Technics SU-G50 help

[Tyler Ernst]

Picked up a Technics SU-G50 recently for free. Get it home, hit the power button, completely dead. Power switch is fine, fuse is good, checked the transformer, everything is good. There is a single burned resistor on the board, R771. Could this single resistor make the whole thing dead? And could it just be the resistor got too hot and burned and replacing it will fix my problems, or is there likely something else wrong with the amp that caused the resistor to fry? Not too knowledgeable at these things yet, but figured this would be a good subject to learn on.

 

[Tom B]

If that resistor is burnt open, it would probably keep the unit shut down. That resistor feeds the 14v regulator. Yes other things could be bad. The 14 volt regulator could be bad, other transistors and or diodes or caps could be bad. But you may want to just replace that resistor with a 1/2w 18 ohm metal oxide or carbon film type and see what happens. If it works great. if the new resistor burns up right away, you have more problems. You may want to find somone with an multimeter, and test that resistor to make sure it is really bad. Some look burnt but still work. It should read no more than 18 ohms. That testing needs to be done with the unit unplugged.

 

[Tyler Ernst]

Thanks for the reply, I do have a multimeter, it doesn’t read anything, so it’s open. I’ll go ahead and order a few of the resistors. Thanks again.

 

[SVI2004A]

These resistors do that... replace it and you will be fine...

Sure it’s all dead? Should still be click after 4 sec from power on

If not check -15V feed R780

Do get service manual free at HiFi engine - it will show how to correctly get main board out

 

[Tyler Ernst]

Resistors came in today, replaced R771, resistor started smoking, and just checked R780, everything’s good there. Very lost.

 

[SVI2004A]

Check Q701 D705 C703 C705 for shorts

D705 is a zener -

While at it check Q705 (6V reg) for shorts

 

[Tyler Ernst]

Should I remove them from the board to check them?

 

[SVI2004A]

The 2 transistors I would... a short over the rest would be obvious