Ferguson 104A

[Tedzed1]

Hello Joe, what a beautiful set, looks really nice and clean inside, should not cause you too many problems,
will sound really nice when completed, more use for that little micro transmitter that you built.
going to build mine this week if all the parts arrive.

[Yorkie]

Congrats on winning the set at the auction Joe!

An attractive set, with a large chassis which should be easy to work on.

Doubltess it will have been an expensive set in its day, in that it has several features which set it aprt from more basic radios of the era, in that it not only has short waveband, but also an RF stage, with a three section tuning cap and an additional valve to what was the norm, making six valves in total, including the rectifier. Intriguing that it has some invoices with it to show its history. It will have been one of the last radios released before the war in 1940 - shortly after that, it was the Civilian radio or nothing. The speaker is mains energised (before the war, the couldn't make permanent magnets with a powerful enough flux density I believe), so hopefully, the field coil (L21 - 1,500 Ohms), which also acts as a smoothing choke, will be intact. Field coils - being thousands of turns of fine gauge wire - are rather prone to going open circuit. Rather than go to the expense of a re-wind, some restorers remove mains energised speaker and fit a modern permanent magnet one, which of course destroys the integirty of the set. As was standard, it has a' hum bucking' coil (L20, which is just 0.2 Ohms, and the speech coil, 1.5 Ohms) - all three coils will be concentrically mounted on the speaker. The extension speaker socket seems to come straight off the HT line at the primary rather than secondary of the output transformer, and an extension speaker of 5000 Ohms is called for. No doubt you'll have studied the circuit and concluded that C25 (.02) and C27 (.005) are definite candidates for changing, come what may.

I wonder if you've taken a chance and plugged it in Joe? If it works, - if only after a fashion, you're half way there! Well worth spending some time on a radio from what was really, the end of the 'golden era' of radio design and production in Britain.

Best of luck with the restoration Joe - do keep us informed of progress!

David.

[Joe]

My plan had been to change THAT cap and then give it a go but after seeing the state that they are all in I'll do the lot. I'll certainly be working off the sheet as they are so discoloured that the values on the actual caps can't be read. I was rather pleased with myself when I identified THAT cap in the flesh, or rather in the wax, without looking at the sheet. The wiring looks OK as it's cloth covered rather than rubber.

   

It being a war-time set certainly make it interesting. It still has all the foreign names on the dial despite most of these been occupied at the time.

As to the speaker, I've had a quick poke around it with my continuity tester and not found anything alarming but will check that over properly before doing much else. It is a bit of a complication that all testing will need to be done through that one so till be putting some long temporary leads on it.

I'm certainly going to take my time on it and enjoy it.

- Joe

[tiv48]

jo. please change the wireing to the mains switch .this is a replacment and is deeper than the original so the contacts will be nearer the metal work so some heat shrink sleave over the connections wont go amiss
rob t

[Joe]

Thanks for the tip, Rob. Heatshrink is handy to protect my fingers as well as anything else. That bit will get re-done in any case as I'll be putting a fuse in it.

- Joe

[Joe]

Well, there's life in the beast.

As planned I had look at the speaker first as if that was u/s there wasn't a lot of point doing anything else.

The first thing I noticed was a bit of foam rubber jammed between the cone and frame which boded ill. However I've no done enough DAC90as to know about un-glued bellows and that's what's happened to this.

I couldn't make sense of the myriad coils or relate the circuit diagram to the real nuts and bolts. The best thing to do seemed to be to just test it.

I changed the two caps that Yorkie mentioned, though on my data THAT capacitor is C26. I hadn't got any 0.0047μF ones but have got 0.0022μF and 0.0033μF and space certainly isn't a problem.

When powered up everything glowed that should but nothing that shouldn't. It didn't actually play but at full volume there was a hum, though not a bad one, coming out of the speaker along with noise when the wave-switch was moved. I tried connecting my DAB radio directly (well direct save for a 0.1μF capacitor) to the grid of the output valve and it could be heard coming out of the speaker, albeit very quietly. I didn't leave it on for long as the lamp-limiter looked a bit bright.

As for the replacement volume pot/main switch, the contacts nearest the metal aren't connected. The fact it's a replacement probably explains the odd knob as the original wouldn't have fitted on the new shaft, at least not without modification thereto.

My next plan is to have a go at reforming the smoothers and then change some more of the small ones and see how it goes.

- Joe

[Joe]

I gave it ten minutes through a 15W lamp with all the valves out bar the rectifier.

I then cracked on with more re-capping doing all the ones around the output stage. The only problem I ran into was a needing a 25μF 25v electrolytic but I'd got a 32μF 450v one so that will do for now.

I thought it was time to test it again and after it had warmed up I touched the gram socket to make sure it wasn't live. This resulted in my getting a shock: not of the electrical sort but at the amount of noise which issued forth from the speaker. I connected my DAB radio to it and it seemed quite quiet and the sound quality was lousy. The latter though was down to the detached bellows and it sounded much better with those held in place.

I then saw if I could pick any stations up, without much hope at this stage but got things on all bands. I'll stick the bellows tonight so it can have a better test tomorrow. I'll also finish the re-cap and I haven't touched the cabinet yet.

Besides that it still needs a new mains lead, fuse and the wiring around the main switch needs attention. I've left that for now as I'm going to completely remove it so I can modify the end of the pot shaft so I can put the odd knob in the middle.

Oh yes: there's also the drive cord to do. I must have blotted that horror out of my mind. I'm worried because it looks like it'll be easy!

- Joe

[ucl82]

Nice work Joe and a nice looking set!

[Yorkie]

Well, there's life in the beast.

I changed the two caps that Yorkie mentioned, though on my data THAT capacitor is C26. I hadn't got any 0.0047μF ones but have got 0.0022μF and 0.0033μF and space certainly isn't a problem.
- Joe

Sorry for the confusion Joe - I was quoting from the ERT Sheet rather than the Trader Sheet, and the use different numbers for 'that' cap - C25 on the ERT Sheet - C26 on the Trader Sheet. (C27 is the same on both sheets - the one across the OPT primary). I should really have stated the source of data to save confusion.

Great news that the field coil on the speaker is intact - they're very prone to going O/C on mains energised speakers, especially if for some reason the set is drawing excess current as the field coil (L22 on ERT Sheet - L21 on Trader Sheet) carries the HT load for the whole set, doubling as the smoothing choke across the two smoothing caps.

Have fun!

David

[tiv48]

an exelent job so far
rob t