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Old 6th Mar 2021, 10:25 pm   #1
Heatercathodeshort
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Default Three Dudes from Slough.

THREE DUDES FROM SLOUGH
[ These two receivers were restored during the first lock down last year. I thought I had posted the details but checking my posts I realize they must have been overlooked.]

A McMichael 14" mains transportable was recently donated to the museum. It was dropped over to me to check if it was worthy of overhaul with a view to adding it to the many working display items.

The receiver chassis dates from 1958 and was marketed under two brand names, Sobell [TPS147] the actual manufacturer and McMichael [MP14] the old established radio company that Sobell had taken over a year or so before.

The MP14 is quite stylish with a two tone milk chocolate and cream wrap around plywood case, the two tone colours of an expensive saloon car of the period.

The Sobell version in a similar Rexine covering but this time in a more jazzy colour scheme notably red and off white. I think Granny would have chosen the Mc Michael and her Grandson the Sobell. This period in design is quite distinctive. Gone is the austerity of WW2. People wanted to see colourful new things as enjoyed by the young generation that followed the horrors of the 1st WW, the 'bright young things' of the 20s and 30s.Victoriana was out!

I have both a McMichael and a Sobell in my crazy collection. The McMichael was restored around 10 or so years ago, the only thing that takes the shine off is the slightly low emission Mullard AW36-20 14" electrostatically focused aluminised tube. It gives a good picture but turns slightly silky on full brilliance. It was one of the first domestic tubes from Mullard to be aluminised together with it's big monster, the 70 degree 21" MW53-20 released a little earlier. Other than that it works very well and is nice and stable.

The back less and knob less bit of rough or rather the Sobell was very scruffy and about 15 years ago got dumped in the loft above the garage. It has a very draughty tiled roof and not ideal to store anything electrical. More of my own terrible twins later. I have no idea where it came from. I probably discovered it shackled and dumped in a large handbag under the clock at Waterloo Station.

A few days later I plonked the McMichael on the workbench. It's back was missing together with the LOPT screening can. These were a right fiddle to refit and often were inexcusably thrown into the bin! All the control knobs were either broken, or the incorrect type and the cabinet was very dirty, simply because the owners did not know how to clean them.

[I may have mentioned this before but many years ago I overhauled a Sobell TPS180 series for a customer. As usual I cleaned the cabinet with FLASH and a nail brush and of course it came up like new. On returning the receiver to the customer the lady of the house exclaimed that it was not her TV because the cabinet was too clean. To be honest I had a struggle to convince her that it was indeed hers. I explained that I always cleaned repairs before returning to them to their owners, it was just part of the service. The lady informed me that she had attempted to clean the Rexine many times without success. In the end I informed her that a special cleaning fluid was supplied by the makers to service workshops only for the safe cleaning of electrical products. My scandalous tale did the trick!]

This at first sight looked like a bit of a non starter but the chassis was very original and a quick check of the Mullard AW36-20 aluminised CRT proved it was 100%.

The cosmetic bits including the card back are the weak points on these models. The volume, on/off, channel selector and fine tuner knobs are made of a plastic material that soon broke down resulting in the knobs literally snapping off the control spindles. I can remember when I was first in the trade in the early 60s, virtually every one of these models that arrived at D & B Television where I worked until I was 18 had broken knobs and a tatty back. At that time replacements were cheaply available from Radio and Allied Holdings, North Circular Road, London NW2. [TEL Gladstone 6454] Funny how you remember the old addresses. They had a massive white board with just the number 719 on it. If you drove past it you were locked on the North Circular Road to end up lost in the depths of Park Royal or the Great North Road A1 never to be seen again!

Well back to the Museum McM. Plug it in? Why not! The mains filter caps in these Sobell chassis are flat silver mica types so no need to snip them. The mains lead was trimmed back and a nice brown 2 pin 5amp Clix plug was fitted and tightened down. After a quick visual check to make sure all the valves were present and in their correct sockets I plugged it into my distribution board and flipped the switch.

