Murphy 310A

[BGmidsUK]

MURPHY 310A - Start of restoration

I acquired this set a few days ago and decided to open it up last night to see what I've let myself in for! It's been stored in damp conditions and there is quite a bit of white mould on the inside of the case, mostly on one side, and on the speaker/control grille. The glue has also given way on part of the back cover and the tube protector has broken loose but these should be fairly straightforward to take care of. I won't try to guess what the very sticky coating on the outside of the case is!

This has now been taken to bits and the case sprayed with soda solution (I hope this doesn't do it any more harm than the storage conditions!) - I haven't actually tested the speaker but it does look in good condition now I've cleaned the muck off the cloth and removed the spider remnants from around the cone.

I'm hoping the transformers are OK as they seem to have escaped the worst of the damp, this being mostly around the bottom right of the set. The cover is also missing from the timebase section. I'm also keeping my fingers crossed that the scan coils will be OK. Luckily the RF section is clear of any obvious exposure to damp. There is no apparent evidence of any previous repairs.

I gave the chassis a bit of a clean up, it's not in bad condition but there is some minor corrosion in places. The top two valves and holders on the frame stage are a bit delapidated - green valve pins! These have been cleaned up a bit. Then a quick lash-up with a lampholder and some leads (I'm doing this in the kitchen as it's freezing in the loft, not had the heating on up there for a few days!) I also bought a few 150W and 200W (!!) bulbs from a local hardware shop.

The mains switch is O/C on both terminals so I just linked it out as a temporary measure. It took me a while to work out what the black plastic tube and metal clip beside the channel knob is for - there should, it seems, be a long tube between this and the tuner to allow a twiddling tool to be inserted.

The voltage selector was also O/C due to oxide on the contacts, this has been cleaned up and is now working as intended. The droppers measured OK.

I've attached the speaker via some leads to the audio transformer.

There was no continuity on the valve heaters, due to 2 duff valves (gone to air), Mazda 30F5 and 6D2. I found a 6D2 in my valve box but I don't have a 30F5. Would a Mullard EF80 (or EF85) be a close enough match at least as a temporay measure?

I've been gradually running the set up with the lamp limiter in the hope that the electrolytics will reform. The TCC waxie next to the LOPT started spluttering so I have clipped the lead as a temporary measure. Is this likely to do any harm since I'm not running the set on full mains yet ... or would I be better replacing this before applying more power?

The mains filter cap also decided to dispense with its contents. The spitting and fizzing revealed where the clever so-and-sos had concealed this (it can't be seen without tipping the set over, something I was wary of doing as I've heard the oil can leak out of the LOPT can). I did warn the friend who was eagerly looking into the set that there would probably be a loud bang and some smoke but this event was spared.

The set will need a full re-cap of course but thankfully there appears to be no more than a couple of dozen. I'm on the lookout for service data so I'll post in the appropriate section.

I'll also need a power connector but this shouldn't be too hard to make if necessary.


This is the first time I've attempted a hand-wired chassis and to be honest I'm surprised at the ease of access. Tracing the circuit will take a bit of getting used to but it's all a learning curve.


More later


Brian

[oldticktock]

Brian,

Think this might be of use, I can scan R&TS pages for you too if you would prefer theirs as all component values are on the schematic, unlike the trader which you have to keep looking up.

All the best
Chris

p.s.

I have used EF80 as a temp measure for 30F5 and they suffice.

p.p.s.

Z329 is GEC equiv of 30F5 if you ave one of those knocking about.

Edit:
Removed the PDF as pointed out by Trevor it was the wrong version, sorry about that, I did wonder but I could not find anything with A. Just checked R&TS also no mention of the "A" double sorry, I would delete the post but it would spoil your thread contnuity

[murphyv310]

Hi Brian.
A nice set to restore, two things though the diagram OTT has posted is the wrong one your set is the "A" version is the fringe model Chris has posted the basic version without flywheel sync AGC etc.
Secondly EF80's will do in the meantime and if you need some once you get the set running let me know.
The tuner biscuits are hard to find but hopefully you will have the correct ones.
The plastic tube as you say is a guide for the long thin knitting needle you will need to adjust the oscillator in each biscuit, a new guide tube is easy to make from a bit of plastic tube.
Good luck

[ppppenguin]

Originally Posted by BGmidsUK

There was no continuity on the valve heaters, due to 2 duff valves (gone to air), Mazda 30F5 and 6D2. I found a 6D2 in my valve box but I don't have a 30F5.

