Murphy V310 1957.
 

Against all promises to myself not to purchase any more junk I purchased this Murphy V310 at the NVCF.

It is an early version with the self oscillating line output stage that was prone to frequency drift as the chassis warmed up. Later models were fitted with a separate line oscillator employing a 6/30L2 double triode in a conventional circuit.

The cabinet of this example is finished in a light oak colour, rather nice contrasting with the dark Bakelite surround. These were produced in small numbers as this light colour was considered rather 'racey' even in 1957.

A quick removal of the shell cabinet revealed a very clean chassis that appears to be totally original. The oil filled LOPT is completely devoid of leaking oil very unusual for any Murphy oil filled LOPTs and appears to be the original.

I snipped the mains filter and plugged it in. The valves lit and after a short warm up the line timebase whistle could be clearly heard. A spark test at the anode of the U26 EHT rectifier showed plenty of AC, A further test at the tube anode produced nice loud cracks so at least we had good EHT.

Turning the brightness up produced a blank screen and a quick check to pin 10 of the Mazda CRM172 read only 35V instead of around 350V! A circuit check showed the A1 supply was feed from the boost rail via a 1m resistor decoupled by a .5uf waxie. Snipping the cap produced a dim raster that was completely off centre with severe corner cutting. After removing the plastic focus dome the ion trap was found to be miles off. It was covered in dust so must have slipped during years of storage. A quick adjustment produced a very welcome raster that was soon centered by the joy stick adjuster. The 17" CRM172 is without doubt one of Mazda's better tubes.

Now to apply a signal. Was the four position Murphy tuner fitted with Ch 1 & 9 coils? Unbelievably it was and a flick of the channel selector produced a brilliant but overloaded test card. The V310 does not have AGC and is fitted with separate gain controls for BBC and ITA. Turning down the BBC gain produced a surprisingly acceptable picture, poor frame linearity, cogging and poor video amplifier response but considering how long this receiver had been sleeping I was surprised at the results.

A quick cap change of the usual culprits cleared up all the faults. Frame timebase linearity feedback, A1 decoupler, boost cap not forgetting the .002uf cathode decoupling capacitor to the video amplifier. It is hidden away and goes O/C producing smearing with slight vertical displacement.

In all around an hours work and I must say it produces one of the best V310 pictures I have seen for a long time. It has been running for around 2 hours and so far no LOPT saturation.

The above is the basics and of course it will require a bit of cleaning and tweaking to finish it off. This has been a very easy project and I am feeling guilty having had such an easy result.....:-)Regards, John.

Re: Murphy V310 1957.
 

Hi John,

That set was clearly destined to go home with you! Great results, do you find much drift in the line output stage in this one?

Cheers,
John Joe.

Re: Murphy V310 1957.
 

Hello John , that Murphy 310 looks really great , I remember some time ago you saying about the fact that they had no form of vision AGC and Murphy did not like AGC on sets intended for sets within the service area of the transmitters .
I think you did tell me why ,but I cant remember.
Perhaps you could refresh my failing memory.
Best regards
Alan.

Re: Murphy V310 1957.
 

Not so far John. It is fitted with special 30P4 line output valve [30P4MR] but none of the circuit mods have been carried out prior to the introduction of the separate line oscillator.

It must have been one of the few that performs as Murphy had originally intended.

Hello Alan. I think it was easier to retain the correct black level that simple mean level AGC destroys.
The fringe model had full [gated? service manual not to hand] vision AGC and flywheel sync but was of course more expensive.
John.

Re: Murphy V310 1957.
 

You didn't waste any time getting that one going John!
I was with you when you bought it at the NVCF.
I'm amazed it works that well after only an hour's work and what a good CRT.

Robin

Re: Murphy V310 1957.
 

Looks a goodun John, my own example is still awaiting restoration, like yours, it actually worked when powered up. My CRT is also nice & bright.

I had one in my bedroom back in the 70's, cracking set, but passed on when i got myself a GEC dual standard with BBC2!
:beer:
Mark

Re: Murphy V310 1957.
 

Correction. The AGC on the Murphy fringe model V310A is sync cancelled.

