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Old 8th Oct 2011, 4:05 pm   #1
PaulR
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Default Marconi 559 restoration.

I have a few pre-war short superhets and wanted a more expensive example. Finally I saw a fairly rough looking Marconi 559 advertised on ebay. Luckily it was in St Helens which is quite local. My son works in St Helens and agreed to pick it up for me. It has 5 valves plus rectifier and tuning indicator so maybe it could be described as a long superhet!

When it arrived I could see that it wasn’t exactly a fine example of its type and to be fair it wasn’t advertised as such. The veneer around the curved edges was lifting and the chassis was very dirty and showed signs of damp. It has clearly seen a lot of use over its long life and the leads to the inevitable pitch block had been cut with replacement Radiospares electrolytic capacitors dotted around the underside of the chassis held on with insulating tape. The valves are all Octals although the Trader sheet showed 7 pin types. Fortunately they all tested ok with the exception of the Y63 tuning indicator which had no emission whatsoever.

I removed the chassis in the garden in view of the amount of dust and dirt on it and brushed it as clean as I could.

There was no question of applying mains in view of the overall condition so I tested the mains transformer for resistance which seemed OK, removed the valves and applied mains to it via a lamp limiter. I got a healthy amount of HT and the correct heater voltages so I assumed that the mains transformer was basically working. The output transformer tested correctly for resistance as well, but the insulation crumbled as I moved the leads. The mains energised speaker has been replaced by a permanent magnet one at some time but the field coil had been retained as it acts as a smoothing choke.

If it was to look remotely good when finished I was going to have to paint the chassis and try to clean up the rest. I therefore removed the tuning capacitor, noting that the rubber grommets were in as new condition, and took the covers off the IF transformers etc. I carefully masked the rest and sanded the rusty chassis with emery paper. I then sprayed on a coat of primer followed by two coats of silver metallic paint. The aluminium cans cleaned up well with a Brillo pad. A friend offered to put the tuning capacitor through his dishwasher and, never having tried this before, I very pleased with the results. Fortunately this set has a friction drive for the tuning set up and a chain (!) drive for the wavelength indicator so there was no rotten tuning cord to replace.

I decided to re-stuff the capacitor can so I made sure that SWMBO was out of the way and heated it up sufficiently to pull the old innards out – never a nice job! I got a piece of thin ply wood to fit inside and screwed tag strip to this. I don’t know where others get tag strip but this was disappointing quality as the terminals easily pulled out of the paxolin strip. I then soldered the replacement capacitors to this and found correctly coloured leads from an old computer power supply. The whole thing then slid into the can which I has also painted silver and this was screwed back onto the chassis.

With the exception of the output transformer leads which I re-insulated with heat shrink most of the rest of the wiring was in good condition so it only remained to replace all the wax capacitors and out of spec resistors. I then re-built the chassis with the cleaned up tuning capacitor and framework that holds the tuning dial etc in place. The mains dial lamp had long gone along with its wiring but the holder was still in place so I re-wired it and put in a sewing machine lamp which is small, sufficiently low wattage and gives a nice glow.

Applying mains for the first time brought lots of stations and lots of mains hum. I couldn’t find the cause of this so asked for help on here. It turned out that there is probably some leakage in the mains transformer which was causing this. It was partly cured by increasing the values of some of the smoothing capacitors and is within acceptable limits now.

I try to retain the original finish to the cabinet where possible and in this case the veneer on the front was in too delicate a condition to attempt to strip the finish. I rubbed wood glue into the flaking veneer as best I could and fastened it down with masking tape. The sides and top are solid wood. The condition of the sides wasn’t too bad but the top was beyond redemption so I sanded it down to bare wood and stained it. I cleaned up the rest and applied several coats of Danish oil. I then cut this back with Brasso and found that together with the wood glue it has secured the flaking veneer quite well. It will never be pristine unless some of the veneer is replaced, but in view of the original condition I am pleased with the results. The speaker grille is brass and was almost black. I was tempted to strip and re-polish this but I decided that it would make it too bright so I removed it and washed it thoroughly. It now looks clean but suitably patinated in keeping with the rest of the set.

