Jands 920 temp cut-out

I'm trying to tune up a Jands series 920 amplifier,the service manual says to turn up the voltage on the temperature VR to approx 5.80v and it will cut-out, then turn it down 0.5v to set it correctly The relay is supposed to switch off and the front LED light comes on,Ive done this(turned the voltage up) but nothing happened,Ive tried both channels and turned the voltage up to max but its not clicking off? Any ideas?
Do you have all power to the protection circuits and are they otherwise intact and functional?
With no schematic available free and little distribution outside Oz, it won't be an easy ask to find specific advice.

My email notification isn't working and Ive just noticed your reply,sorry about that.Ive been able to contact someone who says that they know the head of the service dept at Jands and knows the two designers of this amp? I got some basic trouble shooting tips from him but I haven't received any replies to specific questions regarding the temperature protection circuit? The problem is that the badly hand drawn schematic for the Jands 920 from what I can make of it is in in some parts different to what I have here on my boards? If someone by chance has the bonnet up on their 920 could you please send me a photo of the temperature circuit so I can copy it? So far Ive recapped both boards,replaced the relays and the LM3900n ICs and re-flowed most of the solder joints,then gave it a good clean up. The 500 ohm temp trimmers measure 500 ohms and all the transistors are OK.I don't know if its getting the right voltages because the schematic doesn't show them? Ive set the DC offset and bias and the amp sounds excellent,now if I could just stop it from overheating and exploding:eek:


  • Jands temp 002.jpg
    Jands temp 002.jpg
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