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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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24th Jul 2017, 10:41 pm | #1 |
Hexode
Join Date: Jan 2012
Location: Weymouth, Dorset, UK.
Posts: 422
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Solartron scope.
I have an all valve Solartron scope today. I plugged it in .for the first time in weeks and as soon as I switched on the screen lit up green. Now my question how can this happen? It can't be cathode emmision because it was instant not enough time for the cathodes to heat up, also there was no preheating or anything like that. When it worked normally it would take a minute to warm up. So what's happening where is this instant glow from??
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24th Jul 2017, 11:30 pm | #2 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,876
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Re: Solartron scope.
some makers put flood guns in their CRTs to provide illumination of internally-etched graticules. These turn on pretty immediately, but I didn't know that Solartron ever did it.
Is it a storage scope? David
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24th Jul 2017, 11:44 pm | #3 |
Dekatron
Join Date: May 2003
Location: Edinburgh, UK.
Posts: 3,274
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Re: Solartron scope.
It's not just the graticule illumination is it?
Peter |
25th Jul 2017, 1:23 pm | #4 |
Hexode
Join Date: Jan 2012
Location: Weymouth, Dorset, UK.
Posts: 422
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Re: Solartron scope.
No it's not a storage scope it's way too old. As I say it's all valve except for the selenium rectifiers. This is a total new thing previously when switched on it would take around a minute before any trace would appear on the screen. The graticule illumination is there but even with that turned right dowd the screen is still a bright green.
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25th Jul 2017, 6:04 pm | #5 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,396
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Re: Solartron scope.
Could the tube have become slightly gassy? I'm wondering if there could be some sort of cold-cathode ionisation avalanche going on with the at-switch-on high EHT from the selenium rectification.
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25th Jul 2017, 7:50 pm | #6 |
Hexode
Join Date: Jan 2012
Location: Weymouth, Dorset, UK.
Posts: 422
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Re: Solartron scope.
Yes I must admit I was thinking it mite be some sort of effect from the EHT I haven't dared to leave it on for long in this state just incase I blow the tubes heater which obviously is fatal. Looking carefully at the glow it has a barely noticable flicker My next question is the scope salvageable or is that it?
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25th Jul 2017, 9:45 pm | #7 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,396
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Re: Solartron scope.
Good question! I'm not familiar enough with practical in-depth 'scope tube stuff- I wonder if it's the sort of thing that would improve with running, or if a 'scope tube just doesn't really get warm enough like a valve in order to wake the getter up a bit.
Thinking about it, some gun/focussing assemblies have EHT or thereabouts on one or more of the focus cylinders/apertures near the cathode- that would mean a high localised potential gradient that could initiate a cold strike with a small amount of gas/air in the tube, this local glow quickly then spreading towards the screen area, giving the "involuntary fluorescent tube" effect. (I may of course be barking up completely the wrong tree, but it's the best I can come up with....) Does the tube have any clear glass patches around the gun or the cone flare that show a glow with the covers off? |
25th Jul 2017, 11:14 pm | #8 |
Nonode
Join Date: Dec 2012
Location: Kirk Michael, Isle of Man
Posts: 2,350
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Re: Solartron scope.
My pal had a big valved Solatron 40 years ago, but I dson't think I ever worked on it. It struck me as a decent one.
I have seen that "Instant screen illumination" myself in the past, a sort of "high voltage in vacuum glass fluorescence". I bought a very rough Telequipment D67A supposedly in good working order. At switch on I got the fault. No idea, and no suggestions from knowledgeable pals. Once the CRT was warm, the underlying display looked OK, but the unwanted glow persisted. I eliminated various things, but then it suddenly made a loud CRACK, electrical sound not glass. When I recovered from the fright, I saw that the horizontal scan was reduced at one end. One or both of the X output transistors was now S/C. Replacement restored normal scan, and the glow had vanished. Why? I don't know, but I think it must have been some sort of short on the X-plates,, or an unusual leakage fault in one of the transistors. I suspect it may have been within the CRT. Can I suggest a bit of gentle tapping near the X and Y plates of the tube, then try the same on the two Y output valves and the two X output valves. And please report back. Les. |
25th Jul 2017, 11:15 pm | #9 |
Hexode
Join Date: Jan 2012
Location: Weymouth, Dorset, UK.
Posts: 422
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Re: Solartron scope.
I will have a good look with the the covers off to see if I can tell what's happening but it will have to wait till Thursday now I'll report back then. Thanks for your advice so far
Hi Les, yes I'll have a go and post back what I find. I'm so pleased someone else has seen this fault at least its not unique to me. Sort of a relief to know that!! |
26th Jul 2017, 11:31 am | #10 |
Octode
Join Date: Oct 2007
Location: Exeter, Devon, UK.
Posts: 1,554
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Re: Solartron scope.
What model scope is it.
I am wondering if the eht comes from stick rectifiers fed off the AC mains transformer. In which case the glow could be the eht voltage applied. The heater of the crt could be warming up very quickly, or the tube slightly gassy. I assume it is not the usual after glow from shining a bright light on the screen which then glows, often for some time if a long persistance screen. wme_bill |
29th Jul 2017, 5:57 pm | #11 |
Hexode
Join Date: Jan 2012
Location: Weymouth, Dorset, UK.
Posts: 422
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Re: Solartron scope.
Hi guys I've done some more testing and even after running the scope for an hour the green glow is still present I should add I did it with the brightness and focus controls set to minimum it did disappear briefly but as soon as I touched it it came back😢 tomorrow I'm going to take out the main control unit out and clean all the switches and check any internal plugs. The tube is covered by a metal cover over its whole length and you can see the green glow out the rear end of the tube I don't want to try removing the tube cover because I mite damage something and I don't want to risk it
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