4.5kV Power Supply GW4RWR

This was built in 1990 to supply the 3CX1500A7, and was conceived to provide plenty of power, just in case I ever had grander designs. The transformer is rated 3500V 1.5A.

The mains input is switched via a relay from the amplifier cabinet, arranged such that excess anode current will cut out the anode supply. There's a front panel switch in parallel with this relay, to enable the PSU to be used 'without protection'. I've operated the PSU with the rear panel off since I build it, but with a two year old who is more inquisitive each day, I finally fastened the rear panel securely in December 2011. If my wife ever understood what went on in my 'shack'..

GW4HBZ is to be thanked for the large current meter, which was suitably printed with 1500mA FSD. By luck I eventually discovered an identically sized meter, 50uA fsd, perfect for measuring EHV. I like large meters, and plenty of them. Too many commercial amps use multi-function metering. But a meter is an insignificant portion of amp's cost, and it's convenient to be able to glance at the meters, rather than have to switch to the function required. Update: The voltmeter (50uA) has failed open circuit - has anyone a replacement I could buy?

I have had the HV meter chaing resistors fail open-circuit, even though the volts across each were within limits. Symptoms were that the volt meter would display fluctuating readings, and then settle near zero. I replaced the chain with twice as many resistors with of half as many ohms, and not had a repeat.

My only complaint is the weight. This thing is huge. I had to remove the transformer, itself a difficult task since it must weigh over 500N, just to move this monster across the room. I had it on casters, but they collapsed! Please don't ask me to bring this along to VHF NFD!

The PSU always brought up to 230V using a 25A Variac, by which point the transformer has quite a perturbing buzz.