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Old 8th Dec 2018, 5:07 am   #1
Catkins
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Default 1938 Murphy A56V television restoration

Hi everyone,

Back in 2014, Steve Harris advertised a pre-war 1938 Murphy A56V television for sale, for the low price of 2950 (as pre-war televisions go). There was of course a reason for the low price, the A56V didn't have a working CRT, and it was a bit of a wreck. In "Airwaves" of Apr/Jun 2014, Steve described it thus "It is far from pristine condition ... If this was a Murphy radio of the same year, in this condition, it would struggle to make it to the bargain basement page, more likely it would be dumped in the store to be raided for any useful parts".

Being rather deterred by that description, and the associated photographs I did nothing, even though I was tempted by the fact it was a pre-war Murphy television and the only one I'd ever seen come up for sale. To my surprise it appeared in the next Airwaves (perhaps everyone else too was deterred by its state). I rang Steve Harris up, booked an appointment to view it, and having taken pity on its state (it really was almost a lost cause), decided it needed it needed to go to a good home, and took it home with me. I was undoubtedly biased by the fact Murphy is my favourite 1930s manufacturer, and it was probably the only chance of getting a pre-war Murphy television, but it was still a wreck.

When I got the set home, I stripped out all the electronics to enable the cabinet to be woodworm treated, the woodworm in the cabinet looked mostly historic but I was not 100% sure, and it is always better to veer on the safe side (the cabinet of the previously restored HMV 904 again looked to have historical woodworm, but, it proved to be still active). This allowed me to have a good inspection of the condition of the electronics. In fact I had already had one surprise when removing the electronics, as I found a detached mica-capacitor in the bottom of the case, which I was quite sure hadn't been there before the journey home, which didn't bode well for the level of corrosion. The first thing, perhaps obviously, was to discover where the mica-capacitor had come from. I found the possible place, but, in fact found 3 places where the mica-capacitors were missing, simply leaving two corroded "legs".

The inspection showed many of the capacitors/resistors were showing corrosion, with a couple attached by one leg only. Some of these, if still in spec, could be carefully repaired. All of the wiring was completely rotten, and would all need to be completely replaced. The wirewound trimmer pots in the chassis were corroded and open-circuit. The pots mounted on the cabinet were very rusty and stiff, but might be repairable if stripped down. The transformers on the power supply unit (Mains and EHT) and on the main chassis (frame and audio output), were completely rusted and probably needed rewinding. The deflection coils were in a similar state. The CRT is mounted and clamped, and the focus and deflection coils adjusted, via some fairly elaborate mechanism, and all of that mechanism was rusted solid and would not move. The tuning control (one of the occasional controls) which physically trims the local oscillator inductance by moving a brass rod was also rusted solid and would not move. The inductances/air-coils within the chassis showed some signs of corrosion, but I could not inspect the coils within the air-cans, without removing the air-cans which was beyond this relatively quick inspection.

Beyond that, all metalwork was completely rusted to a high degree, without any plating remaining. The power-supply chassis and the main chassis are painted, rather than plated. I initially hoped this paintwork could be saved, but examining the paintwork under a strong light showed the chassis to be heavily pock-marked with extensive rust underneath the paintwork. An experiment with a blunt screw-driver showed the paintwork easily came off revealing a layer of rust underneath (in a hidden part of the paintwork which was in a better condition than elsewhere because it had been relatively protected).

The set on this inspection thus turned out to be in a bit worse condition than even I expected, but, I already knew it was in a bad state, and so it didn't really change anything. If I was going to restore the set, it would be a massive undertaking, requiring a complete strip down of the set, and of the individual components themselves and complete rebuilding, before it would ever work again. It really was only on the edge of restorability and maybe a little bit beyond. If I thought the restoration mght fail, it in fact might be better to leave it as an unrestorable but untouched display item only.

At that time in October 2014, I was in the middle of restoring a 1938 HMV 904 television. This television too had numerous problems due to rust and corrosion (although not as bad), and I had got disheartened. I had spent over 30 years restoring 1920-1940s radios, but this HMV 904 was my first foray into television restoration, and I wondered if I should have attempted something easier for my first television restoration. So I started to look for another pre-war television to work on, and then found the Murphy A56V which was obviously much much worse. Paradoxically this did the trick, in respect to the fact I discovered I could be in a far worse position, and so persevered with the HMV 904 restoration with renewed enthusiasm, and succeeded with the restoration after about another year of work. My experience with that restoration is written up elsewhere on this site (https://www.vintage-radio.net/forum/...d.php?t=115533).

