05-10-2017, 07:26 PM
Hi.
The White 1500 Jellypot came today and the red and white one came totally unexpected from Bob.
The Red and white one is the first incarnation of the jelly pot and probably the most useful one for us that want to substitute something better for old transformers.
It did have problems as it could supply 16 to 18Kv without a doubler and it was known to breakdown. In older sets where the EHT is lower these transformers are ultra reliable as they can be "throttled" back either by lower HT or by reducing the the drive, using the VDR in the Thorn circuit is one way and the most ideal or by simply making sure the drive is lower by circuit design.
In the TV22 the line is generated by a multi-vibrator between the the ECL80 Triode and the PL38, you can't do this with the jellypot so either a separate multi-vibrator or blocking oscillator is needed.
In my original TV22 mod fitting the Thorn Jellypot I just reduced the HT to the line stage. 110V works beautifully with excellent width and EHT of 8Kv fed from a single diode connected to the transformer. The set runs down to 240 lines fine.
This time I'll have a stabilised line stage and some degree of reduction of HT. I'll only need 6Kv for the CRT and less power for scanning.
Hope to get results by the weekend.
