I am looking how to identify the wiring coming out of a D&A Phantom transformer. I am going to try and use this transformer in a Apollo 500 amp that I have that fried transformer. I see 2 reds, 2 greens ,grey, and others. Thanks
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D&A Phantom Transformer wiring color code.
- Thread starter Jimbo165
- Start date
Should have two reds and one red with a yellow stripe. The red wires are the 630 Volt secondary, the striped wire is the center tap.
The two green wires should also include a third one with a yellow stripe. This is a 12.6-Volt secondary, the striped wire the center tap.
The two remaining gray wires should be the 120-Volt primary.
The Apollo probably used a transformer with less than half the voltage on the HV secondary as the D&A unit. Best I remember Apollo used a full-wave voltage doubler with a transformer secondary under 300 Volts. Had two 450-Volt filter caps in series.
The D&A transformer works best with a full-wave bridge rectifier, not a doubler. To boot, it will produce too much DC voltage for just two 450-Volt filter caps in series. You'll need either three 350-Volt caps like D&A used, or three of the easier-to-find 450-Volt caps. Just be sure to put a bleeder resistor across each cap. We use 220k, but anything between 180k and 330k works okay, just so each cap in the string has the same resistance value across it.
The D&A isn't a direct drop-in substitute but with a little adaptation it should hold up better than the factory transformers. They were just too small.
73
The two green wires should also include a third one with a yellow stripe. This is a 12.6-Volt secondary, the striped wire the center tap.
The two remaining gray wires should be the 120-Volt primary.
The Apollo probably used a transformer with less than half the voltage on the HV secondary as the D&A unit. Best I remember Apollo used a full-wave voltage doubler with a transformer secondary under 300 Volts. Had two 450-Volt filter caps in series.
The D&A transformer works best with a full-wave bridge rectifier, not a doubler. To boot, it will produce too much DC voltage for just two 450-Volt filter caps in series. You'll need either three 350-Volt caps like D&A used, or three of the easier-to-find 450-Volt caps. Just be sure to put a bleeder resistor across each cap. We use 220k, but anything between 180k and 330k works okay, just so each cap in the string has the same resistance value across it.
The D&A isn't a direct drop-in substitute but with a little adaptation it should hold up better than the factory transformers. They were just too small.
73
Thank you nomadradio. i am going to give it a try. Amp does not work now . I may ask more questions later.
One D&A Phantom transformer is rated about 500 watts. It would be pushed very hard in the Apollo amp but not likely fail. Peak HV voltage would drop to 800 volts vs 850 volts in a D&A amp..
I was going to run 2 D&A transformers in parallel . In a phantom there is 850 v at tubes.
I remember seeing closer to 900 Volts, but it's been a while since I poked a meter into one of those. I did learn the hard way not to just put two 450-Volt caps in series to filter a Phantom's HV. They just don't last very long.
73
...runna pile-up on 6m SSB