C70: Fuse Blew

[avionic]

Caramba. Is 547 the one closest to the back of the unit?

Yes. Its labeled on the top of the circuit board as 47.

 

[Gary D Olson]

TR547 needs to be removed. Its one of the two big heatsinked transistors.

It's out

 

[avionic]

There is a dead short to ground in the negative portion of the regulated power supply.

 

[avionic]

It's out

That was quick. Do you know how to check a transistor with your multimeter ?

 

[Gary D Olson]

No but I'm a quick learner. Usually. Sometimes.

 

[avionic]

looking at the front of the transistor the pins are BCE..

 

[Gary D Olson]

That was quick. Do you know how to check a transistor with your multimeter ?

fwiw, it's a Mastech MS8268

 

[Gary D Olson]

looking at the front of the transistor the pins are BCE..

ok

 

[avionic]

Measure the resistance between the collector and emitter both forward and reverse -- in the Ω's function.

 

[Gary D Olson]

Measure the resistance between the collector and emitter both forward and reverse -- in the Ω's function.

Both OL

 

[avionic]

Between Emitter and Base

Between Base and collector -- oops..

 

[Gary D Olson]

Between Emitter and Base

Between Emitter and collector

OL
13.22 (MM positive on B)

 

[avionic]

13.22 (MM positive on B)

13.22 ?

 

[avionic]

Between Base and collector -- oops..

Both forward and reverse

 

[avionic]

Between Emitter and Base

Both forward and reverse

 

[Gary D Olson]

13.22 ?

Sorry, the MM slipped into the wrong mode. Rechecked those and both were OL.

OL on both b/c and c/b

 

[avionic]

See post # 55

 

[Gary D Olson]

See post # 55

On post 56. Both OL.

 

[avionic]

On post 56. Both OL.

OK.. that looks bad...
Post # 55 reading ? Emitter and Base ?

 

[Gary D Olson]

Maybe we're both getting tired

OK.. that looks bad...
Post # 55 reading ? Emitter and Base ?

OL both ways between emitter and base