Service Manual/Full Schematic for Biddle BM10 Megger

I removed the 1N5400s, they tested fine when isolated. Probably a Huntron would have helped in that regard.

Perhaps someone has suggestions on testing TO-92-cased transistors in circuit? I've Googled it but find ambiguous, sometimes confusing instructions. One method even said it of itself, it was potentially destructive...yikes.

The Boz

"The Boz" bravely wrote to "All" (26 Nov 05 22:12:07) --- on the heady topic of "Re: Service Manual/Full Schematic for Biddle BM10 = Megger"

TB> From: The Boz TB> Xref: core-easynews sci.electronics.repair:349653

TB> I removed the 1N5400s, they tested fine when isolated. Probably a TB> Huntron would have helped in that regard.

TB> Perhaps someone has suggestions on testing TO-92-cased transistors in TB> circuit? I've Googled it but find ambiguous, sometimes confusing TB> instructions. One method even said it of itself, it was potentially TB> destructive...yikes.

To test the TO-92 transistors in-circuit just use a dmm on diode function to test the junctions. If you want to be thorough, then isolate 2 of the 3 transistor terminals to run a hfe gain test. I haven't met a TO-92 transistor I couldn't desolder using a solder pump or a solder wick.

A*s*i*m*o*v

... Letterman of Borg - "Ok, Top 10 reasons why resistance is futile:"

One instrument that I use on occasion is a "Supercricket". It will test transistor gain incircuit.The other method is the back to back diode check with a multimeter.Not quite as reliable and not always useful on FET's.

Andrew