Get together

[Valvebloke]

As a quick post-script to this very jolly day (thanks again to Mike and Gill !) those who were there may remember Chris - Herald1360 - offering a 500V 1A power supply to someone with strong arms and empty bench space. I was the lucky winner. Chris and I heaved it into the boot of my car yesterday evening and I powered it up, for the first time in quite a while apparently, this morning. Given that there was a possibility of bangs and smoke I thought I'd better do it outside. Here it is driving two nominal 200W mains bulbs in series - actually 210W at 240V if the meters (480V, 0.88A) are accurate. It seems to work fine.

It's purely convectively cooled and all the active devices are on heatsink plates inside the rack cabinet, so it's been conservatively engineered. The regulator pass element is a bank of 2N5240s - 100W dissipation BJTs in TO3 cans. There are 54 of them, plus a few extra in what I guess are 'driver' roles ! So the thing is large - 7U high by 47.5cm deep. The substantial mains transformer also makes it heavyish - more than 35kg in total. The next challenge is to get it up the workshop stairs !

Thanks again Chris.

VB