Not sure what happened....
...but with HV applied to the chamber, all of a sudden the cooling fan to the turbo wound itself up to jet-turbine speed, just before the power supply to it packed up.
I figured that meant the power supply had gone mental. From the same output, though, were connected both of my high vacuum gauges, my PKR251 and AIM-S. U-oh..I feared the worst - if these babies got a full wack of excess voltage then did they survive?...
PKR251 - looks dead.
AIM-S - still looking normal.
So did the PKR251 die from an HV transient in the chamber, then killed my PSU, or the other way?
I have a Farnell LT30-2. It is a classic analogue bench supply with two outputs, each with 4 x 2N3055H to regulate each supply. The other half of the PSU was supplying a CCFL feeding some big V's. That side is fine.
The duff side blew its 2A fuse. After refitting a working fuse (and removing the loads!!) there is a 48V output on the terminals that cannot be regulated by the control knobs on the front.
Well, no point crying over it. Best get on with a fix...
Not sure how to approach the PKR251. It looks quite dead, draws what looks like a near short circuit worth of current at just a couple of volts. Any thoughts welcome. I may just have to manage without it, which I can just about do.
My PSU is where I'd like to get some quick responses from. This is a basic thing, transformer cap and regulating transistors. Not one of these delicate SMPS things, it has seen biiiig transients before and never had a problem. I have dismantled it, thinking it is probably one of the transistors. Do you think I am on the right path? I can detect a short to ground, in-circuit, on the transistors of the failed side that is not present on the working side. Maybe a transistor, maybe something in the circuit further back? I have desoldered one of the transistors, that one is working. Looks to me like the 4 transistors are in full parallel, so is the best first-step to desolder all of them and check them out one by one? Or are there better ways to start the investigation?
thanks in advance...