Bush Dual Standard Colour Restoration - Page 3 - UK Vintage Radio Repair and Restoration Discussion Forum

davidh1041 · 4th Apr 2022, 9:29 pm

My MK3 CTV25 had a knackered LOPT and i replaced it with a Decca Bradford LOPT which works well on both standards. I am using a tripler with an isolator capicitor on the input and have the PD500 connected up as normal. The beam limiter works well, being fed from the diode conection on the tripler.
Might be a more reliable way to go for you.
Regards David

Niechcial,Steve · 15th Apr 2022, 3:59 pm

If I had a Bradford LOPT that would certainly be a quicker way to do it, but I doubt it would be more reliable in the long run. The Mylar insulation I've used plus modern enamelled wire are both much more durable than anything that was in use in the 70s- especially as regards heat resilience. Plus of course . with a quadrupler, the LOPT is running 2kv lower than a Bradford with tripler Time will tell! Did you need to make any other circuit changes?

davidh1041 · 17th Apr 2022, 6:57 pm

Quote:

Originally Posted by Niechcial,Steve

If I had a Bradford LOPT that would certainly be a quicker way to do it, but I doubt it would be more reliable in the long run. The Mylar insulation I've used plus modern enamelled wire are both much more durable than anything that was in use in the 70s- especially as regards heat resilience. Plus of course . with a quadrupler, the LOPT is running 2kv lower than a Bradford with tripler Time will tell! Did you need to make any other circuit changes?

Removed the desaturation choke and had to wind extra turns around the core of the LOPT to get enough line pulse for the decoder. It was a few years ago, but can't remember any other significant changes. Very handy that the Decca LOPT had a 405 line scan coil tap. The LOPT i used came from a scrap Rediffusion MK1, the same as a Bradford LOPT and looks quite well made.

Niechcial,Steve · 18th Apr 2022, 2:13 pm

Yes I was fascinated to see in a previous post (yours?) that the Bradford LOPT was designed for dual standard

dazzlevision · 18th Apr 2022, 3:57 pm

If my memory is correct, the initial Decca Bradford chassis LOPT (the 10 series) was made by Mullard/Philips - possibly a variation of the AT2055 series. Later Bradford chassis LOPTs were made by the (then) Decca subsidiary Weyrad.

The AT2055 LOPT was, I think, also used in the ITT-KB CVC1 dual standard hand wired colour chassis.

4th Apr 2022, 9:29 pm	#41
davidh1041 Pentode Join Date: Mar 2009 Location: Norwich, Norfolk, UK. Posts: 228	Re: Bush Dual Standard Colour Restoration My MK3 CTV25 had a knackered LOPT and i replaced it with a Decca Bradford LOPT which works well on both standards. I am using a tripler with an isolator capicitor on the input and have the PD500 connected up as normal. The beam limiter works well, being fed from the diode conection on the tripler. Might be a more reliable way to go for you. Regards David Attached Thumbnails

15th Apr 2022, 3:59 pm	#42
Niechcial,Steve Hexode Join Date: Jan 2007 Location: Beckenham, London, UK. Posts: 373	Re: Bush Dual Standard Colour Restoration If I had a Bradford LOPT that would certainly be a quicker way to do it, but I doubt it would be more reliable in the long run. The Mylar insulation I've used plus modern enamelled wire are both much more durable than anything that was in use in the 70s- especially as regards heat resilience. Plus of course . with a quadrupler, the LOPT is running 2kv lower than a Bradford with tripler Time will tell! Did you need to make any other circuit changes?

18th Apr 2022, 2:13 pm	#44
Niechcial,Steve Hexode Join Date: Jan 2007 Location: Beckenham, London, UK. Posts: 373	Re: Bush Dual Standard Colour Restoration Yes I was fascinated to see in a previous post (yours?) that the Bradford LOPT was designed for dual standard

18th Apr 2022, 3:57 pm	#45
dazzlevision Dekatron Join Date: Sep 2003 Location: Near Swindon, North Wiltshire, UK. Posts: 3,622	Re: Bush Dual Standard Colour Restoration If my memory is correct, the initial Decca Bradford chassis LOPT (the 10 series) was made by Mullard/Philips - possibly a variation of the AT2055 series. Later Bradford chassis LOPTs were made by the (then) Decca subsidiary Weyrad. The AT2055 LOPT was, I think, also used in the ITT-KB CVC1 dual standard hand wired colour chassis.