If it was a cap you could probably smell it. Even if there's no smell, I'd have to look at the filter caps to start with.....if it's gone you can see it when you take the chassis outta the cab and look at them.

If that ain't it, holler back and someone here can probably help find out what it is.

Rod

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Rod's Place

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Rod's Place

If it's in both, I would certainly heed the advice on your power tubes and check the PI tube....that may be your problem.

I would bet the farm that it's either a tube problem which is easily fixed, or a solder joint problem, which is easier to fix.

Oh, and when you find that rectifier tube please e-mail me it's approx location, I can't seem to find the rectifier tube in any of my twin reverbs......

PMS
Britney's Louisiana Love Dumplin'

[This message was edited by Patrick Smith on 01 November 2001 at 08:04 AM.]

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Rod's Place

PMS

Good Luck!
Matt Farrow
Pharaoh Amplifiers

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Matt Farrow
Marlen 9-string 6+2
Kustom K150

http://www.skybolt6.com/pharaohamps

At any rate, I always keep spare caps, tubes etc... I popped some caps in while everyone else smoked and we took off again.

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Rod's Place

Robert, let us know what you find out when they get it all fixed up.

Good luck with the amp - it shouldn't cost too much to fix, at least it wouldn't if I were fixing it, can't speak for other techs.

Matt Farrow
Pharaoh Amplifiers

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Matt Farrow
Marlen 9-string 6+2
Kustom K150

http://www.skybolt6.com/pharaohamps

A tube slowly burns Itself up. If you turn one on for only a half hour at a time the deposits will build up and It will start frying bacon. Ask your repair man about how to make tubes last longer.

I always thought of the standby switch as a fast way of coming up to power without the filament warm up period normally required. I changed tubes the same way I change strings.
On a regular basis and not like the old joke; when they break. I still do the same with my Tube-Fex. If I waited until they ran down I know I'd be caught with my drawers down some night in the middle of a song. No need for that when a couple dollars worth of tubes would avoid that risk.

I once had someone write to me that the standby switch was to save "Filter Caps." All I could think was : Huh ??

I used to take old tubes apart and examine them. I've seen hot spot on plates and breaks in the screen or control grids but never any deposits. You can see the errosion of the cathode coating but I wouldn't consider that a deposit. I would attribute the frying sounds so commonly reffered to as intra-elemental gases probably caused by leakage in the tube seal. This would also affect the inter element capacitance values and change the tube parameters a bunch.

They went so far as to say, If you use your amp on and off during the day and evening, to leave It on all the time, but put In standby when not using It.

I won't say the person that wrote the article you cite is or isn't technical. I've never seen the article.

quote:

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Do pre-amp tubes need to be replaced more often than power tubes?

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No,in general,I wouldn't change a tube out just because it has a little time on it. If it is noise,gassy,or obviously exhibiting a low gain problem,then one,of course,would replace it.

Someone stated above about the blue glow in the power tubes. At a high plate voltage this is completly normal. Now, a red plate element IS NOT NORMAL.

I,like Mr.Stoner,grew up on tube stuff and today,I find many mis-beliefs by the younger generation about tube circuits. Many techs now-a-days haven't even had any training in tubes. There is a reason tube amps sound better than SS amps. While I won't go into this area,the techs that understand tubes,know where I'm comming from.

Replaceing tubes just because (bla,bla).......is a myth. Most of you don't remember when RCA, G.E. and other brand tubes were abound. they were good tubes,made here in the U.S.A. The crap we are forced to purchase from overseas today,is floor-sweepings.

Please send me all your tubes you have changes out for new ones !!!

Rule of thumb.....
Unless the amp is giving you a problem.... leave the tubes along !!

Maybe it's a cost factor that is most influential in the matter and while I don't change strings like this I have seen bands that restring before each show. That would be cost prohibitive for me but on the other hand I don't wait for one to fail either. There has to be some middle ground in both matters and background and the situation have a lot to do with it.

If you are just practicing at home is one thing but playing a show for a top name act is something else. You act accordingly.

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sho-bud,session 500,american standard strat,shecter tele,peavy classic 50

Don't claim to be a tube amp expert, but I've always been able to keep my own working,
and what he said makes sense to me.

When you said the tubes In your power amps at the station would last for years, isn't that telling us something.

Bob Carlson.

[This message was edited by Bob Carlson on 11 November 2001 at 08:04 PM.]

Have you looked at the way the tubes are mounted in your Fender Twin? They are upside down. If the flakes fall from the cathode..they fall to the top of the tube, and can collect on the mica insulating washers around the plate and grid structure...maybe causing some popping and noise...maybe not.
Most tube guitar amps have the tubes upside down.
Over the life of a tube certainly part of the cathode may become "dead" and in some cases flake off. Unless you are into rejuvenating tubes (a whole subject in itself) it is better to just replace the tube.
Paul, There is no rational accounting for the way the military does things. Like Jack, I've found factory fresh tubes that were bad. There is no absolutely accurate way to predict when a tube will go on on you. Back in the days of analog, tube type television, we kept accurate records of our tubes parameters, measureing the camera tubes once a month and replacing any that had started to weaken. However, we never replaced all at once, because there is drift and aging to be accounted for and a completely retubed camera would be unstable for several days and require constant adjustment.
I agree, when you are with a Major Act you want to be in the best shape. I was never in that league, but when I played for money, I always carried a spare set of tubes for the amp, just as I carried spare patch cords.
You probably had one or more complete amps as back up.
In tube techonlogy, it is fun to discuss things like this...but there are no absolutes. Too many variables in the tubes themselves, in the equipment and in the way the equipment is used.
Bob, I'm not sure what you ment by your last comment?
Blake

[This message was edited by Blake Hawkins on 12 November 2001 at 06:35 AM.]

I recall walking from WRAL studio engineering to the studio, very carefully carrying a Vidicon tube to be replaced in a camera. Those you replaced based on degradation of any gun and not on a routine basis. Redundancy of cameras was our CYA.

You also reminded me of something from my military past. We used to have to fill out EFRs (Electronic Failure Reports.) and your spare replenishmnet program was based on your failure trends. I never made out an EFR on a fuse because I felt that when it blew, it didn't fail; IT WORKED ! That was what it was supposed to do. If it didn't blow and the circuits following it were destroyed; then it FAILED !

When I ran out of fuses I called for bench stock and was refused. You show no consumption. And like so many others I learned the hard way; You don't mess with the system or you loose. It isn't nice to fool with Father USAF !!