Telefunken "Adante" 1352 table radio

[Tim]

TELEFUNKEN Adante 1352

German made AC mains powered two speaker wooden cased table radio.
VHF,MW, LW and SW Circa late 50’s early 1960’s
Valves ECC85, ECH81, EBF89, ECL86, Metal rectifier. EM84 Tuning indicator.


This lovely thing belongs to a man in Shrewsbury but he has a friend who lives only two streets away from me, in the same village. The owner says it was bought in Germany and hasn’t worked for some years. He also told me it had been repaired once before (but went wrong again after a week!) and that one of the valves glowed red hot! Should make faulting relatively easy!!
Access is fairly easy, and once the layer of dust had been brushed from the printed circuit previous repairs were evident.

Electrical repairs

The previous repairer had fitted an un-branded ECL86, and also replaced the ECL86 Pentode section’s cathode resistor and bypass capacitor. The replacement resistor (2 watt) was of far higher power rating than the original, but even that showed signs of getting hot and bothered. I have found the cathode resistor replaced in sets a few times, and am particularly suspicious if it seems overly large for the job. Why did the original fail in the first place? Probably due to excess current flowing through the output valve, which is in turn USUALLY (although NOT always) caused by a leaky grid coupling capacitor. The capacitor in this position in any set is often referred to as “That” capacitor, and should be thoroughly investigated.
I ran the set up on the lamp limiter, which unfortunately did its job and prevented enough current flowing to reproduce the red hot glowing valve.
I was hoping to re-form the HT capacitors, but HT only rose to 70 volts The ECL86 was removed before power was connected, and a whopping 22 volts W.R.T chassis was measured at the grid pin connection in the socket. The suspect grid capacitor (an ORIGINAL-the last repairer hadn’t even replaced it!) was unsoldered and lifted at one end. It tested 500k ohms with the Megger. A new capacitor was fitted and the set run up again with the ECL86 re-fitted. There was a burst of music and silence, followed by a nice (!) red glow from the output valve. A QUICK measure across the cathode resistor gave a reading of 21 volts. Switch off quick!
The aforementioned cathode resistor measured 260 ohms (a non preferred value, so had probably changed as it was under strain) so by my reckoning that gave a current of some 80milliamps!! No wonder the valve was glowing! No doubt it had been damaged by the excess current. Due To the excess heat, the printing had burned off the existing valve, but fortunately there was a valve map printed on the receivers rear cover.
A rummage through my hoard of valves turned up a half decent Mullard ECL86, which was duly fitted.
Music, music, music!
The original valve was indeed faulty, the replacement giving a much more sensible cathode voltage of 6.9 volts (So with 260 ohms cathode resistor gives a valve cathode current 26mA-a bit low but OK), and performance on all bands was very good. I can only suppose the HT rose high enough to make the set work for a second, before being dragged down by the excess current draw as the output valve warmed up. The customer was extremely lucky that this hadn’t resulted in damage to the output transformer or metal rectifier, as is often the case. Now all that remained was to check and replace all the other likely capacitors (some in this set had resin ends and tested OK). The tired cathode resistor found in the set was replaced by a 200 ohm ½ watt metal film type, which seemed a reasonable value.
The only other task was to renew the rubber bands securing the ferrite rod. This was accomplished with two thin sections of bicycle inner tube.
Since BBc Scotland was receivable here in Wiltshire I didn’t consider AM alignment was necessary. FM was also excellent, with a good variety of stations all across the band.
The red/brown resistors commonly found in West German stuff of this period rarely seem to go faulty, and all those in vunerable positions that were checked were well within tolerance.
I had no service information for this set, but voltages seemed reasonable around the circuit, and hum almost inaudible.
The mains cable fitted to this set is of the single sheathed type (looks a little like bell wire) and as this is an AC set, it can and should be earthed.
In agreement with the owner, it was decided to fit a length of gold 3 core, of the type usually used for decorative lamps. It actually matches quite well with the typical continental styling of that era, light coloured cabinet, cream knobs and gold trim. Only one half of the double pole mains switch was being used, so after a quick check of the other half with a meter, the unused section was used for the Neutral of the new cable. Care was taken to ensure the internal fuse was in the mains live, and the voltage selector in the neutral. Earth was connected to a tag fixed by a self tapping screw through an existing hole in the galvanised steel chassis.
A new ECL86 was ordered and fitted, along with some replacement scale lamps. The 6.5 volt tubular ones I initially tried seemed very bright though, (actually illuminating the wall behind the set!) so after a quick rummage I turned up some ex post office lamps 26J, which gave a nice mellow glow. The set was on test for 12 hours a day for about a week now and drove the family nuts. Voltage across the newly fitted resistor is a stable 6.8 volts, and the resistor barely warm after about 8 hours use.. It does sound good though, and VHF tuning up-to 108 MHz means it is still a very practical radio.

CABINET
As you can see this was excellent and needed only a quick clean of the tuning scale, keys and knobs and replacement of the chassis mounting rubbers(3/4" tap washers x8 ).

[howard]

Good work Tim,

And an elegant looking 1960s table radio it is too (1962-3). I always change THAT capacitor .......

Howard

[Tim]

ERRATA

Part of Electrical repairs, paragraph two should read

I was hoping to re-form the HT capacitors, but HT only rose to 70 volts. The ECL86 was removed before power was re connected

Reason for re-editing not using the re-editing thing-----my wife called me away to do something and by the time I got back the editing deadlline had passed.

Thanks Howard.
Wasn't that last repairer a wally! (Chances are he's an old man now, or even in the great workshop in the sky)Fancy not changing the grid capacitor, or even not realising why the original resistor burned out.
Still an attractive set some 45 years after it's manufacture. Must have been made for export though, since it has LW, BBC stations on the dial and a 240 volt voltage tap. The din sockets visible in the rear view are for the gram input. I think there is also an output for a tape recorder too. I forgot to mention it in the original post, but the low value electrolytics tested fine too, including the 5uf discriminator capacitor.

[Steve_P]

These German sets are very good and on FM exceedingly so.

Reason : The Germans were first with VHF (Or Ultra Short Wave) because after the war there wasn't really a Germany. It was spilt in two in 1947 but given very few radio channels.

So, for the German people, they started new frequencies. This was picked up by Britain in 1954/55.

Cheers,

Steve P.

[ajs37]

Good job Tim and thanks for the write up - very informative!
Your old Telephone bench is still giving good service by the way - it was a bu**er to get it down the garden and into the shed, but it's been worth the effort!
Cheers
Andy

[johnn]

Good careful work there! What a very nice set Tim.
John

[Tim]

Thanks everyone. I'm still enjoying it for the moment, 'cos the owners friend hasn't come to collect it yet.

That's a good bench Andy. It's all(very) solid Beech.
I fixed loads of stuff on that, including two Bedford engines and a Land Rover gearbox! It'll probably see me out!

[telstar]

Hi Tim. Good to see someone else collecting & restoring German "piano-key" valve radios. I have a Telefunken Adante in my collection, which I hope to restore soon. I have the circuit diagram for this radio (somewhere), but can not find it at the present time.
Regards
Mike

[Tim]

I have the circuit diagram for this radio

I wish I had known that Mike!

I couldn't hold onto it much longer though, I've had it since July!!
You won't regret getting yours going, they are great sounding radios.
I seem to remember reading somewhere those Telefunken speakers with the red bit on the magnet are much sought after, and often found to be missing!
Luckily this one's been in a cupboard for the last 30 years.
I don't think the style has dated at all.

If it was a piano it has enough keys to play a decent tune.