SAE Mark XXX1B power amp transistors question

[gkargreen]

Howdy, trying to revive an SAE Mark XXX1B power amp, and am testing the transistors in it, however, some are marked SAE XXX, so I cannot figure out which is the configuration (EBC) or what the replacements would be. I can test the outputs as they are marked EB and the collector is the can. However, the tabbed transistors have SAE marks on them. Was told a while back that one channel is bad, well the outputs all test good, so now it is on to the tabbed transistors. Thanks!

 

[clinic-audio]

Hello gkargreen

What is your problem ?

All power transistors are in TO3 packing and so Base and Emiter are always at the same place
In your case you just have to see where are the PNP and NPN output transistors so no difficulties here

 

[hamrules]

Hope it’s readable.

 

[gkargreen]

Thanks guys, yes, I can use how the circuit is wired to determine the BCE config, which I will do, but how about replacements for those, what would they be? I did check the TO3 case outputs and they were all good.

 

[hamrules]

The one I did a little while back I used CENU07 & 57 for the tabbed transistors, the old MPSU06 & 56.

 

[llwhtt]

The tabbed transistors are MPSUxx, EBC. I've been using MPSW06 and MPSW56, may be hard to find now, with heatsinks attached. The four transistors towards the middle of the board are the VAS transistors and the four closer to the right edge of the board are the VI limiter transistors.

Craig

 

[Grainger49]

There is a way to determine BC&E. It takes a meter and some time. You have to measure in one direction then swap the leads and measure in the opposite direction.

In the case of NPN transistors B to E is low resistance, just a diode drop. C to B is higher, a reversed diode.

In the case of a PNP transistor E to B is reversed, a diode pointed to the base. C to B is a reverse biased diode, B to C is forward biased.

 

[Grainger49]

My XXXIB was serial number 901.