Advice about repairing an IBM 5151

1 Sep 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. 

-tony

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Advice about repairing an IBM 5151