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Old 11th Apr 2024, 9:59 pm   #1
Studio263
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Default Sony KV-1820UB HV / HSTAT block

Following on from this thread:

http://www.vintage-radio.net/forum/s...d.php?t=202566

I've been making some progress with this. I used miniature 2CL20/2CL77 20KV diodes and 470pF 30KV disc ceramic capacitors, these parts just make the ratings and a small enough to fit inside the casing. The input resistor was a bit of a guess, I chose 100 ohms but the best looking one in the box was 120 ohms so I picked that.

The assembly places points at great potential difference as far apart as is possible (see photos). The circuit is a bit confusing but luckily it is shown in detail in the service sheet, albeit without component values.

It can't be run at full voltage without potting it of course but I'm planning to test it with about 50V at the input on the bench first. The resin I've selected is Robnor PX700C which is available in small quantities. Once that goes in its a couple of days for full cure at room temperature and then the moment of truth - ooh er!
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Old 12th Apr 2024, 9:00 am   #2
simpsons
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Default Re: Sony KV-1820UB HV / HSTAT block

Wow. This is reverse engineering at its best!

I too have 1820 but no spare parts otherwise your request for a replacement would have been met.

Thankfully, touch wood, the H-Stat is OK.

I'm sure your effort will be rewarded, the KV2000 etc give a stunning picture.

Chris
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Old 12th Apr 2024, 10:24 am   #3
Welsh Anorak
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Default Re: Sony KV-1820UB HV / HSTAT block

Fingers crossed Tim!
The excavation can't have been much fun - are you still finding bits everywhere?
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Old 23rd Apr 2024, 9:33 pm   #4
Studio263
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Default Re: Sony KV-1820UB HV / HSTAT block

I've had some success with this repair. The next step was to pot the assembly with the Robnor PX700 resin. It is supplied in a vacuum packed bag which is folded in two and secured with a clip. Once both parts are mixed one cuts a corner off the bag and pours it in. It stays liquid for plenty of time and so runs into all the gaps between the components.

To make sure it had completely cured in the middle I left the unit in the airing cupboard for two days.

Re-assembly was simple and the set worked right away. The picture size was about right, as was the brightness and focus. The picture size didn't change with the brightness of the picture either, all these things suggesting that the EHT voltage is correct. The convergence was miles out though; the HSTAT control gave the correct results in the centre of the screen at the mid point of its travel but the dynamic convergence was poor. I can't see what the link between this and the EHT unit is but a good picture could be obtained within the range of the controls (see photos).
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Old 24th Apr 2024, 7:57 am   #5
Nickthedentist
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Default Re: Sony KV-1820UB HV / HSTAT block

Nice work!

Looks a very clean set inside.
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Old 24th Apr 2024, 9:12 am   #6
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Default Re: Sony KV-1820UB HV / HSTAT block

I was just thinking that, it's the rarer "rosewood" effect cabinet as well. Had one similar but it was lost in a storage unit fire.

Well done in fixing it Tim - where there's a will there's a way!
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Old 24th Apr 2024, 10:20 am   #7
Welsh Anorak
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Default Re: Sony KV-1820UB HV / HSTAT block

Great result as always Tim!
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Old 24th Apr 2024, 8:13 pm   #8
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Default Re: Sony KV-1820UB HV / HSTAT block

Excellent repair! What an immaculate set with a pleasing rosewood finish.

Regards,
Symon
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