So at this point in October 2014 I simply put the Murphy A56V back together after woodworming, to wait and see how I faired with the HMV 904 restoration.

In November 2015, after the successful restoration of the HMV 904, I had to decide whether to attempt a restoration of the Murphy A56V, knowing it would be an even more difficult task. Flushed with the success of the HMV 904 restoration, I decided I could do it, and in fact as it was going to be a rebuild anyway, it would be a good opportunity to restore it to pristine condition. This was one set where a minimal restoration preserving patina simply wasn't possible, as no patina existed having disappeared under thick layers of rust years ago (preserving patina is one thing, "preserving" rust is another, I believe rust should always be treated/removed and the resultant metal treated to protect it against further rust, and if you do that, you may as well refinish it to the original condition).

I started the restoration in November 2015, and I finished it in November 2018, which makes just over 3 years from start to finish, which I think in anyone's book is a long time.

But I think the attached photographs show it was worth it. As I'm limited to 5 photos per post, I have attached 2 photos showing the original state, 2 showing the current state, and a photo showing the restored television displaying the test card. The CRT is a replacement CRM92, rather than the original CRM91 which was broken, and the CRT mounting has had to be adapted to accommodate the different CRT dimensions.

This is a video of the television on You-Tube https://youtu.be/8XaaeC7idIQ.

Further posts if anyone is interested, will show more photos of the restored television, and a description of the work undertaken.
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Old 8th Dec 2018, 8:22 am   #2
Jac
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Default Re: 1938 Murphy A56V television restoration

Hi Catkins,

A tremendous undertaking with a sublime result!
Thank you for posting it.
Please do post a bit more info and photos of the restoration of this very rare set.

Jac
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Old 8th Dec 2018, 9:39 am   #3
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Default Re: 1938 Murphy A56V television restoration

Quote:
Originally Posted by Catkins View Post
I believe rust should always be treated/removed and the resultant metal treated to protect it against further rust, and if you do that, you may as well refinish it to the original condition).
Bravo. I really like what you did with this, great job.

I once restored a very rusty 1948 Admiral set and went for a similar color blue, perhaps a shade darker (see attached pic).

We must be kindred spirits. I have also restored a 904, the article is here

http://worldphaco.com/uploads/HMV__904_ARTICLE.pdf
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Old 8th Dec 2018, 9:42 am   #4
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Default Re: 1938 Murphy A56V television restoration

Great write-up. Thanks for posting.

Peter
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Old 8th Dec 2018, 11:08 am   #5
mark pirate
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Default Re: 1938 Murphy A56V television restoration

Excellent restoration, having had to fully rewire my Murphy V136C certainly reminds me what you must have gone through!

Please most more photos of the restoration, it may rekindle my desire to get back to my set, (I put it on hold after suffering from frame collapse).

Mark
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Old 8th Dec 2018, 11:20 am   #6
Peter.N.
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Default Re: 1938 Murphy A56V television restoration

I've never seen one of those, in fact I didn't know Murphy made TV's before the war. You have certainly done a brilliant job on it.

The CRM91 seems quite a modern tube for a pre war set, they were still using them in the '50's and they weren't a lot of good then, at least the 12" one wasn't, we had many fail under guarantee, but yours looks fine.

We scrapped a number of pre war TV's in the '50s - I wish I had them now!

Peter
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Old 8th Dec 2018, 12:24 pm   #7
chriswood1900
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Default Re: 1938 Murphy A56V television restoration

Great restore and write up, please post some more info and pictures on the stages you went through if you have them.
Chris
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Old 8th Dec 2018, 12:25 pm   #8
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Default Re: 1938 Murphy A56V television restoration

Great write up and what an epic journey!
The CRM91 pre war tube is an odd one and was certainly 'wide angle' at 64 degrees, compared with it's post war replacement the CRM92 57 degrees listed as a replacement for the CRM91.

It is a short stubby tube and considerable difficulties could be experienced attempting to squeeze the 92 into a 91 chassis. Mazda gave very little information stating only that the bulbs physical dimensions differed from the original..

As far as I know it was not used post war. The 1947 Ekco TSC30 employed the 92 tube.

Peter mentions the appallingly short life of Mazda tubes at that time. There were numerous complaints from Murphy dealers writing in the Murphy Service News. Apparently Ediswan knew there was a serious problem but just stated that 'the situation should get better in the future'.

