- 2025
- Oct
- 3
A Viz WP-705 Power Supply part 1: Analysis.
On the bench while I wait for parts for the Heathkit AG-7 is this Viz WP-705 power supply. This came from the TUSCO show earlier this year, and while I didn’t need it, the price was cheap. The vendor originally was asking half a bill for it, but when he plugged it in and the ammeter didn’t light up, he reduced it to $10. I took it for that, just because a nice linear supply is always useful.
Viz is the “company” that took over RCA’s test equipment division as it was phased out. RCA contracted out this division to start with, so it was more of a rebadging than anything else. The company that took this over, Jetronic, was already one of their big contract manufacturers, some new paint in the logo area and Viz was born. It still looked just like the RCA device, was full of RCA parts, but had a different name on the front.
Jetronic Industries Inc. appears to have continued until 2000, when they filed for bankruptcy. It was a shell company for some time, before finally being dissolved and removed from records in 2012 for failing to file necessary reports with the SEC. That’s all there is to their story.
Here’s the device in question:
This is a single-output power supply with the ability to use it’s internal meters as external meters - that’s quite unique. It’s part of a series of supplies, with each successive model number adding more features and outputs. This appears to be a middle of the series unit, or bottom of it’s tier depending on where you place it in the model stack. It’s 0-50VDC, 0-2A, and is a linear device built out of discrete components with only the displays having ICs in their circuit.
Inside is a big chonky transformer:
So what’s wrong with this? When I bought it, the ammeter wasn’t working at all. That is, the display was dark. When I put it on the bench, the ammeter lit up, but the display rolled all over the place and didn’t respond to anything. It was like whatever A/D this thing was using was bad and just floating.
What’s on the board?
The unit uses two older RCA chips to do it’s work - the CA3161 and CA3162, which are a driver/converter pair. There’s some glue circuitry as well, which looks like it’s for the display select during driving. As you can see, there’s some different-shape transistors on the board, as well as some ECG parts with a much nicer (i.e. later date) marking, indicating that this device has had some work done to it in the past.
Since there’s not a whole lot here, and the display is still scanning - that kind of points to the CA3162 A/D converter. Unfortunately, with NTE being gone, there are no more new replacements, but NOS devices exist. It’s just a matter of finding one.
I have a schematic on order, I’m going to study that for a bit before proceeding just to make sure I’m not missing anything. Stay tuned!
Next part of this series: https://wereboar.com … 2-musings-on-faults/