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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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19th Sep 2006, 10:10 pm | #1 |
Pentode
Join Date: Feb 2006
Location: County Durham, UK.
Posts: 234
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Decca Bradford 1830 no raster
Hi
I have an 18" Decca Bradford model CS1830 it has no raster, but if I short the RGB leads to chassis I get a bright screen of the colour shorted. I suspect the MC chip - any ideas ? |
20th Sep 2006, 9:38 am | #2 |
Octode
Join Date: Jan 2006
Location: Borough of Gateshead, UK.
Posts: 1,420
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Re: decca bradford
Hi GP,
Is the sound OK with signals present? The 3rd IF transistor might be responsible but this would usually result in distorted/low sound and an unmodulated raster in a darkened room. If all is ok here the MC does seem suspect. Ironic how the valves are easier to obtain than the ICs! Cheers, Brian |
21st Sep 2006, 10:10 am | #3 |
Octode
Join Date: Jan 2006
Location: Borough of Gateshead, UK.
Posts: 1,420
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Re: decca bradford
Further to the above the J.McCourt "Comprehensive Colour TV Manual" gives TR 201, TR 202 (both BC148) and C200 (12.5uF) as possibles for the no raster with EHT condition.
Cheers, Brian |
22nd Sep 2006, 12:08 am | #4 |
Nonode
Join Date: Jan 2004
Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area.
Posts: 2,965
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Re: decca bradford
Hi GP
If you have got sound, and you have already proved the CRT and EHT are OK, then the fingure of suspicion points to a possible fault around the luminance circuit which on these is part of the MC1327 IC. I also remember dry joints around the luminance delay line could cause similiar effects but sometimes with this you would see just the chrominance; ie just the highly saturated coloured areas of the picture. It looked quite weird.
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Simon BVWS member |