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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 19th Jun 2019, 5:15 pm   #1
mark2collection
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Default Cossor 501AC 'Melody Maker'

Known in our house as ‘The Snowman’ set, owing to the title of Raymond Briggs festive film from my childhood, where such a set makes a brief appearance. The film, introduced by David Bowie, twenty seconds in, and there in the attic, left of David, a Cossor Melody Maker.

Having always liked the idea of such a set & long before I was into radios, how did I ever buy one, not knowing which make or model to seek? eBay! Whilst looking for a British set to revive, at the bottom of the screen some pictures of other sets under the ‘you may also be interested in these’ banner. Sure enough, I recognised the set immediately, this also gave me a make and model number to go by.

Many years later, after seeing these sets sell for more than I was willing to part with, or typically, too far away to collect and not wanting to risk postage, one was finally listed and was only a short drive away, another bonus being, the sole bidder.

The set belonged to the sellers’ mother; she had it from new and was used up until the mid-60’s, where it was then placed in a cupboard, only seeing the light of day again in 2017. The seller didn’t recall any previous repairs, but as he said, he was only a small boy back then but remembers the set being put to good use in the kitchen.

Quite possibly the fluffiest chassis ever to grace the bench, it had indeed been ‘preserved’ by cooking oils, plus a good layer of fluff. The only non-original part, the dial lamp, which being rated at 12 volts, was incorrect for the set, but would have lasted many years more!

First things first, remove the rear cover & check all the coils (including the ‘speaker) plus transformers for continuity, then onto the switches, resistors and capacitors. The mains lead was original, but dangerous & leaving debris all over the bench. Removing the mains lead from the set revealed the lead was dead-short, as the internal rubber insulation had failed in a number of places. Checking the chassis over proved the set was a worthwhile repair, thankfully, the cabinet was cosmetically complete too.

Whilst the HT capacitor was reforming, which came back remarkably well over a period of a few days, the cabinet was given a buff outside, with a jolly good going over inside, and the four knobs needed a stiff brush to remove grime from the knurled bits. The bezel, which is out of shape and was very loose, amazingly the remaining spire clips were either amongst the fluff, or attached to the speaker magnet. Once the cabinet had been cleaned, the bezel was secured with the original spire clips plus a spot or two of Araldite, to ensure security.

The speaker cloth was a mess, not only did it have some holes, but had over the years ‘absorbed’ the kitchen atmosphere. Cleaning just made things worse. The only answer was to re-cover. Looking around, ended up at Dunelm where they had some cushions knocked down to £4, sure enough, the speaker cloth of my Melody Maker came from a cushion.

With the cosmetics coming together, I ventured into cleaning the dial glass. Having the voices of other people’s experiences with such things, the outer side of the glass had to be cleaned with Cif, as it was caked in grease; the inner part had a light film. Trialling an area of the dial glass which goes un-noticed when assembled revealed ‘optical instrument cleaner’ from RS removed the film, but not the silk-screen! Phew … the correct lamp now fitted too. The whole chassis at this point was then given a good dusting off, but I left the light oily film, which has protected the internal metalwork very well over the years.

Time for a temporary mains lead, the original output valve grid-coupler removed & a modern replacement ‘tacked’ into place, slowly with the Variac-volts the set crackled into life, hmmm. Powered down, then used some switch cleaner on the potentiometers, the waveband switch, valve holders & gave the valve pins a good clean until shiny, the reward for this was glorious sound on all wavebands, well, glorious in that we had sound at all, albeit, quiet and distorted.

Checking around against the datasheet I have, showed a number of supply lines were down, owing to resistors going high, the 25uF output valve capacitor being leaky plus the rest of the waxies acting more like resistors. Being original waxies, I decided to re-stuff them, madness I suppose, must be the solder fumes!

By the time I had replaced the out-of-spec resistors (all 4 of them) and re-stuffed the waxies, the new mains lead had arrived, which closely matched the original. Not happy with the security arrangement of the original mains lead, I made good use of the available hole next to the mains lead entry point, and secure the new lead with a P-Clip.

Other modifications include:- silver tape down the sides & along the bottom of the dial glass, to ‘bounce’ the light around a bit more, capacitor across the power switch to remove the ‘pop’ through the ‘speaker when switching off and spots of Araldite to better-secure the bezel.

All in all, a pretty easy-going repair, lots of elbow room, no live chassis to worry about and the alignment is so good, it’s not worth trying to re-adjust.
The set has been used regularly since the work and performs pretty well, all the better when used with a long bit of wire. The restoration came together rather quickly in the end.

Some photos to following, painting many more words.

