Prs custom 20 tube replacement and a problem I had with mine

Vexed73

Vexed73

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Apr 2, 2017
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Just wondering where new tubes should be biased at and what brands do people like? Bought a demo model from sweetwater and it did not come with the manual.

Also had a problem the lead channel would not work and boost function did not work. Light would come on when switching channels but no sound and clean was perfect. Tried different preamp tubes and could hear a faint sound and static while turning knobs.

After a while I realised that mashing on top of cabinet it would cut in. So screwed in the chassis bolts as they were loose! Thought it was working but nope. Scratched head and loosened a bit and found the chasis bolt closest to lead channel if touched with screw driver or finger the channel would work.

Took chasis out and everything looked beautiful! Looked at cabinet and part of the foil tape was bent over so layed the tape flat with a finger and bolted it back in and everything works fine.

I am guessing that ground/sheilding was necessary to completely switch into the lead channel. The boist also worked after that. Anyone have an idea about that?
Debating whether I should keep it as I paid too much if it is going to be troublesome. Played it loud and for 2 hours after fixing so probably be fine. Either way love to hear your opinions.
 
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Sounds like you fixed it. It also sounds like there was a short -- it may not have been at the tape, you may have fixed it just by taking it out of the chassis and putting it back in. Or perhaps a tube was not seated properly. This often happens during shipping.

Regarding biasing, I would email or call customer service. There's probably not much you need besides the bias and how to bias, and ...was there a footswitch? Is there a place for a footswitch? Most Sewell designs are biased around 30, but I would still ask customer service first.

Regarding tubes, I would ask customer service as well. And then use only those.
 
Yeah it came with original packing and footswitch just not the owners manual or hang things. Really weird how touching the screw made it work and a bit scary. Lol
 
Dusty is right about the bias. The PRS amps that I have/had have all been 30. Still, I would email customer service to make sure. Also wouldn't hurt to mention your issue in that email. Although, it sounds like you have corrected it. Crank it loud, and enjoy!
 
Everything is working but seems a little too loud to be "right" are your amps this loud on gain channel with nothing plugged in? Theres a crackle in there but dont think it was picked up in video.
 
Vexed73 said:
Everything is working but seems a little too loud to be "right" are your amps this loud on gain channel with nothing plugged in? Theres a crackle in there but dont think it was picked up in video.
Click to expand...
Unless your wife is running the vacuum cleaner in the hallway right outside your music room, you've got a problem. Les is right though, don't ship it back without checking the tubes. They can test great at the factory, get bounced a couple times in shipping and fail. Check the tubes with the usual "one at a time with a known good tube" swap method.
 
Yeah checked tubes and sent back. Be a while til they get another in stock though. Nice tone in this amp might get another eventually.
 
Sorry to hear that. I bet you love it when you get the next one. I had a belated and major revelation with my Custom 50 tonight. A legit "holy crap" revelation. I'd love a 20 head or combo after what I got tonight. I'd drop my Red Fang Alnico in that thing and just play Robin Trower all day!
 
I boosted the lead channel with a Wampler Tumnus the other day... holy cow! The sound was really lively, added just enough cut and aggression. I'm sure most Klonish pedals would do the job... but it was cool.
 
Vexed73 said:
Everything is working but seems a little too loud to be "right" are your amps this loud on gain channel with nothing plugged in? Theres a crackle in there but dont think it was picked up in video.
Click to expand...

That is a lot of noise. On the other hand, you've got the gain CRANKED and the master pretty high too. The Custom amps have a ton of gain on the lead channel, I've never used mine turned mine up past about 1 o'clock, and master at noon as you have yours is getting close to the actual volume ceiling of the amp, if it tapers similar to the 50, I would say 2 o'clock is about the max. Definitely go through your preamp tubes, then power tubes, could be a gain stage, phase inverter. Also, it could be a power issue from your electrical, if possible try power in a different room, or even a different building, if you've not already.

If you'd like, I can set mine up similar to your settings and see how it does with noise when I get home later tonight.
 
andy474x said:
I boosted the lead channel with a Wampler Tumnus the other day... holy cow! The sound was really lively, added just enough cut and aggression. I'm sure most Klonish pedals would do the job... but it was cool.
Click to expand...

I was ready to buy one of those then saw the Pete Thorn demo of the new Deluxe model. It sounded great!
 
Sorry you sent it back. I bought a Custom 20 head that went back to the factory once. Yeah, the gain channel was/is a bit noisy for me, but it sounds fantastic. I'm strictly a basement player and am always within 6-8 feet of the amp. The clean channel is fairly righteous, too. I won't part with this amp.
If you find another, snatch it up.
 
From the clip, sounds like a preamp tube problem. IME, noise issues are usually tube related and easily solved with a low noise "balanced" replacement

My Matchless Indy was a white noise terrorist until I put balanced replacements into V1 and the PI slot. High gain Mesa's also tend to go "white" when preamp glass goes out of whack, but easily fixed

Hope you find a good replacement amp - I am still gassing for a Custom 50, but getting them in the UK is a nightmare these days. And for whatever reason, HX/DA's are unavailabe to the UK market .. word from the distributor direct :mad::mad:
 
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