UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Radio (domestic)

Notices

Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only.

Closed Thread
 
Thread Tools
Old 7th Feb 2019, 9:36 pm   #1
MichaelWay
Retired Dormant Member
 
Join Date: Feb 2018
Location: Londonderry, Northern Ireland, UK.
Posts: 8
Smile [Restoration AND Light Modification] Murphy 146

Dear All,

I finally purchased my dream radio: a Murphy 146. I got this beautiful model for £55 at an auction in Northern Ireland.

The bad news? I have no experience with radio restoration. The benefits? I am very willing to learn and take my time and money to do this safely and do this right. I also have a kind of father-in-law in his 60s who was a trained electrician for most of his adult life.

So, dear Vintage Radio users, I ask you to be my Senseis.

My goals:

1) To restore and preserve the original sound, functionality, and look of the radio.
2) To add a reversible modification that would allow me to input unamplified digital audio through the tube amplifiers, such as the circa 1940s Abbott and Costello radio recordings. Perhaps with a customised Raspberry Pi.

Step 1 is obviously my first goal.

Here is an album of photos of my radio: ********************a/NLVaGBr

So dear users, what is my first step? Replacing all the wiring with modern wires is what I would assume. Also would it be worth getting the radio revarnished? Do you think a furniture restorer could conceal that particular piece of damage to the wood?

Looking forward to your guidance and input.

Best wishes,

Michael
MichaelWay is offline  
Old 8th Feb 2019, 12:32 am   #2
TrevorG3VLF
Rest in Peace
 
TrevorG3VLF's Avatar
 
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
Default Re: [Restoration AND Light Modification] Murphy 146

There are circuit diagrams (schematics) available top right. The moderate cost supports this site.
I have the CD and do not see a bare 146 but there is a A146C which looks very much like yours. It should be powerful enough to rattle the walls.
The diagram is very useful to be able to specify particular components.
Do not switch on without some changes.
1. Check or change C34 and C35 to protect the output valves, speaker transformer and power supply.
2. The set has an autotransformer so that the mains is connected to the chassis. You would be well advised to use an isolating transformer when working on the set.
3. C38 and C39 will need to be reformed or replaced.
4. Always start up for the first time with a lamplimiter in circuit.
5. The speaker appears to be connected to the back of the extension speaker socket.
6. An external earth could be less noisy but is frowned upon as the house earth could be at a different voltage.
6. I would start by measuring all the voltages applied to the valves. It is unlikely to work properly if the voltages are wrong and damage may be averted.

I do not do woodwork restoration, I get my sister to do that.
TrevorG3VLF is offline  
Old 8th Feb 2019, 1:59 am   #3
Clydeuk
Hexode
 
Join Date: Mar 2012
Location: Liverpool, Merseyside, UK.
Posts: 453
Default Re: [Restoration AND Light Modification] Murphy 146

Unless the insulation of the wiring is crumbling and falling off there is no need to replace it, and doing so may lead to wiring mistakes.

Having not seen the diagram, I assume you should be able to connect an external audio source to the gram input. Others with more knowledge will be able to advise better.
Clydeuk is offline  
Old 8th Feb 2019, 2:40 am   #4
dave walsh
Dekatron
 
Join Date: Jan 2006
Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex.
Posts: 5,814
Default Re: [Restoration AND Light Modification] Murphy 146

Hello Michael and welcome. You've spent a fair amount on this set so don't plug it in [as advised already]. Note what has been said already even though you probably don't understand it. You're willingness to listen and learn puts you ahead already. This is not You Tube! The site owner [Paul Stenning] has produced a very good Guide To Restoration but I can't do the link. Don't guess what you should do just read and ask. It's possible to do damage as Clydek said. Forget the woodwork for now-it's the very last item! Both your ambitions are easily achievable especially if you proceed methodically but read up as you go along!

