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On Wednesday, August 10, 2016 at 3:07:10 PM UTC-4, Gareth Magennis wrote:
I have a fairly vintage valve amplifier with a dead HT (standby) switch.

It's this kind of format, SPST rocker:
http://uk.farnell.com/arcolectric/c1...ack/dp/2068581


Now, this switches the rectified HT winding from the transformer, which is
around the usual 500v with no valves in place.


I've been looking at replacements, but have not found any such switch that
has a rating of 500v DC.
Here's a typical search result:
http://uk.farnell.com/webapp/wcs/sto... 110173704&vw=


Many of these seem to be only rated,or at least tested, at 24v DC (?)
Nothing I have found has been anywhere near 500v.


And, here is a Carling switch typically found in Fenders, Mesa etc, to
switch the typical 500v HT.
http://www.hotroxuk.com/carling-spst...-sw110-63.html
It has a maximum DC voltage rating of 250v, way higher than anything else
I
have managed to find, but definitely not 500v rated.


This gets you to 400VDC:
http://76.12.210.115/pdf/s-toggle-sw-rocker-400v-dc.pdf

and then, if you use a relay, you do not risk arc-welding the switch:

http://www.vsholding.com/datasheets/7107%20D3F500D6.PDF

Hope it helps. Keep in mind that at higher voltages, arcing is the concern.
But you knew that already or you would not be asking the question.

Peter Wieck
Melrose Park, PA






Interesting that the switch you linked to uses a magnet to steer the arc, as
used on some Speaker Relays.

I'm guessing that valve amp manufacturers have used underated HT switches
for decades now, in much the same way that they have often put way higher
voltages on pre-amp valves than they are designed to cope with. (Fender,
Mesa reverb drive circuits for instance).

So I guess I shouldn't be so shocked at this revelation.



Gareth.