap job ? Dying caps tend to pop intermittently  or pop away and suddenly stop, as they lose their ability to store and feed power consistently. That can cause sudden volume drops too.

Has your camera got a macro function ? It's best for close ups.
The pic from the distance is the best at the moment.
[img=600x500][/img]

[Oinkus]

Crappy cheapo cam is all I have without any functions whatsoever. Been several years since the work maybe 9 ? I found the cap by sight the first time it was blown up good . Nothing is bulging or obvious this time. Only thing that I can see now is where it was resoldered before , brown on the PCB. Those big gray ones on the right side and the 2 blue ones to the right if I remember correctly and a few resistors too. The guy told me he wouldn't warranty the work if I used JJ tubes had never heard of the company ? Oh yeah and he tested it buy playing a CD through it at volume all day long sheesh.