BUSH TV161 Boost Voltage setting - UK Vintage Radio Repair and Restoration Discussion Forum

simpsons · 21st May 2018, 7:31 pm

Colourvision kindly gave me his Murphy V2015D which I have sucessfully given a new heart in the form of a Bush TV161 etc. LOPT.

Everything is fine but I need expert help in setting the boost voltage to give the tar version of the transformer a long life.

The schematic calls for a boost voltage of 780 which the preset was correctly set.

Will I reduce the stress on the transformer by reducing the boost voltage to say 710 volts, with the test card castellation just about right, or am I missing something.

On both voltages the LOPTX is cool to touch but I remember at a Murphy Welwyn Sunday a couple of years ago, this transformer, after a few hours of use, in a Murhy V1910 gave the impression of being under stress with some LHS foldover.

Any recommendations?

Chris

Heatercathodeshort · 21st May 2018, 8:09 pm

The original boost setting for the dual standard Philips colour receiver, the G6 was 600V. This was reduced first to 580V and then 560V. This was official Philips information.

I used to set the boost voltage to just fill the edges of the mask. This gave an EHT of around 22KV with a good picture. The line output transformers life was greatly extended.

The tar overwind was a very weak link in the 640 as it was in the first colour chassis, the CTV25.

You may well discover that it still plays up even with the reduced boost setting. Good luck with it. John.

HamishBoxer · 21st May 2018, 9:29 pm

The amount of TV161 LOPTX,s I removed working ,then when I needed them were duff too many to mention.

AJSmith625 · 22nd May 2018, 12:43 am

I also had the pleasure of replacing quite a few pitch covered LOPTx in the A640 chassis. In saying that, the second family set we had, a Bush TV166u which my dad bought in 1968 was still going strong on its original LOPTx ten years later. In fact I fitted a re-gunned A59-11W around 1975 when the tube went flat and would no longer respond to a boost. I also used to set the 'set boost' control just enough to fill the screen and I think this did help a lot in putting less strain on the new transformer.

Alan.

neil29 · 22nd May 2018, 12:50 am

I've never left most of my sets on long enough to see whether the lopts hold out. but I have a Murphy V1914 which doesn't take long for the tell tale signs to show and its the tidiest set out of them all.

Cheers
Neil.

Nuvistor · 22nd May 2018, 8:05 am

If you search Chris’s Radios and TV forum you will find a fix for at least one type of failure of these LOPTX’s. It’s an insulation breakdown between seperate windings, it’s messy but can be fixed, at least a couple have been fully repaired.

https://www.radios-tv.co.uk/community/

Fascinating watching the progress of the repair.

simpsons · 23rd May 2018, 9:50 am

Hi Frank

I did read the article by PYE625 and thought to myself, I hope I don't have to do this.

As it turns out, so far all is well and the LOPTX, which has sat on my CH boiler from August 2017 to just now to "dry out", seems to have pulled through!!

The DC ohm readings for the overwind I didn't have and so will be written down or the idea of using a polythene cover around the winding to stop moisture ingress. I wonder if Insulation Varnish would do the same?

Colourstar's experience with this set goes back to 2011 and I do agree the CRT is excellent now its been given a couple of hours of use.

The boost voltage has been set to minimum and the attached picture is the result.

Thank you all for your help and to Steve for donating the set to me

Chris

Nuvistor · 23rd May 2018, 11:55 am

I replaced transformers back in the day, I posted the link in case it saves one being thrown away, the poster has done a couple both with the same fault. It’s possible that was the original cause of quite a few failing.

Looking at the initial photos of the overwind I would not have thought it had a chance.

Anyway the information is out there if it’s required.

The picture on your set is excellent, the Achilles heal of the range was the LOPTX the rest of the set was really good.