The thing that amazes me is that the Murphy V310 is now 52 years old and required very little to put it back into working order. It's my guess that the original owners of it probably purchased a colour receiver around 1972 resulting in the V310 being laid to rest when still very much alive 8-o. It would have been 15 years old, well within the life span of these well designed and constructed receivers.
Hats off to Welwyn Garden City and all the lovely ladies that knitted them together.
John.

Re: Murphy V310 1957.
 

That was a quickie John! It looks smashing too.

Re: Murphy V310 1957.
 

Actually it is 62 years not 52 so even better.

Re: Murphy V310 1957.
 

Indeed! Unfortunately I am still 70! J.

Re: Murphy V310 1957.
 

That's an excellent result there- how nice (if just a little dissatisfying!) to get that outcome with just a few "usual suspects" changed and a good tube makes for a double dose of luck.

I'm impressed by that chassis construction and layout- makes me wonder if Murphy had taken on some folk with aluminium/airframe/avionics type background,

Colin

Re: Murphy V310 1957.
 

I guess there were a lot of guys available that had been in that activity only 12 years after the end of WW2.
Many early post war receivers reflected this. John.

Re: Murphy V310 1957.
 

When I went to work for a R & TV dealer in the early 60’s we serviced many of these sets and all the rounded 405 line Murphy sets produced excellent pictures. Compared to the other sets sold or rented these sets flew out of the door in a ratio of about 10 to 1. A lorry load arrived about every 2 weeks and it was only a small shop.

Re: Murphy V310 1957.
 

Could that have been the shop in Rustington village? They were very early Murphy dealers. J.

Re: Murphy V310 1957.
 

Not Rustington but Bexleyheath Broadway.

Re: Murphy V310 1957.
 

Thanks! J.

Re: Murphy V310 1957.
 

Well done John, im pleased you had that set off me at the NVCF. Im also pleased it was in need of so little attention as it had been stored for many years. I got it from an elderly chap in Bournemouth who was a long retired TV engineer and this one and many other were stored around his house and garage. It does look nicer with the light wood case too.
Enjoy!
Dave

Re: Murphy V310 1957.
 

Thanks Dave and thanks for letting me have this superb example of a Murphy V310.

There is some cleaning to do. The screen has some dust trapped between the glass and the CRT faceplate and the rest is just a general tidy up.
Thanks again. John.
PS Odd thing is Dave it was on your stand for most of the day and nobody snapped it up!

Re: Murphy V310 1957.
 

Getting a picture was the easy bit. It was time to clean up the attractive cabinet and buff up the Bakelite.

Two blocks of wood that held the shell together had come adrift. The glue had literally dried out but a squirt of PVA glue and some cramps soon put that right.

The loudspeaker and lid assembly was removed for cleaning. Being positioned upright the speaker was full of dust balls and the small speaker cloth was clogged. This was soon cleared up with the vacuum cleaner and a little work with Brasso soon returned it to it's 1957 condition. The control knobs were soaked in hot water with a little Fairy Liquid and with the aid of a nailbrush were brought up nice and clean.

There was dust and a slight bloom between the implosion protection glass and the face of the CRM172 CRT. This involved removing the front Bakelite surround together with rubber mask and toughened glass. Just four screws plus a time consuming fiddle to get all the 'smuts' clear of the mask and glass...

Just a few caps to be replaced as a precaution against failure in the audio stages and all looks good.

There is incredible gain resulting in the BBC preset gain control being set only a third on and the contrast just a quarter. Advancing either turns the picture completely negative. This is a standard service area model and must have given a good account of itself in difficult areas. The full fringe model the V310A must have been a difficult act to follow when it comes to fringe reception.

The tuner has coils fitted for Channels 1, 4 and 8.
Picture 3 shows the result when you advance the contrast and gain controls 'over the top'.

When the wood glue has hardened I will post the final pictures.
Regards, John.

Re: Murphy V310 1957.
 

Well done John. I can't believe how much better your test card looks compared with what I ended up with on my V310 and you only spent an hour to achieve it!:angry::).


Regards
David