G07 HOT bad out of the box?

kelleyphd

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Hi Everyone,

I have a rather basic question. I just received an order from Bob Roberts and I immediately tested the HOT before installing in my G07 chassis. I recently watched Randy Fromm's video on transistors and thought I was pretty solid on testing transistors. So, when I test this 2SD871 I immediately got a short between base and emitter. I get a .437 junction drop between base (red) and collector (black) and between emitter (red) and collector (black). And open between emitter (black) and collector (red) and between base (black) and collector (red).

So, is there something I am missing? or is it possible to have a bad transistor out of the box?

Thanks,
Daniel
 
you actually can't measure a HOT on diode (meter setting) for all measurements, you need to measure resistance as well. look at the datasheet for the part it has an internal resistor as well as the transistor. Where you measure a short change the setting on the meter to resistance you should get >10 Ohms if I remember correctly.
 
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base to emiter on a g07 type hot will be about 37ohms so your "like short" reading is normal..
collector to emiter or base you will have your normal .6v drop across.
 
Makes perfect sense - and it tested good. Still haven't found the problem with the short that is blowing the fuse but I have eliminated several components.
 
Was the flyback replaced?

Yes, flyback and HOT were both replaced along with a cap kit. I have double checked all caps for polarity. I have check most of the transistors and all the 900 series resistors and diodes. I did find X901 to be bad and replaced that. It blows the small fuse immediately. I do hear a brief squeal before blowing the fuse.

Any thoughts on hunting down the short?

Daniel
 
Did you put the mica insulator back on?

Go through all the diodes and transistors, then start checking resistors, etc....
 
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Did you put the mica insulator back on?

Go through all the diodes and transistors, then start checking diodes, etc....

I put a new mica insulator on it and checked with a meter to make sure it was not grounding to the chassis. I have started checking each of the components.
 
Which fuse though? .your main or second fuse after the power conversion?
 
Which fuse though? .your main or second fuse after the power conversion?

The small one, F901 blows immediately after powering it up. The hot and VR are both insulated and test good. I even took them off and tested them to be sure.

Daniel
 
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