开云体育

To wrap up my PS cap replacement:

I replaced all 5 power supply filter caps. See thread above for details on replacements. I spent a couple of afternoons carefully pulling old supply caps. With all the new parts in hand I got the new caps and adapter boards put together in another afternoon. The next day I spent the morning installing the new caps. See photos in:

/g/TekScopes/album?id=258720

For the large negative terminal holes in the A9 board I used a pieces of aluminum ducting tape. Not silver duct tape of Mythbusters fame, but actual aluminum foil tape used for sealing stove exhaust vents. I used a three-hole punch to make nice little circles that matched the trace pad around the large hole. I just needed it to stop the solder from running through and pooling on the cap. Worked pretty darn well.

By afternoon I had everything put back together, held my breath, and pulled the power switch on. Nothing. Not even a low voltage light. No channel indicator lights, no trace. Turned it off. It didn't take long to find the problem. I first checked the outputs of the rectifiers at the new caps. Good voltages and no more deep voltage dips. Output of 110v regulator good, output of 55v regulator 0v. Or just a couple of volts. After some investigation I found that the 57.3v at the anode of CR1532 was zero. Strangely the voltage at R1528 was zero, tho the + terminal of C1512 was fine.

Tracing the trace between R1528 and C1512 I discovered that the via through A9 at the + terminal of C1512 lost its metallization when pulling the old cap. With no metal in the via reflowing the solder on the cap pin didn't allow solder to connect to the other side of A9 and left no connection to the trace to R1528. It took several attempts today to try to replace the metal via. I tried aluminum foil, but the solder wouldn't flow on aluminum. I realized I needed to use copper, and had some copper foil. I was able to reinstall C1512 and confirm the continuity to R1528.

So finally all caps are installed and working now. I've started the calibration procedure and all PS levels are working perfectly. Setting the 55v supply to 55.0v results in all other supplies being within 20mV of perfect. I've a ways to go through the calibration, but I'm back where I was when C1513 failed.

Dave