Marconi CR100 - £30 bargain

[AmateurRepairer]

Thanks uncle Bulgaria, I’m planning on swapping the part if anyone wants it, it doesn’t need much, only cleaning and the glass sliding in.

Oh it was blown anyway I think haha, all black around the top and bottom. I’ll look in the owners manual and see what it is, no doubt they are £15 a pop knowing my luck lol.

[AmateurRepairer]

P.S on the subject of nuts bolts etc, I’m blessed to have a photographic memory due to my aspergers, so I can more or less know where a certain length screw or whatever goes. Very useful

[Radio Wrangler]

Originally Posted by AmateurRepairer

Is this what my set should look like, If so I’m more than willing to swap the S meter with someone who needs it in return for the missing parts I need, if anybody would like and has spares lying around?

THere were versions in that family both with and without S meters.

A lot of amateur radio people and shortwave listeners in the fifties and sixties cut big holes in the front panels to add them to those which lacked them.

A working S meter is rather nice to have. The better your AGC is working, the less well you can peak a signal by sound. And if you want to remove the meter to have the set in original condition, you'll be left with a huge hole in the front panel, probably with a rather rough edge. If you make a blanking plate for the hole then that won't look original either so you may as well stick with the meter.

I have in the past made blanking discs for non-original holes in panels and welded them in. It's a lot of work doing tiny TIG tacks and waiting for each to cool. This is needed to prevent the panel warping. Then there is all the work of sanding and repainting the panel. It can be made invisible on the outside but the work involved is only justified for something very special, and there the lettering is engraved so it can be re-filled after the paint-job.

You could do a panel swap with someone who wants an S meter.

David

[cathoderay57]

Time for a reality check, I think. Unless you have considerable experience of restoring vintage electronics you are, with respect, going to struggle getting a receiver such as the CR100 working properly. You've already discovered that it can be difficult to remove the valves; as already stated, you should pull them by gripping the black valve base ideally, but because of the metal screening skirts around the bases of some of the sockets this is not always possible. However, that is the least of your worries. Some, if not all, of the 0.01uF or 0.1uF metal cased capacitors right at the top of the coil box below the chassis are likely to be leaky and unless you replace them the set is unlikely to function satisfactorily. Dismantling the coil box can be done but is not a task to be undertaken lightly. Once you have replaced the necessary capacitors you will almost certainly need to realign the receiver. Unless you have a signal generator and frequency counter that process is not going to end well. I'm sorry if this appears negative, but I just wanted to make you aware of the complexity of the task you are proposing to take on. That said, with patience, advice, the right test equipment and a lot of time, you might get there. If it were me, I would put it to one side for now and tackle a couple of simpler radios to get your eye in. Best of luck! Jerry.

[dave walsh]

By the time you have the set looking pristine Martin that meter may look totally original. Circuits to add an S Meter onto WD gear ranged from relatively crude to sophisticated ie just measuring current or some form of balanced bridge for sensitivity. I recall an article illustrating several methods somewhere. You'd do better to hang on to yours and find out later. Missing parts might appear anyway, knowing the generosity of Forum members and enthusiasts in general! Despite the wiring issues it might well be a useful addition and there wouldn't be an ugly hole to "spoil the ship" [recalling the Naval background] as David said. The red switch will be easy to replace with something more appropriate by contrast!

Dave W

[HamishBoxer]

If all the lead are there that can be resoldered and fixed back to the valve base.

[cmjones01]

Originally Posted by AmateurRepairer

Oh it was blown anyway I think haha, all black around the top and bottom. I’ll look in the owners manual and see what it is, no doubt they are £15 a pop knowing my luck lol.

Black around the top and bottom is a good sign, and generally means that the valve isn't "blown". The black smudges are the leftovers from the getter, a bit of metal inside the valve which absorbs any impurities in the vacuum. If those black marks turn white, the valve is no good any more because the vacuum has been lost. Black is good.

With care, it may be possible to reattach your valve to its base by resoldering the wires to the right pins and then cementing the glass bottle back on to the base.

I think the CR100 uses valves which aren't considered desirable by the audio world, so they're unlikely to be too expensive to replace, though because they're 1930's Marconi ones they might be a bit harder to find.

Chris

[turretslug]

Apart from the U50 and KT63 that is! Though the 5Z4 and 6V6 may well be found in sets that have survived this long. Other than that, the signal valves are still to be found pretty easily and inexpensively. There is a lot in a CR100 relative to domestic sets, but it's all standard stuff repeated, as it were. A CR100 was the first valve radio I overhauled from bare chassis up and it worked from switch-on. Good luck with it,

Colin

[Graham G3ZVT]

Here's a sobering thought, when I was interested in these boat-anchors in the late 60s, some of them only just qualified as being Vintage by the standards of this forum.

A CR100, AR88 or R107 etc had a good chance of working as soon as you got it home and plugged it in. Nearly 50 years have elapsed since I sold my R107...

[Graham G3ZVT]

Originally Posted by AmateurRepairer

Oh hell, pardon the french, what have I just done here, just pulled this thinking it was a valve. Have I FUBARD it or can it be fixed?

Which position (V number) did it come from?


If none of the wires have sheered off at the glass pinch, and the glass hasn't cracked, then the valve is repairable with a bit of fiddling.

We better catalogue those Soviet equivalents to make sure they are suitable.

[AmateurRepairer]

I’m sure it was V.10 Rambo.

