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Old 28th Jun 2020, 4:58 pm   #1
Heatercathodeshort
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Default Peto Scott 12" console model TV122 1948

PETO-SCOTT 12" CONSOLE MODEL TV122 1948
Part one.

As explained in the 'Melted mask' thread, this receiver was discovered in a scout hut type outbuilding a few decades ago. It's appearance suggested it had suffered an internal fire. The face plate of the tube was covered in what I first thought was melted black plastic that had dripped from the dissolving tube mask but later discovered it was in fact broken down rubber that over the years had dripped downwards then set rock hard. The laminated implosion protection screen was cracked probably due to transportation into the hut in the distant past. It was after all a twelve year old scrap receiver.

Upon first examination I was relieved to discover that a fire had not been the cause of this horrific looking mess.

The loudspeaker a nice 8" ELAC that now had it's magnet encased in a liquorice coating and there was a huge heap of what looked like the result of a poor elephant being caught short in the entire width of the front bottom of the cabinet. Other than that the actual 'works' looked clean and dry so there was hope [life is nothing without hope] of this potentially smart receiver displaying test card C again.

I packed it away in the workshop and covered it with a cabinet 'muff'. These were used when transporting receivers in vans to and from customers houses and protected receiver cabinets in the workshop while waiting repair. They consisted of a padded bag, basically containing what appeared to be the old fashioned carpet underlay with a tightly stitched vinyl cover. They were produced in various sizes with straps to secure them firmly to the TV, rather like a straight jacket. They were a life saver in a busy workshop and you earned Brownie points from your customers when they noted you were taking such care of their treasured, and they were in those days treasured television receivers.

Recently I decided to have a go at getting it working, the mask mess having been one of the reasons it had been set aside for so long.


The Peto Scott Company was established during the very early days of radio. The 'Wireless World' show advertisements for them in the 1920's with a London address.

They moved to Weybridge at a guess, maybe just before the war or during the war under government war time direction manufacturing radio and television receivers together with high quality test equipment. They produced their first television receiver in 1937, a large electrostatic monster with the huge chassis supported by what appears to be a 'Dexion' frame. The W.W. featured a test report on it with good results but I don't think it was ever fitted in a cabinet for retail sales.

As the 1950's rolled on Peto-Scott were getting known for their TV broadcast equipment including closed circuit TV systems and cameras. They continued to produce television receivers and to a lesser extent radio receivers and built upon their good reputation. They were known to have enjoyed what could be termed a middle class appeal, a bit like Hacker Radio and were sold by mainly respected establishments. This TV122 has a label on the back stating it was supplied by MELFORD RADIO SERVICES, [shop] 181C High Street, Hampton Hill Middlesex [It was only a stones throw from P.S. at Weybridge.] so this would back this up. MOLsey was a manual telephone exchange well into the 60's.

Unfortunately they were one of the major TV manufacturers that ran out of steam in that fateful year, 1961. Like Cossor at Highbury they were taken over by the Philips group around 1961, no doubt in the case of P.S. for their studio TV manufacturing side. From that year P.S. receivers were fitted with Philips chassis. The Peto Scott name was quickly wound down by Philips and the brand was soon to fade from TV shops windows.

The story of the mask is well covered [Ha! ha!] in another thread so I will dive in and describe what was needed to bring the P.T. back to life leaving the final cabinet details till the end.

The TV122 is of substantial build quality. The cabinet is nicely proportioned of a light wood typical of the late 40's and has none of the problems of the GEC radiogram and the super little McMichael T909 recently dealt with.

It does have quite a number of old woodworm holes but these were treated using a syringe of the type used for filling ink cartridges and Rentokil. Finally I liberally brushed the whole of the cabinet interior after having given it a good clean with hot soapy water. It looks very smart even before the holes were filled with wood filler.

The receiver itself consists of three main chassis all connected with Philips type octal plugs and sockets, you know the type with the twist off metal covers. The tube and it's gantry is mounted on an inverted board slid into a slot in the cabinet top.

The heavy power supply chassis sits on the bottom with the timebase chassis complete with it's piggy back IF unit, mounted on the middle shelf. Oddly the sound I.F. strip consisting of two EF42's and a EB91 is mounted in an isolated strip on the timebase chassis connected by a co-ax plug and socket similar to the type used on car radios. It's almost looks as if they forgot about the sound I.F. stages then suddenly realized that it would not all fit on the vision unit! The sync pulses are passed to the timebase chassis via a single wander type plug and socket. It's certainly a neat job.

