Advice about repairing an IBM 5151

tony duell ard at
Tue Sep 1 13:56:08 CDT 2015

> > Are you sure TR23 is good. The horizontal output transistor in many monitors
> > often fails.
> I am not sure. I assume I have to desolder it to check it right?

Yes, but it's only 3 connections to desolder.

Obviously if the 2 junctions don't test properly as diodes, or if the Hfe is much lower
than it should be then the transistor is dead. But due to the high voltages that should
be around, most transistor testers don't do adequate testing of such transistors. 


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