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Old 31st Jan 2015, 10:47 pm   #8
mark pirate
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Join Date: Mar 2008
Location: Worthing, West Sussex, UK
Posts: 5,185
Default Re: Marconiphone VRC74DA

Quote:
Your set has the later crt with the evacuation seal in the middle of the base connector so it may have had a replacement crt.
There is a rubber cover on the bowl covering the evacuation seal, so very likely the original tube. does your set work by the way?

I carried out the usual pre power up tests and could not find any reason for the blown fuses, but had a heart stopping moment when checking the CRT for heater continuity, luckily just a poor contact on the tube base!

I first switched it to radio and wound up the variac, all valves light but no audio at all. Possibly no HT or the output tx is open circuit.
Next I switched to TV and once again wound up the volts, firstly the audio came up, followed by the line stage.
I can draw a small spark from the boost diode, but no EHT at the CRT. Line hold alters the whistle, and the tube heaters look healthy.

So it looks promising, but it will have to wait it's turn for some workshop time.

Mark
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