Help!!! Some good days... some... not so good..
Posted: Sun Oct 02, 2011 1:24 pm
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...
...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...