Murphy 12" V180C console 1950

[Heatercathodeshort]

In another thread David Boynes mentions his Murphy V180C 12" console that he obtained recently. His example is in generally poor condition and will require a replacement CRT and some cabinet work that I'm sure David will be well able to cope with.
Spookily, at the same time I was awaiting deliverey of a Murphy console that I was informed was a V118C, the earlier model to the V180C, the 180C being Murphy's first with flyback EHT.
Upon arrival it was discovered to be another V180C! Can you believe that?
It was very kindly obtained for me by another Forum member who had recovered it from a very dry loft in the Midlands. My example of the Murphy arrived just a day after David's opening thread!
Originally I decided to put it to one side until the winter nights but curiosity killed the cat and after several strange sleep walking experiences, was surprised to discover the hulking chassis on my old faithfull work bench..
The empty cabinet was discovered in the garage. How it got there I have no idea but it was in the way so something had to be done. The filthy cabinet was checked over and discovered to be in very good condition other than a few very old woodworm holes. I decided to thoroughly clean the interior and give it a liberal soaking with woodworm killer, just in case.
With this completed it was time to take a look at the large vertical chassis. The style of construction dated from the A56V of 1938 following on to the post war V114 series. At first sight it looked a real beastie but once I had began to work on it I realized what a gem this receiver was to work on.
The restoration has proved to be one of the most enjoying so far taking just a few hours a day to electrically complete.
The pictures show the cabinet after treatment and the chassis prior to commencement of the work including the power supply with that lonely UU8 sitting so innocently.
More to come. Regards, John.

[HamishBoxer]

That cabinet inside looks excellent,very clean indeed.

Wonder what worm killer you use?

[Lloyd 1985]

Very nice! Must have another go at mine sometime soon...

Do you have a copy of the original Murphy service manual? If not, drop me a PM with your email, and I'll send you a copy

Regards,
Lloyd.

[FERNSEH]

Hi John,
Looking the pictures of your V180 gives me something to aspire to.
At first sight you'd be fooled into thinking here is a set that is going to be difficult to service, it is in fact a very easy chassis to carry out most servicing tasks. Only in the event the line output valve needs replacement or testing the chassis has to come out.
I'm making two "L" shaped brackets to locate the chassis in the cabinet. These will be secured to the sides of the cabinet, two wooden blocks will carry captive nuts. I'd rather use machine screws instead of wood screws.

The pictures show the correct shade of grey for the chassis. Blue was the colour of pre-war Murphy metalwork.

DFWB.

[Heatercathodeshort]

Rentokil Hamish. J.

[Restoration73]

Nice to see that set John.
Many years ago we would have the odd 16mm film show at my school. The Cadbury film yielded a small bar of chocolate, whereas the Rentokil one opened with the immortal line (narrated by Richard Baker) "the main constituent of trees is wood" !

[Heatercathodeshort]

Many thanks Lloyd. Your service manual came via the help of David Boynes! The 120,134 and 180 manuals are the only ones I don't have. Thanks all the same. John.

[Heatercathodeshort]

