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mole42uk · 28th Nov 2018, 7:47 am

Well, I decided that I’d make an extender cable to outrig the pre-amp PCB as instructed in the service manual.

I am glad I did because it made testing much easier and soon a 120k resistor dropping 260V because of a s/c zener was discovered. I can’t work out why the 1.3W 120V zener had failed when the supply resistor is only ⅛W and was undamaged. There wasn’t a suitable zener in the drawer so that’s it for a day or so.

28th Nov 2018, 7:47 am	#11
mole42uk Nonode Join Date: Aug 2010 Location: Resolven, Wales; and Bristol, England Posts: 2,608	Re: Gould 407x display help Well, I decided that I’d make an extender cable to outrig the pre-amp PCB as instructed in the service manual. I am glad I did because it made testing much easier and soon a 120k resistor dropping 260V because of a s/c zener was discovered. I can’t work out why the 1.3W 120V zener had failed when the supply resistor is only ⅛W and was undamaged. There wasn’t a suitable zener in the drawer so that’s it for a day or so. __________________ Richard Index: recursive loop: see recursive loop