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Old 11th Sep 2011, 7:04 pm   #85
dominicbeesley's Avatar
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,733
Default Re: Restorers dream part 2 the chassis.

Hi Col,

You could do worse than measure the voltages as Steve suggest. You should be getting something like HT volts at the LOPT valve's screen. To find the fuse look for the 6k8 resistor connected to the LOPT valve and then trace where the other end is connected to. I wouldn't be surprised if it is one of the 2A fuses and someone in the past has "upgraded" it!

If the voltage at one end of the 6k8 resistor feeding the screen of the LOPT valve is very low the 0.003 decouplin cap might be a bit leaky and pulling it low?

I'd measure voltage of all the under-chassis pins of V12b and V14. I'm not sure about your DMM but mine are all rated at 750V and I've not broken one yet.

Have you got an oscilloscope handy if so A poke around V12b might be in order to see if it is doing anything.

Listening for line-whistle can be tricky, I know you worked in an engineering firm and whenever I've been doing any grinding on metal I can barely hear line whistles for a few days afterwards!

Your discharger looks good. But beware that it may take a while to completely discharge the CRT and that CRT's are sneaky beggars and magically charge themselves back up on their own so once you've discharged it you might want to leave your discharger connected via a jump leads...but remember to take it back off before you switch on!

I wish I wasn't so busy at work at the moment - I'd pop round and have a look!

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