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Old 22nd Jun 2017, 9:22 pm   #1
MickMcmichael
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Default Murphy Acoustic Deluxe. RBM A640 Chassis.

Evenin' all.

It's been far too long since I last came on here and shared one of my old sets with you all so here's my latest adventure with a lovely iconic old trooper from the late 1960's.

This set came my way a little while ago. I paid far too much for it like we do but I'd always wanted an acoustic deluxe so the budget was jettisoned! Unfortunately I didn't take any pictures of it as it was when I got it so you'll have to take my word for it as to its condition at the time, which was not too good.

Bits of white veneer were missing here and there and the paint had cracked in vertical lines down each side of the cabinet. The original Murphy "Quite White" colour tone had faded to something more like a browny yellow - yuk in other words!

I tried the set as soon as I got it home. Slowly on the variac...don't be too hasty... ah goo on... a bit more ... give it some welly ... and a little bit more. Suddenly the sound stage fired up and then line whistle was heard, which by the tone was obviously 405. Then a raster of sorts appeared. Tube looked good ...briefly.

As I reached for the co-ax from my Domino converter, the pitch overwind decided to give up big time. Smoke shot out from a small hole which was burning on the side of the overwind and that was that. Barb and hooked!

I had another LOPT of dubious condition stashed away amongst a pile of junk in the corner of the workshop. I tried that and the set worked on both standards. After ten minutes the width started to pull in a bit and the picture looked a bit murky. More overwind problems!

The next day I decided to put the lopt through a drying out exercise. I cobbled together a very unregulated set up with a bridge rectifier and 470uf smoother and set the output to 30v by judicial setting of the variac. One connection to the overwind input and one connection to the top cap of the DY802. The overwind warmed up and after 30 minutes I upped the voltage to 50v and left it for about three hours. It bubbled away like a witches cauldron for a while until I switched the power supply off. I was able to keep smoothing the pitch over the overwind with a knife so as I didn't lose any. I let it cool down overnight and refitted the lopt the next day with little hope of a cure.

Oh he of little faith ... perfect results on both standards until smoke puthered from the line board and left a very bright frame collapse across the screen. The PCB was badly burnt around the PCL805 and was arcing badly and whatever I did I couldn't stop it. The PCB had charred over time and become conductive between the pins.

My mate Rich found me another line board which just about worked. Sync was a bit iffy, line was a bit cramped and the frame made everyone look like long headed boffins. All simple rudimentary stuff. A few capacitors and a couple of resistors and the line board worked like a dream. Replaced the 8uf on the signal IF board and a couple of resistors and I was amazed at how well this old codger performed. The tuner needed some mechanical lubrication to ease things up a bit and then that too worked really smoothly once a new set of knobs had been fitted (old stock leftovers).

The cabinet wasn't so easy. The vertical cracks in the paint went right down into the wood of the cabinet. After completely stripping the set out I had to sand the paint right off and fill the vertical hairline separations in the wood several times before it was smooth enough to re paint. I used a grey primer first overall and then three careful coats of "Hycote" white spray. It looked good but I now had to put it all back together without damaging the newly painted cabinet.

It took three times longer to reassemble it than it took to strip it down but the results are there to see. It may not be completely original and I had a very strong urge to repaint it in either red or orange, but that wouldn't be right. It was originally white so that's how it has stayed. Lovely old set.

All the best.

Mick.
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Old 22nd Jun 2017, 9:30 pm   #2
Nuvistor
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

Great restoration, I remember these sets well, good performers but they had some reliability problems. One major problem was not electrical, but sets that were in rooms with coal fires, desperately trying to keep my grubby hands off the white paintwork.

Happy memories.
Frank
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Old 22nd Jun 2017, 11:37 pm   #3
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

Thanks for bringing an A640 back to life, it was my teen-years favourite.
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Old 23rd Jun 2017, 7:16 am   #4
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

What a great job! It looks like an early version with the 19" tube. I have a spare mains dropper if you need it. Was the original 'white' finish gloss or matt? Regards, John.
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Old 23rd Jun 2017, 8:15 am   #5
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

These are scans from the August 1968 Murphy brochure.

