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Bajazzo 55

Bajazzo 55; Telefunken (ID = 59019) Radio
 
Bajazzo 55; Telefunken (ID = 441601) Radio
 
Bajazzo 55; Telefunken (ID = 441602) Radio
 
Bajazzo 55; Telefunken (ID = 441604) Radio
 
Bajazzo 55; Telefunken (ID = 441603) Radio
 
Bajazzo 55; Telefunken (ID = 59020) Radio
 
Bajazzo 55; Telefunken (ID = 441605) Radio
Bajazzo 55; Telefunken (ID = 218950) Radio Bajazzo 55; Telefunken (ID = 156587) Radio
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Bajazzo 55; Telefunken (ID = 11625) Radio Bajazzo 55; Telefunken (ID = 156586) Radio
Bajazzo 55; Telefunken (ID = 156588) Radio Bajazzo 55; Telefunken (ID = 312459) Radio
Bajazzo 55; Telefunken (ID = 441600) Radio Bajazzo 55; Telefunken (ID = 526129) Radio
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Bajazzo 55; Telefunken (ID = 218950) Radio
Telefunken: Bajazzo 55 [Radio] ID = 218950 644x466
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For model Bajazzo 55, Telefunken Deutschland (TFK), (Gesellschaft für drahtlose Telegraphie Telefunken mbH
 
Country:  Germany
Manufacturer / Brand:  Telefunken Deutschland (TFK), (Gesellschaft für drahtlose Telegraphie Telefunken mbH
Year: 1955/1956 Category: Broadcast Receiver - or past WW2 Tuner
Valves / Tubes 7: DC90 DF96 DK96 DF96 DF96 DAF96 DL94
Main principle Super-Heterodyne (Super in general); ZF/IF 460/10700 kHz
Tuned circuits 7 AM circuit(s)     11 FM circuit(s)
Wave bands Broadcast, Long Wave, Short Wave plus FM or UHF.
Details
Power type and voltage Line / Batteries (any type) / 110; 127; 150; 220 / 1,5 & 90 Volt
Loudspeaker Permanent Magnet Dynamic (PDyn) Loudspeaker (moving coil) - elliptical
Power out
from Radiomuseum.org Model: Bajazzo 55 - Telefunken Deutschland TFK,
Material Various materials
Shape Portable set > 8 inch (also usable without mains)
Dimensions (WHD) 380 x 270 x 150 mm / 15 x 10.6 x 5.9 inch
Notes DEAC-Zelle D3,9.
Auch in Luxusausführung lieferbar (DM 349,-).
Net weight (2.2 lb = 1 kg) 7.5 kg / 16 lb 8.3 oz (16.52 lb)
Price in first year of sale 338.00 DM
Collectors' prices  
Source of data HdB d.Rdf-& Ferns-GrH 1955/56 / Radiokatalog Band 1, Ernst Erb


All listed radios etc. from Telefunken Deutschland (TFK), (Gesellschaft für drahtlose Telegraphie Telefunken mbH
Here you find 3412 models, 2978 with images and 1962 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.




 


Forum contributions about this model
Telefunken: Bajazzo 55
Threads: 3 | Posts: 12
Hits: 2216     Replies: 5
telefunken: 55; Bajazzo
Georges Giralt
08.Aug.09
  1

Hello !

My 1955 Bajazzo runs fine on battery but has hum on mains.

so far, I've tried to replace the selenium heaters rectifier for a silicium one, the smoothing capacitor but to no avail. Owning a couple of DL94 I tried them in order to find the one with less hum. All I've found is that my GEC NOS one is microphonic !

As a last resort, I tried inserting a 1000 µF /10V capacitor in parallel on the NiCad regulating battery. It changes NOTHING !

So I get my scope and saw that the ripple on the 1.4 V heater voltage is less than 8mV and very small (buried in the noise) on the  HT. So what's wrong ? What did I miss ? 

I'm now exhausting all my knowledge on this matter, so I would _really_ appreciate your help and advice to make this set as perfect as it should be !

Many thanks in advance.

Best regards.

Joe Sousa
11.Aug.09
  2

Hello Georges,

You gave some very good information, especially the 8mV of hum at the filament.

8mV at the filament of the audio preamp stage DAF96 is the equivalent of 4mV at it's grid, because one end of the filament has presumably zero hum.

