015-0058-01/Repairs

The DC output connector is a Tektronix design that is unusually fragile. This complete power supply could probably be rather easily replaced by any common "wall wart" with an output of 18-25 V_DC. The total current draw is less than 100 mA. If you do this, it would be best to replace the cord on the 134 with a modern barrel receptacle that accepts the existing connector on the end of the "wall wart" connector. This would eliminate the original, but fragile, Tektronix connector. You could also add a reverse polarity protection diode inside the 134.

Unfortunately, there is no room inside the 134 for a modern barrel connector receptacle, but inline barrel receptacles exist.

Here are some photos of a power supply with an intact output connector, one with a broken connector, and a pair of broken connectors after removal. I managed to find some replacement 131-0190-00 connectors online and replaced these, but I didn't think to take a photo of the NOS connectors before installing.

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  Intact Output Connector

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  Power Supply w/broken output connector

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  Broken Output Connectors, removed

If you look closely at the broken connectors, it is clear that the plastic broke where the gold plated disk that forms the base of the outer conductor is so large that there's very little plastic outside of it. Note that this is below the level where the barrel ID stops. When the plastic shrinks over time, from loss of plasticiser, the plastic cracks. In fact, ALL my intact connectors were cracked there, even the untouched NOS ones. I let some super glue wick into the cracks in the hope that this would prevent further damage. If you do this, remove the plastic body shell first, or you're likely to glue the shell to the connector, preventing any future access.

I wonder if Tek ever fixed this problem with a 131-0190-01. Documentation of the 131/134 power supply mechanical parts is poor to nonexistent.

It appears to me that one of the broken connectors could have some of the remaining plastic machined away and a replacement 3D printed. This could have a thicker barrel wall which would require enlarging the hole in the body, which is easy to do.

If you happen to have one of these power supplies apart, it might be worthwhile to add some series resistance to the primary, as Tektronix did to make their 230 V version. Add ~40 Ω for each volt that your typical line voltage exceeds 115 (or 230) VAC. This would help avoid transformer core saturation due to today's higher line voltage, and also reduce the power dissipation in the 134 pass transistor.

Around 1995, I was passing thru Portland, OR and was able to visit Deane Kidd in his home. I asked if he had a 134 he could sell me. He had one, but had to build up a power supply for it from parts. I watched as he put together the one in the first two photos on this page. After I got home, I discovered that the transformer was open, so Deane had to mail me a replacement. In the process of adding all this 131/134 info to the Tekwiki, I also discovered that this supply really wasn't quite right: It should have had another plastic section at the bottom and a line cord. It was also missing the line input fuse, which I have now replaced. It works perfectly.