There are various smaller connectors similar to the battery types fitted to the AD4 and B126 of their day. A final octal plug connects the main control panel to the timebase chassis.

First to deal with was the power supply. This is quite conventional for the pre flyback era consisting of two heavy transformers. One supplies the 380V H.T. line and the 6.3v valve and tube heaters including a 5V winding for the GZ32 full wave H.T. rectifier. It certainly has a classic Plessey look about it with it's two fibre connecting strips and solder tags with the output voltages clearly marked. The focus coil is connected in series with the main HT supply shunted by the usual high wattage resistors and the biggest fatty fat fat 1uf 350V waxie I have ever seen!

The second transformer a warning of which I will give supplies 5.5kv of EHT for the Mullard 12" loctal based MW31-14C tubes final anode. The EHT rectifier is a Mazda U22, odd because all the other valves are Mullard. I wonder why they didn't use the Mullard HVR2? I suspect that the original transformer was also supplied by Plessey and maybe it was only supplied with a 2v winding for the rectifier. The output from the U22 is connected across a bleeder network consisting of seven 3.9m resistors, smoothing being undertaken by a single .1uf 7KV Dubiliar capacitor.

WARNING ! WARNING! Receivers employing mains transformers to produce EHT need special care and servicing procedures. The low impedance 50c/s high current supply is LETHAL.

Danger spots. Any exposed connections in the EHT circuit such as EHT rectifier top caps, tube anode connectors, bleed resistor tag boards and the live connections to the EHT capacitor/s. [Dangerously exposed on the PYE B/D16T PYE so watch out.] Finally check the condition of the EHT lead to the CRT itself [Check the picture..]. Age can harden plastic causing splits with the obvious risk of flash over and shock if handled while live.

Surprisingly many of these are left without insulation. I always fit a BULGIN EHT anode connection to the EHT rectifier but stocks are getting short!

As mentioned in the M.M. thread a torn sheet of paper dated 1960 was discovered under the mess with the words 'EHT transformer' written in pencil.The customer probably purchased a nice new 17 or 21" receiver with a super bright picture and capable of receiving the ITA! [The horror of it my dear..]

The chassis was given a general light clean up and examined for any evidence of overheating. The only ominous sign was the heavily blackened Mazda U22 EHT rectifier. It had definitely taken a bashing and may have been the cause of the original EHT transformers breakdown.

The good quality Dubiliar EHT smoothing cap [the one with the aluminium case and the Bakelite top] read infinity on my meter and I did not suspect this as being the cause of the transformers apparent failure.

A check of the bleed resistors showed that three of them were O/C leading to a very dangerous situation for the service engineer. With the bleeder chain O/C the EHT smoothing capacitor could stay charged for a considerable period there being no leak to ground, just awaiting some poor soul to grab hold of it hours later...The chain also stabilized the EHT somewhat preventing surges that often caused the breakdown of the capacitor, EHT rectifier and mains transformer all in one go.

After a meter check, just to prove there were no short circuits, I decided to give it a little power. The mains input plug and socket are the well known Bulgin three pin circular style but the mains wiring was routed through the chassis to the single pole mains switch on the control panel so I decided to unleash my crocodile clips and trusty variac making direct connections to the mains transformer primaries. The top cap anode of the U22 was removed for the initial test.

I switched on slowly advancing the input voltage. A faint glow in the GZ32 at 90v and a rising meter reading showed that I had at least some HT. So good so far.. No signs of distress from the EHT transformer.

I increased the variac a little. The HT rose nicely and everything appeared to be OK. It was at this point I heard that tell tale bubble and squeak sound that can only translate into an EHT transformer that was breaking down. Well that engineer back in 1960 did tell me!

A good few years back a member of this forum supplied me with a suitable transformer that he had kindly wound for me. [Thanks E.] At the time I simply did not have the time to spend restoring this TV122 and the transformer was carefully packed away for future use.
The mounting and lead outs were different to the original but a nice thick section of Paxolin board was cut and an adapter plate with insulated stand off mountings [wake up David!] fabricated to fit the new transformer and lift it clear of the chassis.

