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Heatercathodeshort · 31st Jul 2021, 7:49 pm

One of the most complicated receivers of the period and it remained so for a few years.
An O/C line linearity coil is almost unheard of with the Pye V4. Did you clean the chassis before starting your work? If so you may have broken a fine wire from the coil. Worth having a very careful examination of the winding.

Start with the HT line. Make sure this is something near the published data. The VT4 are prone to line output transformer and scan coil failure. If you can scope the drive waveform to pin two of the PL81 it will confirm if the line oscillator is working. Replace the boost cap, line coupling cap and test. The scan coils can be checked by disconnection. It's the screened wire but I cannot remember the colour of the other one. Connections are under the scan coil mounting on a tag strip. Don't tackle anything else until you get the line timebase working. You will only mess yourself up! Good luck with it. The chassis has a very high component count. John.

31st Jul 2021, 7:49 pm	#3
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Pye vt4. One of the most complicated receivers of the period and it remained so for a few years. An O/C line linearity coil is almost unheard of with the Pye V4. Did you clean the chassis before starting your work? If so you may have broken a fine wire from the coil. Worth having a very careful examination of the winding. Start with the HT line. Make sure this is something near the published data. The VT4 are prone to line output transformer and scan coil failure. If you can scope the drive waveform to pin two of the PL81 it will confirm if the line oscillator is working. Replace the boost cap, line coupling cap and test. The scan coils can be checked by disconnection. It's the screened wire but I cannot remember the colour of the other one. Connections are under the scan coil mounting on a tag strip. Don't tackle anything else until you get the line timebase working. You will only mess yourself up! Good luck with it. The chassis has a very high component count. John.