Weir SMM300 Switching PSU Not Starting

[dexters_lab]

i have a uk made Weir SMM300SW power supply (a 300 watt chassis psu with multiple otuputs) here which is refusing to start up when powered, i have checked all the output rails and there are no shorts on the host circuits and all the sense lines are connected.

I am going to guess there is an ageing capacitor issue on the switching controller section in the PSU but if anyone has first hand experience of these PSUs that would help if you know what the issue might be? The SMM300 seems to be a very popular PSU from the 90s and used in arcade cabs so hoping someone can help.

interestingly i have had two other of these PSUs do a similar thing, but power cycling them always fixed it so there could be an inherent issue with them that causes them to do this

[fourtytwo42]

I have history with this psu, we (CASE) were probably there largest customer by far, I think I have some schematics somewhere and plenty of people I know have rejuvenated them without trouble.  I have contacts who might sell you a refurb unit if that suits ?

BTW make sure you have an amp or five load on the 5V

[dexters_lab]

thanks, if you do have schematics available they would be handy to have!

i read on another forum that some of the caps on the control side can be problematic, so on my issue 16 board i pulled caps C7, C11, C18, C33, C5 & C6 all located around the primary / control side

C18, C33, C5 & C6 were all serviceable, but C11 was marginal and C7 was leaking and utterly dead, this is also right next to the TDA1060 controller IC too so i suspect this is the issue, i'll know once my replacement caps arrive

[dexters_lab]

in case anyone is referencing this thread in the future, the PSU is now working again after replacing the caps detailed above.

[fourtytwo42]

Sorry for the delay I had to find some ancient files but here is the SMM300 schematic, I have a higher resolution version 1600x1200 but cannot post it here.

[dexters_lab]

thanks, i'll pm you a link so you can upload the higher rez file to me if you don't mind, i don't think there is really enough detail there to be of any use...

[dexters_lab]

here is a slightly better version of the schematic in case anyone is looking for it...