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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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9th Sep 2020, 12:06 pm | #1 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,042
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Scope CRT current
I'm having another look at my Sun engine analyser. It has a scope for displaying various ignition wave-forms. The mains transformer supplying all the voltages has long since died and scrapped.I have one that will provide the -1.2kV and the heater allowing the heater to float. The other potentials , focus and astig are catered for with another transformer. The final anode runs at 2kV This has been a problem! I now possibly have a solution. I have rescued from work a PSU that was originally used to supply an ion pump. It has an EHT PSU as a single block device, 12v in and 4kV out. The data sheet shows the o/p to be directly proportional to the input voltage so to get the 2kV needed I supply it with 6v. All good. The EHT block is rated at 0.75mA at 4kV. nowhere can I find any indication of what a small tube will need as eht current. can anyone suggest a ball park figure for tube current?
The tube is a RCA 4490 and the EHT block is an EMCO E40 Malcolm |
9th Sep 2020, 12:50 pm | #2 |
Guest
Posts: n/a
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Re: Scope CRT current
In my head I have a few 10's of micro amps for a black and white telly, and that lights the whole screen. Should be much less than that.
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9th Sep 2020, 12:59 pm | #3 |
Octode
Join Date: Jan 2003
Location: Birmingham, West Midlands, UK.
Posts: 1,268
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Re: Scope CRT current
.75mA will be more than plenty assuming we are talking monochrome. I think 100uA is roughly were a mono telly CRT would be.
TTFN, Jon |
9th Sep 2020, 1:08 pm | #4 |
Octode
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 1,042
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Re: Scope CRT current
Excellent. Thanks all. I thought it was in that area but it’s good to have it confirmed. I’ll press on and get something together
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9th Sep 2020, 9:44 pm | #5 |
Dekatron
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 8,195
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Re: Scope CRT current
Hi Typical VCR97 scope etc run at 2KV took about 0.5ma (4Meg) on the bleeder chain, actual tube current would be quite a bit less than that.
Ed |