I have a bad transformer in a Zenith 7s633 I purchased on e-bay. very good condition but the transformer is shot. Anyone know a resource to purchase a tranformer?

:I have a bad transformer in a Zenith 7s633 I purchased on e-bay. very good condition but the transformer is shot. Anyone know a resource to purchase a tranformer?

Jim: chances are that it had the dreaded transformer melt-down from a defective 6X5G recifier tube which were prone to have heater to cathode shorts. I think this problem is more prevalent with dual 6X5's however. The newer 6X5GT's with an "X" shaped plates are better in that regard. It would be wise to install a fuse to protect the transformer when you find a replacement, and use a CL-90 current limiter on the transformer primary leads to limit the inrush current at turn-on. It looks like the 6X5G needs 275 vac on the plates, and 6.3 v for the filament. Radiodaze.com should have what you need. You'll have to match up the physical dimentions and style to fit your radio.
Steve

::I have a bad transformer in a Zenith 7s633 I purchased on e-bay. very good condition but the transformer is shot. Anyone know a resource to purchase a tranformer?
:
:Jim: chances are that it had the dreaded transformer melt-down from a defective 6X5G recifier tube which were prone to have heater to cathode shorts. I think this problem is more prevalent with dual 6X5's however. The newer 6X5GT's with an "X" shaped plates are better in that regard. It would be wise to install a fuse to protect the transformer when you find a replacement, and use a CL-90 current limiter on the transformer primary leads to limit the inrush current at turn-on. It looks like the 6X5G needs 275 vac on the plates, and 6.3 v for the filament. Radiodaze.com should have what you need. You'll have to match up the physical dimentions and style to fit your radio.
:Steve

How can you tell that the 6X5G needs 275 Vac on the plates?
Mike Nealon

Here's the schematic, which shows each plate at 275VAC. Since this is a full-wave rectifier, the plate-to-plate voltage would be 2x275 = 550VAC. A replacement power xfmr should have a center-tapped secondary winding approximately equal to that voltage.

The RCA tube manual shows that a 6X5 should have a maximum plate voltage of 325VAC (with a capacitive input filter). Zenith is calling for 275VAC.
Doug

:::I have a bad transformer in a Zenith 7s633 I purchased on e-bay. very good condition but the transformer is shot. Anyone know a resource to purchase a tranformer?
::
::Jim: chances are that it had the dreaded transformer melt-down from a defective 6X5G recifier tube which were prone to have heater to cathode shorts. I think this problem is more prevalent with dual 6X5's however. The newer 6X5GT's with an "X" shaped plates are better in that regard. It would be wise to install a fuse to protect the transformer when you find a replacement, and use a CL-90 current limiter on the transformer primary leads to limit the inrush current at turn-on. It looks like the 6X5G needs 275 vac on the plates, and 6.3 v for the filament. Radiodaze.com should have what you need. You'll have to match up the physical dimentions and style to fit your radio.
::Steve
:
:How can you tell that the 6X5G needs 275 Vac on the plates?
:Mike Nealon

:What is the maximum plate voltage for an 80 rectifier tube?
Nealon

:Here's the schematic, which shows each plate at 275VAC. Since this is a full-wave rectifier, the plate-to-plate voltage would be 2x275 = 550VAC. A replacement power xfmr should have a center-tapped secondary winding approximately equal to that voltage.
:
:The RCA tube manual shows that a 6X5 should have a maximum plate voltage of 325VAC (with a capacitive input filter). Zenith is calling for 275VAC.
:Doug
:
::::I have a bad transformer in a Zenith 7s633 I purchased on e-bay. very good condition but the transformer is shot. Anyone know a resource to purchase a tranformer?
:::
:::Jim: chances are that it had the dreaded transformer melt-down from a defective 6X5G recifier tube which were prone to have heater to cathode shorts. I think this problem is more prevalent with dual 6X5's however. The newer 6X5GT's with an "X" shaped plates are better in that regard. It would be wise to install a fuse to protect the transformer when you find a replacement, and use a CL-90 current limiter on the transformer primary leads to limit the inrush current at turn-on. It looks like the 6X5G needs 275 vac on the plates, and 6.3 v for the filament. Radiodaze.com should have what you need. You'll have to match up the physical dimentions and style to fit your radio.
:::Steve
::
::How can you tell that the 6X5G needs 275 Vac on the plates?
::Mike Nealon

From the tube line-up, it looks like he'll need one with at least a 3 amp rating on the filament supply. Not sure about the plates, but maybe 200 ma looks reasonable. 6X5 tube data shows a 210 ma peak plate current, and it isn't being driven that hard in this application.
Steve