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Sets, Parts and Service Information Wanted (private buyers only, no swaps) If you need help obtaining components, sets or equipment, post a message here. Private buyers only - no traders. No swaps.

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Old 27th Aug 2019, 3:00 pm   #1
telstar
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Default Volume control and d.p mains switch

I am in the process of restoring a Philips B3G97U valve radio, and have discovered that the volume control is faulty, the only time that I get volume is at the top end. The device does not seem to respond to switch cleaner, and from what I have read on your site it seems that others with this set have experienced similar problems.
I do not have any controls this length of shaft or value (2M log I believe?), nor do I have tap and die facilities to make the hole for the grub screw. Does anyone have a suitable control ready for the repair, please?
Cheers
Mike
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Old 27th Aug 2019, 3:31 pm   #2
Jon_G4MDC
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Default Re: Volume control and d.p mains switch

This is a probably a break in the carbon track near the top tag (where the control does work).

Some say you can cure it with silver loaded paint. Paint across the gap which must be say somewhere in the last 2-3mm. Once connected you will probably never need to turn the wiper that far again...no danger of scratching it off.
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Old 27th Aug 2019, 9:33 pm   #3
cathoderay57
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Default Re: Volume control and d.p mains switch

Hi Mike, here's a 2.2M log pot with switch https://www.ebay.co.uk/itm/Switched-...-/361903936725. The shaft is too short so you'll also need a 6mm to 6mm motor shaft coupler which are available from Amazon eBay and other vendors. Then it' s simply a matter of cutting off the shaft from the old pot and fixing it into the shaft coupler. Hope that helps.Cheers, Jerry p.s. I notice the switch on this item has one set of contacts normally open and one normally closed and so you'd need to use it as a single pole switch but providing the live line in is the switched line that should not be an issue I'd have thought. If you're unhappy with that there are plenty of 1m log pots with switch available that have standard contacts and a 1M pot should do the job OK.

Last edited by cathoderay57; 27th Aug 2019 at 9:41 pm.
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Old 27th Aug 2019, 9:56 pm   #4
Biggles
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Default Re: Volume control and d.p mains switch

I might have one but need to have a look. What length shaft is required and what is the diameter of the pot body as I think mine may be the larger type, which may still fit if there is enough room.
Alan.
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Old 28th Aug 2019, 5:11 pm   #5
cathoderay57
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Default Re: Volume control and d.p mains switch

Here's a scrap chassis going for not much money: https://www.ebay.co.uk/itm/VINTAGE-P...kAAOSwXqddVox~
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Old 28th Aug 2019, 7:36 pm   #6
Biggles
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Default Re: Volume control and d.p mains switch

I have found three which might do the job. The NOS RS one measures about 3M despite being "brand new out the box". I have two used ones marked 2M, the nearest one to the right value measures 2.2M. I doubt whether it will make much difference in circuit. They all have DPDT switches which check out ok continuity wise. You are welcome to the one of your choice free of charge, if you think it will be of use.
Alan.
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Old 31st Aug 2019, 4:04 pm   #7
telstar
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Default Re: Volume control and d.p mains switch

Hello Alan.
Many thanks for your replies.
I am just in the process of measuring the control out (lengthwise). It looks to be quite some length. Do they have the screw holes for the knobs, please?
Cheers
Mike
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Old 11th Sep 2019, 3:24 pm   #8
telstar
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Default Re: Volume control and d.p mains switch

The control really needs to be round and not "D" shaped, and have the threaded M3 hole for the screw to secure the knob to the shaft (passing through the shaft).
Cheers
Mike
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Old 11th Sep 2019, 4:10 pm   #9
Diabolical Artificer
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Default Re: Volume control and d.p mains switch

I've looked in my small diminishing stash of switched pots and don't have anything, sorry. There seems to have been a lot of requests for these recently.

Needs to " have the threaded M3 hole for the screw to secure the knob to the shaft (passing through the shaft)." Easy enough to drill a small hole Mike, start with a centre punch, small drill then drill to finla diameter.

Andy.
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Old 27th Sep 2019, 9:41 pm   #10
hillmanie
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Default Re: Volume control and d.p mains switch

Quote:
Originally Posted by cathoderay57 View Post
I notice the switch on this item has one set of contacts normally open and one normally closed and so you'd need to use it as a single pole switch but providing the live line in is the Iswitched line that should not be an issue I'd have thought..
--------------------------------------------------------------------------------
Pricked up my ears at that as I'm considering changing a doublepole pot to switched live only because one of the poles has gone open circuit
TT
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Old 27th Sep 2019, 10:20 pm   #11
cathoderay57
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Default Re: Volume control and d.p mains switch

Hi TT, I'd like to qualify my previous statement. It is unarguably always safer to use a double pole switch if reasonably achievable. However, there is not always sufficient chassis space, shaft length or shaft diameter to find exact replacement switched pots. Second best is to use a single pole switch ensuring that it is always the live line-in that is switched if the set is AC only and has a mains transformer and that in an AC/DC "live chassis" set the live line-in goes via the single-pole switch to the top of the series heater chain and the un-switched neutral line-in is connected directly to the chassis. Also always worth checking that the polarity of a 13A socket outlet is correct because reversals are not unknown. I've also come across AC/DC sets with a single pole switch between chassis and neutral line-in, which means the chassis is live with the set plugged in and switched off! Cheers, Jerry
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Old 28th Sep 2019, 5:44 am   #12
hillmanie
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Default Re: Volume control and d.p mains switch

Quote:
Originally Posted by cathoderay57 View Post
Hi TT, I'd like to qualify my previous statement. It is unarguably always safer to use a double pole switch if reasonably achievable. However, there is not always sufficient chassis space, Cheers, Jerry
.................................................. ..........................................
Thank you Jerry, agree on all points. I intend to swap so that the live is switched. Although - I have repaired these many many yrs since. Plug polarity is of course the starting point, easy enough with the 3 pin plug but a different k. of fish in the old days of '2 pin and side earth ' Then you put a polarity mark on your TV plug since most TVs were AC/DC and I have been known to handle a live chassis. Was in the days when I bought a 1s TV each weekend at one of many jumble sales, Scouts being best. Many were stripped and dumped because of too expensive LOPT failure. Could yield up to 20 valves though. If I got one going I'd get 1 ten shillings or two pounds from the local newsagents' notice boards. New TVs cost 3 months wages. I didn't get rich except in valves.
Regards
TT
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