Output transformer question

sniffin

Member
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387
what would be the max DC resistance difference between the two sides of the primary on an output transformer for a 4x6L6GC amp?

thanks
 

neteraser

Member
Messages
1,993
About 1 ohm on my Dagnall 50W, if I'm correct. But that won't give you anything, I've been told they try to make them equal. This could be completely different for Fender transformers.

I'd email Mercury Magnetics and include details of the problem.

Sorry. Can't help.
 
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826
If you want to be fancy, you can put the pair of 6L6s which naturally draw more idle current on the side with the higher DC resistance. This would improve the DC balance for the OT. (Though I doubt if it would make any audible difference.)
 

pdf64

Member
Messages
9,168
I'm getting around 10 ohms difference, the amp is a peavey 6505 head...
Yes, the actual resistance readings of each leg would give some sense of scale.
If there are shorted turns in the primary then the primary won't have it's necessary inductance, so the primary load may be pretty much its primary resistance and so the power output will be hardly anything.
 

pdf64

Member
Messages
9,168
If you want to be fancy, you can put the pair of 6L6s which naturally draw more idle current on the side with the higher DC resistance. This would improve the DC balance for the OT. (Though I doubt if it would make any audible difference.)
I don't think that in itself it would make much in the way of electrical difference either.:)
As with beam tetrodes/pentodes, the screen grid acts to 'buffer' plate current from plate voltage, making screen grid voltage far more significant to plate current than is plate voltage.
So a few volts difference in plate voltage between identical (!) tubes wouldn't, if the screen grid voltages were the same, affect plate current.
 




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