NPN or PNP

skippy_ps

AK Subscriber
Subscriber
Got atransistor here with a broken leg. How can I tel if it's NPN or PNP? :scratch2: Marked BC, 414C. McIntosh MR-77.

Murray
 
with a diode checker, a + on the base and a - on the emitter you will get I flow and .7 volts, a silicon diode. Reverse and it should be Hi Resistance, no I flow. NPN.

anode cathode
B+ ---!>--- E-
I flow >>>
 
Thanks. I think I found the specs on it - NPN, 45v, 200ma. Now to try and chase one down. Seems all the 'net sites I found are just offering quotes - no one actually offering them for sale. Maybe I can buy 1,000. :D

Murray
 
I sent you a manual on the MR78, it uses the same (I hope) audio board as the late build MR77, this is the one with the filter module on it. You could use an ECG(NTE)123 to get it up and running, just watch the lead layout.
 
Thanks for the MR-78 schematic Terry. Makes more sense now. Transistor is Q407 which supplies "signal" to multipath tube. Ha Ha, kept trying to find the 6HU6 tube on the MR-78 schematic and couldn't find it - makes sense because there isn't one on the MR-78. :)

Cut the other 2 transistor legs shorter and glued it back in.

OK, now why does the multipath tube oscillate in time to the music? Transistor ng?

Murray
 
Try a different station you may have Multipath reflections and that is exactly what you would see.
 
MR-73 doesn't do it at all. All the stations, afaik, are all transimtted from the same place. Have an outside tv/fm antenna aimed there (east) but have a high mountain range about 2 miles west. So, zip from LA or SD. Had an omni antenna but multi was so bad that I took it down.

Both tuners sound great. No popping/fuzz like when multipath is bad. :shrug:

Murray
 
NTE Cross Ref

Just figured out that if you go to Mouser, click on suppliers, then NTE, there's a link to dl NTE's X Reference.

Punch in the id on your device and it gives you NTE's number and the specs. Cool.

Murray
 
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