With the chassis on the operating table, a very detailed examination took place. The chassis was dirty as would be expected but very original. The only peculiarity was the absence of the 6K25 thyratron line generator valve. The chassis is of a very large construction dating back to the pre war A56V and almost identical to the V114, the first Murphy post war receiver. The power supply is mounted at the base with it's fat UU8 H.T. rectifier, all on it's own having lost it's little brother the U22 employed in the V114, with it's mains derived EHT. The V180C is Murphy's first flyback model leaving the power supply quite bare compared with it's dad. The receiver chassis is stamped 'B' in two places so I reckoned this was a Midlands model tuned to Sutton Coldfield channel 4. The valves are mostly Mazda 6.3v international octals but curiously two of Mullard manufacture are employed, a EL38 line output and ECH42 frequency changer. More of these later. The R.F. and I.F .transformers are super size more suited to a pre war radio and mounted together with the audio and video stages on a hinge down chassis. The Mazda version of the EF91 the 6F12 provides R.F./I.F amplification and video output. Three 6D2's [EB91] take care of sound detector/limiter, vision detector/limiter and surprisingly sync separator, a method rather dated for even 1950. The frequency changer is a Mazda 6C9 in some models and a Mullard ECH42 in others. Line output is a Mazda 6P28 again in some versions and a Mullard EL38 in others.Damper diode is the stumpy, hatless U291, EHT rectifier, the old fashioned looking Octal based U24. Sound and frame output use a pair of excellent 6P25's, Mazda's version of the EL33. The CRT in original form is the infamous CRM121 but this receiver appears to have the later aluminised CRM123 fitted.
I was gagging to feed it some mains but made a few basic checks before 'just plugging it in' via one of my beloved 'Clix' plugs
The frame 6K25 was placed in the vacant line generator position and the continuity across the mains lead checked. It was O/C and it was necessary to clean the mains fuse clips and free off the mains switch. With this completed it was time to apply some juice, something that had not been done I guess for around 50 years, yes half a century!
With the valves glowing there was little if anything happening and after a few minutes of sniffing, observing that UU8 and listening for happenings, something happened!
There was a sloppy 'pop' followed by a bubbling and hiss. I switched off to discover that the .1uf wax cap decoupling the screen of the line output valve had protested violently at it's abrupt waking up after so many years.
This was soon replaced and the checks continued. A strained line whistle could be heard and it was soon discovered that the U24 EHT rectifier was glowing pale purple.
You know what comes next! The bakelite .001uf Visconol was almost S/C and was soon unhooked for test. This time, under very subdued lighting, a frame collapse could be observed on the face of the 121. It was a reassuring first light proving that the CRT has some life left in it.
It was time to raid the valve store and a NOS 6K25 was soon discovered. It seemed almost a shame to unpack it so I hunted around the loose valve boxes and fished out a very scruffy example that turned out to be 100%. [The new one was probably duff..] This produced a lot more frame scan than I had expected considering all the original wax caps were still fitted.The picture shows the result with a 6K25 fitted.
To be continued. Regards, John.

[HamishBoxer]

Yes John,you are right about the NOS valve being duff.Got a NOS PEN45DD here that lasted 2 minutes.

Thank You for mentioning your wood worm killer.

[Hunts smoothing bomb]

It's looking very promising John, I'm looking forward to the next installment.

Cheers

[Lloyd 1985]

Hi John,

Good to hear you got a copy of the manual That looks a good result so far! The CRT looks nice and bright.

Regards,
Lloyd.

[mark pirate]

Good progress John, the CRT looks nice and bright
A few new caps should get it sorted!

Mark

[Heatercathodeshort]

With a reasonably shaped raster on the screen it was now time to feed in some RF and see if the old girl could still sing. As expected it turned out to be more a Mrs Mills than a Deanna Durbin. [If you remember DD you're a lot older than it says on yer profile]
With my Advance B4 connected at full blast to the aerial socket, a weak modulation could be seen around 60mc/s proving it was in fact a Birmingham model. Murphy Radio were almost unique in providing two stages of RF amplification before the frequency changer. This was followed by another two stages of video IF amplification resulting in a very sensitive receiver. This configuration presented problems five years later when these receivers were converted to Band 3 with the excellent Brayhead or Cyldon universal tuners. Murphy provided a factory tuner with modification sheet to overcome the unusual front end arrangement.
The pins of all the valves were cleaned and the holders lubricated with RS electrical cleaner. This improved the gain a small amount but it was necessary to replace all the Hunts 'cockroaches' .001uf .01uf [The brown cases crunch when squeezed by the thin nosed pliers] and the few waxies that were leaking badly. This improved the gain considerably and it was necessary to reduce the sensitivity control to resolve those reassuring bars!
The Aurora covers all 13 channels but to be honest I did not wish to fiddle with the tiny and probably delicate selector switch. It's a miniature magic box and deserves the respect it gets. It was necessary to convert the front end to Channel 1 and being a superhet of course should not have proved too difficult. Consulting the Murphy manual provided details of how to reset the tuned circuits but this also involved replacing the aerial and both R.F. transformers with the correctly coded type..What a palava!
As my lady friend on the parts desk at Murphy Radio probably retired in the 1970's the only solution was to modify the existing circuit by the addition of a few 10pf capacitors, thus bringing the frequency down to 43mc/s. The pictures show the tiny caps across the primary and secondary of the RF transformers. A Philips beehive trimmer was connected across the oscillator tuning and powering up proved the modifications were a success. With the trimmer set about mid way the vision came through on channel 1 quite well. Rocking the generator to around 41mc/s provided a weak sound signal and it was only a matter of minutes to trim the R.F. transformers up to produce a good balanced response on both vision and sound as can be seen in one of the pictures.
It was time to connect the workshop RF system from the Aurora, Channel 1 45mc/s vision 41.5mc/s sound and see if my efforts have not given the old girl ideas above her station. Sutton Coldfield to Alexandra Palace. Quite a move up the ladder in society circles .
To be continued. Regards, John.