After a tense wait expecting the valves to glow or a fuse to blow, I was awarded with nothing.. A quick check at the conveniently positioned heater thermistor revealed there was no voltage arriving at the start of the heater chain. I know this series of S/McM very well having carried out minor repairs was I was 16....[So long ago] They had a long service life. Sobell produced high quality receivers with a very enviable reliability record very much to the annoyance of the snooty HMV etc dealers of the time.

The mains droppers are surprisingly reliable so I went for the mains switch to discover it had an odd 'click'. A tiny squirt of DeOxit [other switch cleaners are available] soon sorted that out and we now had valve heaters.

Other than some crackles from the speaker there appeared to be little if any action from the line timebase. As expected the EY51 EHT rectifier remained unlit but at least there were no signs of overheating or bubbling capacitors.

After approximately 3-4 minutes the line time base began to wake up and the EY51s heater began to glow. The reason for the extended delay was the use of the early version of the Mullard PY81 boost diode. These were fitted with an insulating ceramic sleeve between the heater and cathode to maintain a very high heater to cathode insulation at pulse voltage. I think it was rated at 4.5kv.

With the brightness turned full on a faint frame collapse could be seen and a check on the Ion Trap magnet confirmed it was a long way off it's correct position. with a little juggle the frame collapse was now very bright proving that the good old Mullard AW36-20 tube still had some fire in it's guts.

Worth an overhaul? Yer I recon it is..

Removal of the chassis is a bit of a struggle as it is a very tight fit in the case. The control panel has to be pulled back to allow clearance and the bottom case feet have to be removed. With the chassis clear a quick examination proved that it was safe enough to power up.

With the tube removed to gain access to the vertical chassis, Pins 1 & 12 of the CRT base were shorted to maintain heater continuity and the EHT lead was safely tucked out of harms way. The scope confirmed there was a complete absence of output from the frame oscillator. I quick check confirmed their was voltage on pin 6 of the frame output valve confirming that the output transformer primary was in good condition.

The moulded paper capacitors were all original HUNTS solid black type and had survived very well considering they were 50 years beyond their design life and had been stored under very bad conditions. [OK they all leaked but nothing like the early cardboard wax paper types manufactured by all capacitor manufacturers up to around the mid 50s.] This would have to be done with care in an orderly manner if time consuming mistakes were not to be made. The chassis being vertical made access to some of the components difficult and it would have been a pain to remove and refit the CRT to test between component changes, normally a procedure I would recommend.

First to replace were the boost capacitor .1uf, line coupling capacitor .01uf, A1 decoupler .05uf and then with care the rest of the black beauties.

It was encouraging to discover on powering up that the chassis now produced a really good frame scan together with a bright raster. Operating the channel selector produced bright flashes on the screen and loud clicks on the sound suggesting that the tuner and both sound and vision I.F. stages were probably capable of amplification.

All the valve holders were cleaned together with the preset pots. The bottom can of the Cyldon tuner was removed to discover coil biscuits fitted for channels 1-5 and 8-11. Their contact studs were cleaned and lubricated together with the looped spring contacts taking care not to bend them out of shape.

With some RF fed into the aerial socket it took only a few minutes to set the chassis up to discover a very good performer indeed. The gain, contrast, EHT regulation and sound all performed to a high standard, a real credit to the guys at Sobell that designed it.

When I think of Slough I always recall the John Betjeman poem simply called SLOUGH. You have to smile at it's words but very unfair when you think of the industry and employment that could be credited to the Slough Industrial Estate. The electrical trade alone owes a lot to it.

Being one of the 'New Boys on Block' Sobell were not recognized by the long established somewhat snooty dealers. It was their loss as Sobell produced a very well made product at their factory at Slough. Compare them to the post 1948 EMI receivers!

The chassis was lightly cleaned of dust with a small paintbrush and the vacuum cleaner. Nothing too heavy! Your cleaning a TV chassis not the gold fish pond.

