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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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16th Dec 2014, 2:14 am | #21 |
Dekatron
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 7,444
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Re: Murphy V240C Any help whatsoever.
As far testing the CRT is concerned, an interesting suggestion from JohnHKS is to consider the grid and cathode of the tube as a diode. The grid and leads are removed for this test. Supply the correct heater voltage to the CRT which for the Mazda CRM141 is 12.6 volts, leave the tube running for a while. Using a multimeter switched to the resistance range connect the meter to the grid and cathode pins. If the CRT has any emission this will be indicated as a meter reading. The internal battery supplies the necessary voltage for the conduction test. If there is no reading, reverse the meter leads and try again.
I have never tried this procedure but I'm certain it works. A few words of caution. The correct heater voltage for the CRM141 is 12.6 volts but some rebuilt tubes were occasionally fitted with 6.3 volt gun assemblies. DFWB. |
16th Dec 2014, 3:07 am | #22 |
Retired Dormant Member
Join Date: Aug 2014
Location: Bath, Avon, UK
Posts: 235
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Re: Murphy V240C Any help whatsoever.
Thanks DFWB
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16th Dec 2014, 10:55 pm | #23 |
Dekatron
Join Date: Jun 2005
Location: Warnham, West Sussex. 10 miles south of DORKING.
Posts: 9,147
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Re: Murphy V240C Any help whatsoever.
This is a rough test for 'some' emission. If reading as David has suggested it is likely to produce a picture and may well be OK but not of course a reading of quantity or quality of emission. Makes a good test for an unknown tube and is completely harmless. John.
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17th Dec 2014, 11:57 am | #24 |
Octode
Join Date: Jan 2009
Location: Falmouth, Cornwall, UK.
Posts: 1,989
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Re: Murphy V240C Any help whatsoever.
This is exactly the method used by all Taylor valve testers in conjunction with the CRT adapter.
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Stephen _________"It`s only an old telly" ___ |
21st Dec 2014, 11:03 pm | #25 |
Retired Dormant Member
Join Date: Aug 2014
Location: Bath, Avon, UK
Posts: 235
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Re: Murphy V240C Any help whatsoever.
That book arrived yesterday DFWB, very informative reading but will be a lot better when I have read and understood it a few times. I am now trying to find the same books on the Bush TV22s a b c, and also hopefully a few books on my radios, many thanks for the heads up DFWB, regards And a good Christmas, Andy
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