Unused Output Taps?

vincei

vincei

aka MasterControlMedia
I am just finishing my EL34 build and was wondering what do I do with the unused output transformer taps? I am only using the 8 ohm tap and have 3 others just hanging, do I just leave them or do I have to connect them to anything?

Thanks again for all the help! I post final pics when I am done. :music:
 
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You should only use one tap at a time. The unused ones usually are left unconnected to anything.
 
Thanks! I plugged in the new build amp this evening and there was massive hi pitched feedback and wondered if that had anything to do with it. I must have got something wrong, at least no smoke!
 
If the amplifier uses any kind of negative feedback from the output transformer
secondary (the side connected to the speakers) to some stage near the input,
you may have the output transformer connected to provide positive feedback
instead. Reversing the connections on one side of the output transformer
should help in that case.

Posting your schematic would help a lot. Good luck.
 
electroking said:
If the amplifier uses any kind of negative feedback from the output transformer
secondary (the side connected to the speakers) to some stage near the input,
you may have the output transformer connected to provide positive feedback
instead. Reversing the connections on one side of the output transformer
should help in that case.

Posting your schematic would help a lot. Good luck.
Click to expand...

Could be the case, the positive speaker out is connected to the cathode of the first stage 6CG7 via a 6.8k resistor, which was the way it was originally set up, but I did replace the OPT with new units, I have to look at it over the weekend. Thanks for the tip. I'm sure it's nothing serious, but it did wake up the house when I turned the amp on! (It was very late!) I may infact rebuild it as the popular RH EL84 schematic as it is different from the one I am using.
 
electroking said:
If the amplifier uses any kind of negative feedback from the output transformer
secondary (the side connected to the speakers) to some stage near the input,
you may have the output transformer connected to provide positive feedback
instead. Reversing the connections on one side of the output transformer
should help in that case.

Posting your schematic would help a lot. Good luck.
Click to expand...

You were right on, I reversed the primary leads of the OPT TX and all is good, now I have to run sound tests and see if I need to tweak anything. I will post pics of the final product tomorrow. Thanks again EK!
 
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