Changing output transformer ?

dubtrub
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Re: Changing output transformer ?

Postby dubtrub » Mon Oct 24, 2011 2:37 pm

Well. I'm back to square one. I checked the OT numbers and it is the correct transformer for the Bassman 100. This has got to be one of the nastiest corroded interior of an amp I've ever seen. What had me thinking the transformer had been replaced ended up being one of the power tube socket splices. I've checked the circuit with the diagram and everything seems to wired correctly. So next I guess I'll go back to checking all voltages.

Mr.Bill, what are your thought on running an 8 ohm speaker from a 4 ohm OT?
Danny Ellison

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Re: Changing output transformer ?

Postby Mr. Bill » Mon Oct 24, 2011 10:05 pm

Tube amps in general prefer to be mismatched with a lower load rather than a higher one, just the opposite of a solid state amp.

Running the amp with an 8 ohm load will reduce power and will probably not do any permanent damage to the amp. That being said you may find that output tube life may be reduced and if the output transformer is already damaged, it may not take the additional stress. I'd suggest trying to get the amp into the best running condition before doing this though, to reduce the stress that the mismatch will add to the circuit.

Corrosion can do all sorts bad things to electronic circuits, do you know the history of the amp? You're on the West coast so salt air can cause all sorts of problems. Worst case scenario is every connection needs to be checked and all tube sockets cleaned and tightened. When you replaced the electrolytic caps, did you do all of them or just the big filters? How old are the tubes in the amp? When you set it up did you adjust the bias or did you just use original balance control? What sorts of test equipment do you have access to?

dubtrub
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Re: Changing output transformer ?

Postby dubtrub » Mon Oct 24, 2011 10:29 pm

Thanks Mr. Bill. At this point I'm going to have a buddy of mine that was a technician for Demeter Amps come over and check everything out. I only know basic electronics but I think it needs someone with diagnostic experience to do a hands on evaluation.
Danny Ellison

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zarfnober
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Re: Changing output transformer ?

Postby zarfnober » Mon Oct 24, 2011 11:43 pm

I know it sounds too simple but, clean all your pots thoroughly with DeOxIt. Then clean them again, along with your tube sockets as Mr Bill suggested. I've worked on amps where everything seemed to spec out fine, but had dirty pots, some even had spider eggs in them. Completely cleaned and they worked fine. You could also clean the board with flux cleaner and a q-tip after checking your solder joints. Does the board look like it's been worked on? I've even had shorts and arcs from wire strands, look at everything very closely. Good luck,

Rocco
www.rockometeramp.com Vinatge spec American and British style cabs, custom cabs, recovers, regrills and restorations.


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