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Posts: 5881
Location: Colorado Rocky Mountains | Until last evening, I had been using my '66 Bandmaster amp almost exclusively. Then last night after it powered up, I had only about 10% of the previous volume, and no depth whatsoever. Time for a tube change? Anybody know which one? |
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December 2005
Posts: 109
Location: Alabama | Try www.ax84.com for tube amp info. They have a number of forums for OT stuff and surely some folks will have suggestions of how to trouble shoot your problem. They also have some good safety tips for dealing with amps. |
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Posts: 10581
Location: NJ | check the power tubes first. should be a pair of 6l6's then the preamp tubes. 12ax7 or 7025 and probably a 12at or au7 if it has reverb.
if a tube looks white it is bad or if it looks like it has a funny glow.
you may have blew the bias or need new filter caps. |
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April 2006
Posts: 2491
Location: Copenhagen Denmark | Could be anything , most likely a capacitor gone ,doubt if it`s a valve.....anyways , Time to see a competent repairman :)
( Valve equipment is not for novices ,can be very Dangerous indeed ) :)
Vic |
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Posts: 13303
Location: Latitude 39.56819, Longitude -105.080066 | Brad, call Scooter Barnes. He is a master at working on old Fender tube amps...and very reasonable to boot! |
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Posts: 54
Location: Kingston Ontario | Which model of Bandmaster do you have? It should be marked on the paper label inside the head. It could be a 5E7 or a 6G7. The 6G7 has vibrato.
Let me know which model you have and I can probably help you out.
Not good to speculate until I know what you have.
Tom (Formerly The Amp DR. ) |
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Location: Colorado Rocky Mountains | Thanks much for the advice.
StephenT, check for a PM. |
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Location: Colorado Rocky Mountains | Cantom: 1966 blackface, stacked, with Vibrato. This is it:
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Posts: 54
Location: Kingston Ontario | I've got the schematic for your Bandmaster. I have do an early gig this morning but I'll get back to you this afternoon with some tips.
Tom |
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July 2005
Posts: 354
Location: Flushing, MI | Sounds like a power tube problem to me. Yank and replace the two 6L6's and see if that fixes the problem.
Also of major importance, have your electrolytic capacitors been changed? They're supposed to be changed every 15 to 20 years. If they're over 15 years old, then they're on borrowed time. You absolutely do NOT want your electrolytics to die while using your amp, as it may very well take out other expensive parts (like a transformer).
I have owned several old Fenders, and still own a 69 Deluxe Reverb, and a 73 Pro Reverb. Once you've re-capped 'em, and keep the output tubes changed (about once a year), then you've got a friend for life. They'll outlast your grandchildren! |
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January 2006
Posts: 5881
Location: Colorado Rocky Mountains | I checked (what I believe are) the two power tubes last night. They both light up with the power on switch, the first more so than the second. When I activate the standby switch, the first tube jumps to life with a bright blue glow. It looks to be a newer Groove tube that, if I recall correctly, the former owner installed just before selling it a little over a year ago. The second power tube also turns slightly blue, but remains very faint. I removed it and discovered it is a Russian Sovtek 5881WXT, whatever that is. It looks fine out of the head, clean with no burn marks. I'll replace it with a new 6L6 and see if that solves the problem. If not, I've already lined up a local amp tech to go through and check everything out. Thanks for the tip on the capacitors, Trago. |
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Posts: 354
Location: Flushing, MI | You should always replace ALL power tubes whenever you change them (as opposed to the preamp tubes - where you only replace the problematic tubes).
Also, just in case you don't already know, NEVER let an amp tech talk you into changing your preamp and output tubes. The output tubes are changed on an annual basis, depending upon how much use, and how hard you use it. The preamp tubes stay put unless there's a problem. You keep good preamp tubes in there for DECADES and never let 'em go.
But DEFINATELY change the other power (output) tube as well. You don't just change the problematic tube in an output section, since they work in tandem, and wear in tandem with each other.
