FSP 228-3F01 - No go.

[Turnip]

Hi folks,

Old one, but trying fix. S/by supply missing so replaced usual popped bits - Outlined.

S/by now OK but 24v supply doesn't power up. Gather 24v supply IC1 has VS feed from PFC transformer secondary.

PFC secondary voltage is pulsing about a bit, but not enough to turn on Q6 so Q9 can start IC1.

Natch' changed all the electros. Had to check board out of circuit, as can't do it otherwise. To enable power on, short circuited QS4

Bit puzzled - Thanks for any useful thoughts - Chris.

[michael first]

hi Chris,

the voltage on pin#12 of ic1 must be +12V,if lower the ic doesn't work;in my case replacing q6 & q9

cured the problem.

[Turnip]

Thanks Mike,

Will give it a go - Chris.

[t1412]

hi chris not sure if i'm right, low 24v was down to capacitor that's got a black sleeve around it when i took it off  the cap was bulged,

regards
shaun   

[Turnip]

Hi folks,

Noticed a YouTube video covering the problem and rather impressed. Replaced transistors and zener as outlined then replaced IC3 and IC1 as it still wouldn't fire up 12v and 24v.

Sort'a Bingo as set now works OK but the PS is making a loud buzz.

Note chap in video suggested the voltage across the main cap should be about 330v but mine is 430v so suspect the PFC is going nuts.

Out of interest used a variac on 150v but the PFC still produced 430v and the variac was screaming too, also local FM radio reception was wiped out on the bench radio.

Guess he was right about 330v after the mains bridge, or with PFC fault condition. Good video though, much better than watching TV - Chris.

https://www.youtube.com/watch?v=RJnpG-SK_OQ