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Old 24th Dec 2007, 12:03 am   #1
Silicon
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Default Mains Lead Upgrade

The Cossor Melody Maker model 500/501 AC (1954) I am working on has 2 core ‘bell wire’ for the mains lead.
It may be original since the hole in the chassis and the gap in the back board don’t line up. Any replacement cable will have to do an ‘S’ bend to exit the rear of the radio.

If I don’t modify the chassis I will need a slim flexible cable. The heat resisting white EPR/CSP ‘rubber’ flex might work.
Alternatively I could drill a hole in the chassis and use a PVC or vulcanised rubber flex. Were mains flexes of this era normally black PVC?

Is there a neat way of fixing the cable so that it won’t pull out of the radio (an alternative to tying a knot in the cable)?


Further info (not relevant to the above questions):
This model is fitted with Cossor B8a valves 62TH, 62VP, 62DDT, 67PT & 66KU. The ‘Dial’ window is marked ‘501’ but the rear panel is marked ‘500 A.C.’
It works on SW and MW at the moment. LW needs attention. I greatly reduced the excessive background hum by replacing the wire going to V3s grid with screened cable.
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Old 24th Dec 2007, 1:16 am   #2
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Default Re: Mains Lead Upgrade

If the rubber flex will work, use that. Take off the bell wire as it is now illegal. Make sure Live and Neutral are the right way round though. Don't drill holes in it, if you must drill holes do it in the back not the set!

I think you've got a set made out of two there!

As for the other fault, you'll get the circuit up top there. Check that the Wavechange switch is clean, and go on a capacitor hunt around the oscillator stage. C13, C15 spring to mind.

Cheers,

Steve P.
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Old 24th Dec 2007, 1:32 am   #3
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Default Re: Mains Lead Upgrade

Quote:
Originally Posted by Silicon View Post

Is there a neat way of fixing the cable so that it won’t pull out of the radio (an alternative to tying a knot in the cable)?
Use a zip-tie (Ty-Wrap) so that the lead won't pull through the grommeted hole. On my 'Melody-Maker' I used a small plastic 'Insuloid' cable-clamp mounted on one of the transformer fixing-bolts, in addition to a zip-tie.

Incidentally, I used black 3-core 5A PVC cable, and it doesn't look out of place. You could always try some of the gold-coloured cable and see what it looks like.
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Old 24th Dec 2007, 11:05 am   #4
kalee20
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Default Re: Mains Lead Upgrade

Hi, I also have a Cossor 500. The cable exit hole on the chassis and the rear cover slot don't line up on mine either!

The original cable was originally secured with a knot inside the chassis (very inelegant). At the risk of some originality, I enlarged the hole in the chassis so that it would take a screw-in cable gland - this then clamps the cable. I then made a 7/8" hole (positioned so that it DOES line up) in the rear cover, using a brace and auger bit. Finally, I extended the original slot to intersect the new hole, with a sharp scalpel. Now, the back can be slipped into position - there's no nasty S bend required in the cable, and no strain on the back as a result of the S bend if somebody ever pulls the cable taut

See attached photos - I don't have one on file of the assembled back, but you should get the idea.
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Old 24th Dec 2007, 12:02 pm   #5
'LIVEWIRE?'
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Default Re: Mains Lead Upgrade

You could also use one of those 'clamp grommets' that are widely used in commercial equipment to secure mains leads, etc. They are available from suppliers such as CPC. Not 'vintage' maybe, but they ensure that the mains lead is safely & securely held in place
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