21st May 2018, 7:31 pm	#1
simpsons Octode Join Date: Feb 2007 Location: Harrow, London, UK. Posts: 1,493	BUSH TV161 Boost Voltage setting Colourvision kindly gave me his Murphy V2015D which I have sucessfully given a new heart in the form of a Bush TV161 etc. LOPT. Everything is fine but I need expert help in setting the boost voltage to give the tar version of the transformer a long life. The schematic calls for a boost voltage of 780 which the preset was correctly set. Will I reduce the stress on the transformer by reducing the boost voltage to say 710 volts, with the test card castellation just about right, or am I missing something. On both voltages the LOPTX is cool to touch but I remember at a Murphy Welwyn Sunday a couple of years ago, this transformer, after a few hours of use, in a Murhy V1910 gave the impression of being under stress with some LHS foldover. Any recommendations? Chris

21st May 2018, 8:09 pm	#2
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: BUSH TV161 Boost Voltage setting The original boost setting for the dual standard Philips colour receiver, the G6 was 600V. This was reduced first to 580V and then 560V. This was official Philips information. I used to set the boost voltage to just fill the edges of the mask. This gave an EHT of around 22KV with a good picture. The line output transformers life was greatly extended. The tar overwind was a very weak link in the 640 as it was in the first colour chassis, the CTV25. You may well discover that it still plays up even with the reduced boost setting. Good luck with it. John.

21st May 2018, 9:29 pm	#3
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,932	Re: BUSH TV161 Boost Voltage setting The amount of TV161 LOPTX,s I removed working ,then when I needed them were duff too many to mention. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

22nd May 2018, 12:43 am	#4
AJSmith625 Pentode Join Date: Nov 2017 Location: Birmingham, West Midlands, UK. Posts: 171	Re: BUSH TV161 Boost Voltage setting I also had the pleasure of replacing quite a few pitch covered LOPTx in the A640 chassis. In saying that, the second family set we had, a Bush TV166u which my dad bought in 1968 was still going strong on its original LOPTx ten years later. In fact I fitted a re-gunned A59-11W around 1975 when the tube went flat and would no longer respond to a boost. I also used to set the 'set boost' control just enough to fill the screen and I think this did help a lot in putting less strain on the new transformer. Alan.

22nd May 2018, 12:50 am	#5
neil29 Heptode Join Date: Dec 2004 Location: Newport, Gwent, UK. Posts: 962	Re: BUSH TV161 Boost Voltage setting I've never left most of my sets on long enough to see whether the lopts hold out. but I have a Murphy V1914 which doesn't take long for the tell tale signs to show and its the tidiest set out of them all. Cheers Neil.

22nd May 2018, 8:05 am	#6
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	Re: BUSH TV161 Boost Voltage setting If you search Chris’s Radios and TV forum you will find a fix for at least one type of failure of these LOPTX’s. It’s an insulation breakdown between seperate windings, it’s messy but can be fixed, at least a couple have been fully repaired. https://www.radios-tv.co.uk/community/ Fascinating watching the progress of the repair. __________________ Frank

23rd May 2018, 9:50 am	#7
simpsons Octode Join Date: Feb 2007 Location: Harrow, London, UK. Posts: 1,493	Re: BUSH TV161 Boost Voltage setting Hi Frank I did read the article by PYE625 and thought to myself, I hope I don't have to do this. As it turns out, so far all is well and the LOPTX, which has sat on my CH boiler from August 2017 to just now to "dry out", seems to have pulled through!! The DC ohm readings for the overwind I didn't have and so will be written down or the idea of using a polythene cover around the winding to stop moisture ingress. I wonder if Insulation Varnish would do the same? Colourstar's experience with this set goes back to 2011 and I do agree the CRT is excellent now its been given a couple of hours of use. The boost voltage has been set to minimum and the attached picture is the result. Thank you all for your help and to Steve for donating the set to me Chris Attached Thumbnails

23rd May 2018, 11:55 am	#8
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,431	Re: BUSH TV161 Boost Voltage setting I replaced transformers back in the day, I posted the link in case it saves one being thrown away, the poster has done a couple both with the same fault. It’s possible that was the original cause of quite a few failing. Looking at the initial photos of the overwind I would not have thought it had a chance. Anyway the information is out there if it’s required. The picture on your set is excellent, the Achilles heal of the range was the LOPTX the rest of the set was really good. __________________ Frank