Oltronix B32-10R Power Supply

2025-06-17

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Oltronix B32-10R Power Supply

Linear (but pre-regulated) 32 volts, 10 ampere power supply (PSU), from 1970ies or 1980ies. With adjustable overvoltage protection.

My device goes up to 36 volts and up to 11 amperes. But I suppose not both at the same time, due to guaranteed power delivery of max 320 watts. I did not test this because I do not have a load that could take that number of watts.

The PSU has a cool, dark blue, shining housing.

0.01% to 0.03% voltage stability. Dutch (or swedish?) company Oltronix created a whole series of such PSUs and named them “Oltronix RACPAC”. This is a RACPAC 300, because it delivers roughly 300 watts.

Even has some visible housing scratches and bumps. On arrival, I saw that I’ve got a different device with fewer scratches and bumps. After some cleaning and work at the housing, it looked well again.

Pre-Regulation feature

This is a linear type power supply (PSU). These PSUs usually have the problem that a significant part of the systems power is wasted as heat dissipation. Some improve this by switching transformer voltages with relais, but the issue remains, it’s just smaller.

For Oltronix B32-10R, they went another way and added a secondary-side thyristor pre-regulation circuit, which means the regulating transistors always get an input voltage which is only slightly above the output voltage required. By doing this, only a small part of input energy is wasted as warming in the regulating transistors. Very nice feature.

More details

A nice meter for both voltage and current. Automatically operated lamps for CC and CV. Also automated meter range selection (8V/40V and 3A/12A) and range display with lamps. Voltage sensing can be internal or external.

The voltage control knob is not complete, I replaced it with a complete one from my parts box.

Top cover removed:

Backside. Replaceable power transistors are below a metal cover. At the left, there is a remote control connector. In hot environments, an external fan can be connected at two sockets.

Giant capacitor 22mF/63V:

Main control board:

Bottom cover removed:

Minor repair: replacement of some old capacitors

On main control board, I found one RIFA capacitor with visible cracks. I replaced that.

Rectifier section below. Here we find a bridge rectifier, built from 2 power diodes and 2 power thyristors.

This area contains 7 capacitors, all with cracks. These also need to be replaced, despite they are still seem to work. There is the danger that they become a shortcut, which could trigger harm to the PSU. All capacitors are RIFA brand (the capacitors from that company from 1970ies and 1980ies usually have these issues).

Some minutes later: While I was testing the PSU, at some point, it really happened, one of the capacitors blew up with much stinking smoke. I switched the device immediately off, so nothing further happened.

I removed after that all the capacitors, see next image. The exploded one looks quite impressive.

It is not easy to access the capacitors. I am planning to solder the replacement capacitors directly onto the old legs, because otherwise I would have to remove the whole rectifier box.

Solder side of rectifier box:

All the capacitors mentioned aim to supress high frequency interference, which could disturb the voltage regulation and even the attached consumer circuit. The PSU theoretically could work without them, but as said, to ensure a clean output voltage, they are needed.

The next image shows capacitors with their values to be replaced: