RGD RV227 ITT KB VC3 chassis.20" D/S. - UK Vintage Radio Repair and Restoration Discussion Forum

beltinge bore · 28th Jan 2016, 10:41 pm

I have got this up & running with good sound & picture geometry.The 405 contrast control had been damaged which I have replaced.All the blue & white caps & some of MR Hunts finest have been changed.All the Mullard "mustards" test OK.
The fault I can't clear is a strange bright flicker on the screen which is worse as the brightness control is advanced.It occurs on both standards & on a blank raster.I have subbed the brightness control & components around it test OK.
When the brightness is increased the bright flicker increases & a sound which sounds akin to frame flicker emits.On low brightness settings a good but obviously dark steady picture is available.Ht tests OK .
The fault cleared for a good while but re appeared on switch on some days later.The only other symptom is that on switch off the white spot is quite intense & is slow to disappear.
My thought is possible damp LOPT.
Any help would be most welcome.
Thanks & regards Steve.

FERNSEH · 29th Jan 2016, 1:25 pm

Have you tried another DY87 EHT rectifier valve? I don't wish to alarmist but it could be a gun fault in the CRT.
The KV227 was one of the first 20" CRT sets to be marketed in the UK.
The 20" CRT in some KV227 and RV227 models was sourced from SEL in Germany.

DFWB.

beltinge bore · 29th Jan 2016, 4:19 pm

Thanks for your reply David.I did wonder about the tube .The fault disappeared after the set had been stood on its side for cap replacement.I have tried 3 NOS DY87 also PL36 & PY801- to no avail.
The only other symptom is that on a cold start on both standards the width controls work but after about 5mins. the width expands OK but the controls have no effect .
The tube has a small white label stating STC/ITT manufacture but no country of origin.I assume a 20" tube would be as rare as a good 9" Mazda or GEC.
Regards Steve.

FERNSEH · 29th Jan 2016, 5:25 pm

Hi Steve,
I think your attention should drawn to the width stabilising circuit. The fact is if the width is excessive that means the EHT is too high as well. In these sets without the line timebase stabilising network working properly the EHT can rise to over 20KV. That can't be good for the CRT.

DFWB.

beltinge bore · 30th Jan 2016, 9:51 am

Thanks David.I have the CES manual so will have a good look at the width cct.
Not much time to play at the moment,(family duties).
Regards & Thanks again.Steve.

Hybrid tellies · 30th Jan 2016, 1:38 pm

On this chassis there is an interesting tie in with the AGC line being connected to the width VDR. This gives the AGC greater dynamic range especially on stronger signals but also means you can get strange effects with line output faults affecting the boost voltage and -ve developed across the width VDR.
I am confident that if you sort out the width problem the set will work perfectly.

28th Jan 2016, 10:41 pm	#1
beltinge bore Pentode Join Date: Dec 2012 Location: Herne Bay, Kent, UK. Posts: 233	RGD RV227 ITT KB VC3 chassis.20" D/S. I have got this up & running with good sound & picture geometry.The 405 contrast control had been damaged which I have replaced.All the blue & white caps & some of MR Hunts finest have been changed.All the Mullard "mustards" test OK. The fault I can't clear is a strange bright flicker on the screen which is worse as the brightness control is advanced.It occurs on both standards & on a blank raster.I have subbed the brightness control & components around it test OK. When the brightness is increased the bright flicker increases & a sound which sounds akin to frame flicker emits.On low brightness settings a good but obviously dark steady picture is available.Ht tests OK . The fault cleared for a good while but re appeared on switch on some days later.The only other symptom is that on switch off the white spot is quite intense & is slow to disappear. My thought is possible damp LOPT. Any help would be most welcome. Thanks & regards Steve.

29th Jan 2016, 1:25 pm	#2
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: RGD RV227 ITT KB VC3 chassis.20" D/S. Have you tried another DY87 EHT rectifier valve? I don't wish to alarmist but it could be a gun fault in the CRT. The KV227 was one of the first 20" CRT sets to be marketed in the UK. The 20" CRT in some KV227 and RV227 models was sourced from SEL in Germany. DFWB.

29th Jan 2016, 4:19 pm	#3
beltinge bore Pentode Join Date: Dec 2012 Location: Herne Bay, Kent, UK. Posts: 233	Re: RGD RV227 ITT KB VC3 chassis.20" D/S. Thanks for your reply David.I did wonder about the tube .The fault disappeared after the set had been stood on its side for cap replacement.I have tried 3 NOS DY87 also PL36 & PY801- to no avail. The only other symptom is that on a cold start on both standards the width controls work but after about 5mins. the width expands OK but the controls have no effect . The tube has a small white label stating STC/ITT manufacture but no country of origin.I assume a 20" tube would be as rare as a good 9" Mazda or GEC. Regards Steve.

29th Jan 2016, 5:25 pm	#4
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: RGD RV227 ITT KB VC3 chassis.20" D/S. Hi Steve, I think your attention should drawn to the width stabilising circuit. The fact is if the width is excessive that means the EHT is too high as well. In these sets without the line timebase stabilising network working properly the EHT can rise to over 20KV. That can't be good for the CRT. DFWB.

30th Jan 2016, 9:51 am	#5
beltinge bore Pentode Join Date: Dec 2012 Location: Herne Bay, Kent, UK. Posts: 233	Re: RGD RV227 ITT KB VC3 chassis.20" D/S. Thanks David.I have the CES manual so will have a good look at the width cct. Not much time to play at the moment,(family duties). Regards & Thanks again.Steve. Last edited by beltinge bore; 30th Jan 2016 at 9:52 am. Reason: spelling

30th Jan 2016, 1:38 pm	#6
Hybrid tellies Nonode Join Date: Jan 2004 Location: 1966-1976 Coverack in Cornwall and Helston Cornwall. 1976-present Bristol/Bath area. Posts: 2,965	Re: RGD RV227 ITT KB VC3 chassis.20" D/S. On this chassis there is an interesting tie in with the AGC line being connected to the width VDR. This gives the AGC greater dynamic range especially on stronger signals but also means you can get strange effects with line output faults affecting the boost voltage and -ve developed across the width VDR. I am confident that if you sort out the width problem the set will work perfectly. __________________ Simon BVWS member