selenium HV rectifier

[DaveWM]

anyone ever try using a modern HV diode in place of those somewhat hard to come by rectifiers? I see there are 10kv diodes that are easy to get.

oh this is for the focus not the HV for the CRT anode.

[DaveWM]

for fun I think I may try testing one by simply using my simpson 260 in the 5kv mode, and hooking up a Se rectifier to the same place on the flyback. Mearsure the voltage, then turn the rec around and switch to DC- and see what happens.

[ctc17]

I bet it will be way more efficient and may even cause some weird interference. I have the guts out of several microwave ovens and they use that diode. I guess I could try it too.

[DaveWM]

if you do let me know how it works out. I was doing some reading on Se diodes, seems age be a problem, even if you find a NOS Se.

[peverett]

I restored some small GE solid state sets from the mid 1960s that used selenium HV rectifiers. The originals were bad, but I was able to get NOS ones from Moyers. They seem to work fine.

[DaveWM]

yea I come across them now and then. Just wondering if a modern would make a difference. My guess is the voltage may be too high.

[cbenham]

Originally Posted by DaveWM

anyone ever try using a modern HV diode in place of those somewhat hard to come by rectifiers? I see there are 10kv diodes that are easy to get.oh this is for the focus not the HV for the CRT anode.

If the set used seleniums originally, you can replace them with newer seleniums or probably HV silicon rectifiers.

However, if the original was a tube, I'd still use a tube. Using a selenium or a silicon diode may overload the flyback transformer because the capacitance is so much higher and the reverse resistance of these diodes is so much lower than what the tube offers.

I've tried this with both solid state plug-in 1B3s and 3A3s, etc., as well as for 1V2s in B&W and color sets and found this to be fairly universal.

Stick with a tube if the original rectifier was a tube. Just my experience.

Cliff

[kx250rider]

I've replaced 2AV2s & 1V2s with special focus rectifier diodes, but the focus voltage goes up, and you need to be sure the control will still be in range. Same should be true if you replace a selenium with a silicon diode. If the control is out-of-range with the replacement rectifier, you might have to put a resistor in line, and by the time you do all that, it's easier to just get a new tube. Maybe not so easy to get a new selenium though. But you can use a 1 or 2 volt tube in stead of the selenium by making one full turn of wire around the iron core of the flyback, and feeding the tube filaments from it.

Charles

[DaveWM]

yea, I thought about going the 1v2 route. I did end up replacing the old SE with a NOS SE, the range completly shifted, I guess the old Se was getting weak.

[wa2ise]

I wouldn't have thought that any TV set would have used a selenium rectifier for the high voltage. Selenium rectifiers tend to be leaky and lossy. And tube HV rectifiers are fairly cheap, but do require filament power, which is always gotten off the flyback circuit. Submini HV rectifiers, IIRC the 5642, are small and can do up to about 10KV, not enough for color TV though.

[DaveWM]

its for focus, I know the title is missleading

[dieseljeep]

Originally Posted by wa2ise

I wouldn't have thought that any TV set would have used a selenium rectifier for the high voltage. Selenium rectifiers tend to be leaky and lossy. And tube HV rectifiers are fairly cheap, but do require filament power, which is always gotten off the flyback circuit. Submini HV rectifiers, IIRC the 5642, are small and can do up to about 10KV, not enough for color TV though.

Some of the early Japanese color sets used the 5642 as the focus rectifier. Only one chassis model RCA made used the selenium focus rectifier. That was the CTC15, the model everyone else cloned. All the large sets, before it and after it had focus rectifier tubes. Tells you something, doesn't it.