Marconi 858

[kevin.Hoyland]

Hello i have just started working on this Marconi 858 radio from 1938 it has LW/MW/SW. All the Capacitors are leakeing and are being change one at a time. The wireing in the set is poor so that will be the next job when i get it working. You can see from one of the photos that the radio is chain driven.

                   

Regards Kev.

[tiv48]

a fantastic looking set looking forward to your restore
rob t

[kevin.Hoyland]

Thanks Rob.
More Photos of the Marconi 858. One showing me testing the new capacitors on an Hunts CRB 3 tester.

                               

Regards Kev.

[Steve_P]

The thing with capacitor changing like this is that one mistake and you're chasing your posterior.

Replace 'That' capacitor, check for any shorts in the wiring and then hit it with full mains. Pre-war capacitors are generally not as bad as the 'Hunts' variety.

If you're a coward, use a variac. If you're a proper man, just go for it...

You may have a pleasant surprise!

Cheers,

Steve P.

[kevin.Hoyland]

Steve,
has i said in the first post all the caps i have taken out are leaking. When I started working on the 858 i had a good look all over it, then i put the Avo 8 on the Pos and neg pins of the plug and the reading was ok so the heater chain and the Transformer may be ok then i put power on to the radio by my lamp limitor all looked fine so then out came the Variac with time 240 volts were going in to the 858 but still no sound no smoke no bangs. Had a good prod all over the joints and parts still no sound so then started with the Capacitors takeing one out at a time and testing it and then replaceing it. And has i said i have taken 8 out and not a good cap in the 8. Steve has you can see on the photo C16/C23/C24/C30/C34/C47 are all in one block on top of the Chassis so i will see to this six one by one and see if i can get some sound out of the 858 and then report back.
Kev

[Geaney]

Fantastic looking set Kevin. I'll have to keep an eye out for one of them! That is one impressive electrolytic condenser pack!

Cheers, John

[kevin.Hoyland]

    Thanks John.
I have taken more capacitors out to day.
Kind Regards
Kev.

[Aerodyne]

It is a nice looking set, Kevin. Well worth restoring, I'd say. I know what Steve meant when he cautioned about changing caps - possibly he suspected you were going to do the lot at once and besides, often it isn't necessary to change more than the odd coupler - but with a set of this age plus unknown storage conditions, you are wise to check all and change any that appear suspect. Same with resistors but remember that valve circuitry is tolerant of quite wide 'drift' in resistor values - it is only in the case of bias resistors where things get a bit critical.
Many's the 1930s set where I've checked caps and changed only the faulty ones, only to find a week or two later that one or more of the apparently blameless ones have failed during running tests.
Tony

[Radio Fixer]

Yes! as others have said another good radio from EMI. I would restuff all of the wax caps in the chassis, some may not need it but as Tony said they can come back and get to you. These caps are particularly easy to restuff (more info on how I do it on request). Is it worth restuffing? To me and many a big Yes! as no hurry its a hobby and if it takes longer so what? Like model making the fun is in the doing, most dont play the radios much afer the initial newness wears off.

If you dont re-stuff can I have the old caps? Really happy to pay postage. Many of the radios I come across have the, to me, terrible yellow perils, naked in all their shame. I cant wait to get them out and obtaining period cases is getting difficult.

I would strip the slow mo drive to the tuning and clean and re-lube.

Enjot Gary

[Joe]

I've got loads of old waxies you can have, Gary.

- Joe