Reforming caps and CRTs

Eric J Korpela korpela at
Mon Apr 20 20:29:53 CDT 2009

On Mon, Apr 20, 2009 at 6:03 PM, js at <js at> wrote:
> You can't "variac" any device that uses a switchmode power supply.  You'll
> need to go through and test each cap in the machine, taken apart.

I'm aware of that.  Unless I've forgotten something, no switching
supply is involved in these machines.  Unless the supply that provides
HV to the CRT is a switcher.  That's one of the reasons I ask.  I'm
not too familiar with the guts of a CRT.

> Proper reforming (assuming any of the caps even need reforming) by variac
> alone is extremely tedious to do.. and probably not even possible especially
> if you're attempting to variac an entire machine at once.

Yes, it takes weeks to get to operating voltage.   I'm not sure it
really counts as tedious, when most of what is involved is tweaking a
knob daily and checking for heat or smoke.  Voltage and/or current
monitors would be nice, but who's got a working chart recorder these
days?  I suppose I could turn an old laptop into one.


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