- 2025
- Nov
- 17
A Viz WP-705 Power Supply part 5: Wrapup and final thoughts.
This was an interesting device that required following a fault back to what was (most likely) it’s original source.
I’m going to assume that the regulator was probably destroyed by the noise spikes coming from the power supply transformer’s broken leads - either the spikes in the voltage caused it, or the excessively low voltage eventually destroyed the device. Who knows, but ultimately, the regulator was bad and the transformer board needed a complete re-solder.
In addition to the regulator board, there were a couple of 4.7μF capacitors on the display board - those were replaced, as were the 470μF capacitors on the display supply. There are larger capacitors on the actual regulator board, and those will need to be replaced as well - but they’re oddball sizes and will take some finding.
The last thing is to calibrate the display as best I can. While I have a manual, it’s of no use here because it’s for a different rev. I eventually discovered that the potentiometers on the display board calibrate the external measurement, and then the internal measurement. This was just turning them slightly and seeing what happened, and it was easy enough to dial in the correct values.
It was then buttoned up, ready for use. I’m not going to talk more about the calibration, since all of these seem different - but don’t be afraid to turn things just a tiny bit to see what happens, but always be aware of what you could be causing before doing so! Make sure you can fix it if you break it.
The two takeaway points on this were:
The manual you can purchase, while it claims to be the correct one (and mine is indeed for the WP-705) may not be the correct one, especially if the manufacturer assumed lines from another company.
The fault you see up front isn’t always the cause of the problem. In this case, tracing all the way back to the input revealed what probably caused the issue here.
With that, this unit goes on the shelf, waiting for it’s use. I suspect it’s going to see service with a coming project, something where some oddball voltages are needed. Stay tuned!