I hate to see friends go to an amp tech and get screwed because they don't know a few things. Many good preamp tubes have been lost that way ("Oh yeah, we gotta change THOSE too y'know..."). |
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January 2006
Posts: 5881
Location: Colorado Rocky Mountains | Thanks, Targo. Good information. Since the power tubes are only sold in pairs, I figured they are to be replaced in pairs, which I did. No help. The problem remains, so I'll take it in next week. StephenT recommends the amp tech and I trust his judgment. I'll post the resolution next week when I get it back. |
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Posts: 354
Location: Flushing, MI | No help. The problem remains Dagnabbit! I thought fer SURE that would solve the problem.
I've had amps do that on the gig. They'd sound great all night, and then - in the middle of a set - all of a sudden I have about 1/10th the power. Turn it to 10, and it's still not loud enough. I'd go out to the car and get the spare 6L6's out of the glove box, take the old ones, out, put the new ones in, WHAM - back in business!
Soooooo..... if it's a case of your caps dying then DON'T TURN YOUR AMP ON ANYMORE - until you see a qualified tech. Be wary of the "tech" guys that work at your average music store (see above).
Where exactly are you located at? Maybe I can help find a good one in your area.
I go through Tim Swartz in Lansing, Michigan. He is DA MAN! with old Fenders. |
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July 2005
Posts: 354
Location: Flushing, MI | Here's a link to a few qualified amp techs in Colorado. I don't know any of them personally, but this "Lord Valve" person is quite well known all over the internet. He's also supposedly THE place to shop for tubes.
Good luck, and let me know how things work out!
Colorado Amp Techs |
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August 2006
Posts: 2804
Location: ranson,wva | take a look at the plates inside of the tube/valves you choose the lingo,if they are discolored and the inside suface of the tube is white you got a bad tube,ive never worked on a guitar tube amp but i have worked on amature radio tube linears and i would asume that the tubes wear the same.
question for al...we used to use 6ql6 sweep tubes from tvs for low power key tubes,i think they were something like 35watts a peice, do they uses 6ql6's in guitar amps? jason |
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Posts: 2491
Location: Copenhagen Denmark | Have a Competent Repairman working on it , BUT...If U must try your self ,then remember to keep your Left Arm Behind Your Back while Fidling with a Valve Amp... High Voltage Can Be Lethal .. I presume that U want to stay alive , so do yourself a favour talk to your friendly radioman ,He will have your precious Amp. back in the running , and your hair wont look like don king ;)
Vic |
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August 2006
Posts: 2804
Location: ranson,wva | heres's the most usefull peice of advice i can give you..when working on tube equipment with high voltage plate and grid tuning caps never rest our hand on your bench.. KEEP THAT SONOFABITCH ABOVE YOUR HEAD.....jason |
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Posts: 2491
Location: Copenhagen Denmark | And never work on it in the shower,or better yet..never work on it :p ..unless U wanna take up belly-dancing..they have their hands above their head do n`t they.. :eek:
:cool: ;)
Vic |
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January 2006
Posts: 5881
Location: Colorado Rocky Mountains | StephenT's recommendation is actually the assistant tech for the Lord Valve. The shop is close to home and work so I'll swing by there this week and drop off the head. |
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Posts: 13303
Location: Latitude 39.56819, Longitude -105.080066 | LORD VALVE is affectionately known as FAT WILLIE....hell of a keyboard player. His repair shop is massive but it is so full of odds and end parts that you can't walk into the shop more than 10 feet before you are blocked.
He sends a lot of his work out to Scooter because he is so busy (and why I recommended Scooter in the first place). Cheaper to go to the man who will probably do the work and cheaper (+ much faster) also.
I have dropped stuff off at Scooter's house on many occassion and always been satifisfied.
BRAD....take him a breakfast burrito from Qdobas and instantly become his best bud! ;) |
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Posts: 5881
Location: Colorado Rocky Mountains | Got it, Stephen. Will do, but it will be from Chubby's original. |
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April 2004
Posts: 13303
Location: Latitude 39.56819, Longitude -105.080066 | Well, Qdobas is his favorite but I am sure that a Chubby's original will be an acceptable substitute :D |
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Vintage Bandmaster problem
