LisaList2

Quote from: berskyboy on Today at 05:20:25 PM

Quote from: sigma7 on Today at 04:36:09 PMurn it off... the capacitor is rated for 50V.

I suppose that means you need a load on +33V... don't turn it on again until you have one attached.

Since it appears the PSU is working now, if you don't have anything suitable to use as a +33V load, I'd put the PSU in the Lisa and check -5 and -12 on the I/O Board. If the video works fine, then +33 is ok.

Rats... so is there any test (or re-test) I can do to see what part I need to replace.  LOL.  Sighh... You mentioned the 50V capacitor maybe I can start there?

As far as I can see, no damage occurred, so no parts to replace. The only susceptible one was the cap rated at 50V, C25 while being subject to ~71V. Look it over carefully to see if it has swollen at all. If the video is wonky, then you might suspect the +33V filter cap.

If ordering parts you could get a spare for C25 1000uF @ 50V 100V. Or perhaps the one you previously removed when re-capping is still good... (does your DMM measure capacitance?).

If you want to keep going on testing the PSU out of the Lisa, then add a +33V load to your card edge test jig.

The +33 output is rated around 0.6A.

To load it at half the rating, you'd want to draw 0.3A, which means using a 110 ohm resistor dissipating 10W.

Or you could use the three 910 ohm resistors in parallel, making a load of 303 ohms drawing 0.11A at 3.6W (1.2W each).

I'm thinking I'll replace C25 with 1000uF @ 100V in the future. If the Lisa is powered up with no video card installed, there will be no load on +33V, so this may save the PSU.