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Old 13th Sep 2011, 1:54 pm   #101
Heatercathodeshort
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Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 6,386
Default Re: Restorers dream part 2 the chassis.

Hello Colin,
Please forgive me if I repeat here the good advice that other Forum members have posted. I have attached the timebase circuit of your Ekco with the relavent components marked in colours. The red ones are very much to do with the line timebase and obtaining 'first light'. You have snipped off the mains R.F. bypass cap and I think you have replaced three others, the boost cap, decoupling cap and line coupling cap. This should get the line timebase working fully producing enough EHT to give a glow of sorts on the screen. The valves,other than the U25 will probably be fault free and as you can hear the timebase whistle and draw a spark from the U25, it should work to some degree. You should be able to draw a spark from the single wire end of the U25 simply by holding a well insulated screwdriver tip close to the connection and drawing around a quarter inch of arc. Do not short the blade to chassis at this point. Moving to the twin wire end, heater and cathode, you will need to hold the blade to the chassis and advance the blade towards one of the twin end connections. It should produce a loud cracking spark [it may make you jump] quite harmless to both you and the receiver if you use a good quality screwdriver. The U25 should show a faint red glow from inside the bell looking from the twin wire end. If you can see the glow there will be usable EHT available. No glow will probably be down to a faulty valve if there is plenty of AC spark at the single wire end. The circuit does not use a CRT anode 1 decoupling capacitor so if all is working well around 300v should be available on the tube base. [Pin 10 counting clockwise] If the timebase is under strength it could be due to low H.T. that can be measured first on pin 8 of the PY32/33 and last on the 200uf section of the smoothing block. Expect around 200v plus for a working receiver. Once you have established that EHT is present, the receiver will give up it's secrets by way of tell tale displays on the picture tube itself. The green and yellow components will then have to be investigated. Keep cool! Regards, John.
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