# Red Plating Tubes?



## Tone Chaser (Mar 2, 2014)

My Mesa F-100 works fine in the 60 watt mode. Sometimes when it is in the 100 watt mode, popping may start on the outer right 6L6 Tube, then cause the next 6L6 to the left (inner) to red plate. I always have shutdown quickly. When I fire up it then seems to work fine for a while, and things repeat. This happens with new tubes as well. The inner tubes run the 60 watt power and the outer pair boost to 100 watts. I have rolled the 4 tubes and 2 new tubes in matching pairs as they should.

What should I look for? Other than a service tech; I have a couple of amps that need to go in for service in the new year, when I can hopefully afford to do so. I just want to have an idea of what, why, and can I do something proactive. I just ran the amp long enough to see what was going on.


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## dcole (Oct 8, 2008)

I'd certainly take it into a tech to check out (I wouldn't actually cause I am that guy!). Sounds like something might be going in the bias circuit for that outer tube. If it doesn't red plate in 60 watt mode but does in the 100, then don't use the 100 until its been checked over.


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## Tone Chaser (Mar 2, 2014)

dcole said:


> I'd certainly take it into a tech to check out (I wouldn't actually cause I am that guy!). Sounds like something might be going in the bias circuit for that outer tube. If it doesn't red plate in 60 watt mode but does in the 100, then don't use the 100 until its been checked over.


Thanks, I don't need, or use that amp often, due to the weight and I am not aging well. I just like everything that I own working. I have lots of equipment to choose from and use.

It is nice to have a 100 watt beast in a 212 combo, except for the 100 pound weight that feels like 200 pounds. It is well built, versatile, and can play a low volume with great tone.


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## PTWamps (Aug 5, 2016)

I had a Bassman in with similar symptoms, where the tubes would start to red plate and heat up to the point where you had to turn off the amp to avoid something drastic happening. Turned out to be a failed bias capacitor -- basically, no control over the voltage on the plates of the output tubes. You would need a tech to fix it, but it might be worth suggesting to one that this is the possible problem.


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## nonreverb (Sep 19, 2006)

Since it seems to happen in 100watt mode only, it suggests an intermittent bias grid short or open condition somewhere to or on the right outermost socket affecting the bias to the adjacent tube in the process.
As stated, unless you're comfortable with more detailed investigation, best to take it to a competent tech.


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## Tone Chaser (Mar 2, 2014)

Thanks for all suggestions. I have never taken the time to look inside this amp, (other than tubes). I will likely pull the chassis and at least take a cautious, thorough, peek inside, looking for the obvious, if it is visible.

I may take it to the tech as a removed chassis. It is much lighter that way.


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## PTWamps (Aug 5, 2016)

Okay, but a note of caution: If it is indeed a bias issue, you are unlikely to see it merely by opening up the amp and looking inside. When a cap fails, it doesn't melt or turn black -- or anything obvious to the eye. You would need to pull the ends of components and check them with a multimeter. This is not something you should do yourself unless you are well-versed in the safety procedures for working on amps.


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## Tone Chaser (Mar 2, 2014)

I have not sent the amp in yet to be investigated. I will do that in the new year.

L&M gave me a set of 2 Mesa, supposedly new tubes that I installed in the primary, half power setting, and it was quite loud, but not really better than what was in the amp already.

I bought a set of 2 Mesa tubes from a local guy who had them for years, still in the box new. The price on the package was about $30 less than what L&M would charge, and he gave me an even better price. I installed these tubes in the primary, half power position and I was blown away with the power output increase. The two tubes in the half power setting, practically doubled the volume (in contrast to the 4 original tubes at 100 watts), with just two tubes installed. It was definitely louder than the four original tubes. There is no need for 4 tubes and 100 watts at home.

When I installed the "new" L&M supplied Mesa tubes in the empty spots to get 100 watts, there was a definite increase in volume.

