High Voltage supply for old CRT tube ?

[lordvader88]

I have a RCA-WO33A CRT oscilloscope from he 1960s, and the transformer is busted, I've yet to take it apart, maybe its fixable. But if not, what are some ideas to make 600-700V at 10-20mA I think.

I have 3-4 CRT TV PCBs with SMPS, and 1 from the 1970's, not sure if it's linear or switching kind. I have 2 microwave transformers that could maybe be rewound ? Or make a SMPS from scratch ? For now I don't want to spend much money, and I guess any suitable off the shelf transformer would be +$50 easy w/shipping

[AutogolazzoJr]

I don't think a microwave transformer would get anywhere near the voltage you need. It would probably saturate. Perhaps an ebay flyback transformer?

[Rog520]

You could probably find a cheap, used plate transformer (for vacuum tube equipment) at auction. Or find a transformer with a more common, lower voltage secondary and use a voltage multipler to get your required output. An SMPS in a scope is a bad idea unless it's specifically designed to be very low noise.

[vk6zgo]

Some of the older radios (from the 1930s & maybe early '40s) used  285v a side " or even "385v a side" transformers with tube full wave rectifiers.
The full voltages of these centre tapped secondaries are 570v & 770v respectively.
Used with a bridge rectifier, these would give dc voltages of the order you require.

1950s & 1960s  transformers usually had secondaries of from 450 v to 480v total, but would work with a voltage multiplier.

Unfortunately, these smaller transformers aren't as common in the USA as in Oz, as they used transformerless construction for most of their "mantel" radios.