Sansui AU-317 Protection Circuit / RED LED issue

[john cronin]

Hi All
I bought a 317 on eBay. The most filthy dirty unit Ive ever seen but I can see it will scrub up nice.
Both main fuses on the PCB had blown etc so I just got stuck in on the restore and clean up.
Cut along story short I replaced the standard components that normally needs changing on this model. I also replace Diode 606 to 609 as I found 608 had cracked in two (Hence blown fuses)

I powered up with a variac and dim bulb but noticed the red LED was not flashing. It was on and stable and also no relay click. The relay did not engage.

I was able to set bias to 10mV and DC offset to 0V but still no relay engage and still a steady glowing red steady LED at power on. I was able to test Amp with signal generator and scope and the amplifier works fine.

I just have the Power Amp F-2754 installed and nothing else.

I think I have two problems here. Any ideas ?

 

[DougBrewster]

Relay contacts welded?

 

[john cronin]

Relay contacts welded?

Hey Doug how are you and thanks for helping. Its a brand new relay. There is no voltage potential across the relay coil . The fact that the LED does not even start to blink makes me think I have two issues. I will do some further investigation over the weekend. I done the DC Offset reading before the relay.

 

[skippy124]

Hi,

The red led on the 317 is a power on led only, it doesn’t blink when “in protection” whilst powering on or when abnormal operation occurs like the 517/717 etc.

Check the transistors etc in the protection circuit, annd also the supply to the protection circuit.

Cheers
John

 

[john cronin]

Hi,

The red led on the 317 is a power on led only, it doesn’t blink when “in protection” whilst powering on or when abnormal operation occurs like the 517/717 etc.

Check the transistors etc in the protection circuit, annd also the supply to the protection circuit.

Cheers
John

Hey Skippy124 I had it in my head that the 317 blinks but there is no multivibrator flip flop circuit in the diagram. I recently done a 517 so that was in my head lol. Massive thank you. I will concentrate on the protection circuit over the weekend and provide update

 

[john cronin]

Hi everyone. The issue is now fixed. The problem was me putting in a 4.7uf cap in C601 instead of a 47uf. What a plonker

Thanks again for all the responses and attention.