Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: ncusack on January 14, 2016, 06:08:54 pm
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Hello,
I recently scrounged a power transformer from an old Stromberg Radio and I'm wondering if anyone here could take a stab at what the current ratings might be on the windings. I was able to find the original service manual here http://pacifictv.ca/radioschematics.htm (http://pacifictv.ca/radioschematics.htm) the radio model is Stromberg-Carlson 1162. The radio ran a 5y3, 6v6, 6AT6, 6BA6 and 6BE6. I figure it would be good for a little champ build at the very least but I'm curious how far it might be able to be pushed.
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I don't know about your transformer but your 5Y3 has a max of 125mA of current.
I wouldn't expect your transformer to handle too much more than that.
I definitely wouldn't expect it to be able to handle a 5U4's output.
Maybe it could, but I wouldn't expect that.
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I would keep to a champ or vibro-champ style single ended amp.
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> The radio ran a 5y3, 6v6, 6AT6,... blah blah blah
Then it IS a one-6V6 Champ, except with a tuner where the preamp would go.
If you have the whole chassis, best to leave the audio section alone. It isn't significantly different from a Champ. For guitar you need one more stage before the volume control. 6AT6 is "almost" a half a 12AX7. You could cobble the 6BA6 stage into a audio preamp, but if that is not obvious you should just jam a 12AX7 in.
The rectifier could support a larger amplifier, but the PT is probably low-low-cost and would not support all that a 5Y3 might carry. 5Y3 was just the cheapest power rectifier.
It is like finding the same steering-box on an old Firebird and on a K-2500 3/4-ton truck. It's overkill on the Firebird but GM made these boxes by the million, used them everywhere.
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Champ it is, most likely. Your problem may be if it only makes say 250 B+ volts in full wave through the 5Y3. Yours may be an exception, but I have found that few electronic "tube things" make ~~~350/400 volts unless they were specifically made for amplifier use. Meters, test gear, radios...usually not. Before getting overly committed, I'd plug it in and get a feel for the no-load AC volts put out by the HV winding. SS rectifier would give you about 50 more B+ volts and maybe you could squeak by with that. Maybe you can make a Tweed (5E1, 5F1) champ, probably not a blackface one. Well...you *could* make a BF one but it would end up being a 2-3 watt champ instead of a 5 watter. Maybe w/an efficient speaker you could do OK.
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Did some no load measurements yesterday and with 121VAC at the wall I got 377VAC-0-377VAC on the high voltage secondaries, 7.8VAC on the 6.3 heater tap and 6VAC on the 5V tap.
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... with 121VAC at the wall I got 377VAC-0-377VAC on the high voltage secondaries, 7.8VAC on the 6.3 heater tap ...
Assuming the ratio of unloaded-to-loaded for the 6.3vac winding holds for the high voltage winding, it like like you have about 300-0-300vac when loaded.
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Then you're in great shape, my low-voltage cautions are out the window. Champ is easily done. Is there anything left of the chassis, specifically looking for voltage rating(s) on ecaps?