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Forum 135

B&W TV Bush TV22 repair.

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Till Eulenspiegel
(@till)
Posts: 4947
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Last Friday this set was bought to the workshop for repair.
Yesterday, I set about finding what had caused the set to break down.
The mains fuse inside the set was found to be OC. To cut the story short the PZ30 HT rectifier and boost diode was the culprit. Fireworks display inside the valve. The faulty valve had taken out other components, a heater chain capacitor in the RF deck, a yellow capacitor fitted in 2014, now replaced by a polyester. See pic 1.

TV22 Repair May 2023 1

 Switch on the set, only a tiny spark at the anode of the EY51 EHT rectifier.
Fearing the line output transformer was faulty I continued fault finding. Check the boost capacitor, dead short! After replacing the capacitor with a temporary component the results can be seen in pic 2, a badly focussed picture. EHT only 4,5KV.

TV22 Repair May 2023 2

 Readjusting the line drive trimmer improved matters considerably, EHT 7KV and a bright picture with good focus.
Like all TV22s the interlace is not good. We learnt that was the result of too much integration in the frame sync filter circuit. a simple modification will improve interlace and reduce line pairing.

TV22 Repair May 2023 4

Till Eulenspiegel.

 
Posted : 21/05/2023 2:58 pm
LSmith, WayneD and Lloyd reacted
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