Mark
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Old 19th Jun 2019, 5:17 pm   #2
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Default Re: Cossor 501AC 'Melody Maker'

Last photos, but not least ...
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Old 19th Jun 2019, 5:52 pm   #3
Wellington
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Thumbs up Re: Cossor 501AC 'Melody Maker'

That's come up really nice, Mark . I particularly like the new speaker cloth. Also, it was worth restuffing those caps, I think.
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Old 19th Jun 2019, 8:03 pm   #4
Lloyd 1985
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Default Re: Cossor 501AC 'Melody Maker'

Very nice! I’ve got a similar set, the difference being the bezel is actually part of the cabinet moulding and just painted cream! My uncle also has one for sale, but he wants 20 quid for it and it’s in poor condition.

You were very lucky with the print on the dial!! I still remember the horror when I cleaned one with glass cleaner and most of the print came off! Certainly never did that again...

Regards
Lloyd
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Old 19th Jun 2019, 10:32 pm   #5
kalee20
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Default Re: Cossor 501AC 'Melody Maker'

Well done! I have a 500ac, same chassis but wooden cabinet (actually, there are different versions of the chassis, yours has B8A rimlock valves, mine has B8G loctals).

Sound quality is good in this set, but sensitivity is mediocre. It needs a good aerial.

One point: the mains transformer in mine went kaput, shorted turn symptoms, heat and smoke. I rewound it, but it may be a weakness in the design or materials. So don't leave switched on, unattended.

Last edited by kalee20; 19th Jun 2019 at 10:33 pm. Reason: Typo
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Old 20th Jun 2019, 3:57 pm   #6
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Default Re: Cossor 501AC 'Melody Maker'

Thank you for your kind words gentlemen, and the timely reminder from Kalee20 about not leaving sets unattended.

I'll keep an eye on the transformer, although there is evidence of some wax seepage, it appears not to be recent. After a few hours of running, it's mildly warm to the touch.

Below, there should be a PDF scan of the dial glass, which may be useful should anyone wish to reproduce. It's not perfectly clean, as I feared any cleaning would remove the text, luckily, it hasn't and I didn't want to push my luck

Printing the attached onto A4 acetate(?) should produce a fair result.

Mark
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File Type: pdf 02 Cossor 501AC Dial Scan Post-Clean.pdf (218.6 KB, 44 views)
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Old 20th Jun 2019, 8:51 pm   #7
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Default Re: Cossor 501AC 'Melody Maker'

A superb job Mark ! It looks fantastic, I would never guess the speaker cloth came from a cushion! Its a very good replacement.

Rich.
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Old 23rd Jun 2019, 2:45 am   #8
batterymaker1
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Default Re: Cossor 501AC 'Melody Maker'

That set turned out sharp!
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Old 23rd Jun 2019, 12:56 pm   #9
dave walsh
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Default Re: Cossor 501AC 'Melody Maker'

Thanks for the thread Mark. I've got one of these-donated by a Form member about a decade ago. Cosmetically pretty nice [although the speaker cloth is not as good as yours of course]. It's mainly been a display item but a quick check last night indicated it's gone a bit buzzy, the tuning mechanism is a little wonky and there is a tendency towards overheating so I will keep an eye on "that" transformer [having been pre-warned by Kalee20 and yourself]. Anyway, I've now got a restorers guide to hand as and when I get round2it

Cheers,
Dave
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Old 24th Jun 2019, 10:07 am   #10
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Default Re: Cossor 501AC 'Melody Maker'

Well done on a superb restoration! I'm half way through a woody with the same chassis and I've been feeling torn about the waxies. Yours look great, how did you do them? I was going to scan the dial glass but I don't need to now!
David
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Old 24th Jun 2019, 1:09 pm   #11
mark2collection
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Default Re: Cossor 501AC 'Melody Maker'

David,

Once the waxies had been removed from the set, I placed one leg of each in a vice, & heated with a hair dryer to soften the outer wax coating. Some of the outer wax landed on the vice, the rest wiped off the capacitor body with an old cloth.

With a scrap bit of wood, around 4" x 2" and around 10" long, I laid the capacitors (one at a time) along the wood (writing facing away from me), placed a steel rule along the edge facing me, then with a Stanley knife, gently cut along the capacitor body. (The capacitor being clamped by my free hand between the bit of wood and the steel rule).

Once through, gently open the outer paper sleeve and remove the contents. (These original Cossor waxies have end-caps, some with eyelets where the legs were also soldered, another just had end-caps but no eyelets).

I then placed the new capacitor inside the paper sleeve, slipped the end-caps on, soldering where required and using contact adhesive along the cut, then held the capacitor together over night with clothing pegs.

When it came to refitting to the set, the cuts are hidden from view with the label proudly facing outwards.

Looking back, I should've used the wax gathered on the vice and resealed the end-caps.

Thanks again for the positive feedback guys, the sets being put to good use.

Mark
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Old 24th Jun 2019, 7:58 pm   #12
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Default Re: Cossor 501AC 'Melody Maker'

smashing bit of lateral thinking with the grille. I like the cossors, just unusual enough to be interesting but not rare enough to be silly money. Might have to pay a visit to a certain soft furnishings shop this weekend!!
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