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Old 23rd May 2019, 12:20 pm   #1
LyntonP
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Default Unknown radio. Identified as a Murphy A34.

I have been offered this radio from an old school friend. No idea what it is and haven’t seen it first hand yet. Anyone know what it might be?
Lynton
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Old 23rd May 2019, 12:24 pm   #2
ms660
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Default Re: Unknown radio

Murphy A34:

https://www.radiomuseum.org/r/murphy_a34_a_34.html

Or D34:

https://www.radiomuseum.org/r/murphy_d34.html

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Old 23rd May 2019, 12:38 pm   #3
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Default Re: Unknown radio

Thanks Lawrence. I did have a quick look on the radio museum site but couldn’t find anything.
Lynton
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Old 23rd May 2019, 12:52 pm   #4
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Default Re: Unknown radio

It is indeed a Murphy A34. There is currently an example of the AC/DC variant (D34) on offer on eBay.
https://www.ebay.co.uk/itm/Vintage-M...UAAOSw2-pc2Cwj
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Old 23rd May 2019, 1:02 pm   #5
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Default Re: Unknown radio

There are threads on here via a search Lynton, including one set that's "motor boating" ie oscillating. Google "Diagram Dungeon" for a great Murphy site. Click on the model number for an illustration of your set and the Radiogram version. The table top was £17 in 1932 it says, reduced to £13 by November!
I wonder why?

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Old 23rd May 2019, 1:36 pm   #6
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Default Re: Unknown radio. Identified as a Murphy A34.

The A34 was from 1937 - I think it's the A3A from 1932 that you're referring to Dave !

Regards,
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Old 23rd May 2019, 2:57 pm   #7
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Default Re: Unknown radio. Identified as a Murphy A34.

Oh yes, quite right Andy 1937 I was looking at the correct sets but the wrong info. I'll blame it on a Windows 10 unstable scroll up or Spec "Saviours" Price correction the table top was £10-10/- in 1937. I might have clocked the date mistake but the A34 looks a bit basic for 1937. Maybe it was built down to a price

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Old 23rd May 2019, 3:00 pm   #8
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Default Re: Unknown radio. Identified as a Murphy A34.

According to the schematic it has an inter-station noise suppression feature.

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Old 23rd May 2019, 3:12 pm   #9
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Default Re: Unknown radio. Identified as a Murphy A34.

Oh really Lawrence. I suppose that and the magic eye takes it up scale a bit
I've got the same feature on my [unrestored] Marconiphone 296 RG. It seems to be an electro-mechanical system and it is specifically mentioned in the original Instruction Book that came with it.
I recall that an electronic "no hiss between stations" feature was promoted in some solid state Tuners during the 70's. When I got the Radiogram in the mid eighties, I very was surprised to see that "silent tune" was a feature back in 1935! Nothing new under the sun eh?

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Old 23rd May 2019, 3:52 pm   #10
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Default Re: Unknown radio. Identified as a Murphy A34.

For inter-station noise suppression, the A34 uses the cathode & g3 of the IF amplifier as a diode which is connected by way of, what are in effect (for explanation purposes) two resistances to the cathode of the detector diode, the two resistances form a potential divider to which the anode of the detector is connected, the cathode voltage of the IF amplifier is lower than that of the detector's cathode, that therefore makes the detectors anode voltage lower than the voltage on its cathode, the voltage difference being the threshold voltage for detection.

I've never owned or used one of these receivers so I've no idea how effective it is in reality.

Lawrence.
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Old 23rd May 2019, 6:28 pm   #11
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Default Re: Unknown radio. Identified as a Murphy A34.

The set has been delivered and it is indeed the MW/LW variant with the interference suppression operated by a switch on the rear. A very quick inspection shows that the cabinet is not too bad, would need refinishing, but even before removing the chassis it is obvious that it will need a complete rewiring job done. All the exposed insulation on the cables is crumbling to dust. The tuning scale doesn’t seem to work, and the set is very mucky inside (only to be expected really). I have printed the service manual - very extensive! And the valve complement are numbers that I have never heard about! It was made in 1937 and as mentioned the original price was around £11.00. The valves are listed as Mazda AC/TP, AC/VP2, AC/PenDD, UU4, and AC/ME. Are such items still available?? An unusual feature is that the loudspeaker is housed in a draw string bag! Never seen that before.
Is it worth progressing with me being a novice, or is this more for an experienced person?
Lynton
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Old 23rd May 2019, 6:40 pm   #12
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Default Re: Unknown radio. Identified as a Murphy A34.