Dave W

Last edited by dave walsh; 8th Feb 2019 at 2:48 am.
dave walsh is offline  
Old 8th Feb 2019, 10:11 am   #5
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: [Restoration AND Light Modification] Murphy 146

Quote:
Originally Posted by dave walsh View Post
The site owner [Paul Stenning] has produced a very good Guide To Restoration but I can't do the link.

Dave W
https://www.vintage-radio.com/repair...ion/index.html

Given that the OP is inexperienced I would suggest that his "dream radio" is not the ideal first restoration project. He'd be better off starting by practicing on a cheap Woodie where it doesn't matter if it gets damaged.
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is offline  
Old 8th Feb 2019, 12:14 pm   #6
TrevorG3VLF
Rest in Peace
 
TrevorG3VLF's Avatar
 
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
Default Re: [Restoration AND Light Modification] Murphy 146

The screws are probably 6BA. Beware of metric screws, they go in easy then jam solid.

The circuit is fairly simple with little complicated switching. There is push-pull output which should be understandable.
The power supply is on a separate chassis and should be the first to be serviced and soak tested.
TrevorG3VLF is offline  
Old 8th Feb 2019, 2:16 pm   #7
Edward Huggins
Dekatron
 
Join Date: Sep 2015
Location: Southwold, Suffolk, UK.
Posts: 8,302
Default Re: [Restoration AND Light Modification] Murphy 146

I'm wondering just how aware the OP is of the fact that this is an AM only radio and without a reasonable external aerial, his choice of off-air radio stations in Londonderry (to achieve that "original sound") may be quite limited.
__________________
Edward.
Edward Huggins is offline  
Old 8th Feb 2019, 5:25 pm   #8
dave walsh
Dekatron
 
Join Date: Jan 2006
Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex.
Posts: 5,814
Default Re: [Restoration AND Light Modification] Murphy 146

His second ambition was to be able to play vintage recordings [without disturbing the integrity of the set] through the audio stage Edward, which suggests he has considered a lack of live Broadcasts. I must admit I hadn't thought of that aspect myself until you brought it up!

Whether you try something simpler or not Micheal, there are many threads that can be accessed via the search box at the top.

Two that will give you an idea of what may be involved are-

"Murphy A146" by paperboy 2/3/16 and
"Murphy A146CM by Hermit 6345 16/6/07

Cheers,

Dave W
dave walsh is offline  
Old 8th Feb 2019, 5:31 pm   #9
Station X
Moderator
 
Station X's Avatar
 
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
Default Re: [Restoration AND Light Modification] Murphy 146

Links:-

https://www.vintage-radio.net/forum/...d.php?t=124361

https://www.vintage-radio.net/forum/...ad.php?t=18081
__________________
Graham. Forum Moderator

Reach for your meter before you reach for your soldering iron.
Station X is offline  
Old 8th Feb 2019, 5:43 pm   #10
music-centre
Heptode
 
Join Date: Sep 2007
Location: Brentwood, Essex, UK.
Posts: 687
Default Re: [Restoration AND Light Modification] Murphy 146

Hello Michael,
A nice radio, I like these they work very well.

If I remember correctly the A146C used an Autotransformer but the A146CM used an isolating transformer, so important to identify which you have as the radios look the same.
Steve.
music-centre is offline  
Old 8th Feb 2019, 6:55 pm   #11
ajgriff
Nonode
 
ajgriff's Avatar
 
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,583
Default Re: [Restoration AND Light Modification] Murphy 146

Really like these. You clearly have the enthusiasm and the dream. If you can add tenacity and a desire to learn I'm sure you will reach your goal.

Looking at the photos I'm pretty certain that this is the early auto-transformer version ie, the A146C. Please don't proceed until you fully understand the safety implications of this arrangement. Happy reading!

Alan
ajgriff is offline  
Old 8th Feb 2019, 10:20 pm   #12
TrevorG3VLF
Rest in Peace
 
TrevorG3VLF's Avatar
 
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
Default Re: [Restoration AND Light Modification] Murphy 146

Quote:
Originally Posted by music-centre View Post
Hello Michael,
A nice radio, I like these they work very well.

