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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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16th Mar 2007, 9:01 pm | #1 |
Octode
Join Date: Feb 2006
Location: Ilkeston, Derbyshire, UK.
Posts: 1,397
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Hitachi CPT2226 - shading and greyscale
This 23 year old Hitachi CPT2226 has a strange picture fault. The left hand side of the screen is at peak white all the time, whilst the greyscale on the remainder is all over the shop. Turning the brightness up or down only affects the right hand part of the picture. Occasionally the whole screen flickers white for a moment. Presumably I'm looking at a duff tube, but wouldn't a grid/cathode short in one of the guns affect the whole picture?
If it is the tube, I suppose it will have to join all those other unloved woodies at the tip this weekend. A shame as it's a quality set and I guess we really should be saving decent 1980s sets now in the same way that we rescued all those 60s tellies back in the 80s! Steve J |
16th Mar 2007, 9:13 pm | #2 |
Dekatron
Join Date: Sep 2003
Location: Bolton, Greater Manchester, UK.
Posts: 6,644
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Re: An Unhappy Hitachi
Don't tip it!
I'd start with an emissions test and a clear short circuits session while the tube tester's out. See what that does. Then a trip round the luminance/video stages and the flyback circuits. Come back with what you find. Tip it?... I thought you knew better LOL! Cheers, Steve P
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16th Mar 2007, 9:19 pm | #3 |
Rest in Peace
Join Date: May 2003
Location: Harlaxton, Lincolnshire, UK.
Posts: 3,944
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Re: An Unhappy Hitachi
I think the most likely cause of this fault is a faulty electrolytic smoothing the HT to the video output stage(s).
An HT of 200 volts or so is usually derived from the LOPTx for the video output. If the electrolytic in this supply (typical value 10uF) goes o/c the picture gets shaded at line rate. |
16th Mar 2007, 9:36 pm | #4 |
Dekatron
Join Date: Sep 2003
Location: Bolton, Greater Manchester, UK.
Posts: 6,644
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Re: An Unhappy Hitachi
Is that so? I haven't got much post-1980, maybe it's time I should. Colourstar, find this cap and change it before you do anything else.
Cheers, Steve P
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If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...? |
16th Mar 2007, 9:39 pm | #5 |
Pentode
Join Date: Jan 2007
Location: Stockport, Greater Manchester, UK.
Posts: 229
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Re: An Unhappy Hitachi
Hi Steve,
Try C715 (4.7uF/250V) Regards Stu |
16th Mar 2007, 10:50 pm | #6 |
Octode
Join Date: Jan 2005
Location: Hyde, Greater Manchester, UK.
Posts: 1,074
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Re: An Unhappy Hitachi
My Gran has one of these sets; I got it for her about 4 years ago from 'Cash Generator' in Hyde for the princely sum of £2.
Most of the controls were intermittent, but with a dust-out and a shot of contact cleaner, all was well, and the picture on the set is truly exceptional. I have a Hitachi portable CAP 162 with the same problem as the set above, albeit not quite as bad. Although I have not had time to look into this fault yet, I did look at some fault reports which suggested a leaky 4.7uF electrolytic, smoothing the HT to the video output stage. I know it's not the same set but a similar fault maybe. Jay
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The light at the end of the tunnel is probably the headlight of an oncoming train Last edited by Mike Phelan; 27th Dec 2007 at 3:03 pm. Reason: Edited for readability |
16th Mar 2007, 11:18 pm | #7 |
Octode
Join Date: Aug 2005
Location: Saltburn-East, Cleveland, UK.
Posts: 1,785
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Re: An Unhappy Hitachi
I would agree with what col, stu and jay say here, look for a faulty electrolytic that smooths the HT to the video output stage.
From memory I think that the offending item may be situated on the tube base PCB. Regards Andrew |
17th Mar 2007, 12:23 am | #8 |
Octode
Join Date: Feb 2006
Location: Ilkeston, Derbyshire, UK.
Posts: 1,397
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Re: An Unhappy Hitachi
Thanks everyone, your suggestions and help are really appreciated.
Steve P- The tip was an idle threat! I got the set from a charity shop across the road from work, where it was stood on the pavement looking a bit vulnerable. It was only a fiver so there was nothing much to lose. Luckily I have several friends who want 'retro' style TVs and also older relatives who want something simple to use, so these 80s models generally fit the bill very well and I'm glad to find them good homes. Nearly all of them still give excellent results. I'd much rather take a set from the tip rather than to it and I'm sure many other members feel the same. Time to hit the Ovaltine now, but hopefully I'll be able to look more closely at the Hitachi over the weekend. 'Night all. Steve |
17th Mar 2007, 2:00 am | #9 |
Pentode
Join Date: Jan 2007
Location: Stockport, Greater Manchester, UK.
Posts: 229
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Re: An Unhappy Hitachi
Steve
If the whole pic flickers white intermittently, resolder the field chip as well as changing the cap Stu Last edited by Mike Phelan; 27th Dec 2007 at 3:04 pm. Reason: S&P |
17th Mar 2007, 6:36 pm | #10 |
Heptode
Join Date: Dec 2006
Location: Milton Keynes, Buckinghamshire, UK.
Posts: 696
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Re: An Unhappy Hitachi
I seem to remember a cap being responsible for this ?
Anyway, BLIMEY ! You must have the only living example with a good LOPT !
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17th Mar 2007, 6:49 pm | #11 |
Octode
Join Date: Feb 2006
Location: Ilkeston, Derbyshire, UK.
Posts: 1,397
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Re: An Unhappy Hitachi
Glad to report another success thanks to the mighty forum! Stu- you were bang on the money. C715 was whipped out and changed and now all is well. In fact the picture on what appears to be the original tube is excellent as you'll hopefully see. I'll also follow your tip regarding that chip.
Just hope the LOPT holds out after Dr Watts comments! Thanks again to all who have helped me. That's another set saved. Steve |
17th Mar 2007, 8:19 pm | #12 |
Pentode
Join Date: Jan 2007
Location: Stockport, Greater Manchester, UK.
Posts: 229
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Re: An Unhappy Hitachi
Well saved Steve
Picture looks great! As regards the LOPT, in the event you were unfortunate with yours, I wouldn't be at all surprised if there wasn't still a Konig equivalent available. It might be questionable economically, but I guess it depends how much you like the set! Well mended once again Regards Stu |
18th Mar 2007, 7:28 pm | #13 |
Nonode
Join Date: Jun 2005
Location: Western Lake District, Cumbria (CA20) - UK
Posts: 2,136
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Re: An Unhappy Hitachi
Well done - I remember having this fault on a brand new set (such a long time ago)!
It took me all one afternoon to find it, after having phoned Hitachi tech. services to be met by their standard reply - "Dunno mate, never seen one of these, if you find out let us know." It has to be said that Hitachi were no worse than anybody else in this respect. These sets outperformed most of the opposition though - with the exception of Sony! (Ducks behind the parapet to aviod the inevitable brickbats ) Regards,
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Brian |