Sobell T91 - UK Vintage Radio Repair and Restoration Discussion Forum

chroma04 · 13th Mar 2019, 9:58 pm

Hi,

After successfully restoring my Bush TV22 (with the kind help of forum member Ed Dinning supplying a rewound frame blocking transformer), I have come across the above Sobell T91 television set, and wondered whether it would be a suitable contender for restoration?

Unfortunately, after searching on the internet, I appear to be able to find little information about this set. Has anybody seen such a TV or know where I might be able to obtain the service manual? Or has anybody seen or serviced such a set?

I'm still fairly new to the world of vintage television, so if there are pitfalls for the unwary/inexperienced, then it may be beyond me.

Many thanks,

Adrian.

petertheorgan · 14th Mar 2019, 2:18 am

I am having an guess but i wonder if the H M label on the chassis referes to Holme Moss which means that the TV set will be tuned to channel "2" , not a problem but something to be aware of

FERNSEH · 14th Mar 2019, 11:11 am

Circuit diagrams of the Sobell T90 and T91. Gas thyratrons are used in the timebase oscillators.
Local oscillator can be adjusted for Channels 1,2 and 4. H.M. = Holme Moss channel 2.

DFWB.

beery · 14th Mar 2019, 11:14 am

Hi Adrian,
that's a very nice set and one that was once on my wish list.
I quite like Sobell sets. They are basic and made down to a price, but can give good results.
The biggest unknown will be the Mazda CRM92 CRT.
The set used a metal rectifier which won't put up with the current needed to re-form the old HT smoothing caps. Best to re-form these caps first before powering the set. The metal rectifier might still be tired, so be prepared to fit a 1N4007 and a series resistor in place of the original rectifier.

I think I have the diagram in an early Newnes book. I will have a look tonight and scan it in.

Good luck with the set.
Cheers
Andy

beery · 14th Mar 2019, 11:16 am

I see David has beaten me to it

Peter.N. · 14th Mar 2019, 11:19 am

I don't think I have ever seen one of those, lots of later Sobell's though. Looks to be in very good condition, a worthy project I would think.

Peter

chroma04 · 14th Mar 2019, 9:41 pm

Many thanks everybody for the responses and to FERNSEH for kindly uploading the schematic diagram. The wealth of knowledge and resources of this forum is truly amazing!

Your responses have prompted me to go ahead and make a few basic checks on the set to see whether it is indeed a viable project. Initially, I plan check the CRT heater for continuity. If this checks out OK, I'll make some cold checks on the other wound components and then I'll attempt to reform C57A/B. After snipping C58, which is wired across the mains input, I'll carefully apply some mains and see what happens! I intend to do as little as possible to the set prior to applying power.

The CRT looks rather vulnerable when the chassis is withdrawn, so I'll need to take care whilst working in this area.

I'll be back to give an update on my progress if the set looks to be salvagable. Here's hoping the CRT has some life in it!

Adrian.

Freya · 15th Mar 2019, 8:34 am

Hi Adrian,
would be great to see some pictures of the other side of the chassis, looks a nice set.

Heatercathodeshort · 15th Mar 2019, 9:17 am

I'm certain I noticed a full service manual for the T91 on Ebay recently.

Service data for the T91 can be found in volume 4 of the original set of R&TV servicing pages 383-387.
I can scan these at high resolution and let you have them on a CD [FOC] if you would like them. Cheers, John.

chroma04 · 15th Mar 2019, 9:25 pm

Photo's of the withdrawn chassis.That c.r.t. certainly looks odd, mounted as it is. Also, the chassis is unbalanced when removed from the cabinet and tends to want to fall onto the c.r.t.'s face!!

I'll need to proceed with caution when working on it.

Many thanks John (Heatercathodeshort) for the offer of the scan of the R&TV servicing pages. I'd like to take you up on this if I may? I'll send you a PM shortly.

Adrian.

Freya · 15th Mar 2019, 10:21 pm

The genuine service manual is still listed, it could be a good investment to go with this rare set.
I like the use of the glasses case

mark pirate · 15th Mar 2019, 10:59 pm

Nice little set, if the CRT is OK it should be quite an easy restoration after a TV22

I do like these early Sobells, nice and simple to work on and capable of good performance once restored.

Mark

chroma04 · 15th Mar 2019, 11:26 pm

Many thanks Freya for the heads-up on the service manual. I have purchased it and have now placed the chassis back into the cabinet for safety whilst it arrives.

Regards,

Adrian.