With this completed and the wiring checked, power was once more applied. This time no sparks or bubbles. I connected the top cap to the original U22 and slowly advanced the variac.

The U22 eventually produced a very attractive internal purple glow. It had been destroyed probably by a breakdown between it's heater winding and the EHT winding due to the incredibly high peak inverse voltage, ending it's days in a spectacular show.

The U22 has a huge cylindrical cathode that is designed to heat very slowly. This delay allows the timebases to build up fully before and EHT is applied to prevent burns to the delicate screen phosphors in the event of the slow heating line and frame timebases.

With a new U22 fitted the EHT rose gradually to 5.5KV, spot on!

At this point I thought it a good idea to replace the original 1949 H.T. reservoir and smoothing capacitors. They are two tall units, 16uf R and 60uf S. They actually performed OK but were a bit slow getting going showing some ripple on the H.T. line for the first five minutes. OK they may have reformed but they are 70+ years old and it was not worth risking a GZ32 and possibly the mains transformer. I will repack the originals as the excellent modern short types look a bit odd on such a large chassis.

Oddly there are no fuses in this receiver and considering the heavy house fusing that was around in the 1940's and especially with mains derived EHT, a couple of 2 amp mains fuses would not have gone amiss. I will sort out a retro fuse holder before completing restoration of the TV122.

After a long soak test the power supply was put aside and part two will deal with the timebase chassis followed by the I.F. sub panel. John.
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Old 28th Jun 2020, 9:01 pm   #2
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Default Re: Peto Scott 12" console model TV122 1948

Brilliant: another fascinating HCS restoration saga gets underway! I do love all the background details, makes for a very interesting read.

Keep it up John, I'm looking forward to part 2!

All the best
Nick
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Old 29th Jun 2020, 12:27 pm   #3
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Default Re: Peto Scott 12" console model TV122 1948

John,

I always enjoy reading about your escapades and look forward to the next instalment.

Thanks for the write up.
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Old 29th Jun 2020, 4:18 pm   #4
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Default Re: Peto Scott 12" console model TV122 1948

Quote:
Originally Posted by eddie_ce View Post
John,

I always enjoy reading about your escapades and look forward to the next instalment.

Thanks for the write up.
+1

Peter
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Old 29th Jun 2020, 9:06 pm   #5
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Default Re: Peto Scott 12" console model TV122 1948

Comprehensive information for these early Peto-Scott TVs can be found in Volume II of the Malloy and Poole Television Servicing book. Pages 395 through to 401.
Also covered in the book is two earlier models, TV91 and TV121.
The servicing notes inform us that the vision stages are optimised for full 3Mc/s bandwidth. I'm sure with a good CRT these sets will be capable of displaying extremely good pictures.
Blocking oscillators are employed in all models. The early models employ different valves in the frame timebase, an EBC33 as the oscillator and a large pentode for the output, an EL33. In the later sets Peto-Scott must have noticed that for the frame timebase Pye had got away with a double triode, a Mullard ECC34, so why not do the same?

In 1956 Peto-Scott were one of the first firms to market a TV set with a stabilised line output stage, something you'd only find in high quality monitors.

DFWB.
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Old 1st Jul 2020, 10:08 am   #6
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Default Re: Peto Scott 12" console model TV122 1948

Nicely made power chassis, Peto scott made good quality sets. I have owned my HU52 radio for over 40 years, still working on all it's original parts!

I purchased my set from a jumble sale in Weybridge in the late 70's, so it must have lived it's life within a couple of miles from the factory?

Mark
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Old 1st Jul 2020, 10:23 am   #7
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Default Re: Peto Scott 12" console model TV122 1948

Part Two. The timebase chassis.

With a working power supply the time had arrived to sort out the timebase chassis. I decided to carry out some quick essential tests before continuing further.

Continuity tests were carried out on both the line and frame blocking oscillator transformers, audio, line and frame output transformers and the scanning coils. The focus coil had already been checked while servicing the power supply. To my relief all gave typical readings and were assumed serviceable.

Starting with the line output stage. This is entirely conventional with an EF50 valve in a blocking oscillator circuit driving the well known and almost indestructible EL38 octal based line output valve. Due to the EHT being developed via a mains transformer the circuit is very simple, similar in fact to a class A audio output stage.

