PYE B18T/LV20 whats the difference? - UK Vintage Radio Repair and Restoration Discussion Forum

newlite4 · 11th Mar 2014, 12:27 pm

What are the differences between the above sets apart from the one year age gap? They look identical but a year is a long time in early TV development.
Neil

radiomarktv · 11th Mar 2014, 12:44 pm

Hi Neil,

As far as I can see the only difference visually is in the cabinet design. The speaker fret and the front corners are different.
The chassis look's the same.
The BV20 is the Birmingham version and the LV20 being London.

Mark

newlite4 · 11th Mar 2014, 12:54 pm

Thanks for that Mark, I will have to take a closer look, very subtle then,
Neil

Freya · 11th Mar 2014, 1:14 pm

Also the B18T would have had two separate HT smoothers C9A and C10A, the LV20 has a combined. Although this is not seen very much now as they mostly have been replaced already once.
The same for the LT decoupling, the B18T has wax throughout where as the LV20 has ceramic.
This is only what I have come across in the few that have been my way.

radiomarktv · 11th Mar 2014, 1:23 pm

I have in my collection both the B18T and LV20. I restored my B18T for the NVCF television display in 2006 which can be seen here:

http://www.youtube.com/watch?v=k5ePyNlGTXs

The set performed well all day with a slight adjustment of the focus after a few hours. I've been told this is common for the focus to go out after a few hours use.

Without having a closer look I'm not 100% sure if Pye made any changes to the circuit/components in the LV20.
Mark

mark pirate · 11th Mar 2014, 1:26 pm

Quote:

The same for the LT decoupling, the B18T has wax throughout where as the LV20 has ceramic.

That is interesting, I have an LV20 on it's way to me, I have restored a D18T which is a very similar chassis, but with additional plate on the chassis for the CRT and LOPT, to fit in a console cabinet.
I am hoping that it will have the ceramic caps, as it should make restoration easier.

Mark

Freya · 11th Mar 2014, 3:04 pm

I have also cured the focus drift issue 100% by baking the lopt at 230 degrees for 30 mins (outside the house, it stinks)
Then very carefully remove the paxolin EHT rectifier carrier and replace with a piece of fiberglass plate, this is used by model makers.
The focus is rock steady and the EHT runs at 6.8Kv all day.
If baking the lopt is undertaken i recommend a pair of expendable oven gloves as it pays to rotate the lopt to get the pitch out from all sides.

Heatercathodeshort · 11th Mar 2014, 5:42 pm

The LV20 is likely to have a shorting link on the smoothing choke that shorts part of it out on DC mains. Pye did not design the B18T to actually operate on DC mains, it was the first model with series connected heaters and no mains transformer. 'Transformerless Television Receiver' as they called it.
Of course dealers in DC areas realized that it should work OK on DC mains and experimented to discover it worked fine. The problem was the B18T is not designed to operate below 220v and a lot of the DC supplies were 200V. Pye decided to make provision to short out part of the smoothing choke on DC supplies below 220v, hence the link. It was then fully advertised as an AC/DC receiver! Great receivers and they must have been produced in HUGE numbers. John.

11th Mar 2014, 12:27 pm	#1
newlite4 Octode Join Date: Nov 2003 Location: Bath, Somerset, UK. Posts: 1,806	PYE B18T/LV20 whats the difference? What are the differences between the above sets apart from the one year age gap? They look identical but a year is a long time in early TV development. Neil __________________ preserving the recent past, for the distant future.

11th Mar 2014, 12:44 pm	#2
radiomarktv Pentode Join Date: Oct 2003 Location: Henley on Thames, Oxfordshire, UK. Posts: 244	Re: PYE B18T/LV20 whats the difference? Hi Neil, As far as I can see the only difference visually is in the cabinet design. The speaker fret and the front corners are different. The chassis look's the same. The BV20 is the Birmingham version and the LV20 being London. Mark

11th Mar 2014, 12:54 pm	#3
newlite4 Octode Join Date: Nov 2003 Location: Bath, Somerset, UK. Posts: 1,806	Re: PYE B18T/LV20 whats the difference? Thanks for that Mark, I will have to take a closer look, very subtle then, Neil __________________ preserving the recent past, for the distant future.

11th Mar 2014, 1:14 pm	#4
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,991	Re: PYE B18T/LV20 whats the difference? Also the B18T would have had two separate HT smoothers C9A and C10A, the LV20 has a combined. Although this is not seen very much now as they mostly have been replaced already once. The same for the LT decoupling, the B18T has wax throughout where as the LV20 has ceramic. This is only what I have come across in the few that have been my way. __________________ Stephen _________"It`s only an old telly" ___

11th Mar 2014, 1:23 pm	#5
radiomarktv Pentode Join Date: Oct 2003 Location: Henley on Thames, Oxfordshire, UK. Posts: 244	Re: PYE B18T/LV20 whats the difference? I have in my collection both the B18T and LV20. I restored my B18T for the NVCF television display in 2006 which can be seen here: http://www.youtube.com/watch?v=k5ePyNlGTXs The set performed well all day with a slight adjustment of the focus after a few hours. I've been told this is common for the focus to go out after a few hours use. Without having a closer look I'm not 100% sure if Pye made any changes to the circuit/components in the LV20. Mark

11th Mar 2014, 3:04 pm	#7
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,991	Re: PYE B18T/LV20 whats the difference? I have also cured the focus drift issue 100% by baking the lopt at 230 degrees for 30 mins (outside the house, it stinks) Then very carefully remove the paxolin EHT rectifier carrier and replace with a piece of fiberglass plate, this is used by model makers. The focus is rock steady and the EHT runs at 6.8Kv all day. If baking the lopt is undertaken i recommend a pair of expendable oven gloves as it pays to rotate the lopt to get the pitch out from all sides. __________________ Stephen _________"It`s only an old telly" ___

11th Mar 2014, 5:42 pm	#8
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: PYE B18T/LV20 whats the difference? The LV20 is likely to have a shorting link on the smoothing choke that shorts part of it out on DC mains. Pye did not design the B18T to actually operate on DC mains, it was the first model with series connected heaters and no mains transformer. 'Transformerless Television Receiver' as they called it. Of course dealers in DC areas realized that it should work OK on DC mains and experimented to discover it worked fine. The problem was the B18T is not designed to operate below 220v and a lot of the DC supplies were 200V. Pye decided to make provision to short out part of the smoothing choke on DC supplies below 220v, hence the link. It was then fully advertised as an AC/DC receiver! Great receivers and they must have been produced in HUGE numbers. John.