Mighty Monarch of The Air

[vts1134]

Originally Posted by jeyurkon

There seems to be a design error here. The Sam's doesn't show what the HV is, but a 16GP4 typical operating voltage is 12KV. If they were actually operating it at 12KV, the Peak Inverse Voltage that the HV rectifier would see is slightly less than twice this. A little under 24KV.

The 1X2 is rated at 15KV PIV. So, it would break down. They're probably running the 16GP4 at 10KV or less, maybe 9.5KV. That would still cause the 1X2 to break down.

The 1X2-A, and 1X2-B are rated at 20KV PIV, the 1X2-C is rated at 22KV PIV.

If you can find a 1X2-A,B, or C then it would probably work without the modifications you made.

John

I have a 1X2B. According to my HV probe the 16GP4 is running at 14-15kv right now without the immediate sparking failure on the 1X2 which would be at 28-30kv PIV? It sounds like the 1X2 isn't going to last that long if I'm running it that far over spec. The CRT might not be happy running that far over spec either! One other thing that I have been pondering is what kind of X-ray emissions the 1X2 might be putting out with the voltage that high.

[old_coot88]

Xray emission from the rectifier happens only during electron bombardment of the plate, which occurs only during the positive-going half cycle, and the max voltage is half the PIV value. The only real concern over Xrays was in color sets where 25KV on the pic tube anode was typical, and that hype was hugely overblown (IMHO). Heck, if Xrays were any danger i oughta have been thoroughly cooked many years ago.

[jeyurkon]

Originally Posted by vts1134

I have a 1X2B. According to my HV probe the 16GP4 is running at 14-15kv right now without the immediate sparking failure on the 1X2 which would be at 28-30kv PIV? It sounds like the 1X2 isn't going to last that long if I'm running it that far over spec. The CRT might not be happy running that far over spec either! One other thing that I have been pondering is what kind of X-ray emissions the 1X2 might be putting out with the voltage that high.

They list the maximum anode voltage for that CRT at 14KV. 15KV isn't going to kill it, but it doesn't help.

Does your probe have its own meter or does it plug in to your multi-meter?

old_coot88 is right about x-ray production only occurring during the positive going half cycle which causes electrons to bombard the plate. However, they don't even have half the PIV. The forward drop on these tubes is between 80-200 volts. The electrons only get accelerated to that energy. Those x-rays will never make it out of the 1X2.

If there was a failure of the 1X2 such that the forward drop was as high as half the PIV, then you'd have higher energy x-rays, but the cathode emission would be so low at this point that the x-ray dose rate would be very small because of the very low current.

[vts1134]

Originally Posted by jeyurkon

They list the maximum anode voltage for that CRT at 14KV. 15KV isn't going to kill it, but it doesn't help.

Does your probe have its own meter or does it plug in to your multi-meter?

I have to plug my probe into my meter. It may not be the worlds most reliable reading.

Thanks for the reassuring words on X-ray emissions. It kind of got me nervous when the last 1X2 I picked up had a warning painted right on the side of it about X-Rays.