UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

beery · 18th May 2018, 1:10 pm

That's why I suggested the brightness control pot as well. It is a 50K wirewound with its cold end at 0V and the hot end connected via a 56K resistor to HT, so if the winding breaks then the pot will jump from 0V to full HT causing excessive beam current. I mention it because I have seen it on a couple of these sets.

Another thing to check is the A1 voltage from the metrosil, it should be a stable 300V. Measure this with a digital meter or valve volt meter as it is high impedance. The metrosil is also known to fail, but can be replaced with a diode and potential divider.

Cheers
Andy

18th May 2018, 1:10 pm	#10
beery Heptode Join Date: Jun 2006 Location: Ware, Hertfordshire, UK. Posts: 988	Re: Bush TV22 flyback pulse That's why I suggested the brightness control pot as well. It is a 50K wirewound with its cold end at 0V and the hot end connected via a 56K resistor to HT, so if the winding breaks then the pot will jump from 0V to full HT causing excessive beam current. I mention it because I have seen it on a couple of these sets. Another thing to check is the A1 voltage from the metrosil, it should be a stable 300V. Measure this with a digital meter or valve volt meter as it is high impedance. The metrosil is also known to fail, but can be replaced with a diode and potential divider. Cheers Andy __________________ www.youtube.com/user/andyvalve100