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Old 18th Jul 2007, 8:08 pm   #1
Robert Darwent
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Default Murphy U144 - Alternative Valve Types?

I'm having trouble finding replacement valves for my Murphy U144 portable
Does anyone know of any equivalent types that could be substituted instead? The original types specified for this set are;

V1 - 10C1
V2 - 10F9
V3 - 10LD11
V4 - 10P13
V5 - U404
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Old 18th Jul 2007, 8:30 pm   #2
paulsherwin
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Default Re: Murphy U144 - Alternative Valve Types?

This is a standard 4 valve + rectifier superhet using B8A valves.

V1 - 10C1 - frequency changer
V2 - 10F9 - IF amp
V3 - 10LD11 - recitifier / agc diodes + audio amp
V4 - 10P13 - audio output
V5 - U404 = half wave rectifier

There are no direct equivalents for these valves, but the appropriate Mullard 'U' series valves are near equivalents. You may need to make minor wiring and component changes to use them.

V1 - 10C1 - UCH42
V2 - 10F9 - UF41
V3 - 10LD11 - UBC41
V4 - 10P13 - UL41
V5 - U404 - UY41

The original Mazda types are often cheaper than the Mullard alternatives, particularly the 10P13.

Paul
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Old 18th Jul 2007, 10:29 pm   #3
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Default Re: Murphy U144 - Alternative Valve Types?

I would agree with Paul's comments above, but please bear in mind the 10P13 has a maximum anode current of 29mA, so the output transformer may be designed for this lowish anode current. The UL41 may need "limiting" to near that figure.
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Old 19th Jul 2007, 1:30 am   #4
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Default Re: Murphy U144 - Alternative Valve Types?

Thanks for the replies Paul and Tim

I just wondered if there were any direct equivalents to the Mazda types that were more readily available, obviously not

But thanks for the list of near equivalent Mullard types. Its something to fall back on if I can't locate the original Mazda valves, much appreciated Paul
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Old 19th Jul 2007, 9:01 am   #5
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Default Re: Murphy U144 - Alternative Valve Types?

Hi,

You would be very unlucky to need to replace all the valves.

Jim Fish of Wilson Valves has large stocks of valves and can probably help you, his on-line list is here http://www.flashbacksales.co.uk/wils...es/wvindex.htm

Phil.
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Old 19th Jul 2007, 10:38 am   #6
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Default Re: Murphy U144 - Alternative Valve Types?

Quote:
Originally Posted by rrdmpb View Post
I just wondered if there were any direct equivalents to the Mazda types that were more readily available, obviously not

But thanks for the list of near equivalent Mullard types. Its something to fall back on if I can't locate the original Mazda valves, much appreciated Paul
Although they aren't direct equivalents in terms of characteristics, I *think* they are plug in replacements with the same pinout. You would need to check this if you wanted to make a sub.

As Tim said, the 10P13 has lower current handling than the UL41 so you would need to check the current being drawn and possibly increase the cathode resistor. This is often a good idea anyway since a reduction in the output valve current will result in it running cooler and lasting longer. Even halving the OP valve current will make a barely audible difference to maximum volume.

Paul
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Old 19th Jul 2007, 12:19 pm   #7
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Default Re: Murphy U144 - Alternative Valve Types?

There are Marconi valves which are direct equivalents, according the the WW data book.

V1 - 10C1 - X118,X145
V2 - 10F9 - W118,W145
V3 - 10LD11 - DL145
V4 - 10P13 - N118, N145
V5 - U404 - U118, U145

Maybe not too helpful except in that it gives you a slightly wider target to aim at. I'd have a go at finding the right valve types before mucking about with the circuit to adapt it to near equivalents.

Pete.
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Old 19th Jul 2007, 4:00 pm   #8
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Default Re: Murphy U144 - Alternative Valve Types?

Thanks for all the replies, much appreciated

Quote:
Originally Posted by SWB 18 View Post
You would be very unlucky to need to replace all the valves.
No don't need to replace all the valves. I've had the set about a fortnight and it is working in a fashion, the audio is a little muffled and distorting slightly. Haven't investigated the cause yet, it probably needs several capacitors replacing and/or some of the valves are a bit tired. But in any case I always to try and obtain a spare set of valves as a back-up for my sets, hence my original request.
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Old 19th Jul 2007, 4:53 pm   #9
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Default Re: Murphy U144 - Alternative Valve Types?

Murphies of this era are normally full of 'Orrible 'Unts and require a recap, especially That Capacitor. Don't run the set without changing That Capacitor or the 10P13 will lose emission by being overrun and will need replacing - like UL41s they aren't cheap valves, though conversion to another output valve is possible.

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Old 19th Jul 2007, 5:18 pm   #10
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Default Re: Murphy U144 - Alternative Valve Types?

Quote:
Originally Posted by rrdmpb View Post
I've had the set about a fortnight and it is working in a fashion, the audio is a little muffled and distorting slightly.
I agree with Paul. "A little muffled and distorting slightly" could well be that the DC blocking cap to the output valve grid is leaky and the bias is wrong. They don't need to leak that much to wreck the output valve and maybe the o/p transformer. Definitely don't run the set any more without changing that at least for a nice new one.

Pete.
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Old 19th Jul 2007, 6:52 pm   #11
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Default Re: Murphy U144 - Alternative Valve Types?

Quote:
Originally Posted by paulsherwin View Post
...full of 'Orrible 'Unts...
Good phrase Paul, I like it! Very appropriate!

Thanks for the advice Paul and Pete, but I haven't actually run the set at all. I know enough not to risk powering it up until I've checked things out and replaced what needs replacing.

The chap I bought the set from was the last to plug it in, in order to demonstrate his claim that it was in a working condition. It was at that time I noticed the condition of the audio and got him to turn it off again fairly quickly!

Obviously its not a major problem (famous last words! ) and cosmetically the set was in such a very good condition, that I went ahead and bought it!
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