Overall I am pleased with the results. The case was never going to be perfect but at least it is stable now and has polished up well with wax polish. The 50Hz hum is disappointing but has been greatly reduced. The performance is excellent and it was clearly a good set in its day. Since I bought it I have seen several variations at auction so it must have been a popular design. I haven’t yet bought a new tuning indicator for it as they cost around £25, but I think I may well do to finish it off properly.
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Old 8th Oct 2011, 4:28 pm   #2
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Default Re: Marconi 559 restoratione

I suspect a lot of the hum is due to the fact that the 'humbucking' coil has been dispensed with. I think it's part of the speaker. Whatever you do, don't increase the value of the reservoir capacitor as it will almost certainly damage the rectifier. It should be OK to increase the smoothing capacitor without problems.

It looks similar to this 557 https://www.vintage-radio.net/forum/...ad.php?t=19439 that I did way back in 2007.


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Old 8th Oct 2011, 5:11 pm   #3
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Default Re: Marconi 559 restoratione

I am not sure that the lack of a hum bucking coil will be the problem here as I think it is intended to cancel out the hum induced in the speech coil by the field coil. As they are no longer near to each other I assume there is no hum to buck as it were.

I see that your report mentions the variable capacitor tone control. The vanes in mine have warped and now touch each other. I assumed it would not work and as it is connected to the HT I disconnected it. I couldn't get any resistance reading across it, however. and so I tentatively reconnected it to find that it works perfectly. I have taken the precaution of putting a .01uf capacitor between it and the anode to be on the safe side
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Old 8th Oct 2011, 5:37 pm   #4
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Default Re: Marconi 559 restoratione

Smart looking result, there, Paul. I'm interested to read about the thought-processes you went through to decide what was an appropriate level of restoration/ cleaning, and what would be too much. This is always fascinating.

You must be very pleased - hope you can maybe sus out the remaining hum problem...
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Old 8th Oct 2011, 6:40 pm   #5
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Default Re: Marconi 559 restoratione

Quote:
Originally Posted by PaulR View Post
the variable capacitor tone control. The vanes in mine have warped and now touch each other. I assumed it would not work and as it is connected to the HT I disconnected it. I couldn't get any resistance reading across it, however. and so I tentatively reconnected it to find that it works perfectly.
I think these have a solid dielectric between the vanes so they will touch.


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Old 8th Oct 2011, 9:17 pm   #6
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Default Re: Marconi 559 restoration.

Nice job Paul. I am always impressed by the quality of those early Marconiphone sets.
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Old 9th Oct 2011, 1:19 pm   #7
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Default Re: Marconi 559 restoration.

Thanks all

I also have a classic car so the question of how far restoration/replacement should go arises there. Radios combine furniture and electrics of course and the electrics need to be safe as a priority. I don't re-stuff ordinary capacitors as I believe that modern replacements would have been used throughout the set's life and I am just continuing this. The replacements are part of the history of the set and add to its interest in my view. I have replaced the RS capacitors in the Marconi just as these were replacements of the original ones; it is all part of the continuing life of the set. When I can get modern versions of mulit-electrolytic cans I use those, but if I cannot then I re-stuff the original cans. This is to avoid the difficulties in siting replacements elsewhere in the chassis and to keep everything as intended and neat. Often is seems easier to empty out a can and re-stuff it than it does to find somewhere for replacements.

This was the first time I have repainted a chassis. It was in poor condition and most of the original plating had gone. if the chassis is in at all rasonable condition I would clean it up and leave it. The reasoning is that it is in this state after many years of use and that is interesting in itself.

I apply a similar thought process to the case. Unfortunately many suffer more than an ordinary piece of furniture of that age as the radio has become obsolete and stored in unsuitable conditions. I ask myself whether the condition represents fair wear and tear or whether it is more than that. I try to preserve the original finish if I can, but sometimes it is almost a relief to justify the removal of the old thick coloured laquer to reveal the wood grain underneath, which is often very interesting.

I think that a pragmatic approach is best and each set is different with different requirements.
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Old 10th Oct 2011, 3:56 pm   #8
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Default Re: Marconi 559 restoration.

Paul, A great job there. The set looks amazing, and it is almost identical to the one back at my parents - also Marconi. I will have to let you know when I get it up here to Manchester.
All the best
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Old 12th Nov 2011, 8:20 pm   #9
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Default Re: Marconi 559 restoration.

Thanks Steve. For a bit of fun I have put a video on You Tube of it playing a 78.

http://www.youtube.com/watch?v=NsXnhd_CT0M
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Old 13th Nov 2011, 12:40 am   #10
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Default Re: Marconi 559 restoration.

Very evocative sound, there!

How different does it sound using the modern equipment used for your Isle of Capri playing?
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Old 13th Nov 2011, 10:05 am   #11
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Default Re: Marconi 559 restoration.