According to the Philips data sheet for the DAF96, it runs with a gain over 50 in a similar configuration to the audio preamp in this radio.

This means that the 4mV at the input of the audio preamp will become 200mV at the input to the audio output tube, which should produce a lot of hum.

This filament hum injection happens after the volume control, so it should not be possible to kill it with the volume control.

Did you replace the original NiCd cell? You could leave it in place, but disconnected, while connecting a C size NiMH cell to the filament circuit. It is important that the wire sequence be as shown in the schematic.

The NiCd cell was the main filament filtering element in this radio. The NiCd also works as a regulator for the filament voltage. If the NiCd cell is open too much voltage will be applied to the filaments.

You could probably put back the original selenium rectifier.

An alternative to using a replacement cell is to use two diodes and a capacitor as shown by Gerhard Heiglin his restoration of a portable radio of the same vintage. This thread is in German; if needed, use Google-Translate, or a similar translator.

Good Luck,

-Joe

 

 

Georges Giralt
11.Aug.09
  3

Hi Joe !

Actually, my original NiCd is still in place. As it is not short circuit nor open, I decided to leave it alone in order to save the appearence of the radio. But, I've fitted a 3000 mAh D Nicad cell in one of the battery holders.

I'll try to run the radio with the DEAC disconnected just to see.

As per the DAF96, it seems it is wired in reverse in the Bajazzo schematics. Philips state in the spec sheet that the diode is at the negative part of the filament. In the drawing I've got, it is sketched in reverse, the diode being at the positive end of the heater. I've to check the radio to find the culprit.

Last but not least, on this radio the volume pot is acting on one of the grid of the DAF and not on the output signal to the DL94. 

The things that puzzle me is that the hum is totally independent of the filtration I give. I put a 1000 µF in parallel to the NiCad and it change nothing. As I've got a 1.0 F GoldCap to repair a faulty computer, I used it to smooth the heaters voltage but to no avail !

This leads me that there is somthing wrong elsewhere. As I changed a lot of film caps in this radio, maybe I put a dead one in place or I soldered one lead to the wrong place. (I began to think this is the cause of the trouble because when I first powered it there was not such hum; And as the radio was silent I should have noticed it...)

Anyway, thanks for your help !

Joe Sousa
12.Aug.09
  4

Hi Georges,

I used to have my DEAC battery in place in my Grundig ConcertBoy 57, but removed it recently because it was very leaky, and would discharge the NiMH C cell I soldered hidden in the back of the chassis. This meant that I would occasionally find a dead battery when I would bring the radio outdoors under battery power. I left the old battery in a sturdy plastic back, next to the high voltage NiMH battery pack I built for it.

I would recommend one last attempt at filtering: Tie your 1000uF filter capacitor to the filament terminals of the DAF96 directly, with short wires. You could also try connecting your new NiCd cell to the filament directly, but be very careful with polarity. This gets around any poor connections or voltage drops along the wiring. The external battery location may not be very good for filtering if the wiring is long, or if the battery terminals are corroded, as they were in my radio. The original external Carbon-Zinc battery had a relatively high internal impedance, so it was not relied upon to do the filtering, and the lenght of the wiring to it was not very important, in fact some resistance in this wiring may have been designed in, as discussed in a similar thread about this NiCd-CZ battery system.

A few numbers to illustrate the importance of resistance in the filament power system:

My Grundig 57 draws about 300mA average DC current from the low voltage AC power supply to charge the NiCd and power the filaments (200mA). This means that peak currents approaching 1A are quite resonable to expect to flow through the rectifier. It would only take 8mOhms of resistance in the wrong place for this 1A peak to become 8mV peak.

One purpose of the 250uF cap at the bridge of your Bajazzo 55 is to route this peak current locally, so it does not get into the filament wiring and cause hum. Another purpose is to guaranty a minimum current level flowing into the NiCd when the AC crosses zero volts.

Another design element to consider  is the relatively high internal resistance of the original Selenium rectifier bridge. The Silicon diodes increase the peak currents.

You say that you have replaced many caps in this radio. It would be good to check the physical location of connections for the filament power system, even if they match the schematic.

In my Grundig 57, I still had a persistent residual hum that was caused by a corroded connetion between two parts of the chassis that were made from different metals. After cleaning this junction with Deoxit, the hum disappeared.


