Murphy A48 restoration project

[A48Resto]

This A48 appears to have been well looked after. There are signs of repairs in the past. I have not opened the back yet. I have not attempted to power it up.
Obvious issues that I can see:
2 missing screws for fixing the back cover.
1 missing control knob.
Is the other outer control knob the correct one for this model?
Mains cord will have to be swapped for something less risky.

[A48Resto]

Part 2
The speaker cover was intact when I acquired it.. unfortunately I wasn't able to prevent young prying hands in time.. I console myself with the thought it would have died soon anyway. Any thoughts on a suitable replacement would be appreciated.
The veneer is in amazing condition for an 80 year old item.
Th lacquer does show a very small amount of crazing especially on the top, but this doesn't show in the photos.
I do not intend to restore the case to pristine condition, rather to blend the blemishes in a little so that it retains it's used and loved character.

Anybody know how to post the last 3 pictures in a reply? I'm trying to avoid a separate thread. The "Go Advanced" option takes me to an invalid link.

[Mr 1936]

I restored one of these a year ago. The left hand inner knob looks to be the correct "cup cake" shape.

The audio has transformer/choke coupled negative feedback which is switched out on Short Wave.

Watch out for hardened rubber grommets under the tuning capacitor etc, these can make the dial assembly shift and cause it to rub off its markings.

I don't know your skill level, so won't offer general restoration advice unless you ask further !

Good luck with the Resto.

[music-centre]

Hi,
Looks to be in pretty good condition, should look smart after a little work - the Knobs on this picture I have found look to be original.
Steve.

[A48Resto]

Thankyou Steve. All other photos I have seen including marketing material seem to show them smooth sided with the ribbing at 45 degrees for the last 1/4 inch or so. If the one I have is valid, I may attempt to cast one or more.

[AC/HL]

Originally Posted by A48Resto

Anybody know how to post the last 3 pictures in a reply? I'm trying to avoid a separate thread. The "Go Advanced" option takes me to an invalid link.

Welcome A48Resto, as you've discovered, there is a limit of 5 attachments per post.

[bluepilot]

Originally Posted by A48Resto

Anybody know how to post the last 3 pictures in a reply? I'm trying to avoid a separate thread. The "Go Advanced" option takes me to an invalid link.

Assemble them into a pdf and post the pdf

[A48Resto]

Hi all, managed to get a couple of hours in today, I have attached a pdf with some pictures. It's quite dusty in there. I think a gentle strip down is in order. There are quite a few wires with age related insulation cracking.
It appears that a couple of the valves show internal silvering, V44 (Mazda AC/5 pen) appears to be the worst, is this something to worry about or is it in the range of "they all do that sir" ?
V2 (Mazda AC/VP2) has a coating on the outside of the glass which seems to be slowly chipping/wearing off.. again, is this normal or not?
There appears to be damage to the speaker cone which is not related to the damage caused to the speaker cloth as it is in a different location and does not have a fresh tear appearance. Any pointers to replacement of the cone or entire speaker welcome.
I see lots of comments about "That Capacitor" on this site.. but have not worked out yet what it relates to.. so if there is something you notice in the pics, and definitely needs to be addressed, please just let me know.
Regards A48Resto

[MurphyNut]

I enjoyed your pictures, I have one of these fine sets, mine produce's a particularly warm and mellow tone.
From the look of it your set hasn't got damp in it's past and that's a big bonus. I'd be inclined to repair the speaker diaphragm rather than the challenge in finding the right replacement.
It's amazing what can be done with PVA glue some paper and patience.
Your tuning scale drum is in remarkable condition, my only criticism with this set is the mechanism that rotates this drum. I have two set that employ this system and I've never managed to get them to operate smoothly.
Good luck, we must save all the old Murphys!

[Tractionist]

Originally Posted by A48Resto

Hi all, managed to get a couple of hours in today, I have attached a pdf with some pictures. It's quite dusty in there. I think a gentle strip down is in order. There are quite a few wires with age related insulation cracking.
It appears that a couple of the valves show internal silvering, V44 (Mazda AC/5 pen) appears to be the worst, is this something to worry about or is it in the range of "they all do that sir" ?
V2 (Mazda AC/VP2) has a coating on the outside of the glass which seems to be slowly chipping/wearing off.. again, is this normal or not?
There appears to be damage to the speaker cone which is not related to the damage caused to the speaker cloth as it is in a different location and does not have a fresh tear appearance. Any pointers to replacement of the cone or entire speaker welcome.
I see lots of comments about "That Capacitor" on this site.. but have not worked out yet what it relates to.. so if there is something you notice in the pics, and definitely needs to be addressed, please just let me know.

Hi A48 - that's a lovely set that you've picked up there!

To answer some of your queries:

The speaker cone is definitely repairable - using coffee filter paper liberally soaked in dilute PVA glue [see other posts on this forum].

From what I can see - the 'silvering' that you have reported on/in one or two valves is merely the getter. These valves haven't turned a milky/white [indicating that they've 'gone to air'/lost their vacuum] - so no immediate worries there.

The external surface flaking reported on other valves is probably applied screening - and isn't unusual. Try not to dislodge any more of it. This is an electrically conductive metalised coating - which hopefully remains continuous and in contact with the respective valve pin [it's basically present to prevent or attenuate stray RF being emitted from the valve envelope].

[G0HFCFrank]

In post 8 you ask about "that" capacitor. This term refers to the coupling cap from the AF amplifier anode to the grid of the output valve. If that capacitor goes leaky the O.P. valve takes grid current and can write off the valve itself, the rectifier and/or the mains transformer. In an old Murphy I'm playing with the speaker energising coil went o/c probably for this reason and that's a real pain to fix. In the pic you supplied that cap is the wax covered one next the yellow cap on the tagboard top right of your pic; if you have the circuit it's C43.
regards,
Frank C.

[PaulR]

I restored a Murphy A46 a while ago and found that the small value capacitors in the LW oscillator circuit were troublesome. Not something to be concerned about at this stage but if you cannot get it to tune in to anything when the basics have been done you might find this thread useful https://www.vintage-radio.net/forum/...ad.php?t=92520

Looking at the photo of the speaker cloth it looks like the same "pin stripe" material used on the A46. I got something very similar to replace mine. I may have some left over. if you would like some and let me know the size needed I will have a search in the loft.