[ortek_service]

Originally Posted by GeraldSommariva

Thanks for the pointer on a good video especially the warning on HIGH VOLTAGE, having spent a bit more time investigating my power supply.
This supply uses the following two chips CA339 and TL494CN both have no supply voltage need to do a bit more circuit tracing.

These IC's are normally on the secondary-side of the main 'chopper' transformer. So if that isn't running, then all output side will be dead.
They will be part of the feedback circuit to control the output voltage, and usually drive an optocoupler to reduce the drive to the transformer when the output voltage start to go above what it should be.
The TL494 is a PWM-Controller IC, often used in these.

Note: Some SMPSU's (especially early PC ones) require a min. output load to work. Otherwise output voltage shoots up too high, and they shutdown. So you may have to put some load resistors on the outputs, to ensure this ins't happening.

I can't quite see all the transistors / IC's on the Primary-side, but it looks like there's a couple of regulators at least : 7812 (+12V) & 7912 (-12V) which is quite uncommon in these, but could check voltages around these.
I also see there's an output-side fuse (F2), which is also uncommon, and I presume you've checked it.
Looking at it, I think it may actually be two PSU's!, as it seem there are 2 transformers - the rusty one looks a bit too large for just a power-line filter inductor (common-mode choke).
So I'm wondering if there is a standby supply that is used to power the control circuitry for the main one.
And there could also be some external control switching required, although I assume it did once work OK?


Also note that the incoming mains supply is usually rectified to around 350-380V dc, and probably split across the two large (200V?) capacitors - Which should hopefully have equalising resistors across them, that will also discharge them a bit once power is removed - but may take quite a few seconds before safe to touch.
This nearly 400V (HT) voltage is actually + & - half that with respect to mains neutral (/ Earth), so touching either side can give you a shock.
And they also often connect heatsinks to the negative side, so touching one of these could give you a -180Vdc shock whilst on.
Plus makes taking measurements with non-isolated test equipment like many 'scopes were, a bit difficult.

I thought that RCA RUR-D1610 might be an IC, as they did sometime use TO-3 packages for some SMPSU ones, and I've not seen that one before. But I've found it's actually a dual 16A 100V rectifier diode:
http://radio-hobby.org/uploads/datas.../rur-d1610.pdf