Eddystone 840C restoration.

[Kentode]

I picked this up at Golborne last November. It was basically working, with a little bit of hum, and picked up Talk sport so I went through the circuit diagram to decide what to check.
All the red hunts and electrolytics had to go, some of the other capacitors and some resistors, but the first job was the dodgy mains connection. Although it was a snap in type, I also glued it in with two-pack as the snaps were not fully engaged due to the thickness of the bakelite.
More to follow...

[Kentode]

Next l did the power supply side. R39 was replaced with a 5 watt ceramic, which brought the temperature down from 95c to 23c!

Moving on to the main circuit on the other side, l decided to change 4 or 5 components around a single valve holder and then replace the valve and power up to check.

I wrapped a big length of heat shrink around the wiring loom and hooked it out of the way to access V7

[Kentode]

I carried on around the valves, checking as l went. When finished, I'd made one mistake! The volume was being gradually wound back as the signal got better until the the last component! I'd run one end of R28 to the 18th tag on the strip instead of the 17th.

Now for the fun bit! When you take the cover off the coil box there are about eight more components that need to be checked/replaced. Before you can do that, the band change shaft and three coil packs have to be removed.

[G6Tanuki]

Good to see you have replaced those red and black Plessey electrolytics, after 50+ years they dry out and become about as useful as a urinal in a nunnery.

Working on the coil box of Eddystone radios is really not fun, I had to get down and dirty with the oscillator coils on my 840A to fix a spectacular error that had been there since it was made - the highest frequency range could never have worked. Eddystone seems to have had a distinctly lax approach to quality assurance...

Despite being really just a cheap and cheerful superhet in a posh looking box, the 840 series is kinda fun, I have my 840A as a bedside radio for listening around on the lower HF bands when insomnia strikes.

[Kentode]

Before I plugged in a small Antex iron I'd purchased especially for this job, I had to clean the band switching wafers which were black! I should have mentioned earlier that as each coil pack was removed, it was labelled accordingly to prevent head scratching later!

That's it! All it took was 10 pages of notes and sketches of component placement and order of removal/replacement, 92 photographs and 194 pages of PDFs from the Eddystone Users Group to change 37 components.

I also partially dissembled the dial drive mechanism as the friction wheel occasionally slipped during high speed tuning. I cleaned the inner and outer faces of the pinch-wheel clutch and both sides of the friction wheel with a small piece of cardboard soaked in Deoxit, adjusted the position of the flywheel to remove a small amount of end float and replaced the grease in the bronze bush. If you look carefully at the fourth picture you can just see the cardboard gripped by the clutch.

I quite enjoyed it, better than doing another Philips! Oh wait, I've got a Philips CD 104 on the bench next...

[60 oldjohn]

Originally Posted by Kentode

I carried on around the valves, checking as l went. When finished, I'd made one mistake! The volume was being gradually wound back as the signal got better until the the last component! I'd run one end of R28 to the 18th tag on the strip instead of the 17th.

Pleased you found the mistake, on some sets it can be a right pain. On complicated circuits I usually try the set after one or two component changes. Also it costs nothing to take plenty of pictures from slightly different angles, may not be needed, but once in a while you will be pleased you did.

Post crossed with the above, so you did take plenty of photos and notes, looks like you did the groundwork!
John.

[Kentode]

Actually, it was 50 components! Just reviewing my notes and annotating a circuit diagram for the next custodian, showing which have been replaced.

[G6Tanuki]

Great to hear you have got your 840C fully sorted. While they don't really fit the modern SSB era designation of a "communications receiver" they can still be fun to use for random tuning around.

I have the 840C's predecessor, an 840A, nicknamed 'Unsteady Eddie' on account of its frequency drift (despite fitting an 85A1 stabiliser to the LO supply) as my bedside radio for listening when insomnia kicks in. 03:00z can be interesting to listen around on MW and frequencies up to 6MHz.

[Sideband]

Not for the faint hearted! It's quite a job replacing those caps in the coilbox! I did mine about a year ago and I must say that even after a full realignment (it had been got at) I was somewhat disappointed with the results. At the moment it's sitting under my bench with the casing off waiting for me to find out why it's tripping the bench supply. I suspect it's one of the big ceramic caps coupling the chassis to the earthed outer casing but I just haven't mustered up the enthusiasm to sort it....

[AnalogueMan]

Nice job! I've go a soft spot for old Eddystones and it's good to see another one restored and working.
I did my 640 a while ago (written up in this section somewhere) and can only echo your findings. First, the coil box is not for the faint of heart but is usually where you end up going to get to the bottom of the problem. Second, take plenty of photos and make drawings before dismantling things, especially if taking the tuning mechanism apart or removing the front panel. You'll be so glad you did. And third, I too had a from-the-factory fault, buried in the depths of the coil box, that left me wondering how it had ever worked and what sort of quality control Eddystone actually had. So never assume things are as they should be, they well may be not.

[LyntonP]

Excellent and thorough work Ken.
Look forward to seeing you on Sunday.
Regards
Lynton