Re: DIY Frame for SG5010 etc ???

Harvey White

The AC windings are often put in series.  Getting one out of phase results in far less voltage than you'd want.  The average TM500 mainframe checker should have tests available to make sure that the phases are correct (so they add).

History says that some TM500 mainframes were wired improperly. It made a difference on some plugins where the AC phases were added together to make an on-module power supply.  PG505 is one, and I suspect that the voltmeters were much the same.

There's a way that you can use opto-isolators to check phasing when using a microprocessor.  Another way with the same microprocessor would be to measure peak voltages vs. time to determine phasing.


On 10/6/2021 7:49 PM, Jeff Dutky wrote:
here is the TM500-series plug-in interface page on the TekWiki, which will tell you what voltages are needed

The power modules also provide NPN and PNP series pass transistors that can be (and are) used by plug-ins, so it's just a dumb power bus. Depending on what plug-ins you want to test those pass transistors may be vital.

Finally, there is some important relationship between the different 25 VAC rails that I don't fully understand. They need to have a specific phase with respect to each other (and maybe to the 17.5 VAC rail?) or Bad Things[TM] can/will happen.

-- Jeff Dutky

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