Width adjustment is provided by adjusting the bias of the EL38 and a useful degree of linearity is obtained by applying variable damping to the primary of the line output transformer.

I have a love hate relationship with the EF50. Due to war time conditions and the fact that EF50's [service number VR91] were produced in a number of countries, the characteristics of these valves tended to vary. You may have to try a few in positions that they were never designed to be used in but with patience you will usually find one that works as intended.

In the early post war years EF50 valves and their equivalents were widely and cheaply available on the surplus market. It was soon realized that the American produced valves had the edge on valves produced elsewhere.Valves were graded and the very best had two black stripes painted across the top of the aluminium can and demanded a slightly higher price. As you can imagine the surplus dealers soon worked out that adding the stripes produced a higher profit! To be honest, in those austere post war years, who could blame them? You have to laugh!

PYE were very careful in their use of EF50 valves in the first AC/DC receiver, the famous B18T receiver of 1948. They used the 'double stripe' [genuine] versions in sensitive parts of the chassis.

The usual culprits were then pounced upon. Any capacitor with a wax overcoat was condemned the first being the line coupling .01uf. The resistors as always were very close to their design spec and were left alone. The white ceramic types with bright colours are incredibly reliable, made by the million I believe by The Radio Resistor Company [?].

All the rear presets were checked for continuity and found to be satisfactory.

With the rest of the waxies replaced in the line oscillator I moved over to the frame stage. This comprises a larger than life Mullard ECC34 medium power octal based double triode. One triode generates the frame scanning pulses feeding the other half as the triode output valve, a similar arrangement to the earlier PYE D16T of 1946. The Pye version always struggled for height but the Peto Scott version has no problems in this respect probably due to a better quality output transformer.

Once again I had to enter anti waxie mode and replace all the messy sticky capacitors that were sixty years beyond their design life. The cathode by pass capacitor to the output triode was replaced at this stage as it is always a cause of frame cramp when it dries up. It did check OK on the tester but testers lie...

Now I had carried out all this work without powering the chassis, a sure recipe for trouble. It's takes only a second to make a wiring or component value mistake, no matter how vigilant you are, resulting in at least a frustrating hour to dismantle everything and recheck your errors. Don't feel too bad about it. [Think of the early experimental space rockets that have exploded on take off because somebody failed to clean the EF50 pins..]

The connecting leads were far too short from the original power chassis to reach to the the timebase octal plug. This is where my old Griffin power supply was woken up and and brought back into service. I pulled it off the tip years ago. Like a lot of test equipment, it is not used a lot but invaluable when you need it. The Griffin will supply up to 400v Dc fully smoothed and fully variable and 6.3v for heaters at 4 amps.

I connected it up to the timebase chassis picking up the HT on the tag strip connected to the octal plug. I wired the heater connections directly to the heater pins of the EL38 removed for the initial test.

After double checking everything I connected the scope to the anode of the output section of the ECC34 and with the H.T. pot at minimum I switched on. With the H.T. adjusted to around 250v It didn't take long for a sizable waveform to appear on the scope that could be varied in frequency and amplitude with the vertical hold and height controls. Things were looking good.

Well the frame time base was certainly producing something that would show a scan. so attention was paId towards the line output stage.

As mentioned this comprises an EF50 valve in a blocking oscillator circuit feeding the EL38. The line output transformer is a circular aluminium can with the windings encased in sorbo rubber presumably to reduce the 10kc/s line whistle. The top cap connection to the anode of the EL38 exits via a hole in the top. This transformer appears in many receivers of this vintage and I reckon it is another Plessey product. Vidor and Regentone come to mind.

Yet another waxie extermination expedition and a check of all the resistors in the circuit. Not a lot to go wrong really other than pulse voltage flash over in the LOPT can but I was saved that misery.

Once again with HT and heaters applied a good waveform appeared on pin 5, the control grid of the EL38.[The numbering on the base of these truly excellent McMurdo valve holders always catches me out, yer after 60 odd years!] I plugged the monster valve in and heard a low level line whistle as expected from such a well insulated transformer not bothered with the complication of supplying flyback EHT. A small spark could be seen when tickling the top cap anode of the PL38 with an insulated screwdriver. Things were looking good.