Yes I appreciate this is a gargantuan task for only my second restoration, but I got my PYE vhf 2d running without replacing any parts, only exceptions being a couple of valves and I did solder one broken wire. It now runs satisfactorily, getting ****** sound is another thing

This is what my set would have looked like in ‘45, it’s just a case of swapping the component, no need for T.I.G welding (hope not). I’m dropping the chassis tommorow and I’m going to wire brush the rear with my big drill and wire brush attachment. The front is going to be repainted by a friend in the automotive industry, in Land Rover marine blue. Not exact but it’s a generic paint. The navy would have stuck anything on it, especially in war.

I just need the replacement gauge for the top left as the one previously fitted was an American unit, it’s ******** though, so off to the scrap pile it goes.

Thanks for the clarity on the valves blackening etc, I’m new to this.

[AmateurRepairer]

Catheroderay57 -

I bought this set as a half finished project, the guy had previously replaced quite a few of the caps during its previous working life with him in the North Sea. I also believe he had it realined afterwards - although that would have been the late 80s so I’m not sure. It had been sat in the guys shed since 2002 ish so I have no idea if they are fubard or not. I’m guessing there fine as it was a warm dry insulated shed. He had worked on it slowly over the years but he realised he had no use for it in the end. Apart from a few wires needing soldering, rebuilding the fuse pin and repainting there appears to be no issues electronically or mechanically.

I appreciate your concern about the level of difficulty, I like a challenge and always have done.

[AmateurRepairer]

Just found this in the bottom of the chassis, looks like it never had that meter in the top anyway, so I guess I’ll have it welded then fill and sand and have it repainted. Does anybody have any recommendations for replacement 3 pin plugs as the one supplied was broken. Thanks

[AmateurRepairer]

Here is the schematic.

[AmateurRepairer]

Apologies for the repeated postings. I think rather than fill the hole which is just hassle and money for me, I’m going to put a correct looking speaker in place of the hole. It’s not massive but it doesn’t need to be. Then I will probably dug out an old pc fan cover and paint it the battleship grey colour, I’ll just have to wire it up to the terminal block so on the back.

[Radio Wrangler]

Not all CR100 were blue. Plenty of them were plain old battleship grey. Either colour would look original.

On the surplus market and at amateur radio rallies, the CR100 was never an expensive set so once some semblance of normality returns, you could always pick up another in order to get an unmolested front panel.

Another way of looking at it is that the set has spent >90% of its life on civvy street and that S meter is part of its life-story now. Finding a working WWII era meter in that case style shouldn't be too difficult.Whoever fitted it was right about one thing, having an S meter on a shortwave receiver does make them a lot nicer to use.

Back in the 1960s, I saved up pocket money for years (and Christmas/birthday present money) until I had enough to buy an AR88. It was a rather sorry looking example with the black wrinkle paint a dirty mess. The previous owner had tried cleaning the tuning scale and some of it had come off... so he'd sketched it in - in Biro! Mum wasn't too keen on the outside finish, but didn't say anything, knowing what it meant to me. I took a hint and pulled the case and front panel off. They went away to be shot-blasted and stove enamelled. The local enamellers didn't do wrinkle paints, so I chose silver hammer. It looks gorgeous, but totally non original. Mum was happy, and while it was apart I'd sorted a few issues. I had a great receiver.

Many years passed and I saw something on an American website. They were collecting the histories of AR88 receivers around the world. I found out that mine was a very early example. The front panel was engraved, not screen-printed. The tuning scales were all-yellow background, not alternating yellow and black. It had the very rare original S meter from new. Lots of little details, and a low chassis number. I'm now torn. Part of me wishes I'd found somewhere to re-do it in black wrinkle, the other part of me thinks there's a lot of me in that set and I like the silver hammer. It's been that colour for most of its life, now.

It's a question with no right answers. The CR100 is your radio now. Yours to do whatever you wish with. Neither it now my AR88 are any longer cutting edge machines, so maybe they'd be better in original trim? But they are also examples of what people did after peace broke out.

David

[Bazz4CQJ]

I'd suggest that what you do in terms of 'restoring' it depends on whether;

• you want a useful receiver or
• you want something that's historic and 'interesting' to look at, but not very useful.

The facts are that (i) it's already been got at (ii) it will need a lot of its old parts replacing, so it will be even more got at, and (iii) it's not particularly rare or valuable.

Personally, I would lean towards an outcome based on functionality. I certainly see the S-meter as a useful asset. In earlier eras, there would have been many people who did very useful mods to CR100's (findable in old mags) to achieve good improvements (and perhaps a few less-good improvements). If it was in better and more original shape, I'd say keep it original. But as is, I'd take a relaxed view about what CR100's used to look like and think more about moving toward something that could be a useful radio.

B

[G3PIJpeter]

Originally Posted by Bazz4CQJ

I'd suggest that what you do in terms of 'restoring' it depends on whether;

• you want a useful receiver or
• you want something that's historic and 'interesting' to look at, but not very useful.

There's an interesting refurb blog at
http://chavfreezone.me.uk/2020/refur...g-a-cr100.html
which indicates what you might be letting yourself in for. I've renovated a couple of HROs to get them up to original working spec but they are perhaps easier to work on than the CR100.

Peter G3PIJ

[Radio Wrangler]

You can lose yourself for a good amount of time in Ian's 'chav free zone'! He is one of the most experienced restorers of the RA17 family and later Racal receivers there is (He's ex-Racal) and that CR100 rebuild is fully up to his standard.

David

[AmateurRepairer]

Can anybody reccomend a good speaker to retro fit? Preferably 4”