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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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15th Feb 2019, 8:36 pm | #1 |
Heptode
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 539
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Pye Q4 wavechange switch problem
I have a Pye Q4 lift up lid early transistor portable which works on MW but not on LW. I decided to investigate the problem today, I used another set to listen to the local oscillator (LO). It was evident that when I changed from MW to LW the LO didn't change frequency so suspicion immediately fell on the wave change (WC) switch. A look at the circuit and the wiring showed the contacts where the problem might be and a poke on the suspect contact with an insulated tool made the LW work. I have attached a photo of the WC switch with a ring around the problem contact. The problem is how do I close the contact gap above and below without a messy dismantling of the whole wafer switch assembly? Another point not helping is that mating face that the contacts should touch does not seem to project as far out as it should when compared with other parts of the switch assembly.
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Alan G6PUB, BVWS |
15th Feb 2019, 9:42 pm | #2 |
Nonode
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,386
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Re: Pye Q4 wavechange switch problem
Hi Alan, statement of the blooming obvious perhaps but have you tried a squirt of switch cleaner? Since the contacts are easy to get at you might try squirting some onto a cotton bud and gently wiping the contacts. Looks like there is a lot of oxidation there. It isn't usually a good idea to start bending the contacts as that can end in irreparable damage to the switch. Cheers, Jerry
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15th Feb 2019, 9:52 pm | #3 |
Dekatron
Join Date: Oct 2003
Location: Southport Lancashire, UK.
Posts: 3,236
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Re: Pye Q4 wavechange switch problem
I have recently tried a can of WD40 - no not the original stuff but quick drying contact cleaner and so far it works really well.
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Paul |
15th Feb 2019, 11:24 pm | #4 | |
Heptode
Join Date: Sep 2018
Location: Twickenham, London, UK.
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Re: Pye Q4 wavechange switch problem
Quote:
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Alan G6PUB, BVWS |
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16th Feb 2019, 1:09 am | #5 |
Heptode
Join Date: Feb 2006
Location: Marlborough, Wiltshire, UK.
Posts: 917
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Re: Pye Q4 wavechange switch problem
It is indeed sometimes possible to increase the bend angle on the contact fingers, using tweezers or pointed pliers. Go easy, using a prod of some sort to hold the rivet side of the bend flat. Check for loose rivets etc first. Bending does not work if the metal has lost its spring and there is a risk of breakage but I have had reasonable success.
Ken |
16th Feb 2019, 7:16 am | #6 |
Nonode
Join Date: May 2004
Location: Halifax, West Yorkshire, UK.
Posts: 2,587
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Re: Pye Q4 wavechange switch problem
Personally I wouldn't hesitate to try bending the contact and have done so successfully on a number of occasions. After all, how else do you deal with a bespoke wafer switch in a long obsolete piece of equipment? Also, there's not much to lose since the switch isn't working anyway. I would slip a darning needle under the contact arm and apply light pressure to the contact itself. Loose rivets can often be tightened with a small pair of pliers or even a carefully applied blob of superglue if access is a problem.
Alan |
16th Feb 2019, 10:34 am | #7 |
Nonode
Join Date: Oct 2017
Location: Bristol, UK.
Posts: 2,386
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Re: Pye Q4 wavechange switch problem
Replacement wafer switches are available but you'd no doubt have to figure out how to wire it and cut the shaft to fit etc. There's a 6-pole 2-way at Farnell here; that's just the contact set - the shaft and carrier assembly is extra so when you add it up it's fairly expensive. https://uk.farnell.com/nsf-controls/...-switch-wafers . Good luck
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16th Feb 2019, 11:13 am | #8 |
Heptode
Join Date: Nov 2017
Location: London, UK. Bury, Lancashire quite regularly :)
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Re: Pye Q4 wavechange switch problem
Gentle scrubbing with a fibreglass pencil followed by a few dabs of DeOxit.
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Thermionic Emission, warms the cockles of your tubes. |
16th Feb 2019, 6:21 pm | #9 |
Heptode
Join Date: Sep 2018
Location: Twickenham, London, UK.
Posts: 539
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Re: Pye Q4 wavechange switch problem
As I intimated earlier the problem is not one of cleaning but that the contacts are not touching the wiper. I have come up with a simple solution using part of a bent pin. OK it's a bit crude but it works. See photo.
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Alan G6PUB, BVWS |