The sound I.F. and detector stages occupy a small section of the timebase panel. Two B8A based EF42s and a single EB91 provide a high level of audio feeding the familiar high gain EL33 output valve. Four waxie decoupling capacitors were replaced. They have a value of .01uf much higher than usually employed in this position. Feeding the input of the sound I.F. amplifier with a modulated 9.5mc/s signal [the sound I.F. frequency] resulted in a good signal at the detector output. Things were looking good.

All presets, valve holders, plugs and sockets and valve pins were carefully cleaned paying particular attention to the EF50 with it's short tarnished pins. These I finish off with a dipping in MS4 grease used sparingly. [I have had the same tube since 1964]

Wow! This takes a lot of writing up.

Part 3 will attempt to explain the restoration of the RF and I.F. Panel including the sync separator. Please stay awake for the next installment. Thanks for your interest.
Pictures show The timebase chassis complete with it's pillion passenger the I.F. board mounted on the top. The underside of the chassis with the I.F. board unplugged and the scope showing the line timebase waveform powered from the Griffin power supply. John.
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Old 1st Jul 2020, 11:50 am   #8
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Default Re: Peto Scott 12" console model TV122 1948

Hi John,
many thanks for another entertaining write-up. I particularly enjoyed the comments regarding EF50s.

I remember as a boy being intrigued by these valves in metal jackets. Without wishing to hi-jack this thread I came across a webpage named, if I remember correctly "EF50 the valve that won the war". It makes fascinating reading.

I look forward to reading the next episode of the Peto Scott saga. BTW I'm pleased it is not only my workbench that is "well populated"

Regards
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Old 1st Jul 2020, 12:20 pm   #9
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Default Re: Peto Scott 12" console model TV122 1948

The EF50 was first released in 1939 with 'hooked' pins but I have never seen this version. J.
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Old 1st Jul 2020, 1:18 pm   #10
Edward Huggins
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Default Re: Peto Scott 12" console model TV122 1948

Greetings: This is a lovely story and particularly resonates with me as I was with Pye (then Philips) at time of the acquisition of Peto-Scott. They had some very good people. There soon followed the inevitable culture clash (as there was with Ekco) between the design and engineering teams. Of course the Peto-scott products were regarded as way over-engineered and in the end, of course, the Accountants won!
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Old 1st Jul 2020, 2:12 pm   #11
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Default Re: Peto Scott 12" console model TV122 1948

Thanks guys for your interest. I wonder what the original purchaser would have said if he was told that the television receiver that he was about to purchase in 1949 would survive the 1950's scrappage onslaught to be brought back to life in 2020! If he was 40 when he purchased it he would be 110 today. Weird when you think about it. John.
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Old 1st Jul 2020, 2:49 pm   #12
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Default Re: Peto Scott 12" console model TV122 1948

Very interesting John.

It looks to be a well engineered set with good component accessibility.

Thanks for letting us enjoy the restoration with you!

All the best,
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Old 1st Jul 2020, 4:09 pm   #13
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Default Re: Peto Scott 12" console model TV122 1948

Not absolutely sure about this but I believe the Peto-Scott TV124 is similar except for the method of EHT generation. The mains transformer might have been replaced with an RF oscillator. This was a technique favoured by many manufactures between 1948 to 1950.

There's a TV127 upstairs a model which is totally different for the TV121 series. Flyback EHT and World series valves.

DFWB.
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Old 1st Jul 2020, 4:19 pm   #14
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Default Re: Peto Scott 12" console model TV122 1948

I have managed to miss place my Peto Scott manuals David. They have probably been filled away under the Philips banner. I'm certain that the TV124 is AC/DC with flyback but I could very well be wrong. Must dig those manuals out. [So much junk!] John.
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Old 2nd Jul 2020, 11:03 am   #15
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Default Re: Peto Scott 12" console model TV122 1948

Hello John, I had a school mate whose family rented a Peto Scott set in the 50s to the mid 60s (BBC & ITV), from a Philips dealer in Small Heath, B'ham. It was one of the most reliable sets I can ever remember. Enjoying this read as ever.

Alan.
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Old 2nd Jul 2020, 6:41 pm   #16
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Default Re: Peto Scott 12" console model TV122 1948

Quote:
Originally Posted by Jac View Post
Thanks for letting us enjoy the restoration with you!
All the best,Jac
Thanks Jac and your very welcome. We owe the Dutch company, Philips a dept of gratitude here in the UK for their quality valves and CRTs that helped spread the uptake of television in the late 1940's and into the 50's. John.
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Old 2nd Jul 2020, 8:23 pm   #17
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Default Re: Peto Scott 12" console model TV122 1948

Part 3. The I.F. panel.

