"mick" wrote in message
...
On Sun, 27 Dec 2009 23:16:05 +0000, David Looser wrote:

"mick" wrote

By the way, you may not find it too easy getting hold of a suitable
relay with a 5v coil. Manufacturers often list them down to 6v but
nobody stocks them! The nearest that you will get easily will be 12vdc
and the next one up is 24vdc. 5v coils are usually only on small pcb
relays, which don't have enough voltage rating on the contacts, even in
series (if you can ever find a complete data sheet!).


ISTM that 5V coils are now rather more common than 6V ones, and 5V coils
are just as likely to be available on power relays as any other coil
voltage. BTW why do you think PCB relays won't have enough voltage
rating?, I've just found a relay with a 10kV rating for the contact, and
that is a PCB mounting type.



You're correct that 5v coils are common on PCB relays,

I didn't say that. I said that 5V was more common than 6V on ALL relays.

but there aren't
all that many PCB relays that could switch the HT line of an amplifier.
350vDC at 200mA can be difficult to break (and make). I originally
suggested plug-in devices because they come ready insulated and are easy
to use (the 2-pole ones fit a standard octal socket). Unfortunately I
don't think any manufacturer makes these with a 5v coil.

The octal plug in ones mostly seem to use mains voltage coils. But most
relays these days, the vast majority, are PCB mount types, their voltage and
current ratings are well in excess of what might be needed for this
application (and no worse than those of the octal plug-in jobs)

Having said all that, I've just found this: Tyco Electronics RT424005
(Farnell 162-9052).

Or this one?

http://uk.rs-online.com/web/search/s...ct&R=198695 5


Someone suggested that a contact isn't needed.

I suggested that. It isn't, not if you don't unplug the PSU from the load
when it's powered up! IMO by far the best solution is to NOT do that. Either
keep people stupid enough to try doing so away from the kit, or if you can't
do that make sure that the mains has to be disconnected first. Of course
the "PSU" is only the transformer, there is no point in having the rectifier
and reservoir capacitors remote from the load, so as soon as the mains goes
off the PSU output is safe.

David.