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TonyDuell · 9th Apr 2021, 4:11 pm

My experience is that most SMPSUs will start up on a lamp limiter but you should short out the bulb before applying significant load to the output. So that's what I did. The lamp was not in-circuit when I put the 1A load (actually a 4.7 Ohm high-power resistor) on the 5V output.

A Variac is probably not a good idea here, with a lower input voltage the chopper will be passing more current. (SMPSUs approximate a contant power load to the mains).

I've replaced all the electrolytics on both the mains and output sides with new ones from Farnell. I think they're Panasonic brand, they are certainly 105 degree ones. I would be very surprised if any of them were high ESR.

I do have a couple of spares of the semiconductors that fail but I don't want to keep on fitting and blowing them as (a) they are not cheap, the transistors are over 5quid at time. and (b) I am not sure how well the PCB will stand up to repeated resoldering.

9th Apr 2021, 4:11 pm	#19
TonyDuell Dekatron Join Date: Jun 2015 Location: Biggin Hill, London, UK. Posts: 5,208	Re: Weir HSS100/4 PSU blowup My experience is that most SMPSUs will start up on a lamp limiter but you should short out the bulb before applying significant load to the output. So that's what I did. The lamp was not in-circuit when I put the 1A load (actually a 4.7 Ohm high-power resistor) on the 5V output. A Variac is probably not a good idea here, with a lower input voltage the chopper will be passing more current. (SMPSUs approximate a contant power load to the mains). I've replaced all the electrolytics on both the mains and output sides with new ones from Farnell. I think they're Panasonic brand, they are certainly 105 degree ones. I would be very surprised if any of them were high ESR. I do have a couple of spares of the semiconductors that fail but I don't want to keep on fitting and blowing them as (a) they are not cheap, the transistors are over 5quid at time. and (b) I am not sure how well the PCB will stand up to repeated resoldering.