04-12-2013, 12:14 PM
I'm working on an RCA 56X2. After completely recapping it (except a couple of micas) and replacing most resistors, it worked well for a while, but then the primary of the output transformer opened.
By chance I found a junk set in the props storage of a local theatre company and brought it home in hopes of using its output transformer for my set. The junk set worked for about a minute before the same thing happened. So now I have two chasses with open output primaries.
Because I had two transformers fail identically I'm reluctant to buy an antique transformer, even if I can find one. I'd like to try to find a modern replacement. Can anyone recommend a replacement? Radio Daze "improved" their web site so I can no longer see any specs for what they sell, only "transformer -- audio chassis mount" or the like.
The final amp tube is a 35L6. Schematic is here: http://www.nostalgiaair.org/Resources/994/M0014994.htm
I think the primary DC resistance is 225 ohm, though it's hard to read. There is also a 12 ohm tap that the B+ goes through, presumably to help smooth out the ripples. The secondary is 0.8 ohm.
No doubt a modern transformer wouldn't have the 12 ohm tap, but I could probably find a choke to use in its place.
I don't know enough about transformers to understand the specs, other than matching the DC resistances and dimensions. Mouser has a Hammond 146S that matches pretty closely. Primary = 220 ohm, secondary = .7 ohm. The primary has a center tap, which obviously I wouldn't use. They have 2 in stock for $18.46. (Radio Daze lists the same part number for $16.75.) Would this be a good choice?
Any other suggestions?
By chance I found a junk set in the props storage of a local theatre company and brought it home in hopes of using its output transformer for my set. The junk set worked for about a minute before the same thing happened. So now I have two chasses with open output primaries.
Because I had two transformers fail identically I'm reluctant to buy an antique transformer, even if I can find one. I'd like to try to find a modern replacement. Can anyone recommend a replacement? Radio Daze "improved" their web site so I can no longer see any specs for what they sell, only "transformer -- audio chassis mount" or the like.
The final amp tube is a 35L6. Schematic is here: http://www.nostalgiaair.org/Resources/994/M0014994.htm
I think the primary DC resistance is 225 ohm, though it's hard to read. There is also a 12 ohm tap that the B+ goes through, presumably to help smooth out the ripples. The secondary is 0.8 ohm.
No doubt a modern transformer wouldn't have the 12 ohm tap, but I could probably find a choke to use in its place.
I don't know enough about transformers to understand the specs, other than matching the DC resistances and dimensions. Mouser has a Hammond 146S that matches pretty closely. Primary = 220 ohm, secondary = .7 ohm. The primary has a center tap, which obviously I wouldn't use. They have 2 in stock for $18.46. (Radio Daze lists the same part number for $16.75.) Would this be a good choice?
Any other suggestions?
John Honeycutt
