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Transistor Used as a Diode - Sony STR-6045

lieutdan

lieutdan

New Member
I'm currently rebuilding the power supply board on a Sony Str-6045 and have come across a transistor which seems to be used strictly as a diode via the Emitter and Base, with the Collector left disconnected. It is shown on the diagram as a 1T244 diode.

Would this have an advantage over using a regular diode/zener diode? it seems that using a transistor this way should function somewhat like a 6-7V zener. Could I replace it with a zener, or even a 1n4148?
 
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A "temperature compensated zener diode" where the zener diode has a normal one in series.

The schematic indicates it works like a zener diode, so the drawing and text is somewhat misleading (read: erroneous)
 
Any reason you're looking to replace this part? If its working, I'd vote for leaving it alone. Semiconductors generally work, or don't. Not a whole bunch in between.
 
I'll post a pic when I have the board in front of me. Not looking to replace it as it seems to be working fine, just more curious than anything. It looks exactly like a small signal transistor, but with a brown colour, shows up in my tester as a transistor with a very low gain of 17. Seems to be holding voltage down to around 8.5v.
Looks like the tuner board has a bunch of them as well.
 
This is a 8.4 V zener diode used as voltage reference for the +15 V supply rail. The B-E junction of a bipolar transistor can be used as such. These could be rejects rebranded with the 1T244 name or specially selected blanks. Maybe they just had excess production. Rather unusual kludge.
 
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