If I remember correctly the A146C used an Autotransformer but the A146CM used an isolating transformer, so important to identify which you have as the radios look the same.
Steve.
Yes, the circuit for the A146CM is also available top right.
TrevorG3VLF is offline  
Old 9th Feb 2019, 1:43 pm   #13
MichaelWay
Retired Dormant Member
 
Join Date: Feb 2018
Location: Londonderry, Northern Ireland, UK.
Posts: 8
Talking Re: [Restoration AND Light Modification] Murphy 146

Wow. I am overwhelmed by the response. Thank you.

1) Trevor, you are a hero. I scoured the internet for the original user manual and could only find a single page schematic and some old advertising. Thank you. Happy to pay the price. I believe the set is the A146C and not the CM. I will take your advice RE: C34, 35, 38, and 39. I just watched a video on the benefits of an isolation transformer https://www.youtube.com/watch?v=3rvEdHyAd2k Thank you. I just read the instructable on a Lamp Limiter, thank you also. I am a bit confused by point 6. Are you saying I need to plug something in to that earth slot at the back? Or will the three pin plug suffice? What is the best tool to measure voltages of valves? Thank you again.

2. Clyde. Some of the insulation is crumbling so I will at the very least have to replace that, thank you. Do you recognise the gramophone connector? The manual calls it a PU socket but a google brings up nothing re:audio.

3. Dave, thank you for your encouragement and advice. I am definitely aiming to proceed with the methodical approach, and take as much time and care as is needed, even if that means a year or two. I am here to listen, read, and learn.

4. Station X, thank you for linking Paul Stenning's Guide, it looks very helpful. I understand your concern but my finances are stretched enough that I would really rather just focus on this model. Also, old radios are rather hard to find in NI, and most eBay sellers do collection only.

5. Trevor, thank you for your advice on the screws, are they still manufactured, or will I have to seek out old stock? I will certainly service the PSU and soak test it first, after buying an isolating transformer and lamp limiter.

6. Edward, I am aware of how limited AM broadcasting is in my area and the need for a decent external area, though as I said I am aiming to restore functionality and capability, and also input my own media to compensate for the NI AM drought.

7. Dave (again), Thank you for those directions.

8. Station X (again), Thank you for the links!

9. Music-Centre, thanks, I have been chasing this model for well over a year now. I believe from the interior that this is a A146C and not an A146CM. Do you know if the Murphy database is online so that I could verify that with the serial number?

10. AJ, thank you for your encouragement, I have desired an old AM radio for many years (though originally a Philco Cathedral shaped model) and then fell in love with the 146 aesthetic as I became more enamoured with modernism and Art Deco. I will try and become fully aware of those safety implications before proceeding. Time to nag the ol' father-in-law for his experience working with old electronics.

11. Trevor, thanks again for your guidance. I will purchase the CM manual just in case.
MichaelWay is offline  
Old 9th Feb 2019, 5:24 pm   #14
dave walsh
Dekatron
 
Join Date: Jan 2006
Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex.
Posts: 5,814
Default Re: [Restoration AND Light Modification] Murphy 146

You won't be aware Michael but thanks to a surge of interest in "retro" a lot of of people, with a contemporary attitude re an instant fix, now turn up, which is very welcome but there is sometimes an apparent inability to listen or do research themselves. You are clearly not going to have that problem and you will get a lot of help. Yes the wiring needs replacement but [like the capacitors] not wholesale before you've worked out the circuit and ID'd the component parts. It's so easy to get confused if you don't do one wire or component at a time, perhaps highlighting what you do on a diagram. We can't find out were this "wholesale" idea originated from [although US audio forums are suspected]. It may be ok for professionals who work on the same equipment all the time but not in this context really!

