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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE! |
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2nd Jul 2014, 4:40 pm | #1 |
Octode
Join Date: Nov 2010
Location: Cullompton, Devon, UK.
Posts: 1,435
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McMurdo Valve Bases
For what it's worth, broken contacts in McMurdo valve bases can be a pain, sometimes you can reform them with a needle, but more often they are brittle and snap. this is something I came across, If you have an old scart socket cut the pins out and with a nail file or the like, file the slot out slightly, take out the old broken contact, two of these scart pins side by side slot back into the base giving good contact just need a bend on the solder tag to keep them in position. I do not know if it is a long lasting repair but it seems to work.
John |
2nd Jul 2014, 7:23 pm | #2 |
Dekatron
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 14,007
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Re: McMurdo Valve Bases
That's a nice fix - using easy-to-acquire parts, too.
The McMurdo type valve-sockets do seem a major fail after a few decades: I wonder if anyone's ever done an analysis of the brass composition and compared it with the brass used for the contacts on Amphenol-type Octal bases? |
2nd Jul 2014, 7:44 pm | #3 |
Octode
Join Date: Nov 2010
Location: Cullompton, Devon, UK.
Posts: 1,435
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Re: McMurdo Valve Bases
The composition of the brass is probably the same, fatigue is more than likely caused by temperature changes, octal valves have less heat transfer through the thin connecting wires to the pins, where b8a & b9a do not, just my theory anyway.
John |
2nd Jul 2014, 9:53 pm | #4 |
Dekatron
Join Date: Jun 2009
Location: Staffordshire Moorlands, UK.
Posts: 5,274
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Re: McMurdo Valve Bases
My username is in honour of these things!
One small aspect of my day job is restoring valved musical electronics; the famous company Vox (Jennings) used McMurdo and a single organ can contain scores of bases with broken pins, no good for a professional musician. I've always opted to replace the holder complete, though it's not in the spirit of this forum and is a very time consuming affair.
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Kevin |
8th Jul 2014, 1:33 pm | #5 |
Rest in Peace
Join Date: Oct 2006
Location: North Wiltshire, UK.
Posts: 638
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Re: McMurdo Valve Bases
What a good idea. The B7G bases in 1.4 volt portables seem to be the most unreliable possibly due to something coming from the batteries. I have changed a lot of single contacts and a few whole valve bases which can be a pain.. The larger bases, like octal etc. seem to be better.
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