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The Type 131 and 134 power supplies look quite similar, but they differ in an important way. Both supply ~20 VDC at less than 100 mA, and in both cases, the coaxial center conductor is the more positive. However, the 131 power supply is positive ground, while the 134 power supply is negative ground. In addition, the 131 supply has internal zener regulation, while the 134 supply provides unfiltered full wave rectified DC.

In both cases, it would be tempting to replace the OE supply with a modern wall wart and suitable barrel connector. One problem with this is that there is no room inside a Type 134 for the inner workings of a panel mount barrel receptacle. In addition, I've failed to find a suitable 19-20 VDC wall wart. While 19 VDC is common for laptop supplies, those are all rated for much higher currents and are much larger than necessary.

If a good wall wart, with isolated output, and a suitable inline barrel receptacle could be found, it would be easy to make this into a supply that worked with both 131s and 134s.