When Clyde mentioned a "Gram" [for Gramophone] input it's exactly the same as your PU [Pickup] socket, meaning the Stylus/Cartridge [Pickup] on a separate record deck that plugs in to the Radio. This bypasses the Radio section and goes straight to the amplifier. It was often a cheaper or more convenient alternative to a Radiogram which would be a very big and expensive item. The PU is an obvious "way in " with an external audio source but its designed for a particular signal level so there maybe other options in the end for modern sources but don't worry about that for now just trace it's path.

You have a quality item but they are often somewhat underrated. Murphy did these "Baffle" sets in smaller sizes as well. A baffle is simply a board which reproduces the FULL range of frequencies available at the speaker. In the early days these might have been across the corner of a room eg a Radio Workshop. Theoretically the ideal size for an 8" speaker was 5' 6" square. Obviously a speaker will work on a much smaller mounting but folding that area into a smaller, more acceptable, shape and getting all the frequencies reproduced is [basically] what cabinet design is about. Murphy seemed to latch on to this aspect, especially with these sets. I have a design Magazine illustration [somewhere] that shows a 146 in the setting of an Industrial Building converted into apartments with exposed brickwork and timber. It looks great!

Just as an indicator of quality [and note that cannibalising working sets is usually frowned upon here] I'll mention that the innards from the large baffle sets [that have simply rotted away] have been converted into very good quality mono or stereo amps using the power and output [ie audio] stages rescued from the chassis. Sorry to go on at length but your enthusiasm is gratifying!

Dave W

Last edited by dave walsh; 9th Feb 2019 at 5:41 pm.
dave walsh is offline  
Old 9th Feb 2019, 5:34 pm   #15
music-centre
Heptode
 
Join Date: Sep 2007
Location: Brentwood, Essex, UK.
Posts: 687
Default Re: [Restoration AND Light Modification] Murphy 146

Quote:
9. Music-Centre, thanks, I have been chasing this model for well over a year now. I believe from the interior that this is a A146C and not an A146CM. Do you know if the Murphy database is online so that I could verify that with the serial number?
I haven't seen a database of the serial numbers but the Model number should be on the fibreboard back towards the bottom, if it is present, I have checked on my one of these and it does have the "M"

If not you would need to check with a circuit diagram to make sure which you have.
I would think the autotransformer would be smaller.
Steve.
music-centre is offline  
Old 9th Feb 2019, 6:20 pm   #16
MichaelWay
Retired Dormant Member
 
Join Date: Feb 2018
Location: Londonderry, Northern Ireland, UK.
Posts: 8
Default Re: [Restoration AND Light Modification] Murphy 146

1. Dave, you may be correct about the US radio forms being the source of that confusion, I used to read a lot about American restorations. The A146C manual mentions Crystal pickups which led me to this: https://www.youtube.com/watch?v=hb4i_1rdIPI I wonder if it would be possible to create the reverse? To take modern digital audio and essentially convert it to crystal PU output. Also re:quality and cannibalising etc. I certainly have all my desires set on restoration and not on conversion. That would be the very last resort.

2. Music-Centre, you are correct https://i.**********/yFm6CM8.jpg the model number says A146C, that makes things slightly easier in terms of narrowing down parts.

So, if we all agree that an isolation transformer should be one of my first major steps, is circa £100 a good price? https://www.superlecdirect.com/p-cm7...-750va-230230v
MichaelWay is offline  
Old 9th Feb 2019, 8:06 pm   #17
MurphyNut
Heptode
 
MurphyNut's Avatar
 
Join Date: Apr 2016
Location: Croxley Green, Hertfordshire, UK.
Posts: 979
Default Re: [Restoration AND Light Modification] Murphy 146

This is a gorgeous set and they sound amazing and very powerful.
I spent some time on mine last year and I have to admit it isn't the easiest set to work on.
Surprisingly for such as large set there isn't much room in the upper "radio section" so replacing capacitors can be tricky.
As you have found the insulation on the wire used at this time by Murphy will have deteriorated. I had to replace all the wires that run from the top of the set down to the bottom power unit. If I remember there were about 7 or so and all different colours.
I hope this hasn't put you off, it's certainly worth the effort, they are lovely sets to listen to and look at.
__________________
Clive
MurphyNut is offline  
Old 10th Feb 2019, 12:14 am   #18
TrevorG3VLF
Rest in Peace
 
TrevorG3VLF's Avatar
 
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
Default Re: [Restoration AND Light Modification] Murphy 146

BA bolts are readily available on e-bay bur you may have a hardware shop in your area who stocks them. Measure the diameter and check with data tables or find a tame model engineer. Get washers to fit.

