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Old 27th Nov 2022, 7:47 pm   #1
Electricdreams
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Default Philips 1200u LOPT sparking

So I powered up my Philips 1200u since queen Elizabeth funeral. It would not start up, faint and out of sync picture.
I assumed it was my hedgehog as it has sometimes played up assuming a dry joint or something.

I decided to open the back and check all valve were seating and I could hear arching and can see it in the LOPT cage. Ive turned it off and hope I haven’t made it worse by leaving it earlier assuming the fault was somewhere else..


Ive not got round to taking the chassis out but rather concerned. What would the likely cause be? Could it be a spider something or could it be worse like the LOPT insulation breaking down?

Hoping Mikey405 sees this as he has worked on it.
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Old 27th Nov 2022, 8:01 pm   #2
Electricdreams
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Default Re: Philips 1200u LOPT sparking

Just had a closer look at it.. i can see the resistor! i thought that was supposed to be covered in wax! Must be the heatwave…
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Old 28th Nov 2022, 2:55 pm   #3
Heatercathodeshort
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Default Re: Philips 1200u LOPT sparking

I've not looked at the transformer layout but are you sure that is a resistor and not the EHT smoothing cap? If I remember it is buried in a little wax filled coffin on the front of the TX. Chop it out as a test. If it is the cap the chassis will work perfectly OK without it. J.
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Old 28th Nov 2022, 11:37 pm   #4
Electricdreams
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Default Re: Philips 1200u LOPT sparking

Hi John, it’s definitely the resistor, and yes you’re right. Its supposed to be in it’s little coffin covered in wax, but that wax has all gone, the resistor is now arching with the cage.

I suspect the wax melted since the last heatwave, the room it was in reached 40°C!

I wonder if silicone rubber is a good insulator..
Anyone tried this?
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Last edited by Electricdreams; 28th Nov 2022 at 11:47 pm. Reason: Included coffin ⚰️
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