A new pair of backs were made from hardboard and painted light brown for the McM and silver for the scruffy Sobell. A pair of CRT protection 'bowler hats' were fabricated with fibreglass and resin using a food container as a mould. When smoothed these were sprayed a similar colour to the originals. This worked out well and made a worthwhile contribution to the overall appearance of the two receivers.

The cabinet was scrubbed with a nailbrush and FLASH bringing it back to something like it's original smart finish. The glass viewing window and plastic mask also required cleaning to remove years of Nicotine bringing back a new appearance.

To my surprise a hunt through the knob boxes came up with a couple of NOS channel selector knobs but alas only one of the smaller volume types. These were replaced on my Sobell with a couple of small serrated cream Bakelite knobs. They really look the part and match the lighter Rexine. The museum McM knobs were repaired using a couple of sacrificial types as used on the 900/1500 series. First the original knobs had their broken internals ground out with a mini grindstone. The captive part of the Thorn knobs were then cut off and secured into the original knobs with a pool of Araldite. They will never break again!

Conclusion. These excellent little Sobell receivers are well designed and give a good account of themselves as do the traditional table models such as the TS17 etc. The line output transformers are excellent. They never fail and do not suffer from the damp ingress of most other makes. Good quality components are used including a full compliment of Mullard valves and CRT. The circuits are straightforward and therefore reliable. Build quality is excellent.

The cosmetic bits are the only let down as they were on many makes at this time. As mentioned the control knobs are of poor quality and flimsy. The hardboard backs suffer from breakdown especially near the dropper units. These two failures were unfortunately a safety problem as many owners ended up using a pair of metal grips to change channels and note this is a potentially live chassis if connected incorrectly, and they always were! I can't recall any cases of customer shocks but the danger was always present.

A really great series of chassis if you fancy having a go at restoring a worthwhile hand wired receiver. Access is even easier on the table models with good under chassis layout and if you can get hold of an original service manual, all the better.
My really scruffy Sobell turned out to be an almost identical repeat performance giving an excellent account of itself.
Pictures show: The 3 bad boys. Top is the leader of the gang, my tattooed Sobell TPS147. Left is the Museums McMichael MP14 and the one on the right is my McMichael MP14 restored some years ago. The chassis layout and internals and some off screen pictures.

The restored McMichael can now be seen operating at the museum. John and Peter, Television Dept. 3/21
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Old 7th Mar 2021, 3:21 am   #2
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Default Re: Three Dudes from Slough.

Thanks John. It’s always good to read your posts. I did notice it earlier but thought it would make better bed time reading. Those sets look great Andy
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Old 7th Mar 2021, 9:51 am   #3
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Default Re: Three Dudes from Slough.

Great job and a superb read, John!
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Old 7th Mar 2021, 9:57 am   #4
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Default Re: Three Dudes from Slough.

Interesting write up! Sobell's son-in-law was Arnold Weinstock who went on to run GEC. GEC's last TVs were badged GEC-McMichael so the circle completes!
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Old 7th Mar 2021, 10:16 am   #5
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Default Re: Three Dudes from Slough.

Quote:
Originally Posted by Heatercathodeshort View Post
THREE DUDES FROM SLOUGH
[ These two receivers were restored during the first lock down last year. I thought I had posted the details but checking my posts I realize they must have been overlooked.]
I remember your write-up too. Very strange that the search doesn't find it!

Peter
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Old 7th Mar 2021, 10:22 am   #6
Peter.N.
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Default Re: Three Dudes from Slough.

Nice job John. I used those 14" Sobell portables as loan sets - many years ago.

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Old 7th Mar 2021, 10:25 am   #7
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Default Re: Three Dudes from Slough.

Nice work and great write up I always enjoy reading your restorations.

I’ve never encountered a Sobell TV yet! I always fancied getting one of their big Bakelite beasts, I saw one at the NVCF a few years back, but it was out of my price range, don’t know where I’d put it either!

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Old 7th Mar 2021, 11:15 am   #8
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Default Re: Three Dudes from Slough.

A very good write up John, I had one of these back in the early 70's, probably purchased with my pocket money from a jumble sale.

