Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: drumguy on December 05, 2017, 10:18:44 am
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The power transformer in this amp is fried and looking for a replacement.
The part number is TF-135-P. The schematic ilooks to be hand written and
really blurry. The PT specs from it seem to be....
Primary 0-120
Secondary HV 330-46-0-330
Fil 3.15-0-3.15
660v CT
Does anyone know if these are accurate?
I can’t find spec info on this transformer anywhere.
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I’ve contacted a transformer builder and the specks they had on file were...
Primary 0-120
Secondary HV 380-55-0-380
Fil 3.15-0-3.15
760v CT
These were no load measurements but still seemed a bit hot compared
to what the schematic seems to read.
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The PT specs from it seem to be....
Primary 0-120
Secondary HV 330-46-0-330
Fil 3.15-0-3.15
660v CT
I'd use this info. It matches the following schematic.
Does your amp have four 6L6s? If so, here's the schematic...
http://el34world.com/charts/Schematics/files/gibson/Gibson_medalist_6L6_quartet_titan.pdf
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I'd use this info.
+1
a quick look I come up with a Hammond 290CX as close I didn't add up current to see if 4A is close enough
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Awesome, thanks guys!
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that's a twin reverb class amp - 80-100W. a 290CX will have a short life. with the original, the schematic indicates that B+ is 425V from a 660VCT coil. with those numbers, that seems like a heavily loaded PT. all depends on bias as well and 46V would run the 6L6 a bit warmer than fender did. 400-500mA PT is what you need for that amp.
http://www.classictone.net/40-18069.pdf
the classictone in the link above requires a FWB. read page of that spec sheet for more B+ options.
--pete
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If you are restoring that amp it's probably important to get a replacement that will fit the original layout, especially if a laydown PT is required.
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> Secondary HV 330-46-0-330
> I’ve contacted a transformer builder and the specks they had on file were...
> Secondary HV 380-55-0-380
> These were no load measurements
15% high NO-load is about just what we expect for a transformer like this.
Agree this is a 80+ Watt four-6L6 amp, and a two-6L6 PT won't be happy.
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If you are restoring that amp it's probably important to get a replacement that will fit the original layout, especially if a laydown PT is required.
Yes, good point!
I would like to be able to just bolt the new one right on.
The PT specs from it seem to be....
Primary 0-120
Secondary HV 330-46-0-330
Fil 3.15-0-3.15
660v CT
I'd use this info. It matches the following schematic.
Does your amp have four 6L6s? If so, here's the schematic...
http://el34world.com/charts/Schematics/files/gibson/Gibson_medalist_6L6_quartet_titan.pdf
So should I order with the following as loaded specs?
Primary 0-120
Secondary HV 330-46-0-330
Fil 3.15-0-3.15
660v CT
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That's what I'd do. Better carefully measure the mounting bolt spacing dimensions too.
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That's what I'd do. Better carefully measure the mounting bolt spacing dimensions too.
Ok, will do! Thanks!