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Old 17th Feb 2024, 7:40 pm   #1
johnmarshmanagain
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Default Bush TV63 again...

Hi All,
A patent cure for Bush LOPTX disease : wind 900+1400 turns on a ferrite rod, make up a tripler, and ..... well, it's not sparkling I admit, but it's an encouragement to carry on and do something with the sync' sep' (whose transformer is o/c).
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Old 21st Feb 2024, 6:42 pm   #2
FERNSEH
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Default Re: Bush TV63 again...

That's a clever dodge, with further adjustments to the winding it should be possible to obtain full scan. Is the EHT known?
The Bush TV53 and TV63 series employ a very interesting and clever line output stage. Dismissing the EHT winding which has nothing to do with scanning, the transformer is a single winding device. The scanning coils have high impedance windings.
One needs to work out how this circuit works. It's worthy of discussion.
It's obvious the boost diode and the 1uF capacitor C26 perform the usual function, recovering flyback energy from the scan coils to provide the first part of the forward scanning cycle.
A similar line line timebase circuit was employed in Peto-Scott TV sets, in fact Peto-Scott went even further in the design of their sets by incorporating a stabilising loop in the line timebase.

DFWB.
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Old 21st Feb 2024, 8:17 pm   #3
FERNSEH
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Default Re: Bush TV63 again...

The Peto-Scott TV1722 employs a similar line output stage.
Note the stabilising circuit. At the time of sale of this set which was 1957 it was the only domestic TV set to have this feature.

DFWB.
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Old 26th Feb 2024, 8:48 pm   #4
johnmarshmanagain
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Default Re: Bush TV63 again...

Many thanks for the insight there. Strictly speaking that version of the auto-transformer shorted after 30mins, but proved a point, and I will try more insulating tape next time. Target eht is 11kv, but I have no means of measuring it except to remember that sparks break the air down at 30kv/cm !
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Old 27th Feb 2024, 2:38 pm   #5
FERNSEH
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Default Re: Bush TV63 again...

"Target eht is 11kv, but I have no means of measuring it except to remember that sparks break the air down at 30kv/cm!"

From the 1963 Quarington Radio and Television circuits and data book a circuit of a simple EHT voltmeter.
No indication of the polarity of the terminals but we can assume the base drive for the OC71 will be negative.

DFWB.
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Old 27th Feb 2024, 3:57 pm   #6
FERNSEH
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Default Re: Bush TV63 again...

In the June 1957 Practical Television magazine an article about making a kilovolt-voltmeter.
https://www.worldradiohistory.com/UK...on-1957-06.pdf

DFWB.
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Old 27th Feb 2024, 9:01 pm   #7
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Default Re: Bush TV63 again...

Quote:
Originally Posted by FERNSEH View Post
That's a clever dodge,

DFWB.
Yes, I thought the same. I thought John did well working that one out.
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