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Post by mauro on Sept 21, 2018 23:52:32 GMT
I'm evaluating an amplifier from a model B jukebox and I suspect the output transformer is bad.
Resistance readings from the windings to center tap are as follows:
2 of the 6V6 tubes is 361 ohms and the other 2 read 63 ohms.
In my mind this appears that one winding is partly shorted,
Opinions?
Thanks, Mauro
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Post by robnyc on Sept 22, 2018 0:56:34 GMT
Yep, that is as clear-cut as one can get. I've had seeburg trans be bad with both sides only slightly unbalanced and yet having poor output and/or bass response.
FWIW: I'd skip the idea of getting any used tran and go with one from Hammond. Any of their types suitable for 6L6 ckts will work here.
RobNYC
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Post by mauro on Sept 22, 2018 1:01:06 GMT
Rob,
Thanks for the speedy response and confirmation.
It is much appreciated,
Mauro
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Post by mauro on Sept 26, 2018 1:14:36 GMT
Rob,
This amp has 4- 6V6 output tubes, the Hammond specs list transformers for 2- 6L6 or 2- 6V6 or 4- 6L6 but not 4- 6V6.
Not sure if you meant that it makes no difference?
Could you elaborate or even reccomend a replacement?
Thanks,
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Post by robnyc on Sept 26, 2018 8:20:21 GMT
Mauro, the determining factor is the current to be drawn through the tubes as indicated by the B+ and output wattage.
The maximum current drawn through here will be approx the same whether two 6L6G are used vs. 4 6v6 tubes. IOW; it doesn't matter.
Even with the original tran, you could use two 6L6's (on opposite sides) or even just two 6V6's since the plate B+ is within the max for both tubes. However, two 6V6 would be overloaded at higher volume level and the idle current would rise with only two tubes so this would potentially shorten the life of the 6V6's.
Rob
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Post by mauro on Sept 26, 2018 17:05:58 GMT
Rob,
I'll just select a transformer as I would with 2 6L6 then.
Thanks for the explanation,
Mauro
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