Regentone TR20L Width Problem - UK Vintage Radio Repair and Restoration Discussion Forum

DoctorWho · 21st Jul 2006, 7:21 pm

I've been working on a Regentone TR20L which, although basically working did not have a proper EHT circuit, someone had temporarily connected up an old colour TV pripler which did work, but interfered with the picture shape etc. The condensers throughout the set have been changed, including the EHT condenser with a brand new 0.1uf 10kv rated condenser.

A forum member kindly made up an EHT transformer for me which works very well indeed, it supplies the correct EHT voltage for the set.

The problem I have is with the picture width. I have replaced the 6V6 with a 6V6GT and I have replaced the EL38 as the original had a blue glow to it. The HVR2 was missing and so I tracked down a used one

The picture produced is clear and has good focus and definition, the only problem is with the width. It is very difficult to get the width correct, and the only way to get it to fill the screen is to have the edge of the picture folding back over itself, which gives a sort of reflection at the edge of the picture.

The height is fine, the problem is purely with the width. The only other thing I have noticed is that VR5 does not seem to have any effect on the picture.

If anyone can give me some advice on where the would look next I would be grateful. Is this likely to be low emission on the HVR2, or should I be looking elsewhere?

With the old tripler it was possible to get full width, but the width would fluctuate with the brightness of the scene, I presume this was due to the tripler giving incorrect EHT voltages.

Any advice would be greatly appreciated. I have attached a copy of the service data for the set.

Many thanks.

Peter.

Dave Moll · 21st Jul 2006, 8:19 pm

Presumably low EHT would give excessive width. If I read you correctly, your problem is insufficient width.

Steve_P · 21st Jul 2006, 8:20 pm

The EHT Transformer - Does it work off the HT Supply like the Original did, or does it hang off the Line Output Stage?

Cheers,

Steve P

DoctorWho · 21st Jul 2006, 10:13 pm

Yes, the problem is insufficient width.

The EHT is obtained in the original manner, from the mains. A second transformer which provides 5100V AC is connected to the HVR2 and associated circuitry, this in turn rectifies the supply and goes up to the CRT. The circuit is totally un-modified, the only difference is that the EHT is provided by a second transformer sitting next to the original and is earthed to chassis.

If the EHT is a little too high how can it safely be lowered?

Out of interest what exactly is the purpose of VR5 as this does not seem to do anything?

Thanks again,

Peter.

Steve_P · 21st Jul 2006, 10:51 pm

Just wanted to make sure.

Before you try lowering the EHT, change the Resistors and also V11 in the Line Stages. They will have had their load of abuse over the past 50 years too and they may be high in value. Not sure off the top of my head what VR5 does, so just set it halfway.

As for lowering the EHT,if you need to try a cap of about .01uf between V10 anode and earth. The exact value is very much trial and error. What normally happens is that the height is racked up, but not the width. The reason I wouldn't play around with this on this set is that the EHT current are much higher when it comes from the mains.

Be careful!!

Steve P.

P.S. A check/change of R71 might not go amiss, looking at the circuit again.

Dave Moll · 22nd Jul 2006, 12:55 am

Quote:

Originally Posted by DoctorWho

Out of interest what exactly is the purpose of VR5 as this does not seem to do anything?

My information says that it's line linearity.

Mike Phelan · 22nd Jul 2006, 9:36 am

It sounds as if the width is OK, but the foldover is a line linearity or sync phase problem.
Dave Moll could be in the right area. Which side is the foldover on? Does the set have an efficiency diode? Is there a trimmer for the drive to the grid of the LOP valve?
If the EHT is low, the width will be excessive and the picture size will increase when you turn the brightness up - poor regulation.

DoctorWho · 22nd Jul 2006, 2:19 pm

Thanks for the input. The fold over is on the right hand side of the picture. I'll certainly investigate the resistors and the EF50 that you have advised and see what happens, I'll order a new EF50 and report back when I've been able to try it.

Peter.

DoctorWho · 12th Aug 2006, 10:04 pm

Success at last! A new EF50 was fitted and, quite by chance, I checked the 1.8k resistor connected to the linearity control, this was open circuit, so I replaced it and bingo - perfect picture!! Thanks for the assistance.

21st Jul 2006, 8:19 pm	#2
Dave Moll Dekatron Join Date: Feb 2005 Location: West Cumbria (CA13), UK Posts: 6,127	Re: Regentone TR20L Width Problem Presumably low EHT would give excessive width. If I read you correctly, your problem is insufficient width.

21st Jul 2006, 8:20 pm	#3
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Regentone TR20L Width Problem The EHT Transformer - Does it work off the HT Supply like the Original did, or does it hang off the Line Output Stage? Cheers, Steve P __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

21st Jul 2006, 10:13 pm	#4
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: Regentone TR20L Width Problem Yes, the problem is insufficient width. The EHT is obtained in the original manner, from the mains. A second transformer which provides 5100V AC is connected to the HVR2 and associated circuitry, this in turn rectifies the supply and goes up to the CRT. The circuit is totally un-modified, the only difference is that the EHT is provided by a second transformer sitting next to the original and is earthed to chassis. If the EHT is a little too high how can it safely be lowered? Out of interest what exactly is the purpose of VR5 as this does not seem to do anything? Thanks again, Peter.

21st Jul 2006, 10:51 pm	#5
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: Regentone TR20L Width Problem Just wanted to make sure. Before you try lowering the EHT, change the Resistors and also V11 in the Line Stages. They will have had their load of abuse over the past 50 years too and they may be high in value. Not sure off the top of my head what VR5 does, so just set it halfway. As for lowering the EHT,if you need to try a cap of about .01uf between V10 anode and earth. The exact value is very much trial and error. What normally happens is that the height is racked up, but not the width. The reason I wouldn't play around with this on this set is that the EHT current are much higher when it comes from the mains. Be careful!! Steve P. P.S. A check/change of R71 might not go amiss, looking at the circuit again. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...? Last edited by Steve_P; 21st Jul 2006 at 10:59 pm.

22nd Jul 2006, 9:36 am	#7
Mike Phelan Dekatron Join Date: Nov 2003 Location: Near Leeds, West Yorkshire, UK Posts: 4,609	Re: Regentone TR20L Width Problem It sounds as if the width is OK, but the foldover is a line linearity or sync phase problem. Dave Moll could be in the right area. Which side is the foldover on? Does the set have an efficiency diode? Is there a trimmer for the drive to the grid of the LOP valve? If the EHT is low, the width will be excessive and the picture size will increase when you turn the brightness up - poor regulation. __________________ Mike.

22nd Jul 2006, 2:19 pm	#8
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: Regentone TR20L Width Problem Thanks for the input. The fold over is on the right hand side of the picture. I'll certainly investigate the resistors and the EF50 that you have advised and see what happens, I'll order a new EF50 and report back when I've been able to try it. Peter.

12th Aug 2006, 10:04 pm	#9
DoctorWho Rest in Peace Join Date: Apr 2005 Location: Devon Posts: 850	Re: Regentone TR20L Width Problem Success at last! A new EF50 was fitted and, quite by chance, I checked the 1.8k resistor connected to the linearity control, this was open circuit, so I replaced it and bingo - perfect picture!! Thanks for the assistance.