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  RESTORATION OF A 1951 BUSH TV22
                                                                                                    Page 2

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The underneath of the LOPT is arrowed. It's a good idea to make a note of the connections now, before it's removed.

It will be seen that the HT smoothing choke has been temporarily detached from where it normally lives (hiding the LOPT) to give better access.

 

Here is the line output transformer removed from the chassis. Close inspection reveals some surface rust on the laminations but nothing too bad.

The EHT cable (to upper right) is chopped off and will later be replaced.

What follows is optional and holds dangers of damaging the transformer for the unwary. However I always do it to ensure that the transformer will later run as cool as possible.

First, the remains of the old mounting sleeves covering the horizontal laminations is removed. Then the transformer is put in the oven at no more than 200ºF for half an hour to soften the pitch. The pitch is then gently flaked off with the fingers...

...with particular care not to break the very fine wire connections to the EHT overwind (arrowed). If you do this you have a serious problem !

Be very careful also if you pick out pitch from around the inner coil former - only visible when looking down from above the top of the transformer.

Incidentally the diagram seen here underneath came from Andy Beer's site which includes much useful information on the TV22. You might spot I've annotated resistance readings on this diagram. At this stage a quick runaround on the tags with the Avo checks that all is well.

Unless you have a serious case of rusty laminations, it's not necessary to completely disassemble the transformer or remove the lamination stacks. But in any case WD40 is seeped into these to keep them well preserved for the future. Then the horizontal laminations are wrapped with tape. This ensures that the expandable neoprene sleeves which are added afterwards won't get perforated by any sharp edges.

Finally, the transformer is sprayed lightly with a modern anti-corona lacquer. It should now be good for many more years of reliable service.

In the meantime, the various chassis parts have been cleaned down. Now it's time to turn our attention to the mains wiring.

In this example, it's actually still in quite good condition but nevertheless it has to be replaced under my inflexible creed which says that mains wiring must always be replaced.

Safety has to come first, with reliability and originality more or less tied for second place...

 

Naturally, the dropper housing has first to come off. However I can't gain access to its securing nuts underneath unless I also unhitch the vertical form and height potentiometers, along with the screening panel that surrounds the frame timebase valve area.

 

The old 2-pin mains connector has to go too I'm afraid... It's replaced by a little coated aluminium panel and grommet secured through the original rivet holes. Otherwise it would be possible for the chassis to be live (rather than neutral) in the future.

 

The dropper housing is re-mounted and new mains cabling installed. This runs to-and-from the switch (not seen here - underneath at the front).

The cables are shrouded with neoprene rubber sleeving where they pass near the dropper and frame timebase valve, for heat protection.

A new Y-rated capacitor is connected across the mains and araldited into position. This is the small block seen to the right of the dropper housing.

 

 

 

Before connecting up the new cabling at the mains switch end, the switched potentiometer is dismantled and injected with Waxoyl to ensure a long, crackle-free future. Experience has taught me that Waxoyl gives a more durable result than Vaseline in this application. Above all, don't use WD40 here - it can dissolve the carbon track's surface !


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