[Hunts smoothing bomb]

Excellent progress John, it looks like you have been lucky with the CRT, I look forward to seeing test card C on screen.
Cheers

[mark pirate]

Good work on the mods, although I have found the channel switch on the Aurora to be quite robust, I do have to change it for my Sutton Coldfield sets!

Mark

[FERNSEH]

I think that my V180 will be a "Birmingham" Ch4 set. If that's the case I'll leave as it is because I have a channel 4 modulator.
Murphy's approach to channel changing was complex as you'd expect, all sorts of component changes required. John's method was more engineer friendly.
Because the set has two RF amplifier stages before the frequency changer this introduced difficulties when it came to fitting a 13 channel tuner.
I believe Murphy supplied a conversion kit that came with an extra stage of IF amplification to compensate for the loss of the first two RF stages.
If a copy of an old Murphy News could be found there might be some information about fitting a tuner for the then new ITV broadcasts.

DFWB.

[Heatercathodeshort]

Well it was quite a shock when test card C popped up on the screen. It was a little out of shape, a bit pale and slightly low on width. It was time to replace the remaining waxies.
This later model uses the Mullard EL38 strangely mounted upside down and enclosed in a full metal jacket presumably to prevent 10kc/s line pulse from entering neighbouring radio receivers tuned to the Light Programme on 200kc/s long wave. Murphy must have been very aware of this and mounted the line output transformer under the chassis on a front rail thus surrounding itself with the natural screen of the heavy chassis. The cabinet is also lined with tin foil securely earthed to the receiver chassis.
I replaced the line coupling capacitor first. It had a 3m leak, enough to upset the operating conditions of the EL38. The width now filled the screen. The scan coupling 1uf was also replaced for good measure together with the sync coupling capacitor.Surprisingly the two .25 uf 350V oil insulated Hunts capacitors in the frame charging and coupling were tested 100% so were left in circuit. The test card now looking very acceptable but there was more work to do.
The sync separator is unusual employing a double diode 6D2 [EB91] The anodes are strapped receiving the video signal. One cathode feeds line sync pulses via a 50pf capacitor to the control grid of the line generator valve. The other cathode feeds a centre tapped choke with it's centre tap connected to a .001uf capacitor to earth. The inductor/filter knocks off all line pulses leaving a clean frame synchronization pulse to trigger the grid of the other thyratron 6K25. The .001uf capacitor was O/C causing poor interlace. Replacement resulted in perfect interlace.
The focus preset was one ended demanding investigation. This model uses a focus coil connected in series with the HT to the anode of the audio output valve 6P25. The cathode bias resistor is split, a 120 ohm in series with the 100 ohm focus control. Varying the bias, alters the current through the coil and thus the focus. The audio coupling capacitor was replaced together with the O/C cathode bias electrolytic, returning the focus control to dead centre. Over a period of about an hour the focus does drift slightly.
Replacing the 6P25 has helped slightly but the problem with electromagnetic focus has always been the fact that as the coils warm up their resistance increases causing the drift.
It may not be possible to resolve this slight problem and adjustment to the focus will be required a couple of times through an evenings viewing.
The front end and oscillator were trimmed on the test card for best definition consistent with good sound which is superb. Not a trace of mains hum or vision on sound, quite remarkable 'FM' quality.
Almost there! The pictures show the line output transformer, boost diode U281, the U24 EHT rectifier and the newly rebuilt 'Visconol' under the chassis. The test card in full workshop lighting as it appeared at first switch on after channel changing but still needing some work and the full metal jacket EL38.
Just one more episode showing final pictures and conclusion. John

[mark pirate]

Excellent progress, I love the odd mounting arrangement of the EL38, typical Murphy madness.
I am guessing the entire chassis has to be removed to access it?

