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dazzlevision · 30th Jun 2020, 9:36 am

OK, if you are sure that all the critical capacitors have been replaced in the line output stage and you’ve tested and replaced where necessary, all the high value resistors, then I suggest:

1. Is the line drive coupling capacitor C117 47nF OK? If it’s a Hunts, Erie or TCC branded paper dielectric type, it will be suspect.

2. Is R138 2.2k PL504’s g2 feed OK? It’s probably a wirewound, but just in case....

3. Is the line linearity sleeve correctly orientated - the gap in the “paper” cylinder should be the same along its entire length and parallel to the axis of the CRT’s neck.

4. Check for out of spec carbon composition resistors in the line blocking oscillator circuit: R70 39k, R66 4.7k (HT4 dropper). Might be worth trying another 30FL1/2, if you have one.

5. Have you already proved the PL504 and U193/PY801 are OK, by substitution?

I doubt if the value of R135 (1.5k/1.7k) is relevant to the width issue, as HT3 feeds the frame output stage.

30th Jun 2020, 9:36 am	#37
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,611	Re: Marconi 1400 birthday present OK, if you are sure that all the critical capacitors have been replaced in the line output stage and you’ve tested and replaced where necessary, all the high value resistors, then I suggest: 1. Is the line drive coupling capacitor C117 47nF OK? If it’s a Hunts, Erie or TCC branded paper dielectric type, it will be suspect. 2. Is R138 2.2k PL504’s g2 feed OK? It’s probably a wirewound, but just in case.... 3. Is the line linearity sleeve correctly orientated - the gap in the “paper” cylinder should be the same along its entire length and parallel to the axis of the CRT’s neck. 4. Check for out of spec carbon composition resistors in the line blocking oscillator circuit: R70 39k, R66 4.7k (HT4 dropper). Might be worth trying another 30FL1/2, if you have one. 5. Have you already proved the PL504 and U193/PY801 are OK, by substitution? I doubt if the value of R135 (1.5k/1.7k) is relevant to the width issue, as HT3 feeds the frame output stage. Last edited by dazzlevision; 30th Jun 2020 at 9:42 am.