Replacement OT for Silvertone 1420

[samgraysound]

Hi All,

I need to replace an output transformer on a silvertone 1420 tube amp. schematic (1430, mostly the same) attached.

Not that much info on the transformer spec. Amp is 5W. Schematic says 180ohm primary 3.2ohm secondary. Haven't been able to find anything with a primary nearly that low.

Does it matter? Can I use one of these? http://www.hammondmfg.com/125SE.htm

Sam

 

[benb]

180 ohm primary sounds seriously low. I'm guessing they mean the DC resistance of the primary, where the impedance will be much higher.

The 50C5 was the output tube on most miniature-tube table radios, and if you can find a junker one of those, you can use the output transformer (often mounted right on the speaker) out of it. Not sure which one of the Hammond transformers would work best.

Also, the 50C5 filament was part of a series string of power-line-powered filaments on those radios. Looking up the 1420 and 1430 schematics, these are line-powered in the same way, and even more dangerous with a guitar connected. I'd only power this amp through an isolation transformer.

 

[samgraysound]

180 ohm primary sounds seriously low. I'm guessing they mean the DC resistance of the primary, where the impedance will be much higher.

The 50C5 was the output tube on most miniature-tube table radios, and if you can find a junker one of those, you can use the output transformer (often mounted right on the speaker) out of it. Not sure which one of the Hammond transformers would work best.

Also, the 50C5 filament was part of a series string of power-line-powered filaments on those radios. Looking up the 1420 and 1430 schematics, these are line-powered in the same way, and even more dangerous with a guitar connected. I'd only power this amp through an isolation transformer.

Yes I'm definitely planning on modding this with an isolation transformer and a fuse.

 

[samgraysound]

Reading over this thread...https://groupdiy.com/index.php?topic=43796.0

seems like PRR is suggesting a 2.5k primary as spec'd in the 50C5 data. The Hammond can be hooked up for 2.5k:4ohm so that should work. Probably overkill for such a cheap amp. If I can find something to strip parts off I will.

Sam

 

[PRR]

It's the butt-end of a 5-toobe kitchen radio, minus tuner.

I remember when you could find these in every garage, but those days are gone. People think anything with tubes is "collectable".

Ha! Play Things Of Past was doing business this spring, and expects to be back "June/July". Many 50C5 OTs for a few bucks each (but $20 minimum order). He's very old-fashioned, but I bought books from him once and service was good.

 

[CJ]

you have the old one?

 

[samgraysound]

you have the old one?

Yes, it's still attached to the speaker. No continuity through it and the paper looks a bit shredded.

Sam

 

[samgraysound]

Ha! Play Things Of Past was doing business this spring, and expects to be back "June/July". Many 50C5 OTs for a few bucks each (but $20 minimum order). He's very old-fashioned, but I bought books from him once and service was good.

Yeah I saw that. Its for a client so I can't wait indefinitely, unfortunately. A friend of mine says he has a transformer "somewhere" I can have. We'll see if that pans out.

Sam