Re: Tube amp safety



Iain Churches wrote:

> "Patrick Turner" <info@xxxxxxxxxxxxxxxxxx> wrote in message
> news:43A29E2D.15D1EDA0@xxxxxxxxxxxxxxxxxxxxx
> >
> >
> > Iain Churches wrote:
> >
> >> "Bret Ludwig" <bretldwig@xxxxxxxxx> wrote in message
> >> news:1134626648.233435.43060@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> >> > Best fix for the ST70, I think is to build a power supply on a second
> >> > chassis and connect with a properly made cable. Many commercial amps
> >> > were built this way and so were a lot of radio transmitters and
> >> > transceivers. I would simply remove the preamp power/Biaset socket and
> >> > replace it with a male 11-pin octal (yes there is) and follow the
> >> > Heathkit/Collins convention.
> >> >
> >>
> >> Hi Bret. I don't know the situation in the US, but here in Europe with
> >> the
> >> EU regs and CE marking etc, such a thing does not seem to be permitted
> >> The good old octal plug and socket, (both 8 and 11 pin versions)
> >> ubiquitous in the 50s and 60s are expressly forbidden for carrying
> >> DC chassis to chassis.
> >
> > The trouble is that even with the amp cable pins being male,
> > and plugging into the PS female socket, someone could pull out the plug
> > and toch the still live pins, and get a big shock as the B+ slowly
> > subsides.
>
> The chassis connector on the psu is female, with a malke connector on the
> amp end. The only pins on the cable pair are on the plug which fits into
> the
> psu connector. The amp cable end is female.
>
> >> Several of the studios where I work have rack mounted valve amps with
> >> PSU mounted below, and connected by an armoured umbilical. This is
> >> approved in the professional but not in a domestic environment (maybe
> >> at home a Rottweiler will take his last bite - at your cable:-)
> >
> > Yeah, poor old Rotti, but its only a silly dog.
>
> But what happens if poor old Rotti belongs to a neighbour, and is a
> thoroughbread, best of breed, and champion sire?
> His death is gonna cost you a packet!!

Yes, some people love dogs more than children.

But I see why you have used amour shielded wire.


>
>
> > If you do it that way, you'd need the AC loop to be low voltage, lest a
> > male
> > pin
> > which could be touched became live with 240V.
>
> As mentioned elsewhere, I can't see how that can happen. The psu chassis
> connector is female. The flying connector on the cable is male, but the
> screw collar prevents access to the pins when the connector is inserted.
> The other end of the cable has a female connector which fits into the
> chassis male on the amp end.

Just as long as live pins can't be touched.

The range of cables and plugs/sockets I could find that were sensibly small
and still had say 6 pins and ability for 12 amps were very few and far between
and very expensive.

Patrick Turner.

>
>
> Iain

.

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