10-04-2018, 04:31 PM
Hi.
An update on the Ekco.
Over the last year or so I've occasionally given the set a half hour run. This afternoon i thought it time to concentrate on the set a bit. I have the offer of a really good CRM92 but it involves a bit of a travel, something I don't relish these days like I used to, I do though intend to pick it up once the weather improves.
So when I powered up the set today I noticed how slow the tube was to show even a picture! at this point I decided to try the old trick of passing a small current between grid and cathode to help remove some of the poisoning. Once I removed the back I was rather taken aback to see the getter was quite milky and thought this might be a waste of time.
I decided I've nothing to loose.
I fed the heaters externally and connected the cathode and grid from a variable HT supply from between 60 to 400v via a microamp meter and 270k limiting resistor. initially I tried this with 60v between grid and cathode and there was no current flowing. I then increased the voltage until I got a reading of 10uA, this coincided to 340v so I left it at this. it took just over 2.5 hours to increase to 100uA at which I disconnected the HT and heater supply.
Well on reconnecting it all up there is a marked improvement in warm up time, the picture is brighter but it still gives all the signs of a soft tube but it is now watchable in light although not that bright.
I'd say there is an improvement, whether it will last is anyone's guess. I certainly will take up the offer of the decent CRM92 this year.
I have taken some pictures and will post them up later once I've re-sized them for the forum.
The set need some more work as the line linearity changes after about 30 minutes running but I intend to get the set up to full standard this year.
An update on the Ekco.
Over the last year or so I've occasionally given the set a half hour run. This afternoon i thought it time to concentrate on the set a bit. I have the offer of a really good CRM92 but it involves a bit of a travel, something I don't relish these days like I used to, I do though intend to pick it up once the weather improves.
So when I powered up the set today I noticed how slow the tube was to show even a picture! at this point I decided to try the old trick of passing a small current between grid and cathode to help remove some of the poisoning. Once I removed the back I was rather taken aback to see the getter was quite milky and thought this might be a waste of time.
I decided I've nothing to loose.
I fed the heaters externally and connected the cathode and grid from a variable HT supply from between 60 to 400v via a microamp meter and 270k limiting resistor. initially I tried this with 60v between grid and cathode and there was no current flowing. I then increased the voltage until I got a reading of 10uA, this coincided to 340v so I left it at this. it took just over 2.5 hours to increase to 100uA at which I disconnected the HT and heater supply.
Well on reconnecting it all up there is a marked improvement in warm up time, the picture is brighter but it still gives all the signs of a soft tube but it is now watchable in light although not that bright.
I'd say there is an improvement, whether it will last is anyone's guess. I certainly will take up the offer of the decent CRM92 this year.
I have taken some pictures and will post them up later once I've re-sized them for the forum.
The set need some more work as the line linearity changes after about 30 minutes running but I intend to get the set up to full standard this year.
