UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > General Vintage Technology Discussions

Notices

General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc.

Reply
 
Thread Tools
Old 9th Sep 2020, 12:06 pm   #1
Malcolm G6ANZ
Heptode
 
Malcolm G6ANZ's Avatar
 
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 701
Default 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
Malcolm G6ANZ is offline   Reply With Quote
Old 9th Sep 2020, 12:50 pm   #2
merlinmaxwell
Dekatron
 
merlinmaxwell's Avatar
 
Join Date: Jul 2008
Location: Maidenhead, Berkshire, UK.
Posts: 9,679
Default 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.
__________________
Cats have staff, it's dogs that have owners.
merlinmaxwell is offline   Reply With Quote
Old 9th Sep 2020, 12:59 pm   #3
Duke_Nukem
Octode
 
Duke_Nukem's Avatar
 
Join Date: Jan 2003
Location: Birmingham, West Midlands, UK.
Posts: 1,210
Default 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
Duke_Nukem is offline   Reply With Quote
Old 9th Sep 2020, 1:08 pm   #4
Malcolm G6ANZ
Heptode
 
Malcolm G6ANZ's Avatar
 
Join Date: Feb 2006
Location: Bristol, UK.
Posts: 701
Default 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
Malcolm G6ANZ is offline   Reply With Quote
Old 9th Sep 2020, 9:44 pm   #5
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 6,176
Default 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
Ed_Dinning is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 11:57 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.