Hello to members -

I will start with a very GENERAL Question concerning Transistor Amplifier Biasing.

We have all seen on Schematic pages Voltage readings printed on the schematic at various test points and components leads from the manufacturer. These voltage notations usually are a good DC Static State confidence check of various circuits.

What type of Transistor component fault may reduce significantly the collector's bias voltage ?

Yes, in repeated Amplifier circuits replacement of the Cascaded Amp transistor's, corrects the Collectors Bias Voltage.
Curious of what type of internal Transistor Failure may cause this ?
These defective Transistor's interestingly - will Ohm -Continuity Check as though they are fine !

Any suggestive input is appreciated.

cferry7

 

Would almost have to be a collector-emitter short, or at least high leakage. I'd suggest you double check your C_E ohmeter readings. Should be open circuit both ways.

 

"Ylli" -

Yes, I can agree with your suggestion on C-E short !
In taking the C-E ohm readings with a Simpson Analog meter and Fluke digital their was a miniscule Ohm reading difference between Good and Bad transistors ( In circuit ) readings from C-E.
However, it was so so miniscule and these being at the high K ohm range anyway - it didn't seem important !

Can the Transistor faults such as : Avalanche Breakdown, Punch Through, Second Stage Breakdown, Collector Multiplication and others in the semiconductor related breakdowns be detected with a Multimeter only ?

Why do I think all defective transistors can be detected w/ a Multimeter ?

Any suggestions. Thank you.