Question about Federal signal PA-300 (silverface)

nick7542

Member
May 24, 2010
49
Carlise PA ,USA
HI Guys: Need help from a federal siren expert. This output transistor (Motorola- 125B432) is from a federal PA 300 1980's model . Can anyone tell me if you are able to check these transistors with a multimeter to see if they are good or bad? if so what function on the meter to use. thanks nick

0505141353.jpg
 

MtnMan

Member
Dec 20, 2012
1,533
Eastern PA
You can do a basic out-of-circuit check with the diode test function on the meter.


1 Connect the red meter lead to the base pin and the black lead to the emitter pin. Meter should read about 0.6 V.


2 Connect the red meter lead to the base pin and the black lead to the collector (case). Meter should read about 0.6 V again.


If you have a bad transistor, replace both. 2N5885 is the generic replacement.
 

nick7542

Member
May 24, 2010
49
Carlise PA ,USA
MtnMan said:
You can do a basic out-of-circuit check with the diode test function on the meter.

1 Connect the red meter lead to the base pin and the black lead to the emitter pin. Meter should read about 0.6 V.


2 Connect the red meter lead to the base pin and the black lead to the collector (case). Meter should read about 0.6 V again.


If you have a bad transistor, replace both. 2N5885 is the generic replacement.

Thanks Mtn Man , I followed your instructions and was able to determine which transistor was bad, thanks nick
 

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