As mentioned this consists of a sub unit mounted to the rear of the timebase chassis, connected to it by a Philips octal plug and socket with single connections from the sync separator and the feed to the sound I.F. amplifier that occupies a small section of the timebase chassis.

It is a superhet circuit with I.F. frequencies of 13.25mc/s vision and 9.75 mc/s sound. Two EF42 R.F amplifiers in a similar arrangement to the Murphy V200 series are employed providing high gain in weak signal areas. These are followed by another EF42 as mixer. The local oscillator is an EF50. It is of high quality construction and forms an important section of any receiver, particularly when working in low signal areas.

It is interesting to note that adjustment of the local oscillator is a customer preset control, a miniature open vaned capacitor complete with Bakelite knob mounted together with the other usual pots on the rear of the chassis. It is of course a critical adjustment [very] and I think they were somewhat nervous about possible frequency drift but after hours of use I have not experienced this.

Oscillator drift must have been a problem back in '48 [The year I was born..] and probably led to the adoption of the TRF circuit so popular at that time. The PYE and EKCO ranges come to mind. What seemed a good idea at the time led to difficulties with the arrival of Band 3.

The BUSH TV1/2 certainly suffered from sound oscillator drift [the vision was TRF] and was eventually supplied with a TRF sound unit with EF91's replacing the original superhet unit with it's ECH35, EF39 and EB34 valve line up. This modification completely resolving the problem no doubt at considerable cost to Bush. It was certainly not a problem with this Peto Scott.

A single stage of I.F. amplification completes the vision amplifier. A double diode B7G based EB91 demodulates the vision signal, the other half of the EB91 being used as a non adjustable peak white interference limiter directly connected to the control grid of the MW31-14C. The tube is grid modulated as were quite a number of receivers of this vintage. The video output valve is yet another EF42.

The sound take off is from the anode of the mixer passed to the two stage sound I.F. amplifier comprising another two EF42 valves. A single EB91 functions as vision detector and interference limiter. The high level audio is passed to a Mullard EL33 without pre amplification, giving about three watts of very good quality sound from an ELAC 8" speaker.

It was a relief to discover that other than four waxie .01uf decoupling capacitors in the sound I.F. amplifier, the remaining were of the silver mica type and proved to be completely serviceable. Replacing these is not a task I like. It's similar to picking flies out of your soup in a sleazy cafe..

The sync separator is another little red canned EF50 in a conventional circuit. A single 25uf 25v electrolytic capacitor in the cathode bypass was suspect. Upon checking it was completely O/C and was replaced by a modern mini type using the case of the old unit as a shell similar to a hermit crab.

Once again it was time to put the old Griffin power supply to use. With the scope connected to the CRT grid feed and with an aerial connected, I applied some power.

To my surprise a vision signal was present and could be tuned by the local oscillator trimmer, improving it enormously. I disconnected the aerial plug just to prove it was in fact a real signal, not just the end of a 'Whats My line' programme of 1954.These old 405 line signals take some killing off!

Not a lot more could be carried out with these 'cold' chassis and it was time to liven them up and see what my efforts had to offer. [I dread to think]

Pictures show. Rear view of combined unit showing oscillator tuning control and overall gain pot. Top view of unit cleaned. Underneath of combined unit. Close up of I.F. strip. 'Blue' EL38. I forgot to post this one on the timebase page.Don't get concerned if you see a blue glow inside your EL/PL38s! This is quite normal but this example is certainly displaying itself with an almost Peacock appearance. It test 100% on the AVO with 90 m/a anode current.

Part 4 Will relay the results and I will post some off screen pictures.
Thanks for reading so far! John.
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Old 3rd Jul 2020, 4:48 pm   #18
Heatercathodeshort
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Default Re: Peto Scott 12" console model TV122 1948

Part 4. The assembly.

With signs of life in the power, timebase and I.F. chassis it was time to put the whole lot together and see if it worked!