The 640 did have a design problem. There were FAR too many customer adjustable presets on the back! Contrast 405, contrast 625, brightness, frame hold, height, line hold 405 and line hold 625.

These tended to get twiddled mainly due to the black level clamp. It took me a lot of explaining that the screen should go 'blank' if there was nothing to see!

Once correctly set up I would mark the presets with a line of Tipex. Once they were all to the top there was a good chance I would not receive a service call.

The original early tar overwind transformer were manufactured by RBM themselves and was prone to failure. Later plastic transformers were supplied by Plessey and were even more liable to failure. Aftermarket transformers such as those manufactured by Papworth Transformers were excellent and outlived the receiver.

The other weak point was the mains dropper but this was cheap and easily replaced. Added on 'bits' were a sign of scruffy servicing unless of course an emergency measure that would be completed as soon as stocks were available. [And they were]

The heavy swivel stand had to be assembled with a large vehicle type spanner or it worked loose resulting in the ADL looking like the leaning tower of Pisa. Regards, John.
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Old 23rd Jun 2017, 9:17 am   #6
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

I saw the set when it first arrived at Mick's workshop. The transformation is remarkable!
Well done mate!
I too am a fan of the A640 I had loads back in the mid 70's. They weren't quite 10 a penny. 25p each ISR...
I have a few in my collection but only one good LOPT between them!

Rich
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Old 23rd Jun 2017, 1:17 pm   #7
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

Hi
Looks great! I have the Acoustic 24" white version with a cabinet that sounds a bit better than yours was, but not much! Mine has unstable frame which I think is due to the PCB carbonising. The LOPT works for now, but I don't expect that'll be the case for long.
I bought and sold quite a few A640s from a rental shop in the late 70s while at school. They were usually condemned because the tube was flat. I found in most cases the tube would be miraculously brought to life by replacing the BC108 in the video circuit.
Glyn
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Old 23rd Jun 2017, 3:17 pm   #8
MickMcmichael
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

Quote:
Originally Posted by Heatercathodeshort View Post
What a great job! It looks like an early version with the 19" tube. I have a spare mains dropper if you need it. Was the original 'white' finish gloss or matt? Regards, John.
Hello John.

It was difficult to tell whether it was originally gloss due to the severe fading but my guess was that it had originally been a glossy finish. The Hycote which I used is gloss and the cabinet was gently rubbed down between each coat with 1000 grade Abranet paper which helped to keep it smooth.

Thanks for the offer of a dropper. I'll keep it in mind. I do have another chassis which is from a multi standard version of a similar set which I think has a good dropper. It was used on board ships tooing and frowing from the UK to various parts of Europe.

Regards,

Mick.
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Old 23rd Jun 2017, 6:34 pm   #9
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

What a great result
Never seen a monochrome one before
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Old 23rd Jun 2017, 7:41 pm   #10
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

Hi Mick,
An interesting looking set! It's great to see it in context in the pictures in John's brochures. Quite funky in all the different colours The '60's and '70's really were fantastic times for TV development.
I have been trying to get a feel for the amount of temperature you need to dry out an overwind and have yet to do some experiments. But if you got yours to a bubbling stage and it survived I guess that was pretty hot!! I hope it will last for a long time now.
Great to see more '70's sets being brought back to life
All the best
Nick
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Old 23rd Jun 2017, 7:54 pm   #11
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

Quote:
Originally Posted by Heatercathodeshort View Post
The 640 did have a design problem. There were FAR too many customer adjustable presets on the back! Contrast 405, contrast 625, brightness, frame hold, height, line hold 405 and line hold 625.

These tended to get twiddled mainly due to the black level clamp. It took me a lot of explaining that the screen should go 'blank' if there was nothing to see!
Never had that problem once the local/distant control was set corectly, never needed to touch a contrast control again.

