Can I replace a 2SC1969 with a 2SC2312?

[Tetra]

I have a very old side mic 148 that appears to be in need of a final. I dont have a replacement 1969, but I have a few old 2312's. Can I just do a straight swap? If so, should the final bias be set to 50 mA like the stock 1969?

Thanks.

 

[unit_399]

Yes it will work as a straight up swap. And ... yes set the bias to 50ma like the stocker.

- 399

 

[mr_fx]

yes and the 1307 will swap too

 

[n0zna]

a 1307 or a 477 will do also...73 de JW

 

[AudioShockwav]

a 1307 or a 477 will do also...73 de JW

A word Caution
You can replace a 1969/2312/1307 with a MRF 477, BUT the Base/Emitter/Collector pin out is not the same.
Pins # 2 & 3 must be crossed, and insulated with a small pc of heat shrink to prevent them from shorting.
1306/1307 driver/finals are rare as hen`s teeth to find nowadays, they have not been made for a very long time.


73
Jeff

 

[n0zna]

thats right,

the do need crossed...been so long since i fooled with trans...i like glass,tubes...73 de jw

 

[Tetra]

Thank you all!

 

[unit_399]

DE NADA.

 

[Tetra]

Well the original final was bad (open base-emitter junction), but the replacement 2312 didn't solve the issue. After the swap I still get no bias current on the final and the voltage at the base is still sitting about 6.1V. I have a bad feeling that I just popped the replacement final (will test it tomorrow) as something else is the root cause. One thing I did notice is that TR37 gets pretty darn hot. Does anyone know what the voltages should be on that one? Also, the 148 service manual on cbtricks seems to be relatively new (5/15/98), is this applicable to the old 148's from Taiwan?

Thanks.

 

[Robb]

TR37 is the bias regulator. You might pull it off the chassis and see if it checks out OK first. Then, check the bias diodes too (MV1Y's - I think). Just guesses from the past.

 

[Tetra]

I did in fact blow the replacement final. I pulled TR37 and it tested ok. Turns out the culprit was C152. It was leaky and allowed DC to pass from the driver collector to the base of the final with only a 10 ohm resistor in the way. A 6V B-E voltage killed both finals I would say. Replaced the cap, the final again, set the bias and it is back in business.

Thanks again for everyone's input!