SL4000 PSU Thermal Fault

[Hillbilly]

I have just re-capped and replaced all the power transistors in an SL4000 PSU.  When I power it up, the Thermal Fault light illuminates immediately. 

Has anyone ever had this problem, and/or have a possible solution. 

One of the voltage rails took a dump, which prompted the re-build, and I am considering replacing all the thermal fuses. I'm just doing my due diligence.

[waltzingbear]

I'd say more likely something ain't kosher and the tell tale is telling the truth.  Or it took a hit when the supply did. Resistance check should tell you alot.

Alan

[mikelleroy]

Hi,
while at it, please consider to renew the rectifiers of the rails,
helped here a lot!
Good Luck, Mikel Le Roy

[Hillbilly]

I also replaced the rectifiers, I'm considering a wiring fault at this point also. I wasn't the one who dissasembled it initially, and had to piece it back together using a complete one as an example.

About the resistance check, should the fuses be open, or closed at room temperature?

[jwhmca]

I would think typically closed... they "open" up like a regular fuse when hot.

[waltzingbear]

fuses should always have continuity.

thermal switches should open at a specified temperature, and reset when below.

both may be present in a SSL psu.

Alan

[xmax]

It sounds like something is broken or disconnected in the thermal trip circuit it usually takes at least
30 seconds (I would think) for it to be tripped by heat.