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Post subject: Fender "The Twin" 1985? Amplifier problems
Posted: Fri Aug 06, 2010 12:16 am
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Hello and thanks for viewing,

I purchased this amp used several years ago. I had it serviced not soon after because the reverb was not working. When I got it back from the shop everything was fine, good tone and reverb was working. I cant remember all that was done to it, tubes were changed but not sure which ones. I haven't played with it a few years and now the reverb is not working and it generally just sounds bad. The speakers are replacement celestion G12T-75 8 ohms wired in series 16 ohms on the amp. The tubes in it are: Four 6L6GB's, Six 12AX7WA's and One 12AT7. In the manual a fender rep emailed me it states there should be five 7025's and two 12AT7's. Is this ok? Something else I noticed, the bias and balance pots are as clockwise as they could go. My meter only shows 25.9 mV, shouldn't it be 40 mV? The closest fender authorized service center is 50+ miles away and I'm worried that they'd probably do the same "great job" as the last guy I brought it to. Also is there any way to correctly date this amp. I don't remember why but I thought this was a '85 but I cant find anything on them being made in '85. One last thing... The foot switch also wasn't switching channels when guitar was plugged in switching mode. The more I play with this thing the more I find wrong with it. It sat in the corner of my music room untouched for years, I don't understand why its giving me problems. Please Help


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Posted: Fri Aug 06, 2010 8:00 am
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Sounds like the amp has several problems. The first being the bias seems to need adjustment. I'd recommend a good amp tech. You may need to pull the amp out of its cabinet, pull and wrap all the tubes. And carefully package and ship to the best tech in your area. That's prolly the key. Get some recommendations on techs before shipping.

Otherwise, if you decide to "fix" it yourself, it may become a frustrating learning experience. Based on a lot of ppl's opinions on what you should do to it.


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Posted: Fri Aug 06, 2010 1:44 pm
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So you think its more than just needing its tubes replaced? I figured that I could at least change the tubes and then try to bias it. If nothing improves I'll have to bring it to someone who knows what they are doing.

*pulled amp out of cabinet and it is has an inspection ticket with 1988 so I guess its an '88 model. No noticeable bad circuits.


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Posted: Fri Aug 06, 2010 4:23 pm
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Joined: Fri Feb 05, 2010 4:31 am
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Location: Province de Québec, Canada
An amp wich is not use since many years have all its contact dirty , oxided (?)or rusted.
Those contacts are tubes socket contact, input jack, foot switch jack.

Bad contacts can make your bias wrong


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Posted: Fri Aug 06, 2010 7:31 pm
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Everything looks good, even the inside. There isn't any corrosion that I can see without taking it apart further. Footswitch is also in good condition internally.


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Posted: Sat Aug 07, 2010 2:08 am
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Don't try to see rust like an old car.
This kind of "corosion", on tubes socket : you can't see it. It's inside on female connector .You need to kleen those inside contacts.

I dont't talk about the footswich itself, but the input jack on the amp. And All the other input jacks clean the tip and the ring ( the plus and the minus).
The reverb sockets (2 rca plugs ) need to be cleaning too. Inside.

I don't know very well your amp. But I have myself some old Fender Blackface and Siverface and it's appened if I don't use one for many years and sometimes I have same kind of trouble than your amp when I power ON an old one.

Have you any electronic expérience and knowhow ? If you don't, bring it to a good tech


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