You could possibly sort it with guidance BUT Do Not Plug in till certain bits are changed/checked.

Though,if in doubt then let some one else do it.

Yes,I have had a few speakers in drawstring bags,keeps the dust out!
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Old 23rd May 2019, 7:01 pm   #13
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Default Re: Unknown radio. Identified as a Murphy A34.

If you like the set and want to get it working, then go for it. Post a thread on here and you should get plenty of help and encouragement.

Be sure to work safely however, bear in mind that this is a mains powered device, and it needs to be treated with respect... For an intro to repair and restoration, have a read of this site...

https://www.vintage-radio.com/repair...ion/index.html
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Old 23rd May 2019, 7:39 pm   #14
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Default Re: Unknown radio. Identified as a Murphy A34.

Best to check the continuity of the output transformer primary, mains transformer primary and HT secondary, and the speaker field coil before you start.
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Old 23rd May 2019, 7:50 pm   #15
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Default Re: Unknown radio. Identified as a Murphy A34.

Quote:
Originally Posted by PJL View Post
Best to check the continuity of the output transformer primary, mains transformer primary and HT secondary, and the speaker field coil before you start.
I have been watching a series on you tube called Electronics old and new by Marc Calderia. He does the same as you suggest and more checking many things before applying power. He also shows how to construct items which are useful when doing restorations. He favours German sets but will tackle almost anything? Very clever chap whose background is in the electronics field. Worth a watch, and he does respond to comments.
Lynton
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Old 24th May 2019, 2:29 pm   #16
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Default Re: Unknown radio. Identified as a Murphy A34.

Quote:
Originally Posted by ms660 View Post
For inter-station noise suppression, the A34 uses the cathode & g3 of the IF amplifier as a diode which is connected by way of, what are in effect (for explanation purposes) two resistances to the cathode of the detector diode, the two resistances form a potential divider to which the anode of the detector is connected, the cathode voltage of the IF amplifier is lower than that of the detector's cathode, that therefore makes the detectors anode voltage lower than the voltage on its cathode, the voltage difference being the threshold voltage for detection.

I've never owned or used one of these receivers so I've no idea how effective it is in reality.

Lawrence.
Lawrence do you have any idea where I might find more information about this system? Been looking on the net with no luck.
Spent some time cleaning the chassis and cabinet.
Most of the valves have no ID numbers other than the magic eye, and there seems to be an extra valve connected to V1 which is not mentioned in the service data. Looks like an add on with a modified valve holder (see pic).
The extra valve holder was screwed to the side of the cabinet.
Any ideas?
Lynton
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Old 24th May 2019, 2:56 pm   #17
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Default Re: Unknown radio. Identified as a Murphy A34.

The valve holder that was screwed on to the cabinet has been done to use a substitute.

Getting the correct valve line up is no problem.

I notice you already have the valve types and that is looking left to right,excluding the magic eye.
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Last edited by HamishBoxer; 24th May 2019 at 3:03 pm.
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Old 24th May 2019, 3:08 pm   #18
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Default Re: Unknown radio. Identified as a Murphy A34.

Were there valves in all of the 4 valve holders on the chassis (not including the magic eye mounted by the dial) as well as a valve in the additional valve socket fitted sideways?

I am trying to work out if the additional socket is to replace the original one because the only replacement valve they could find was a 5 pin one not the original 7 pin one.

Mike

Hamish posted whilst I was typing.
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Old 24th May 2019, 3:22 pm   #19
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Default Re: Unknown radio. Identified as a Murphy A34.

Quote:
Originally Posted by HamishBoxer View Post
The valve holder that was screwed on to the cabinet has been done to use a substitute.
The extra valve holder on the cabinet has a AC/HL valve fitted, and V1 in my radio is a V4HP. So are these two valves used instead of the original AC/TP which is listed in the service manual? If I had the correct V1 could the ‘adaptor’ which is shown in the photo be removed?
Also V3 which should be a AC/PenDD has a loose top connection (on top of the glass envelope).
Lynton
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Old 24th May 2019, 3:28 pm   #20
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Default Re: Unknown radio. Identified as a Murphy A34.

It could be a case of using 2 valves instead of one, I would try for the correct one. I think you have picked a messy set to start off with as a first, due to unofficial mods.

Re loose top cap, carefully put a bit of Super or similar around to secure.

Also, the magic eye is most likely u/s.
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