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Heatercathodeshort · 7th Oct 2005, 7:35 pm

Peter,
The sync seperator valve in your VC52Da is V10. This is type Z66 and could be faulty but you will have to check the resisitors connected to pins 3 [anode] and 4 [screen grid. R43 is 47K and R44 is 100K. [HMV 1805 circuit]
The KT44 is the line output valve and will not cause your problem. There is a 'snap connector' connecting the sync output from the video amplifier V6, another Z66. It connects to the top end of C31. Check to make sure this is still in place. My bet is R43 0r R44. Try swapping over the Z66's. If you loose the picture you will know that the sync seperator is faulty. As an emergency test, you could try an EF39 or 6K7 in place of the Z66. Thats a starter for now! The anode should read between 25 and 65 volts and the screen 90 to 140. If the resistors are faulty, one of the readings will be almost nil. WATCH THE MAINS EHT and don't snap the neck off the tube if the chassis slips and pulls the tube base wires...Best to pull the base connector off while you do your tests. Peter, Try to find as many PRACTICAL TELEVISION magazines from the 50's as you can get your hands on. There are many articles explaining the stages of a television receiver from a starters angle. SERVICING TELEVISION RECEIVERS by SPREADBURY is essential reading if you want to service these old sets. Regards JOHN.

7th Oct 2005, 7:35 pm	#4
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Marconiphone VRC52A Picture Fault Peter, The sync seperator valve in your VC52Da is V10. This is type Z66 and could be faulty but you will have to check the resisitors connected to pins 3 [anode] and 4 [screen grid. R43 is 47K and R44 is 100K. [HMV 1805 circuit] The KT44 is the line output valve and will not cause your problem. There is a 'snap connector' connecting the sync output from the video amplifier V6, another Z66. It connects to the top end of C31. Check to make sure this is still in place. My bet is R43 0r R44. Try swapping over the Z66's. If you loose the picture you will know that the sync seperator is faulty. As an emergency test, you could try an EF39 or 6K7 in place of the Z66. Thats a starter for now! The anode should read between 25 and 65 volts and the screen 90 to 140. If the resistors are faulty, one of the readings will be almost nil. WATCH THE MAINS EHT and don't snap the neck off the tube if the chassis slips and pulls the tube base wires...Best to pull the base connector off while you do your tests. Peter, Try to find as many PRACTICAL TELEVISION magazines from the 50's as you can get your hands on. There are many articles explaining the stages of a television receiver from a starters angle. SERVICING TELEVISION RECEIVERS by SPREADBURY is essential reading if you want to service these old sets. Regards JOHN. Last edited by Heatercathodeshort; 7th Oct 2005 at 7:40 pm.