You can check whether there is an autotransformer or isolating transformer by switching the radio on, not plugged in, and measuring the resistance between a plug pin and the chassis. Change the power plug with the neutral connected to chassis on the A146C. The A146CM internal transformer will do the isolation for you. You can work on a set without isolation but remember that the advantage is that you can only get electrcuted once.

Earthing systems vary, PME seems to be common here. The neutral is connected to earth at the substation and at the customer. A leaky substation transformer can raise the earth wire voltage. All metal work in the property is connected together so that a shock is not likely even if the earth is not at absolute earth.
Bringing in an earth from outside raises the slight posibility that this may have a different voltage to, say, your water pipes but is likely to be cleaner than the internal earth which is contaminated by switch mode power supplies.

Any cheap digital meter will be adequate to measure voltages but note that the circuit loading will be less than analog meters of days of yore so will show slightly higher voltages. I prefer to use an analog meter for rough voltage measurements because it needs no batteries which can run down. Other posters advocate a posh meter such as a Fluke but I think that it is better to get a cheap one to ruin first.

The A146C will have a two wire mains lead. The A146CM may have the chassis connected to earth. A 3A plug fuse is often advocated but I always use a 1A and none have blown.

If you run new wires through the chassis put in new grommets to protect the wire insulation from being cut. Make sure you get the connections right.

An isolating transformer should not cost a lot. I picked a RS one up at a show in Birminham for I think £4. It was plenty heavy enough to carry home. I recently bought a bigger one from the local amateur radio club, I may have gone wild and paid £1. It needs to be opened and the earth wire disconnected. You could try asking for one in the wanted thread. Always use an earth leakage trip, I have them all over the place.
TrevorG3VLF is offline  
Old 10th Feb 2019, 12:57 am   #19
dave walsh
Dekatron
 
Join Date: Jan 2006
Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex.
Posts: 5,814
Default Re: [Restoration AND Light Modification] Murphy 146

"Don't Panic" as Corporal Jones shouts in Dad's Army. Be sure you need an Isolating Transformer-I'm not certain sure that we all agree on that but if so £100 is way way too much. That one seems like a building site job! Research but don't guess, just ask the members but NOT continuously If the advice is too complex please say so! You do need a meter as Trevor said! The older AVO's may be more accurate as they date from the same period. Modern meters are very cheap and good but more sensitive and can be misleading. Don't pay a lot-you can find an AVO cheaply or maybe even free! The whole Forum ethos is to spend as little as possible to solve a problem-it's very satisfying and not really just about money.

Search the threads! Don't worry about crystal pick ups. You have learned already that they had a high voltage output in order to driver the [often] very basic amps in record players at that time.o Modern Hi-Fi delicate magnetic cartridges and other devices need less but that will be in the future. If the people on here can't solve a problem for you, it's likely that nobody can and they do it with a good attitude as well.

Dave

Last edited by dave walsh; 10th Feb 2019 at 1:22 am.
dave walsh is offline  
Old 10th Feb 2019, 11:19 am   #20
TrevorG3VLF
Rest in Peace
 
TrevorG3VLF's Avatar
 
Join Date: Apr 2011
Location: Matlock, Derbyshire, UK.
Posts: 1,378
Default Re: [Restoration AND Light Modification] Murphy 146

CPC do a 100VA isolating transformer with screw terminals and overload protection and a cover for under £50. You could use a 240V transformer out of an old radio but will need to be put in a box.
TrevorG3VLF is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 9:06 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.