The volume control should have the the high end fed by the AM or FM detectors, and the wiper driving the grid circuit of the DAF96 audio preamp. This makes it impossible to attenuate filament hum with the volume control.

The filament polarity of the DAF96 is very important for AM detection. Either DC battery polarity can be accomodated if the IF secondary coil that drives the AM detector diode is returned with resistance to the filament end where the diode is located, or if an equal voltage to this filament end is provided externally. If the connection is wrong, you will get a lot of distortion at the weaker AM stations, or not signal at all, because their signal must overcome the additional 1.4V filament voltage to be detected.

Good luck with your troubleshooting; this is such a nice radio.

-Joe

Georges Giralt
12.Aug.09
  5

Hi !

I know what to do to try to make this set running !

Alas, in the 3 next weeks my schedule is awfully full so I'll have to wait until september to fix it.

Will report back !

Thanks for your help.

Georges Giralt
12.Aug.09
  6

Hi Joe !

Back from work early I decided to try some of the solutions you gave before setting the Bajazzo aside.

I first returned the selenium rectifier back in use. The silicium replacement was too ugly.

Then I soldered the 1000 µF/10V condenser as close as I could of the leads 1 and 7 of the DAF96, and I soldered a couple of 1N4007 in serie at the same position in order to salvage the expensives valves just in case something goes wrong.

Last, I removed the wiring to the DEAC NiCd  and wired directly the heaters wire to the place for the batteries. I then cleaned the battery contacts (they look like new thanks to my fiberglass cleaner ! )

I then plugged the set on with confidence.

The heaters are at 1.25 V measured using my old analog meter (20kOhm/V) and the hum is still here !

I can't tell if it is less or more, but it is present.

The set runs fine on battery using a 3000 mAh NiCad D size cell or a D size NiMh  8500 mAh cell.

So this set will be devoted to "battery only" and the 1956 vintage Bajazzo I own will do mains ! (this one is in original state, has seen no caps replacement, has no hum a very high sensitivity but unfortunatelly a bad case from a high fall which broke not onmy the Bakelite front and back but also the wooden frame )

Thanks a lot for your help, advice and patience.

Best regards.

P.S. : I will have a detailled look at the wiring and the schematics to see if I've not made a mistake somewhere when replacing components. I'll report back if I find something. But this will be in a few weeks from now.

 

 
Hits: 2149     Replies: 4
telefunken: 55; Bajazzo
Georges Giralt
21.Jun.09
  1

Hello !

I own one of this set. Of course the DEAC NiCd is dead. So I'll manage to make a replacement. So far soo good.

But I need to make an ersazt battery for the 90 V HT. As they are since long gone, I have no information about them.The only thing is the "type Emce Nr. 760 stamp on the cover of the set.  I'll be glad to get as many information you may have. (size, capacity, scan of one model cover to put on the ersazt, schematics, tips for construction ...)

Last but not least, the cas need a good cleaning and restauration. So I'm looking for a replacement of the decorative plastic stapped on the box at the cover opening, as it is broken. (it is somewhat yellow)

Thank a lot in advance for your help and advice !

Joe Sousa
26.Jun.09
  2

Hello Georges,

I have been making high voltage batteries from rechargeable NiMH 9V batteries. I got my packs inexpensively from www.goldmine-elec.com.

NiMH 9V packs are usually made from 6 cells of 1.25V each. This only adds up to 7.5V for NiMH. The 9V value is a standard value that came from 1.5V carbon zinc cells.

I have built packs from the standard sized 9V batteries and from smaller sized 70mAh cels from Varta, shown in the photos below. I got these smaller cells from goldmine, but they are sold out from there now.

They still have the standard 9V size, and some very small 2.5V two cell packs. I have been able to make a 50V pack with 20 of these that has the height of two standard 9V cells.

The following Emerson 838 radio has six 7.5V packs in series for a total of 45V. All packs, except for one pack to the left of the speaker were folded to fit in the space. I charge these packs with 1.4V per cell, which adds up to 8.4*6=50.4V. I limit the max charge current to 50mA. This current only flows for the first few minutes. Then I let the cells charge overnight with the 50.4V supply, without any danger of overcharging.

You can also see a custom pack made from three AAA 1.25V cells for the filament voltage.

The following RCA BP10 radio shows the same type of pack without folding.