13th Mar 2019, 9:58 pm	#1
chroma04 Pentode Join Date: Jul 2008 Location: Doncaster, South Yorkshire, UK. Posts: 116	Sobell T91 Hi, After successfully restoring my Bush TV22 (with the kind help of forum member Ed Dinning supplying a rewound frame blocking transformer), I have come across the above Sobell T91 television set, and wondered whether it would be a suitable contender for restoration? Unfortunately, after searching on the internet, I appear to be able to find little information about this set. Has anybody seen such a TV or know where I might be able to obtain the service manual? Or has anybody seen or serviced such a set? I'm still fairly new to the world of vintage television, so if there are pitfalls for the unwary/inexperienced, then it may be beyond me. Many thanks, Adrian. Attached Thumbnails __________________ Chroma 04

14th Mar 2019, 2:18 am	#2
petertheorgan Hexode Join Date: Dec 2006 Location: Bromley, Kent, UK. Posts: 332	Re: Sobell T91 I am having an guess but i wonder if the H M label on the chassis referes to Holme Moss which means that the TV set will be tuned to channel "2" , not a problem but something to be aware of

14th Mar 2019, 11:11 am	#3
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: Sobell T91 Circuit diagrams of the Sobell T90 and T91. Gas thyratrons are used in the timebase oscillators. Local oscillator can be adjusted for Channels 1,2 and 4. H.M. = Holme Moss channel 2. DFWB. Attached Thumbnails

14th Mar 2019, 11:14 am	#4
beery Heptode Join Date: Jun 2006 Location: Ware, Hertfordshire, UK. Posts: 988	Re: Sobell T91 Hi Adrian, that's a very nice set and one that was once on my wish list. I quite like Sobell sets. They are basic and made down to a price, but can give good results. The biggest unknown will be the Mazda CRM92 CRT. The set used a metal rectifier which won't put up with the current needed to re-form the old HT smoothing caps. Best to re-form these caps first before powering the set. The metal rectifier might still be tired, so be prepared to fit a 1N4007 and a series resistor in place of the original rectifier. I think I have the diagram in an early Newnes book. I will have a look tonight and scan it in. Good luck with the set. Cheers Andy __________________ www.youtube.com/user/andyvalve100

14th Mar 2019, 11:16 am	#5
beery Heptode Join Date: Jun 2006 Location: Ware, Hertfordshire, UK. Posts: 988	Re: Sobell T91 I see David has beaten me to it __________________ www.youtube.com/user/andyvalve100

14th Mar 2019, 11:19 am	#6
Peter.N. Dekatron Join Date: Jul 2008 Location: Charmouth, Dorset, UK. Posts: 3,601	Re: Sobell T91 I don't think I have ever seen one of those, lots of later Sobell's though. Looks to be in very good condition, a worthy project I would think. Peter

14th Mar 2019, 9:41 pm	#7
chroma04 Pentode Join Date: Jul 2008 Location: Doncaster, South Yorkshire, UK. Posts: 116	Re: Sobell T91 Many thanks everybody for the responses and to FERNSEH for kindly uploading the schematic diagram. The wealth of knowledge and resources of this forum is truly amazing! Your responses have prompted me to go ahead and make a few basic checks on the set to see whether it is indeed a viable project. Initially, I plan check the CRT heater for continuity. If this checks out OK, I'll make some cold checks on the other wound components and then I'll attempt to reform C57A/B. After snipping C58, which is wired across the mains input, I'll carefully apply some mains and see what happens! I intend to do as little as possible to the set prior to applying power. The CRT looks rather vulnerable when the chassis is withdrawn, so I'll need to take care whilst working in this area. I'll be back to give an update on my progress if the set looks to be salvagable. Here's hoping the CRT has some life in it! Adrian. __________________ Chroma 04

15th Mar 2019, 8:34 am	#8
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,989	Re: Sobell T91 Hi Adrian, would be great to see some pictures of the other side of the chassis, looks a nice set. __________________ Stephen _________"It`s only an old telly" ___

15th Mar 2019, 9:17 am	#9
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Sobell T91 I'm certain I noticed a full service manual for the T91 on Ebay recently. Service data for the T91 can be found in volume 4 of the original set of R&TV servicing pages 383-387. I can scan these at high resolution and let you have them on a CD [FOC] if you would like them. Cheers, John.

15th Mar 2019, 9:25 pm	#10
chroma04 Pentode Join Date: Jul 2008 Location: Doncaster, South Yorkshire, UK. Posts: 116	Re: Sobell T91 Photo's of the withdrawn chassis.That c.r.t. certainly looks odd, mounted as it is. Also, the chassis is unbalanced when removed from the cabinet and tends to want to fall onto the c.r.t.'s face!! I'll need to proceed with caution when working on it. Many thanks John (Heatercathodeshort) for the offer of the scan of the R&TV servicing pages. I'd like to take you up on this if I may? I'll send you a PM shortly. Adrian. Attached Thumbnails __________________ Chroma 04

15th Mar 2019, 10:21 pm	#11
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,989	Re: Sobell T91 The genuine service manual is still listed, it could be a good investment to go with this rare set. I like the use of the glasses case __________________ Stephen _________"It`s only an old telly" ___

15th Mar 2019, 10:59 pm	#12
mark pirate Dekatron Join Date: Mar 2008 Location: Worthing, West Sussex, UK Posts: 5,185	Re: Sobell T91 Nice little set, if the CRT is OK it should be quite an easy restoration after a TV22 I do like these early Sobells, nice and simple to work on and capable of good performance once restored. Mark

15th Mar 2019, 11:26 pm	#13
chroma04 Pentode Join Date: Jul 2008 Location: Doncaster, South Yorkshire, UK. Posts: 116	Re: Sobell T91 Many thanks Freya for the heads-up on the service manual. I have purchased it and have now placed the chassis back into the cabinet for safety whilst it arrives. Regards, Adrian. __________________ Chroma 04