Mark

[Heatercathodeshort]

It was time to clear up the loose ends and touch up the final alignment. With the sensitivity control set to a low level, just enough to lock the picture, the modified R.F. coils were finally tweaked resulting in an increase in picture definition and a slight rise to the already ample sound.
Picture centering is set by the usual three brass OBA nuts on the focus coil/magnet assembly. During manufacture, many examples of the Mazda CRM121 had guns mounted slightly off centre resulting in difficulty in setting the picture position, in bad cases causing corner cutting. With a circular tube it is often possible to rotate it slightly so the dodgy bit is hidden behind the mask but on this Murphy model, due to the cut out in the chassis for the tube EHT connection, this is not possible. As can be seen in the pictures, the raster is slightly to the left and I don't want to put any strain on the neck by tightening the adjusters to their limits.
As the chassis is such a feature of this receiver I decided to perform a more intense clean than I usually carry out with my vintage dabblings. It was generally grubby and slightly greasy and after a bit of thought I decided to try a popular kitchen cleaner. A small amount of 'Cillet Bang Grease and Sparkle' was applied to an old toothbrush and a small area of the power supply gently attacked. After a few moments a filthy soup of muck foamed up and with a wipe of a damp cloth the original aluminium finish was revealed. The procedure was continued over the entire chassis producing just the right result. I did not want a sparkling factory finish that would look quite out of place on a 64 year old receiver.
Rebuilding the Visconol brought the EHT up to it's correct 7.5kv and it stays constant over a long soak period. The line output transformer is a strange affair sealed in a light brown cardboard box as can be seen in the previous picture. The original CRM121 produced a good picture with only 5-6KV. The later aluminised CRM123 requires around 9KV to produce a very bright picture due to the barrier caused by the aluminising. In this chassis with the lower EHT it displays a good picture lacking slightly in 'punch' but still very acceptable.
Conclusion.
The Murphy V180C as already mentioned follows a line of construction dating back to the popular A56V of 1938. The 180 is the direct descendant of the post war V114 and is very similar in many ways. The main chassis framework is identical and at first sight appears to be a beast to work on. It turned out to be the complete opposite. Access is superb! Everything is accessible even the valves on the rear timebase chassis. The 6P28/EL38 is the only exception but releasing four bolts on the bottom of the chassis allows this to be pulled back for access, the remotely mounted control panel leads being long enough to allow this.
The sensitivity of the vision and sound amplifiers was very good requiring a signal input of only 85uv to give a 10V change at the cathode of the video amplifier. That was good enough to produce a picture of entertainment value in fringe areas up to around 60-70 miles from the transmitter and in the case of Sutton Coldfield with it's greatly increased power, probably more. In weak signal areas pre amplifiers were popular and with the use of low loss cable I guess some surprisingly long distances were achieved. Murphy News reported that a V114 was working well in a dealers showroom in Arlesford Hampshire with just a temporary dipole aerial and that was from Alexandra Palace in 1947!
The design of the V180C was not the end of the Murphy madness and anyone removing the back from the later V200 of 1951/2 would have had quite a shock with it's circular chassis resembling the famous RR Merlin aircraft engine. [ I have one on the shelf..] The madness finally died in 1962 with the end of Murphy design when they were taken over by Bush to form RBM, the company we all knew over the next three decades.
All these manufacturers different designs, circuits and ideas made radio and television servicing so interesting. All gone and never to return!
I will leave you with some off screen pictures to enjoy. My cabinet will be cleaned up in due course and can be seen on David's thread together with his heroic restoration of that very poor cabinet that has not stood the test of time so well as mine. The black printed design on the glass mask has broken down and will have to be repainted/reconstructed. Maybe I can use a piece of Nylon curtain material for a spray paint screen. I will have to think about that one..
This has been an interesting receiver to work on creating much pleasure for myself. Hope you enjoyed the saga as much as I did. Regards, John.

[Heatercathodeshort]

A few more off screen shots.