I wired the packs onto a socket. Each pack is wired to a pair of opposed pins in the socket. So the batteries are completely isolated from each other in the socket. The card edge plug is wired to the radio and has jumpers to wire all the cells in series for a total of 67.5V.

The cells are recharged outside the radio by plugging the blue socket into a different card-edge plug that has jumpers to wire all the cells in parallel as shown here. The battery voltage at the banana jacks is a nominal 7.5V. My charging method is to apply 1.4V per NiMH cell, or 8.4V for these 6 cell packs. This is a safe voltage for infinite charging time. The power supply I use limits the current to a few 100mA. After a few hours the packs are charged up. Often, I just let the pack charge overnight. There is no danger of overcharging if the charging supply is 8.4V.

When the cells are not in use it is best to store them plugged into the parallel charging plug. This keeps the battery voltage matched between the cells.

Hope this helps. Let us know if you come up with alternate solutions.

Regards,

-Joe

Georges Giralt
26.Jun.09
  3

Hello Joe !

Very good idea ! I did not thought about it !

For now I am going the inverter route. I have actually started making a 50 Hz inverted converting a 6 V lead sealed battery into a 90 V supply.

I let you know how it goes !

BTW the DEAC NiCad is recharging well and begin to hold the charge ! Fantastic for a 1955 piece of gear !

Joe Sousa
29.Jun.09
  4

Hello Georges,

This approach to battery building started out when I found the inexpensive Varta NiMH battery packs. Some of my motivation, also came from trying to avoid interference from switching power supplies.

Some battery powered radios also perform poorly when tied to ground by the AC power supply. This problem usually occurs in radios with a loop antenna, that start picking up E-field interference when grounded. These radios were designed to operation with low noise from the M-field of the loop antenna.

But, I don't want to discourage your approach, as it may work very well, and will not require continued recharging or battery replacement.

I had been meaning to make a more extensive post about my various battery packs, along with the radios I built them for. Your question just gave me the motivation to make this post. I will post separatelly, given the general applcation of the topic.

That NiCd cell is trully amazing, wow! It is usually a challenge to get more than 3 or 4 years of service from modern cells. Keep in mind that the NiCd cell in your Telefunken Bajazzo 55 also serves as voltage regulator and hum filter for the filament voltage during AC operation. If you remove the battery and apply power you will apply too much voltage to the filaments.

Regards,

-Joe


The new post about my NiMH battery packs is here. June 29th 2009.

Georges Giralt
29.Jun.09
  5

Yes Joe, I am aware of the fact that without the DEAC NiCd the heaters voltages will be in the range of 3.5 V. so will burn out in a matter of seconds.

This morning I found the DEAC at 1.2 V and it felt at 0.2 V when I plugged a dial lamp on it in less than 5 seconds. When I unplugged the lamp, it recovered to 0.7V. So I start charging it again ;-)

Of course, I do not plan to use it at all, as I own a D Cell NiMh of 8.5 Ah to put in the battery holder. I plan to make a fake DEAC cell containing 2 x1N4007 in series between the positive and negative side of the "cell" and a smoothing condenser to regulate the heater voltage in case one start the radio without the NiMh cell ....(It will help reduce the wheight of the set also ;-)

Regarding the perturbations the switching power supply will make, I am aware of them; I plan to make a 50 Hz oscillator which will force me to use a heavier transformer than a more higher frequency, but which will be easier to smooth and shield (as the set is also a mains one, it has some built in protection for 50 Hz hum and I plan to smooth quite well the 90V output).

I keep your idea of the Varta cells. I know a guy having a set using 67.5 V anode battery so I'll show him your article !

Thanks again !

 
Hits: 1812     Replies: 0
telefunken: 55; Bajazzo
Volker Potthast
04.Nov.08
  1

 Ich besitze ein Gerät, welches dem hier aufgeführten optisch völlig gleicht. Allerdings hat es die Bezeichnung "Jubilate" auf der Front unten rechts (s. Foto). Bei dem hier gezeigten fehlt dieses Schildchen.

Frage: Wurde evtl. bei meinem Gerät die Bezeichnung nachträglich geändert, oder handelt es sich tatsächlich um ein "Jubilate" von 1955?

Da ich gerne Bilder dazu hochladen möchte, hätte ich diese Frage gerne geklärt, bevor ich ein neues Modell anlege,

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Telefunken: Bajazzo 55
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