It just gets me wondering about the quality of tubes available today vs. the new old stock I bought from a local guy who had them in case he needed them for backup. He has a beauty of a custom ordered $4,500 Mesa amp, that he barely played and was considering selling as well. He is one of those guys who prefers acoustic guitars.


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## Tone Chaser (Mar 2, 2014)

I took the Mesa back to L&M today. I will now find out how good the performance warranty that was given with the amp purchase really is. I gave my concerns for their requirement to ship the heavy, still in good cosmetic condition amp, from Windsor to Toronto, and back. In three weeks or so I will know.


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## losch79 (Jul 11, 2016)

I think you could have taken it over to Gibson's over in Roseville, Mi if the head is still under warranty. They have a fast turn around time and are certified Boogie repair station. I need to bring my Mark V over to them; I was concerned about having the head shipped as well.


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## Tone Chaser (Mar 2, 2014)

Thanks for the info losch79. I was looking for an independent that might be affordable and convenient. I was also trying to learn as much as possible about the ongoing problem. Mesa was quite helpful on the phone (several inquiries). The amp got better and better sounding, but the redplating got worse when switched to 100 watts, and some of the results from diagnosis, indicated something was causing the wrong power tubes to work the 60 watt setting. 

Bottom line, I bought the amp used on Black Friday from the local L&M for what I thought was a good price. The deal came with the one year performance warranty. I am a frugal guy, so L&M will do the work and shipping for free. I trust that their main repair depot is quite qualified. They assured me the shipping company will securely pack, to survive shipping.

We will see.


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## losch79 (Jul 11, 2016)

I tried to find someone local as well, but had no luck. I had someone recommend a local amp builder but they never bothered to get back to me after I contacted them several times. I found Mesa to be very helpful as well, they actually couldn't have been any nicer when I contacted them as well. I will let you know how things work out with Gibson's in Roseville, Mi; plus it is close to Guitar Centre so that is always a win.

I haven't been to L&M in over a year now... I guess I should check out the Walker Road location and see what used gear they have in stock.


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## Tone Chaser (Mar 2, 2014)

Update: I got a call from Yorkville Sound today from the tech working on my Mesa F-100.

I sent the amp with an explanation of what was going on. I sent the amp with the 2 blown 6L6 Mesa tube wrapped up loose inside the amp, and 2 working Mesa 6L6 tubes installed where the amp worked best in the 60 watt setting. There is no red plating when there are two 6L6 tubes in the middle, the two outer tube socket empty. Mesa told me that all 4 tubes must be in the amp to run properly. They also told me that the 60 watt setting works with the two outside sockets/tubes; not the middle two... , so something is wrong, send it in. I spent a month making sure what worked, what didn't work, what a set of 4 new Mesa 6L6 tubes would do, what a set of 4 new JJ 6L6 tubes will do. Basically, at the 100 watt setting, new tubes will make the loud popping noises and red plating happen within minutes with the new Mesa tubes, and within seconds with the new JJ 6L6 tubes.

The tech must have spent a couple of minutes looking at the old tubes, which had loose debris and parts in them; and he called to tell me that I need new tubes.

I told him I had two new sets of tubes, I spent a month sorting out with 3 calls to Mesa, and this is what Mesa told me, and what my local L&M agreed I should send to the repair depot. Why should I send my new tubes; they might disappear? I was assured that they had their own tubes to do diagnosis.

The repair guy told me the amp works fine with new tubes and that it is easy to incorrectly install tubes. He also told me that Mesa is wrong about which tubes run the 60 watt setting. But he will leave the amp running for 24 hours to prove he is right about his diagnosis.

I asked him to plug in a guitar, switch the channels. It should happen quicker on the driven channel. I also told him that I have installed tubes since the '60's, in TV's, radios, hi fi stereos, and tube amps. I am not an idiot.

The repair tech also said that he can't warranty the work without installing new tubes and charging me for tubes. He didn't do any work. He didn't do any diagnosis.

I am expecting the amp returned unrepaired.


