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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 12:50 pm
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ok, got the Champ back from the tech today, he said a bad resistor and a bad cap. caused by a faulty power tube, I'm guessing the gray glass RCA I took out, here is pic of bad parts.Image


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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 12:54 pm
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played about a half hour with back off, at first no red plating, but at end it started , less than before, and chassis stays cool, used to be real hot!, ???Image


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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 12:59 pm
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The tech did not finish the job ? :(

Return amp back


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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 1:02 pm
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to give him credit, it was fine when I picked it up, got home and it started, after playing a while, guess it goes back to the shop. :(


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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 1:06 pm
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my56strat wrote:
to give him credit, it was fine when I picked it up, got home and it started, after playing a while, guess it goes back to the shop. :(



A tube may fail anytime . I never give a amp to a customer without testing / leaving at "ON" few hours .


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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 1:07 pm
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Before you do that, insert a known good 6V6GTA in the V2 socket then play it awhile. Never mind if it's a contemporary or vintage tube. So long as it's known to be serviceable. Play the amp then report back.

Arjay

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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 1:25 pm
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Ok, I have a brand new JJ 6V6, I pulled from a brand new reverb unit, I will give it a spin, then report back.


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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 1:42 pm
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my56strat wrote:
Ok, I have a brand new JJ 6V6, I pulled from a brand new reverb unit, I will give it a spin, then report back.


Excellent. I want to completely rule out the possibility of a bad batch of NOS bottles. I've dealt with a few of those situations myself.

Arjay

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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 2:22 pm
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Arjay, if I haven't said it before, You are the man! I guess I should think like Carl in Slingblade, and check the simplest things first("it aint got no gas in it")I would have felt like a jerk bringing it back to my tech.I put the brand new Fender issued Groovetube(not JJ)6V6 in and played a half hour, no redplating, chassis is completely cool to the touch. Looks like a bad NOS RCA 6V6 after all ,Thanks again man!Image


Last edited by my56strat on Tue Oct 13, 2015 4:48 pm, edited 1 time in total.

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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 3:01 pm
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It's been my pleasure, sir......anything to help you save a few bucks and perhaps some "face" when you brought a perfectly good amp back to your tech and insisted that he "fix" it this time.

Rawk on!

8)

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 3:06 pm
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my56strat wrote:
I would have felt like a jerk bringing it back to my tech.


The best tech could forget something

I put the brand new Fender issued Groovetube(not JJ)6V6 in and played a half hour, no redplating, chassis is completely cool to the touch. Looks like a bad NOS RCA 6V6 after all ,Thanks again man!


Your 6V6 could be not well matched with other one . The Groove Tube may be matched .

Keep the old 6V6


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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 3:12 pm
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BTW, don't discard those tubes just yet. It's possible that they might perform together fine in a Princeton Reverb or a Deluxe Reverb (any class AB1 amp). Single-ended amps can be brutal on power tubes because of the 100% duty cycle of the output stage (the tube is conducting continuously). As well, you might try each of them individually in your 6G15 reverb tank. They may function hokay in the power-pentode configuration of that circuit.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 4:23 pm
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If you have issues, again with new 6V6T tubes...

1.) Check the 1k-ohm, 1-watt dropping resistor in the power rail. It's on the side of the circuit board, where the cap can is located. This resistor insures that the screen of the 6V6GT is fed voltage a good 5-10VDC below the anode plate. Important for stability. I like metal oxide, 2 watt or wire-wound 5-watt resistors in the power rail.

2.) Check the 220k-ohm, 1/2-watt grid-to-ground resistor off the signal grid of the 6V6GT. It is the resistor next to the 0.02mfd cap --- above & between the two 12AX7 tube --- in the layout. This resistor helps set the idle bias. Replace with a 1/2-watt, metal oxide resistor.


http://bmamps.com/Schematics/fender/cha ... _schem.pdf


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Post subject: Re: red plating issue
Posted: Tue Oct 13, 2015 4:46 pm
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stratele52, there is only one 6v6 in the champ, so it can't be a match problem, and I won't toss the tubes though, I mark them and save them. Arjay, I pulled the new Groovetube 6v6 from my reverb unit because I run a RCA 6K6GT in there, but I will try this tube elsewhere. BMW2002Ti, I will try other NOS 6v6's in there eventually, and if it acts up I will get it back in the shop. thanks everyone.


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Post subject: Re: red plating issue
Posted: Wed Oct 14, 2015 1:26 am
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my56strat wrote:
stratele52, there is only one 6v6 in the champ, so it can't be a match problem, .


Oups :oops: One tube ..... Yes you are right .

The problem is worst ; the tech is unqualified , you can stop red plating with the right bias resistor .
Or
Redplating is a bias toooooo hot :lol:

What is the value of the cathode resistor the tech put ?


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