"boardjunkie" wrote in message
...
On Apr 20, 10:04 pm, EricM wrote:
Does anyone know of a good source for HV electrolytics (600 or
above)? Or are "NOS" or eBay the only options any more? Are any
companies still making them in small runs for those of us who (in
growing numbers) are still using and preferring tube audio? Most
values can be found in up to 450V or 500V ranges, but most tube setups
use voltages around 600V and I've blown 500V units attempting to use
them as suitable replacements. Been able to find various values at
many different suppliers, but does anyone know of a good 'one stop
shop' for these beasts?

Don't bother with NOS. They deteriorate sitting around unused. If you
need a 600v+ V rating just use 2 in series with balancing resistors
around 220k. Say you need a 40u @ 600wvdc, use 2 80s @ 350 or better
in series. The ESR will add in series but for a plate/filament
transformer based pwr supply it won't make a big difference. Look at
this schemo for an example:
http://www.ampwares.com/ffg/schem/ba...b165_schem.gif

That's standard practice in a HV tube B+ supply. Most of the overvoltage
situations in tube amps occur at startup before the tubes start to draw
current. You can clamp the B+ using zeners to protect your caps at startup
if it's a problem, and/or wire up a switch to apply power to the heaters
before the B+ gets turned on.