I remember the back had disintegrated exposing part of the live chassis
The only problem was having to adjust the frame hold until the set had warmed up for a while.

I have a real soft spot for Sobell products, the set in my avatar was the first post war set from Sobell, although looking like a mid 30's set, it is an excellent performer & built like a tank.


Mark
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Old 7th Mar 2021, 11:47 am   #9
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Default Re: Three Dudes from Slough.

Those tubes look to be belters.
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Old 7th Mar 2021, 12:19 pm   #10
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Default Re: Three Dudes from Slough.

I remember these coming on the market as I was already in the trade.Very reliable sets which rarely went wrong.The main reason they came into the workshop was for screencleaning and we used to have speed competitions to see how quickly this could be done.18 minutes comes to mind. When a newby started they would be given one of these for said screenclean and then observed as they tried to figure out how to get inside.If I remember the soft plastic on the handle had to be pulled to one side to reveal the handle screws,very confusing when seen for the first time.Thanks for the writeup.Peter.
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Old 7th Mar 2021, 12:29 pm   #11
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Default Re: Three Dudes from Slough.

Most enjoyable write up, John. That was one of those 'settle down with a cup of coffee' reads that didn't want to be rushed!

I always like the snippets of detail from what all these sets were like at the time from a customer and a repairer's point of view.

All the best
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Old 7th Mar 2021, 12:37 pm   #12
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Default Re: Three Dudes from Slough.

Quote:
Originally Posted by peterpixel View Post
When a newby started they would be given one of these for said screen clean and then observed as they tried to figure out how to get inside. If I remember the soft plastic on the handle had to be pulled to one side to reveal the handle screws, very confusing when seen for the first time.Thanks for the write up. Peter.
Yes you are right Peter but what really got them scratching their heads, mine included was that you had to pull the volume and on/off control knobs off, [Smash Crunch!] loosen two 4Ba screws on the control panel then push it back to clear the cabinet. It really was a tight fit but I don't remember any chassis overheating problems. It was quite well ventilated unlike that dreadful KB PVP20 Royal Star. Penny washers come to mind. Thanks for your kind comments. John.
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Old 7th Mar 2021, 2:04 pm   #13
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Default Re: Three Dudes from Slough.

Another very enjoyable read. Excellent pictures on all sets. I bet these were popular with small flat dwellers where space was limited. When I joined the trade in 1971, Radio & Allied had moved their service dept a bit further out to East lane, Wembley. Cannot remember the phone number; it would have been an all number one by then.

Alan.
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Old 8th Mar 2021, 12:48 pm   #14
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Default Re: Three Dudes from Slough.

Just a few pictures of one of the cobbled together backs and the side panel with it's delicate control knobs. This was the scruffy Sobell version that actually turned out to be a real cracker! Backs are a real problem. These were easy but the shaped ones can be a task too far. John.
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Old 8th Mar 2021, 9:48 pm   #15
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Default Re: Three Dudes from Slough.

There was loads of these sets in use during the 1960s but I didn't get to repair many because of the excellent reliability. What jobs the sets ever needed doing was simple tasks like clean the contacts on the tuning coil biscuits in the Cyldon type C turret tuner. Occasional valve replacements, PL81, EY51 and that's it.
All the handwired Sobell TVs were reliable, as good as Philips and yet the Sobell brand was derided by many dealers dismissing the brand as a cheap furniture shop product. But the TV rental firms knew how good Sobell sets were. Radio Rentals bought out Rentaset in 1961? and although RR made their own sets Sobell and later GEC TVs were available in their showrooms.

DFWB.
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Old 8th Mar 2021, 11:55 pm   #16
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Default Re: Three Dudes from Slough.

Another great write-up by the tv gaffer! Thanks for the tip about moulding fibreglass matting around a food pot. I shall press that one into service. Oh..and A Handbag?
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Old 9th Mar 2021, 2:53 pm   #17
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Default Re: Three Dudes from Slough.

Try a charity shop Kevin, that is if you must have one. John.
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