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## nonreverb (Sep 19, 2006)

Too bad you're not in my neck of the woods. I'm the Mesa service center in Ottawa and I'd look after you.


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## Tone Chaser (Mar 2, 2014)

Thanks nonreverb, Mesa rambled off London and Ottawa as other available shops. I am sure yours was the Ottawa authorized service.

The email came late on Friday, saying that the F100 was repaired, and there is a charged for tubes. I got the amp back Saturday with a bill for new tubes. Funny thing is that the amp was brought out to the counter and plugged in, switched on, to prove it works.

I got down and looked into the back of the amp, and there were no power tubes. Further investigation found 3 of the 4 original tubes in a bag, at the bottom of the amp. No other tubes to be found. L&M Windsor, put 2 of the used matching tubes in and got another set out of the drawer to install. It worked. I know that the two original tubes were seriously down on power, but still worked.

Yorkville spent 57 minutes on the amp with no written record of what was done.

The amp worked, so I paid for 2 more tubes and went home. I ran the amp for a couple of days with the 2 used weak tubes and 2 new tubes. The used tubes were installed in the center primary sockets, and the new ones in the outer sockets. It was down on power but worked. The next day I reversed the tube positions and it was dynamically louder.

I used the amp every day this week, and rolled in a set of 2 new Mesa tubes that I previously bought and tried. The red plating was back. I finally had enough matching yellow tubes to roll as a matched set to eliminated the faulty tube. Found it!

I called Mesa for the fourth time, they are sending me 2 new matching sets of tubes, next week.


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## Joey D. (Oct 16, 2006)

Don't know if it's of any help but I can't recommend Jeff Larocque enough. He's works out of Picker's Alley in Sarnia but if you can make it Chatham and drop it off at Frank's Music they bring amps to Jeff on a regular basis.


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## Joey D. (Oct 16, 2006)

*double post


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## nonreverb (Sep 19, 2006)

Well done! Although the service center handling your repair should have caught that.


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## nonreverb (Sep 19, 2006)

double post..


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## jb welder (Sep 14, 2010)

Was there no time that you tried a set of 4 new matched tubes, right from the beginning?
I'm sorry you had to go through all this. Obviously the guy you spoke to at Mesa that said there was a fault because the inner pair was doing what the outer pair should do and it needed to be sent in was wrong. That's not even a fault that could occur unless someone got in there and rewired it.
It's hard to fault the Yorkville guy if it turned out to be a tube issue anyway.
Once again, it really sucks that you had to go through all this, glad to hear you got it sorted out!


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## Tone Chaser (Mar 2, 2014)

Thanks jb. I did try 4 new JJ 6L6 tubes that were supposed to be a matched set. They red plated in a flash. I received these JJ tubes unpackaged. I now realized that they may be matched pairs, rather than matched set of four. After rolling them last week, 2 at a time, I found the matched sets. A matched set of two JJ's will work with a matched set of Mesa in the correct low and high power sockets. The JJ tubes are powerful, loud, and articulate. They have a good sound with the amp, different flavor than the Mesa tubes.

Bottom line is know for sure which tubes are a match. The JJ tubes are now marked and work, after I graded them with the knowledge from the school of hard knocks. Also inner sockets are primary, outer sockets secondary.

The new original pair of Mesa yellow tubes; either one is defective or not a match. The second set of yellow Mesa tubes gave me something to work with and determine the faulty tube.

My biggest fear in sending the amp with all my tubes, is the loss of a few hundred dollars, based on my lack of trust, no direct contact with who is the repair person, and shipping. The amp was to be shipped with the new tubes and I was to be billed for them. There were no new tubes. My trust issues are real. The used tubes were likely never even tested, other than visually.

I also never had a major (interactive) tube issue like this in 50 years. Mesa technical information also says that fuses should have blown and been replaced when you have this kind of tube failure. Same fuse in there. Maybe I should replace that as well.


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## Lemmy Hangslong (May 11, 2006)

9 out of 10 times it's gonna be tubes


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