Quote:
Originally Posted by Heatercathodeshort View Post
Was the original 'white' finish gloss or matt?
Thought they were all eggshell myself but will happily be corrected.
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Old 23rd Jun 2017, 7:59 pm   #12
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

Quote:
Originally Posted by Heatercathodeshort View Post
Was the original 'white' finish gloss or matt?
"Thought they were all eggshell myself but will happily be corrected." [/QUOTE]

I'm pretty sure the finish was eggshell. Between 1971 and 1973, I worked for a Murphy dealer and he had some small plastic pots of touch up paint, supplied by RBM.

I also have a colours chart for the original painted cabinet Murphy mono dual standard sets and that looks eggshell finish.
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Old 23rd Jun 2017, 8:36 pm   #13
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

Quote:
I'm pretty sure the finish was eggshell
I had the later Acoustic deluxe colour set in 'Outrageous orange', it was indeed an eggshell/satin finish.

Mark
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Old 23rd Jun 2017, 8:46 pm   #14
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

The control twiddling by the customer was nothing to do with the setting of the local distant control. It was simply a matter that if you give customers knobs to twiddle, they will twiddle them.
They would turn the contrast control full on, then the brightness down, then turn to the hold controls ending in a hopeless mess.
I agree that once the two contrast controls were correctly set and this could take a few minutes with differing programme content, it did not require any further attention until one or other of them was incorrectly twiddled.
It really was a problem that RBM were aware of. The later and nasty A774 had only three external rear mounted presets but I would rate the A640 as one of the best dual standard receivers of all time. The integrated tuner was first class. Reset, gain and sensitivity on all bands was quite amazing. I never had a problem, one being fitted in the Murphy CTV2210D colour receiver I was using at home all those years ago..Where did they go? I'm certain the very early versions of the 'coloured' Murphy's were gloss. John.
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Old 23rd Jun 2017, 8:56 pm   #15
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

I don't remember problems with customers twiddling those knobs but we all saw different problems. The sets did perform extremely well.
Frank
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Old 23rd Jun 2017, 9:04 pm   #16
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

The later mono 23" and 24" and all the ctv acoustic deluxe models were satin finish but some of the 19" model cabinets had a high gloss lacquered finish. Not sure about white but black versions, a colour only used on the 19" sets were definitely high gloss and looked stunning.

John.
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Old 24th Jun 2017, 11:58 pm   #17
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

That's a lovely picture you have there Mick . and i've got a teak version of the acoustic that I cant remember if it works or not. and I've also recently acquired a white CV2212 that is in need of some work on the cabinet .

Cheers
Neil.
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Old 25th Jun 2017, 11:34 am   #18
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

Hi
I see that yours has no component references on the IF panel. Either it's an early version or an Irish made TV.
Must get my 24" sorted out now! I have a NOS LOPT which is the replacement with an EHT stick so I'm OK should the worst happen - or is that when?
Despite the invasion of the knob twiddlers (we had them too), being able to adjust the picture while looking at the screen with little danger of a shock while the back was off was very much appreciated.
I agree about the 640 - they looked good (or quirky in the Acoustic guise!) and were excellent performers. The tuners were a bit clonky but reset every time and were easily converted with those keyplates - you always had a few UHF/625 ones in your toolbox.
Glyn
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Old 25th Jun 2017, 8:40 pm   #19
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

Well, being bouyed and confident after doing this white one, my next project can be seen in the pictures below.

Rich brought this round to me thinking it might be useful for spares. He'd apparently thrown a junk grenade onto his junk pile in his junk room (a formidable collection of all things old, dusty, sometimes wormed but always useful) and pulled the pin! Thanks Rich!

I've decided to give it a go but, a warning to the purists amongst you, it probably won't stay teak unless I cover it in fablon!

We'll see. I may have bitten off more than I can chew!

Will write it up if I have any success. Good luck with the 24" Glyn.

All the best,

Mick.
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Old 25th Jun 2017, 8:48 pm   #20
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Default Re: Murphy Acoustic Deluxe. RBM A640 Chassis.

Do I predict a change to Outrageous Orange?
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