Murphy Radio were one of the first companies to supply a 2v CRT isolation transformer for the Mazda triode tubes used extensively in their receivers at 15/- [75p]. [1952] They were sold out within hours and a new batch had to be produced.
Regards, John.
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Old 8th Dec 2018, 1:11 pm   #9
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Default Re: 1938 Murphy A56V television restoration

Quote:
Peter mentions the appallingly short life of Mazda tubes at that time. There were numerous complaints from Murphy dealers writing in the Murphy Service News. Apparently Ediswan knew there was a serious problem but just stated that 'the situation should get better in the future'.
I recently watched a fascinating film (Made for life on the BVWS 2006 DVD) about Mullard CRT production. The amount of different processes involved and the complexity of the machinery used was amazing. It really did look like they took as much care as they could to ensure a quality end product. After all that effort to end up with thousands of prematurely failing tubes was a real shame. I assume Mazda production used much the same processes but suffered different failure modes.
Unfortunately, 'the situation should get better in the future', sums up the attitude of much of British manufacturing at the time- the BMC was much the same! The Japanese would have been horrified at the idea of continuing to supply products with such a high failure rate, often for years!

Great write up and restoration of a real basket case set. Well done!

All the best
Nick
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Old 8th Dec 2018, 1:25 pm   #10
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Default Re: 1938 Murphy A56V television restoration

Amazing work - well done, thanks for posting. More info and pictures please.
Mike
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Old 8th Dec 2018, 3:55 pm   #11
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Default Re: 1938 Murphy A56V television restoration

Congratulations on a really great job.
Did you have the chassis shot blasted to get rid of the rust ?
I think you were a brave man to take on that but it just goes to show what can be done if your determined.
I`d like to see more as well.

Robin
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Old 8th Dec 2018, 4:54 pm   #12
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Default Re: 1938 Murphy A56V television restoration

Looks lovely inside and out, the youtube video is nice too!
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Old 8th Dec 2018, 4:55 pm   #13
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Default Re: 1938 Murphy A56V television restoration

Superb restoration. These are excellent TV receivers, there are some elements in the circuit design carried forward from the magnificent A42V, Murphy Radio's first TV receiver. I was lucky with my Murphy A58V as the set was in generally good condition. The A58V is the version of the A56V which has the addition of a modified A46 radio receiver.
A CRM92 was used for a time to replace the original CRM91 which had an OC heater. Spacers and special adaptor plates were made to accommodate the slightly longer replacement tube. Later on thanks to HKS John a good CRM91 was found and duly fitted after the adaptor plates were removed. I still have those parts somewhere.
Actually, I think the compact A56V is a much nicer looking set than the A58V.

DFWB.
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Old 8th Dec 2018, 7:12 pm   #14
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Default Re: 1938 Murphy A56V television restoration

Very impressive Catkins. I didn't know that Murphy produced a Pre-War TV either Apart from anything else, you've obviously saved a very rare item. More info/photos would be very welcome. As for the striking blue colour, I think I might be right in saying that some Murphy radio sets have a blue chassis but perhaps a slightly lighter shade It looks great anyway!

I often print off before and after photos just like these to show [particularly] non-tech friends just what can be achieved by dedicated enthusiasts, in a throw-away world.

Dave W

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Old 8th Dec 2018, 9:23 pm   #15
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Default Re: 1938 Murphy A56V television restoration

Fantastic job, thanks!!
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Old 10th Dec 2018, 1:41 am   #16
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Default Re: 1938 Murphy A56V television restoration

Hi Catkins,
Thanks for the write up.
I remember seeing this actual set before I think. It did look a mess.
Great job and nice to see a set on my wish list saved. The A56V just performs really well for a pre-war set and it looks quite futuristic for its day.
Cheers
Andy

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Old 10th Dec 2018, 5:47 am   #17
Catkins
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Default Re: 1938 Murphy A56V television restoration

Quote:
Originally Posted by beery View Post
Thanks for the write up.
I remember seeing this actual set before I think. It did look a mess.
You may well have done. I'm reliably informed it was at NVCF in 2014.

Quote:
Great job and nice to see a set on my wish list saved. The A56V just performs really well for a pre-war set and it looks quite futuristic for its day.
Thanks for the nice comments, from someone who has done such wonderful results, it is really appreciated.

I must admit I really like the look of the A56V, fantastic styling from Murphy as always, even though they were constrained to get it into the 30 "budget" pricing (as we'd called it today, 30 for an attractive telly with a 9" tube, when the competition could only manage 5", which having restored such a 5" HMV 904 I know how underwhelming it actually is, its like watching a postage stamp. I know what I'd have bought for my 30).