I was lucky enough to have a suitable mask and implosion protection screen. This was slightly different to the original Peto Scott but I felt confident I could make it fit. i sprayed it a satin black as was the original. [As if I would forget]

The original laminated plate was fixed to the cabinet with four diagonal metal straps to the corners. These were secured by small woodscrews to the front of the screen opening.

I have no idea what the original mask looked like or how it was held in place to the tube or gantry. Another mystery is the leather cord similar to the type used to drive Singer treadle sewing machines and springs that appeared to hold the FRONT of the tube in place against the gantry. I will never know.

The replacement laminated glass was one 1/8th of an inch too large width wise and one 1/8th of an inch too short height! It was an easy matter to widen the rebated opening in width and glue a small square of wood at the bottom to take up the slack. Fortunately there was plenty of room to carry out the modification.

The replacement mask was formed to take the implosion screen within the front area. I attempted to fit this in one piece as it was originally intended but this left a gap between the front of the cabinet and the screen. The mask had to be fitted separately.

I placed the mask in the viewing window resting the bottom of it on the timber ledge just below the opening. Next I fitted the CRT centrally into the tight rubber cup making sure no muck had dropped into the space between the glass and the CRT face.

Next the scan coils were correctly positioned over the tube neck and with the inverted gantry complete with it's timber support board I carefully slid this into position over the CRT neck and lined it up with the top cabinet rail securing it with 2BA screws and wing nuts. It is very secure and cannot move when the cabinet is returned to it's upright position.

The power supply was next to be refitted into the base of the cabinet secured with four 1" 2BA screws.

The timebase complete with I.F. was offered up next finally leaving the last item, the control panel until the last.

All the interconnections were made and carefully checked. All that was left was for me to pluck up some courage and plug it in!

Being an AC only chassis, the valve heaters being powered from a mains transformer warmed up very quickly and within moments a distorted but bright raster appeared on the screen I plugged my RF signal into the aerial socket and was rewarded with definite signs of Test Card C.

The oscillator tuning was soon corrected and it didn't take long to reset all the presets to obtain what appeared to be a very nice Test Card. [The TV122 must have been one of the first receivers to display TCC. It was introduced in July 1948. W.W.]The focus is very sharp with the manual control centrally adjusted, quite a rare feat for electromagnetic focus arrangements. The scan coils needed straightening with a twiddle hear and there to get it lined up.

The tube is a straight gun tetrode that is prone to ion burn. There is a circle of discolouration in the center but it is hardly noticeable. I doubt if this receiver was used for more than a couple of hours a day. I have seen well used examples of these Mullard tubes giving excellent pictures with a heavy purple stain at the center. It's just something you have to put up with and is all part of the character with vintage television receivers.

The sound is good and strong with the sound gain control set mid way. The balance between sound and vision was slightly odd but I had checked the I.F. coils during the restoration and found them to be heavily sealed with wax.

Careful examination of the aerial input coil showed the single slug to be at the bottom of the coils screening can. The inner former was completely devoid of any locking wax and then I clicked in. Under certain conditions and especially in fringe areas it would have been necessary to adjust this core to match the customers aerial and co-ax to the input transformer. Peto Scott obviously realized this leaving the core 'unlocked'.

It had probably wound itself down over the years and it was a simple matter to bring the core up midway producing 3mc/s bars on the test card and even more sound!

It was noticed that the line frequency drifted a little over a long period but replacement of the EF42 line oscillator completely cleared this up and other than a slight readjustment of the customer focus pot, remained incredibly stable. As the temperature of the winding increases, so does the resistance of the coil. This results in a voltage loss needing a correction with the focus pot.

The interlace is excellent maintained throughout the entire range of the frame hold control.

The pictures show the general reproduction of the Peto Scott TV122. The pictures are very bright considering the low 5.5KV EHT.

The final part will include a few details of the minor clean up etc and the final evaluation of this rather grand television Receiver. John.
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Old 3rd Jul 2020, 7:19 pm   #19
peter_scott
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Default Re: Peto Scott 12" console model TV122 1948

It looks really good John and excellent that it still displays 3MHz with the slugs in the original positions. Thanks for another interesting write-up with a great result.

Peter
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Old 3rd Jul 2020, 7:58 pm   #20
CathodeBias
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Default Re: Peto Scott 12" console model TV122 1948

I've enjoyed the progress of this excellent restoration. A fantastic end result, thanks for taking the time to write this all up.
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