The 6D2 is the same as the common EB91. I think I have several boxed NOS 30F5/PF818. PM me if you're interested. but as Trevor said, an EF80 will work for now.

As for the waxies they are clearly in a very bad way. Not knowing what the spluttering one by the LOPT does I would be inclined to replace it now. I don't have the circuit to hand either but other waxies to replace sooner rather than later are the coupling caps to the audio and field output stages. Looking at the V310 circuit there may well not be a coupling cap in the field output.

If the set has been damp I would strongly recommend leaving it (or at least the chassis) in a nice warm place like an airing cupboard for a week before doing anything else. I know this needs patience but it could save a transformer from destruction.

[murphyv310]

Hi.
The Diagram is in the Newnes books, I will try and scan it but it doesn't always work!

[neil29]

Hi Brian. i had one of these sets, never had it going though. Trevor (above) has it now. so ill be interested to see how good the picture will be once its working. cheers neil.

[BGmidsUK]

Thanks for the offers and advice!

I'll leave the set downstairs in the warm whilst I await arrival of some caps. Is there a component list in the Newnes books? This would be most useful as I'm bound to miss a hidden cap when compiling the order (wouldn't be the first time!)

There is some life in the audio stage, crackling when the channel selector is turned and even a bit of noise on one of the channel positions, though I couldn't make out an actual signal. No apparent illumination of the EHT rectifier and I couldn't hear the timebases but I've not had the set on more than about 180v - 2x200W bulbs in parallel. I won't apply any more power until the Hunts and TCCs have been sorted out as they do look rather the worse for wear.

Seeing the tube heater lit proves the CRT has survived whatever broke the rear cover, that was the biggest concern especially as there's a mark in the middle of the screen which looked like damaged phosphor. In fact it's muck on the glass creating a shadow behind it. Just hope there is some emission as it's the original by the looks of it ...

What I will do next is remove the front and give the screen and glass plate a good clean.


Cheers,

Brian

[ppppenguin]

Chilli and hot sauce are excellent for making a set go with a bang

I also like the novel use of a Schuko distribution block. With that and the ES bulbs anyone would think you were in the Loire rather than Leicester.

[BGmidsUK]

A couple of pics of the case & lid. The veneer is a bit bubbled so I'll have to investigate the Fablon option.

By the way, when I did my TV servicing course circa 1991 one of the lecturers (Paul Squires) often mentioned flip-top Murphys, must have been a favourite of his.


Brian

[BGmidsUK]

Hi Jeffrey, I do have a proper Quick-test block somewhere but I'd heard that 4mm banana plugs were a good fit for Schuko sockets so I thought why not .. - the block has a 5-amp plug on it so I'd need to find the adaptor as well ...

Re the chilli sauce etc. .. just hope nothing in the set gets as hot as my food


Brian

[Electrical]

Hello Brian
The service information is in the 1959-60 volume of Radio and TV Servicing. I have scanned the relevant pages and attached them as a PDF file.
I am working on the very same model at present and have come across a number of component value variations in the various published Trader and Radio and TV Servicing books, so be careful to note the value of the component before using the information on the service sheets. There may have been a number of modifications, which did not make it onto the service circuit diagrams.
Regards Stan.

[BGmidsUK]

That's great thanks Stan! Knowing how many components there are is probably as important as knowing the values.

Also thanks Trevor for the valve offer, I'll let you know in due course.


Brian

[murphyv310]

The set looks OK to me, I am sure it will be working soon.
Don't worry about spares there are plenty here, and yes Neil your 310 is still in Sorn!
The fact the boost cap blew would make you think the line stage came up!

[BGmidsUK]

After a bit of a delay (Christmas and all that) and a good study of the service info I'm about to order the caps for this set (and a couple of others which will be tackled in due course!) - it's had a nice drying-out session in the kitchen and is awaiting further attention!