As far as performance goes, it's really very good, lots of gain, so much so it is easy to overload the stages with the Aurora box. They only used one valve (double diode with separate cathode) for sync separation, but the sync is snap-on, with very good lock. Though of course with a directly connected Aurora box, it has ideal input, with no signal fading.

I had very little problems getting it up and running after putting it all back together, no fiddly nasty problems to diagnose at all.

I don't want to sound bombastic or overly pleased with myself (please tell me if I ever do, because it's a mistake), but I am glad I gave it a chance, it's definitely become my favourite pre-war television.
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Old 10th Dec 2018, 7:15 am   #18
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Default Re: 1938 Murphy A56V television restoration

Quote:
Originally Posted by FERNSEH View Post
Superb restoration. These are excellent TV receivers, there are some elements in the circuit design carried forward from the magnificent A42V, Murphy Radio's first TV receiver.
By all accounts the A42V was a technical marvel, no expensive spared.

I don't have any technical information on the A42V, beyond a couple of references made in the A56V service documentation. Regarding V7 (the vision amplifier), the documentation states "This circuit will be found to be very similar to that employed in the A42V except that the latter employed a push-pull rectifier in order to double the frequency of the IF that appears across the diode load", which implies the A42V had very high vision bandwidth.

The A56V has trimmers which affect the thyratron bias, but also has line/frame hold and height/width controls. It is mentioned in passing "Those who are conversant with the A42V will remember the amplitude control in this set controlled the bias on the thyratron valve. It therefore affected frequency as well as amplitude, a similar control is provided in the A56V, but is mainly used to take up tolerances in the circuit".

This does lead to the slightly weird case where you can control both hold and amplitude by use of the trimmers in conjunction with the normal line/frame hold and height/width controls. In practice I set the trimmers which gave me a good range of line/frame hold and height/width on those controls.

Quote:
I was lucky with my Murphy A58V as the set was in generally good condition. The A58V is the version of the A56V which has the addition of a modified A46 radio receiver.
A CRM92 was used for a time to replace the original CRM91 which had an OC heater. Spacers and special adaptor plates were made to accommodate the slightly longer replacement tube. Later on thanks to HKS John a good CRM91 was found and duly fitted after the adaptor plates were removed. I still have those parts somewhere.
Yes, I had to fabricate new parts to accommodate the CRM92. I'll mention what I did later in the write-up. I'm going to try and write it up in chronological order as that makes most sense, and that's towards the end of the restoration.

Quote:
Actually, I think the compact A56V is a much nicer looking set than the A58V.
DFWB.
The A58V does have some highly innovative "skids" which I've never seen elsewhere! In contrast the A56V doesn't have casters or any other means of easily moving it around. Which does get to be a pain. I have my A56V sitting on a trolley dolly so it is easy to move it around.
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Old 10th Dec 2018, 8:32 am   #19
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Default Re: 1938 Murphy A56V television restoration

Quote:
Originally Posted by mark pirate View Post
Excellent restoration, having had to fully rewire my Murphy V136C certainly reminds me what you must have gone through!
A really nice looking set. Immediately post-war Murphys seem to be almost as rare as pre-war televisions. I've only seen one come up for sale which is the V114 my brother (Draenog on the forum) bought a couple of years ago. I would dearly like a immediately post-war Murphy television.

Does the V136C have the swing down RF chassis like the V114? My brother had great fun with the disintegrating rubber wiring loom connecting that chassis to everything else.

Oddly the A56V didn't have much evidence of wiring looms (that is wiring cut to length and fashioned into bundles with ties). They were used to connect the controls with the chassis, but internally in the chassis it was all point-to-point wiring, one wire at a time. They were routed within the chassis in perhaps specific ways. Knowing that deviating from wire length and routing might cause problems in pre-war sets (its always best to be cautious here, as you don't want to introduce circuit instability or worse), I replaced one wire at a time, keeping everything exactly the same. Which was very time consuming, I redid the wiring looms to the controls in one go, which was a lot easier.

Quote:
Please most more photos of the restoration, it may rekindle my desire to get back to my set, (I put it on hold after suffering from frame collapse).
Mark
I do hope it kindles your desire, if we can encourage each other then hopefully it is for the better. I certainly have gained and got a boost from the efforts of others on the forum.

Sod's law means I got the television working perfectly for hours ... the moment I pointed a camera at it to take a video, it suffered a line collapse within 10 minutes. Lovely.
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Old 10th Dec 2018, 8:36 am   #20
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Default Re: 1938 Murphy A56V television restoration

Thanks for all the great comments. I'll try and find time to respond to comments during the week, but I'm out of time as goes the weekend (and I would be already if it wasn't for the fact I work US time).
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