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Post subject: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 6:10 am
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Bummer, my old bedroom Ampeg Gemini VI is on the fritz. It plays for about 5 mins normally then the sound cuts, if I put the volume all the way up I can hear myself play very faintly but very distorted. What you guys think? Bad tube? Preamp or Power? If I turn it off and back on the same cycle repeats, fine for 5 mins then no output, all channels the same. I think may be a tube stuck open, I have spares somewhere in my guitar junk, I might have to start swapping. Amp expert, let me know what the deuce...


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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 7:11 am
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Man those old Ampeg amps are great. I'd start with the tubes. Could just be power tubes. If the tube swap doesn't work, have a tech give it the once over. If it's never been recapped, it may be due.

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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 7:20 am
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Yea, it sucks, at least the fuse didnt blow so no major upset, dont want any transformer to go so I wont mess around with it until I check the tubes. It's a sweet reverb big 15" amp, I'm stuck playing my reel to reel home made 3W now.


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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 7:25 am
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Possibly tubes, easy enough to swap in new ones to see, it could be a bad preamp or PI or output tube. Make sure to set the bias when changing output tubes (there is an adjustment). It also might be the 470 ohm resistor that feeds the screen grids of both output tubes, has a bad connection like a poor solder joint. Could be a bad connection anywhere, check all solder joints, including the input jacks. :idea:

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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 7:30 am
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Ampeg's are just so clean. I've had a couple in my lifetime. I almost bought a Jet J-20 a while back, but they discontinued them. I tried one out when I was in NY, but was too lazy to carry it around the city, so I waited too long after I got home. I gave up trying to find a used one.

Anyway I hope and doubt it's anything serious.

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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 7:43 am
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I tried all inputs, same result which is was I was leaning toward tubes. If it was some cap or resistor somewhere it would stop working and not come back on, instead of working for a few mins then quit. It's like power tube heater opens and the plate gets charged but the heater does not close or something. Then when I turn the amp off, electrons go away until I turn it back on an tube gets saturated again.

Yea, they are clean to no end those things, this one is a 67 and the reverb is to die for, guess it's why surf guys like those things. Ampeg was the only company giving Fender a run for their money in the 50s amp era.


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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 7:59 am
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Sure does sound like a power tube. Has it ever been recapped? I think Ampeg's new GVT Series will give give Fender a real run for their money. Built like tanks. I've tried a couple and I think they sound great.

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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 8:18 am
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Not sure about a cap jobs, only had it a few years. Have another Gibson Hawk with reverb that needs recap too, different symptoms though, that one is very noisy.


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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 8:27 am
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Noise is a sure sign. If you get a chance, pull the chassis and look for leaking electrolytic caps. If they're leaking replace them. I know you don't want any serious issues with the vintage amps. That Gibson's another great amp. Sounds like you have some great stuff. Sometimes I wish I would have kept all that old amps I've had over the years, but I just didn't have the room for it all.

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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 8:44 am
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That Hawk is an old rust bucket but for less than $200 I didnt want to pass on it, it's completely original, down to the very last cap. Another accident waiting to happen :)
I bought because I desperately need to learn how to fix my own amps but I'm freaked out to touch the wrong thing. What's a good beginner book to learn with? Is there some dummy step by step book out there?


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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 10:07 am
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http://www.amazon.com/Tube-Guitar-Ampli ... B000ESSTJM
Great information by Gerald Weber. There's a lot of other books too. Just do a search on Amazon.

For parts I usually deal with these guys.
http://www.mouser.com/

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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 10:16 am
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Cool, I know there's a lot, just wanted to know what you guys use as a reference. Yea, mouser out of Bklyn, I got parts from there before for pedals. Thnx


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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 5:00 pm
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I don't think is a tube's problem.

It could be a solder , cold joint , or a resistor open when hot . More chance is solder in power supply line IMO.

Speaker connection/ jack are ok ?


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Post subject: Re: Problem with my old Ampeg
Posted: Mon Feb 13, 2012 5:24 pm
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It's wiring in through a Webber attenuator right now, maybe there's a problem with that connection. I dont know, I have to get to the back of that amp in a couple of days.


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Post subject: Re: Problem with my old Ampeg
Posted: Tue Feb 14, 2012 3:11 pm
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I have a late 60's Reverberocket that had a somewhat similar problem. Loss of power and no reverb. Had it serviced for under $200. New transformer and a three pronged plug. It's been great since. Had it serviced 40 years later by the same guy that worked at the Ampeg plant in Linden, NJ back in the 60's!

Westchester to Edison, NJ. Bring it to Lou Rose music and ask for Dennis.


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