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Question Thorn PCB

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crustytv
(@crustytv)
Posts: 12249
Vrat Founder Admin
Topic starter
 

One for @jayceebee or @jcdaze

I have been given this Thorn PCB, I'm fairly certain it is linked to tuning/remote circuit control, as It uses a Plessey ML237B. This is a 6-channel sense circuit ic. There is also a post labelled vol and a preset marked 'set mute'.

The board is marked as U909C (black) S909 B (orange) 909/021 C (green) on the print-side, and there's a sticker 909 110234 on the component side.

So, am I correct as to its function, but more importantly what series of chassis? My gut is telling me 96K, though I'm confused by the U9xx, wasn't 96K U7xx modules. Maybe it's 98K.

Help me Thorn boys, put me out of my misery and reveal what you know.

20230717 133050
20230717 133108
20230717 133351
20230717 133402
20230717 133418
20230717 133422

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Posted : 17/07/2023 12:50 pm
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jcdaze
(@jcdaze)
Posts: 174
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@crustytv  I had a look at the 9800 series service manual from September 1978 and it is the channel control panel for the 22 inch version with neon channel indicator. 26 inch versions used a different panel. In fact manual states that there were 2 types of touch tune panels (PCA860 and PCA862) or another system using 3 panels (PCA456, PCA480) and PCA909). That is all that I know. Cup of tea for me now.

 
Posted : 17/07/2023 1:45 pm
crustytv
(@crustytv)
Posts: 12249
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Topic starter
 

Cheers Jim, need to trust my spidey-sense. Enjoy your cuppa

For completeness to the thread, here's the cct for the module

98ktune

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Posted : 17/07/2023 2:05 pm
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Captain Peacock
(@captain-peacock)
Posts: 26
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Were the touch panels used with this PCB the same as those awful pads fitted to the later Thorn 8800 chassis that kept getting stuck on one channel when someone with the merest speck of jam or some other food on their finger operated the pad? I wish I'd had a £ for every one of those I replaced. They were fixable, but it was such a hassle stripping them apart - especially trying to get the circular grip washers to clamp tightly again afterwards.

 
Posted : 21/11/2023 12:34 pm
Jayceebee
(@jayceebee)
Posts: 2110
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@captain-peacock The PCB shown was used in various 9600 and 9800 models, the former used a mix of the touch assembly you described and a much better non latching switch bank used on the early remote versions of the 8800 and 9000. The troublesome type on the 8800/9000 was later available as a tact switch replacement which solved the problem except when splashed with liquid.

As you say at least repair was possible unlike RBM and I think maybe ITT models where the plastic insulating material between the pairs of contacts would often go conductive.

John.

 
Posted : 21/11/2023 6:58 pm
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