Just a quick question - are the 1nF caps on the valve heaters likely to give any trouble? They appear to be OK but I know some sets do have issues. If these are prone to going s/c I'll replace them as I don't want to nuke any valve heaters.

What do people use for replacement aerial isolator caps? I don't seem to see any suitable matches in JustRadios catalogue (where I'm ordering the rest from). I haven't checked RS/Farnell yet as I'd need to build an order up anyway. I'll get enough for all my vintage sets.

Trevor - I would certainly think the line stage was running having looked at the circuit diagram and I believe I could hear a faint line whistle. The audio and RF stages were evidently working.

I'm looking forward to getting this set up and running


Brian

[TNC]

Brian,

Just thought I would give u a link to a Thread I started last year about
a 310 I have been restoring - you may find some of the observations from
some of our well known Forum experts of interest.

https://www.vintage-radio.net/forum/...ad.php?t=47310

I hope you don't have the shorting/leakage EHT problem I experienced!

Best of luck,
Trevor.

[BGmidsUK]

The caps arrived yesterday. I have some to replace the ones on the valve heaters just in case though these seem to be holding up OK - they will have other uses anyway - and since they didn't have any 470pF safety caps for the aerial isolator I ordered some 1nF instead, these will be used on all my sets.

I also thought it wise to make a safer lamp-limiter/supply arrangement (just need to find a suitable board to screw this lot to!) - especially since I sometimes have an audience when poking around in the back of a set. And I don't wish to give any of you heart attacks


Now for the bit where the fun starts. I replaced the dodgy caps in the line and frame stages and applied power initially via the lamp limiter so as to be kind to the electrolytics, with the second 200W bulb the line stage came to life with a healthy whistle. Full power was then applied and this resulted in a nice strong whistle and a healthy spark from the top cap of the U26. Amazingly the pots on the T/B appear to have survived the less-than-ideal storage conditions, with the line hold control giving the correct range judging by ear. I could not hear any frame buzz but this may be a job for the scope.

At this point I'm unsure if there is any significant EHT (no detectable rustle) but there is a faint glow from the U26 heater and a faint blue glow - this disappears if the EHT cap is removed which suggests there is some current flowing. I found a new U26 in my valve box which gives a slightly brighter blue glow but otherwise the same result. No sign of a raster yet. The CRT vacuum is OK judging by the healthy-looking heater and there are no signs of any dreaded glow from the electrodes. The anode connector and surrounding area on the CRT has been cleaned up as well as the aquadag earthing rod which was green.

I haven't touched anything in the RF side yet and though the sound stage works there are no signals getting through from the Aurora. I connected one via extra isolation so it could be that the coupling is suspect.



Brian

[murphyv310]

Hi.
The fact that the U26 is glowing blue would as you say assume the CRT is drawing current, adjusting the brightness control should change the intensity of the glow in the U26.
Two possibilities here and I think the most likely one is that the ion trap is out of adjustment.
If that is a no no check the cathode volts on the CRT, it could be very low so the CRT is drawing excessive current causing the EHT to go very low, this could of course be low anode volts on the 30F5 video amp perhaps the anode load is o/c or wait for it a H-K short on the tube.
Try that ion trap first.
Good luck

[BGmidsUK]

Hi Trevor,

There is indeed a slight problem with the ion trap magnet after compiling my post I attended to the waxy on the tube base (one lead of which was loose in the post) and discovered that the magnet had lost its grip entirely! Any pointers to approximate position would be appreciated. I took it off and re-tensioned the spring plate so it should keep its position this time. Knowing my luck I've probably put it back on the wrong way ..

I did spend some time slowly moving and rotating it but no sign of any life on the screen as yet.

The U26 glow is barely noticeable with the lights on but there is at least some EHT present since a piece of remaining spider-web was attracted to the back of the tube when I switched off, so that is encouraging.

May have to start changing the caps in the signal stages as some of them aren't too happy, though I would sooner have a raster up first.


Brian

[Sideband]

If I remeber correctly, you can short the g1 to cathode of the CRT to turn it on fully. This should give you a peak white raster. You may have to waggle the ion trap to see it but at least you will have 'first light'.


SB

[BGmidsUK]

Ah yes, I'll try that.

Have audio (albeit not very strong and accompanied with some hiss) on channel 4.


Brian