Wow, two impressive monsters there- widescreen radio? Both very nice sets but the T5001 is easier on the eye, the T898WK is a bit dour and monumental- though it probably has a less compromised AM section. I wonder how the scale glasses fare on these? Also how many survive today. Less suited to a domestic setting, but the Telefunken I'd like to acquire in wish-list land would be the E103, a fist-full of Rimlocks and all of the AM broadcast spectrum uninterrupted in one box, even a front-panel speaker- yet not that complex. Telefunken were big on turret selectors in their professional sets for some decades, I wonder how much the Murphy B40 (appearing as WW2 came to a close) and siblings were influenced by the German practices of sectionalised construction on light alloy castings and hefty turret selectors.
Not much done over the weekend, just rewired the scale lamps. I've taken the speaker and baffle out along with the tuning pointer guide which is sticky with dirty grease. I'll give the cabinet a good clean next and get that smartened up.
I wondered why they had used rubber wiring for the scale lamps and PVC elsewhere? (Similarly with the 462 here) One slightly straw-clutching idea I came up with was that maybe it was felt to be better at resisting the inevitable above-chassis heat convection and concentration but other than that I'm struggling, maybe they just had some rolls left in stores as the new-fangled PVC took over in production.
With its lack of tuning scale glass and a duff output transformer, I decided that the 462 here was a spares-only case- something I always have a bit of a heavy heart about about doing, even with those sets that were acquired as "breakers" in the first place! I suspect I'm not alone there. I unscrewed the scale bulbholders but as I did so, both disintegrated in a tumble of rivet fragments and insulating washers. Oh, well, kinda confirms that this set is abit of a basket case, hopefully the bottles, speaker and mains transformer are in a better state. Trouble is that with any particular set it's often the same things that go, so one can end up with a box full of duplicates and still no go. The 170A is on hold for the mo, I have loads of 100nF 400V and 630V in stock that would be entirely adequate but as Philips used 47nF originally throughout the RF/IF circuits, I'll play the game and do that, a fistful should plop onto the doormat in the near future.
The 462 is at least a little different from its usual 4 + R classmates in taking advantage of the ECH21's separation of oscillator grid and mixer injection grid to cut bottle count by combining IF amp and AF amp in one envelope- the ECH81 is well known for this feature but the ECH21 was an earlier example. It has a slightly interesting background in that I believe it was first devised as a B9G device as EF50 etc. but then went to Sylvania loktal, meaning that the cathode and g5 were connected to the central metal spigot as "9th pin". There is also a similar-but-different ECH22 that has oscillator grid and mixer injection grid internally connected- this was used in the Murphy B40 which ironically uses a separate LO valve, leaving the C in the ECH22 unused.
The only update I can offer at the moment is that I have a couple of new 47uf 500V caps (screw type) arriving from Germany. I could have re-stuffed the old ones but then found I'd run out of 47uF 450V axials so as I would have had to order some I decided I might as well order the rather nice screw types that Ask Jan First can supply new from stock. At least they will drop straight in to the holes in the chassis and it saves a messy job. I can keep the old ones for future re-stuffing.
One of the bulb holders in mine was in a delicate state but at least it stayed in one piece. Both lamps had failed and fortunately I have some of those tubular bulbs from years ago so now they are all ready to be refitted.
Update: The new screw type smoothing capacitors arrived today....not bad, a week to get here from Germany. They are shorter than the originals but saves a messy job. I'll keep the originals anyway for future restuffing. Replacement of these was not quite as straightforward on this set but that happens. Firstly, to get to the nut securing the old smoothing cap, I had to unsolder the two parallel 2.2 K resistors and move them out of the way. Once I had loosened the nut and unscrewed the old cap it was easy to remove. Remember I said that the cans do not return to chassis....there is a paxolin insulator between the bottom connecting ring and the chassis.
Once the old cap was removed, I checked the new one for fitting. Perfect fit in the chassis hole, perfect fit in the bottom connecting ring, but it doesn't fit the paxolin ring of which the centre hole was a fraction smaller than the bush on the new capacitor. No problem and a few minutes with a round file soon had the insulating ring fitting perfectly. It was then simple to fit the new capacitor, bottom connecting ring and insulator. The two connections on the capacitor are marked - and 1...the 1 is positive. I quickly made a resistance check from negative to can......and discovered that the can is isolated. Strictly speaking, the insulating washer under the capacitor can is not required in that case. However to keep things simple and to avoid a rewiring session, I've left the insulator in place. All I had to do was make an additional connection to the negative connector of the cap. That was the smoothing cap done.
Replacement of the reservoir cap entailed removing the tone control....the securing nut is directly underneath so you cannot get to it without removing the control. Once that was done, the sequence of replacing the cap followed the previous description for the smoothing cap. One other point, the two connecting tags have to be pushed right down flat otherwise they will foul the tone control when it is refitted.
One other job I did while in the mood was to tidy up the mains filter cap. I fitted a small tagstrip using the original hole that had taken the P clip for the tar bomb that had already exploded. The original value was 22,000pF (22nF or 0.022uF) at 1000Vdc. I didn't have a .022uF X type capacitor so fitted the nearest I had which was 0.047uF at 300Vac....it's not critical anyway.
On test, the radio performed as before. SW was very lively tonight and I even picked up a couple of amateurs on 14Mhz. It was SSB so couldn't resolve it without finding another set to 'beat' with or dragging the signal genny out but I did just make out a distorted '73's (radio amateur speak for 'Goodbye') so he was obviously signing off.
Apart from connecting the rewired scale lamps, electrically that's about it. There is still some considerable cleaning to do so will decide what to do next.
Some photos of work carried out tonight.
First shows the tone control removed to access the fixing nut of the reservoir cap, second shows the nut now visible, third shows both caps fitted and behind them and to the side of the mains transformer, the tagstrip and new mains filter cap.
Update: I finished the set today. Lockdown may be a pain but at least it gives you a chance to spend longer on projects. Every cloud etc....!
So it was mainly cabinet work, a good clean up, refit the re-wired pilot lamps and holders, the pointer carrier and refit the chassis. I need to repaint the pinstripes and probably another couple of good rub-overs with Polishing Paste no.5 and a finish with beeswax. It looks good though and sounds good as well with plenty of bass. I'm so glad the output transformer I had seems to work very well.
So here is the end result:
First the vacuumed speaker and its dust bag refitted along with the tuning pointer carrier. Second is the cleaned chassis ready to go back. Third shows the chassis fitted. Fourth shows the completed set with tuning scale attached. Fifth shows the plate attached to the top giving the name and address of the dealer who supplied the set back in 1947.
I'm really pleased with the way this set has turned out, particularly the perfect condition of the tuning scale. It was well worth the journey to Portsmouth
Very smart indeed. A great job done there to bring her back to life. 👍
To understand the black art of electronics is to understand witchcraft. Andrew.
