Repair and cleanup of a Power Designs Inc. 5015D power supply that I purchased on Ebay.
This was one of the better looking 5015D power supplies that I have seen on Ebay, that was not overpriced or included an overpriced shipping charge. The listings condition description said ” fully operational and functions as intended”.

The unit took quite a while for the seller to ship but was well packed and arrived in good physical shape.
As usual before I powered up the unit, I performed some basic checks. On the outside the external fuse was good and had the correct rating, and the power cord ground and transformer primary resistance checks passed. I then pulled the covers and checked for loose screws and nuts, and then did a visual check of all the components and wiring inside.

The first item I came across was a blown 4x20 mm 1.5 amp fuse with copper wire soldered on it’s end caps, and then wrapped around the fuse holder terminals. The fuse is supposed to be a 2.5 amp slow blow 3AG, 1/4″ x 1–1/4″ unit.
With a blown internal fuse I don’t see how this supply was tested by the seller as being fully functional, as this is the main output fuse.
I also noticed that there were several signs of leaking electrolytic capacitor electrolyte several places on the board, but no signs of bad capacitors or replaced capacitors on the board?
I replaced all of the electrolytic capacitors using Vishay capacitors with the exception of C4, which I did not have a replacement in stock. I did pull one lead of C4 and checked it with my Peak atlas ESR70 tester, and it was well within specifications. I also replaced C21 which is a tantalum as it had a lot of the residue around it.
Quick checks of all the diodes and power transistors all verified good, and an extra check of the transformer secondary windings because of the blown fuse, also checked OK.

It was now time to power up the unit for the first time. I used my watts up? PRO power meter attached to a variable transformer to slowly power up the unit.
At first there were no obvious issues as the front panel display lit up first at around 65 VAC, and then the neon power indicator light as I increased the line voltage. The idle current was reasonable at 385 mA at full line voltage, and no signs of overheating components.
I set the voltage output on the front panel to 1.00 volts and connected my multimeter to the supply output. The output measured close to 1 volt, but there was quite a bit of drift and erratic voltage changes in the tens of millivolts. As I tried to increase the voltage higher, I could not get past 10 volts on the output, which is not good on a 50 volt power supply.

I decided to check the 10 turn Bourns potentiometer first, as I have had issues with them in the past.
For a 10K ohm potentiometer it only had a maximum resistance of 2.3K which is why it could not get past 10 volts.
For a replacement I decided on a De Young dual-stage 10K potentiometer that I discussed in a previous Hewlett Packard 3551A post. It provides the full output voltage range in 1.5 turns and also a 10:1 fine adjustment on the same shaft.
Replacing the potentiometer solved al the voltage output issues, and the supply passed a full load test across it’s full output range.

I decided to add some protection in the way of heat shrink tubing around the exposed terminals of the main line power fuse on the back panel. This would never meet todays protection standards, but I feel just a little better that the line is protected from shorts at least until it is past the fuse.

This version of the 5015D doesn’t use the Uniply regulator system found in most of the other C and D series supplies including some 5015D units with Uniply. It uses 5 MJ15015 transistors in it’s output stage which all have a date code of the 52nd week of 1983. The latest date code in the supply is the transformer which is dated June 12 1989.

This 5015D is rated at 1.5 amps across it’s full output voltage range of 0 to 50 volts DC. At lower voltages such as 1 to 5 volts the unit dissipates a significant amount of heat at it’s full current rating of 1.5 amps, but is much more efficient at voltages above 12 volts.

I also decided to upgrade the front panel display module with one of the D‑series extra digit resolution ADC display boards from a previous post. This power supply uses the 200 mA full scale display modules, but I will be modifying it to a 2.00 volt system in the near future, like I did in the Power Designs 6010D restoration.

I have always loved the look of the yellow zinc chromate plating on the brushed steel perforated bottom covers used on the Power Designs supplies. The above picture doesn’t do it justice.

I am currently waiting on the fabrication of some new display boards for the 2.000 volt range high resolution modules, and should have an update in a few weeks.
That’s indeed an interesting potentiometer. Are they still available? I couldn’t find them or anything similar when I searched.
Hi Johan,
I picked up the 10K version from “Surplus Sales of Nebraska”.
(RWV) 23A-10K
Greg (Barbouri)