Pye B18T - LOPT or scan coils? - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

acottrell · 17th Jun 2015, 3:14 pm

Hi Guys
Well it worked new caps fitted. This improved it a little but not much. I ordered myself two new EF50s this really did the trick replacing V1F and V1G together. The sound is really strong now

All back together. Only one thing (just being fussy now) after the set has been on over an hour the focus goes out of alignment. I can focus it again no problem. Once cooled down i have to re focus the set again and again if i use it for any length of time. Nothing else like picture size etc is effected. Still a good set now. Thanks to you Guys for your advise and help
Ade

Freya · 17th Jun 2015, 4:48 pm

This focus issue is well documented Ade, you will most likely find the EHT is dropping over the course of the specified time. I ended up taking the lopt out of its housing and baking in the oven, this has cured the focus problem hopefully for a good while. It sits steady for the evening at 6.8kV
I should add this method was just one I adopted as the transformer is so totally covered in pitch there was little other choice for getting the moisture out, had it have had a wax covered overwind it would be much easier to use a low voltage bench supply connected to the overwind at about 20 volts for a few days.

pictures show before, after, and an end shot of the overwind. Still not pretty but it works.

acottrell · 17th Jun 2015, 5:02 pm

Thanks for the advice Stephen
I will probably leave mine as it doesnt really bother me too much just happy to get it working

Freya · 17th Jun 2015, 5:04 pm

May improve more with constant use.

acottrell · 17th Jun 2015, 5:06 pm

Hopefully! will be using it quite a bit now.
Ade

mark pirate · 17th Jun 2015, 6:06 pm

Glad to hear you got the old girl up and running

As Stephen says, the focus issue is a common problem with these sets, my LV51F has the same problem despite living in the front room for over three years, I do have a spare LOPT, but have never got round to fitting it.

Strangely, neither of my D18T's suffer with this problem. the EHT stays rock steady. It will be interesting to see if the two LV20's on the roundtuit pile will be ok, if not I will try melting off the pitch in the oven.

Mark

acottrell · 17th Jun 2015, 6:23 pm

Hi Mark
Yes it will be interesting to see if it will improve in time i have only just started using it for any length of time great little set though

I have an LV20c now to have ago at. Looks quite rusty but cabinet is in great shape.
Ade

17th Jun 2015, 3:14 pm	#21
acottrell Retired Dormant Member Join Date: Nov 2008 Location: Sedgley, Dudley, West Midlands, UK. Posts: 242	Re: Pye B18T - LOPT or scan coils? Hi Guys Well it worked new caps fitted. This improved it a little but not much. I ordered myself two new EF50s this really did the trick replacing V1F and V1G together. The sound is really strong now All back together. Only one thing (just being fussy now) after the set has been on over an hour the focus goes out of alignment. I can focus it again no problem. Once cooled down i have to re focus the set again and again if i use it for any length of time. Nothing else like picture size etc is effected. Still a good set now. Thanks to you Guys for your advise and help Ade Attached Thumbnails

17th Jun 2015, 4:48 pm	#22
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,989	Re: Pye B18T - LOPT or scan coils? This focus issue is well documented Ade, you will most likely find the EHT is dropping over the course of the specified time. I ended up taking the lopt out of its housing and baking in the oven, this has cured the focus problem hopefully for a good while. It sits steady for the evening at 6.8kV I should add this method was just one I adopted as the transformer is so totally covered in pitch there was little other choice for getting the moisture out, had it have had a wax covered overwind it would be much easier to use a low voltage bench supply connected to the overwind at about 20 volts for a few days. pictures show before, after, and an end shot of the overwind. Still not pretty but it works. Attached Thumbnails __________________ Stephen _________"It`s only an old telly" ___ Last edited by Freya; 17th Jun 2015 at 5:08 pm. Reason: more info added

17th Jun 2015, 5:02 pm	#23
acottrell Retired Dormant Member Join Date: Nov 2008 Location: Sedgley, Dudley, West Midlands, UK. Posts: 242	Re: Pye B18T - LOPT or scan coils? Thanks for the advice Stephen I will probably leave mine as it doesnt really bother me too much just happy to get it working

17th Jun 2015, 5:04 pm	#24
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,989	Re: Pye B18T - LOPT or scan coils? May improve more with constant use. __________________ Stephen _________"It`s only an old telly" ___

17th Jun 2015, 5:06 pm	#25
acottrell Retired Dormant Member Join Date: Nov 2008 Location: Sedgley, Dudley, West Midlands, UK. Posts: 242	Re: Pye B18T - LOPT or scan coils? Hopefully! will be using it quite a bit now. Ade

17th Jun 2015, 6:06 pm	#26
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: Pye B18T - LOPT or scan coils? Glad to hear you got the old girl up and running As Stephen says, the focus issue is a common problem with these sets, my LV51F has the same problem despite living in the front room for over three years, I do have a spare LOPT, but have never got round to fitting it. Strangely, neither of my D18T's suffer with this problem. the EHT stays rock steady. It will be interesting to see if the two LV20's on the roundtuit pile will be ok, if not I will try melting off the pitch in the oven. Mark

17th Jun 2015, 6:23 pm	#27
acottrell Retired Dormant Member Join Date: Nov 2008 Location: Sedgley, Dudley, West Midlands, UK. Posts: 242	Re: Pye B18T - LOPT or scan coils? Hi Mark Yes it will be interesting to see if it will improve in time i have only just started using it for any length of time great little set though I have an LV20c now to have ago at. Looks quite rusty but cabinet is in great shape. Ade