- 2025
- Oct
- 28
A Viz WP-705 Power Supply part 4: The fix is in.
We left off with the regulator issue fixed, but still having a problem. There’s not that much more that can be wrong, so let’s move on to the isolated supplies that feed the regulator.
This is a simply supply consisting of two transformer windings (one for each side,) a diode, and a capacitor to make a half-wave power supply. Originally I thought that it might be dried out capacitors, but there’s no reason not to check everything in there. Diodes and transformers all were in acceptable ranges…but in the process, it showed itself.
The ‘ol “Vertically mounted heavy transformer (with short leads) on a PCB” trick.
You can clearly see a crack in the solder, and that’s in the side of the supply with the issue. You can also see the other leads beginning to develop cracks, so it wouldn’t be long before those leads were also broken. Since I’m in there, I replaced the capacitors I originally suspected (they’re old) and reflowed every joint on this board.
And, it works.
I want to replace the main filters at some point as well, but that’s a higher voltage part and I don’t have any in stock that fit the area. I’ll order something and revisit this unit later.
That pretty much takes care of this unit, but it still needs some tweaking on the display calibration. Hopefully the manual is close enough on this that I can assume a cal procedure from it. One more part on the way, stay tuned!