Well done Paul. These are lovely sets, I restored one a while ago and it's now on display in Griptons Wireless Shop at the Black Country Museum.
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Old 13th Nov 2011, 10:54 am   #12
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Default Re: Marconi 559 restoration.

You can certainly tell the difference in performance between this set and my short superhets. The reproduction using a short range MW transmitter is outstanding considering its age and the standards of transmission at the time. I have noticed how many varients there are now I have this one so it must have been a successful design. It would be nice to obtain a field coil speaker for it but as it is oval I don't hold out much hope.

I have to say that the "modern" equipment which consists of a GL75 deck, Fisher valve receiver and Mordaunt Short speakers plays 78s superbly, much better than the blunderbuss pickup I used here, but it is nice to use original equipment sometimes. I had a small radiogram with a slightly later Garrard deck which still took ordinary needles and I thought that this gave better reproduction than the pickup in the video.

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Old 13th Nov 2011, 10:50 pm   #13
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Default Re: Marconi 559 restoration.

Paul, you said that you were waiting to buy a new Y63 magic eye, but it looks nice and bright in your YouTube video! It's worth fitting a bright eye to such a nice radio.

It appears that magic eyes had a life of around 1,000 hours. If you play your 559 sparingly, it should last a lifetime.
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Old 14th Nov 2011, 8:41 pm   #14
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Default Re: Marconi 559 restoration.

It is in fact a new magic eye. It is actually a 6U5G and went for much less than a Y63 would have done as I assume that nobody realised it is an equivalent. I was the only bidder. It had arrow symbols on the box so I think it might originally have been military issue. Anyway, it finishes it off nicely.

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Old 7th Mar 2012, 12:21 am   #15
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Default Re: Marconi 559 restoration.

PaulR, I also have an Octal version of the 559 which was purchased in February 1938 (I have the original purchase agreement). I have the B7 type valve schematic and service information (Trader No.605). The AF section works but the radio is not yet working correctly.

The valve found in the receiver are:-
V1 KTW63
V2 X63
V3 KTW63
V4 HL63
V5 6V6G
V6 5Z4G
V7 Y63

The green label originally stuck inside the wooden case has been ripped off. I can see U50 but no other valve information. The 5Z4G is an indirectly heated equivalent of the U50 and should work OK.
It is possible that unsuitable valves were fitted during its life in order to keep it going.

Can you please tell me which valves are fitted to your radio.
Is there any service information on the Octal version?

Many thanks
Brendan
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Old 7th Mar 2012, 11:13 am   #16
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Default Re: Marconi 559 restoration.

Very nice job Paul, I have restored a few of these and found they work and sound very good.
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Old 8th Mar 2012, 12:11 pm   #17
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Default Re: Marconi 559 restoration.

Thank you Vinrads.

Brendan - The valves in mine are KTW63, X65, DH63, 6V6G, KTW63. The rectifier is 5Z4G and the tuning indicator was a Y63 but I replaced it with a NOS 6U5G which works well. I believe from the previous owner that it belonged to her grandfather and was very well used. Many of the capacitors had already been replaced by RS ones, but this was a long time ago and I replaced them all again. I could not find any information on the Octal version, although plenty seem to have been made.

It is a really good set and it is a pity that the case has been damaged by damp storage in the past. I would very much like the radiogram version, particularly with an autochanger.

Paul

Last edited by PaulR; 8th Mar 2012 at 12:16 pm.
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Old 8th Mar 2012, 1:53 pm   #18
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Default Re: Marconi 559 restoration.

Thanks PaulR, it is reassuring to know that I have the correct valves.
The previous owners grandfather bought my set for £15.4.6 less £3.3.0 for trading in a K.B set. He was a bus conductor for L.P.Y.B!

I will check the mixer valve in my set.

Does the valve information on the green label inside your set match the valves actually installed?

Many thanks.
Brendan
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Old 8th Mar 2012, 7:38 pm   #19
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Default Re: Marconi 559 restoration.

Hi Paul have you seen the loudspeaker on eBay it maybe the one for the radio.
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Old 22nd Mar 2012, 8:25 am   #20
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Default Re: Marconi 559 restoration.

What a great restoration and write up! I keep looking at the before and after pics of the chassis in amazement.

Very interested in using a dish washer for cleaning the tuning capacitor. Made me smile with joy. I've been contemplating different soaking solutions or even ultra sound.. and the answer seems to be much simpler than I thought.
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