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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 26th Oct 2019, 12:45 pm   #61
davidbi
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Default Re: Stella ST1007U

Thanks for that David but I have nearly completed the renovation, I am stuck with a frame fault, it seems to run at twice the speed, the frame wave forms are wrong. I have changed most things in frame stage with most resistors high I have included a picture to show fault. Voltages are not too far out. I hope someone has an Idea.
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Old 26th Oct 2019, 1:00 pm   #62
HamishBoxer
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Default Re: Stella ST1007U

Lack of frame sync?I presume the frame does not lock?
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Old 26th Oct 2019, 1:20 pm   #63
davidbi
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Default Re: Stella ST1007U

The frame does lock.
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Old 26th Oct 2019, 3:37 pm   #64
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Default Re: Stella ST1007U

Check the value of R87. It had gone high in the ST1007 that is the subject of this topic.
For weak frame sync check the decoupling capacitors associated with the video amplifier. C76 10mfd 200V and C42 100mfd. C42 shares the same can as C30.
The circuit diagram of the video amplifier can be found in an earlier post. #48
Frame sync coupling from the sync separator is very simple. C58 (150pF) differentiates the frame sync pulse train. Simple as the circuit is interlace is excellent in these sets.

DFWB.
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Old 26th Oct 2019, 3:50 pm   #65
FERNSEH
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Default Re: Stella ST1007U

Discussion about the same set can be found here:

https://www.radios-tv.co.uk/communit...stella-st1007/

DFWB.
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Old 28th Oct 2019, 2:03 pm   #66
davidbi
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Default Re: Stella ST1007U

All finished the frame fault turned out to be the new Mullard valve ( new 30 years ago ) ECL80
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