Jörgensen Electronic
                        (antique portable electron tube organ)

Everybody knows what a pipe organ is - but did you ever hear of a tube organ?!

This "garden grill with keyboard" is one of the very first portable full- polyphonic electronic organs. I am not sure how rare it is - it may be the 2nd last of its kind. On the internet I found only a single other owner (who is missing the amplifier) and as well the release date 1946 as 1953. Mine is a German version that according to the serial number plate was built by "Jörgensen Electronic", licensed from René Seybold and Harald Bode. Because it contains many common 1950th E- series tubes, I guess that 1953 is more likely. (1940th tubes had rather round sockets with a nipple at one glass corner instead a missing pin as the mark. Only the EL12 look that old, but they may have been a pre- war shelf relict.) The instrument consists of the organ itself (a black, coal- grill- like metal construction on an collapsible iron stand) and the amplifier/ power supply cabinet, which has the size of a large tube radio.
This is the amplifier and its lid...

...and this the paper texture inside the lid and carry case.
The organ has a wooden trunk/ carry case to transport and store it when not in use, and also the amp is built into a similar case which has a lid to cover the back when not in use. Unlike a Hammond and similarly old organs, this one has a fully electronic, analogue sound generator without any mechanical or acoustical oscillator components involved.

main features:

On the upper left corner of the amplifier are remains of a painted brand label, which likely once has been "Tuttivox".  The one at the lower right likely has been "Jörgensen".



This is the back of the amplifier.

Behind the amp are 2 fuse holders (one also selects the mains voltage), the power switch and a speaker mute switch. A bright red pilot lamp warns when the amp is in operation...

...because at this large jack (organ connector) every child or fool could easily grasp into 300V DC high voltage when the organ itself was plugged out. I therefore covered all voltage output holes with protruding shrink sleeve pieces to prevent accidental touching. 

At the very right are 2 sets of jack plug outlets for external loudspeakers; while the upper set is a normal 5 Ohms one, the lower set outputs a high voltage signal for special tube- age speakers with external transformer.

The organ connector has (counted from left to right anticlockwise) the following pin assignment:
  1. "-" 37.8V AC
  2. "-" 6.3V AC
  3. +300V DC
  4. audio in
  5. GND
  6. "+" 6.3V AC
  7. "+" 37.8V AC
The organ tube heaters are wired in series and supplied by the 37.8V AC output (likely to reduce the needed current on the supply cable); the 6.3V output is not used.

The amp's serial number plate.
Now take a look what's inside...
Isophon P 30/31/10
Here you see the large loudspeaker and the 2 big EL12 power tubes on the chassis.
When on, you can see the tubes glow and the bright red shine of the pilot lamp.
Although this mains transformer block may look small and harmless, I estimate that its solid, heavy iron core incorporates at least 65% of the weight of the entire amplifier. 

Above it you see the 2 EZ81 rectifier tubes; in one of the EZ81 and one EL12 tube there is weak blue ionization visible, possible a remain from a previously broken grid capacitor. 

The instrument can play loud enough to annoy neighbours tonight, but I don't think that it is louder than the amp of average 1x EL84 tube radios, despite the 2x EL12 tubes look like something as big as KT88 and by their appearance I would expect rather 30W power than just 5W. It may be that the ionization in one tube eats up the power, or that just the huge loudspeaker has lost most of its magnetism (which is rumoured to happen with that old speakers), or that a small defect in the organ makes it quieter. (Its internal preset volume trimmer is all way cranked up.)
Through the knee lever hole it was extremely easy to touch the high voltage electronics of one of the tone generators; I am not sure if there ever was a protection against this (e.g. in form of a latex rubber bellows that disintegrated over time by oil/ bad treatment, or a brittle bakelite board that broke and thus was thrown away) or if in 1950th they really never cared about children safety. I covered it with transparent sheet plastic to prevent electric shocks. (At the left corner is the hole of the power supply/ amplifier cable.) There is a mystery pair of jacks and the left side. The black knob controls pitch in a very limited range. At the right side is a similar knob for the preset volume control (in opposite to the knee lever volume).

This is the back of the organ with cover cage removed.
There are 12 oscillator modules; each produces one tone of the octave and contains 3 tubes for the 3 octaves of the instrument (top is the lowest).
To tune the organ, this row of trimmers can be adjusted with a screw driver. 

As it came, the tone scale sounded quite detuned (especially the "h"); I am not sure if this is due to broken capacitors (the main oscillators seem to use less prone plastic ones) or if this Tuttivox was intentionally tuned like an ancient church organ. (I read that also Arp Schnittger pipe organs etc. often used much different tunings than the modern well tempered scale.) The POKEY composition "One Man and his Droid" (available on the SAP Atari XL music archive) can be played almost perfectly with this scale, but most normal music sounds a bit strange.

To the right is the pre- amplifier and vibrato unit of the organ. At its right side are 2 trimmer potentiometers; the upper one limits the maximum volume of the organ. (Mine came fully cranked up, but I guess that is was originally built in to prevent kids from playing too loud.)
Here you see the custom made special potentiometer of the knee lever. As expected, the uncovered, dirt prone wiper contact causes some crackling noise when moved.
When we remove the front cover, we can take a look at the heart of the instrument...
It must have been a horrible lot of work to solder all these components together. I have no clue how expensive this small instrument was, but I could well imagine that it costed as much as a grand piano. Unfortunately the fully electronic tone generators contain several dozens of "explosive candy" capacitors, and most of them already have more or less cracks in them. Unlike the solid construction of my Tektronix tube oscilloscopes, the 3 dimensional construction of this hardware is rather awkward to maintain, because it consists mainly of brittle, traceless Pertinax circuit boards those are faithlessly bolted and soldered together without removable connectors. Also the selection of components looks rather like a collection of post- war shelf mess than produced by a single factory.
Beside the 2 trimmer potentiometers mentioned above, there are 3 further, black trimmer pots simply hanging on their bare, flimsy wires among components at a circuit board. It must be a more than unpleasant and challenging task to adjust these during operation, because the smallest mistake can cause things to bend, short and burn out, or makes you slip with your (hopefully gloved) hand or screwdriver into the high voltage electronics.
Every tone generator module contains a small transformer (generating a 4th octave overtone?). The modules are connected at the bottom by a main bus rail. main bus assignment (top to bottom):
  1. +297V DC
  2. pitch pot (+136..175V DC)
  3. vibrato envelope (about 2V AC, stabilized by a big "explosive candy" cap against GND)
  4. GND
  5. 32V AC
  6. 0V (?)

Even behind the tab switches are multiple such small transformers and further "explosive candy" caps.
When I examined the electronics, once the organ smoked badly and made no sound anymore; I guess I toasted the common pitch control potentiometer when its resistor at the 2nd bus line was accidentally bent against the grounded case. After I bent it back, the organ fortunately still works.

Behind the keys are lots of small resistors.
Here you see the metal lever under a key, which plastic end presses down 3 spring wire contacts. Behind the keys are the springs those hold them up. At the right keyboard end is a small wire lever to clean the key contacts.
The spring feathers those hold keys up have all different strengths - I don't know if this is because it was a post- war product or because someone incompetently tried to fix stuck keys. (Initially mine had a few stuck keys, but the reason were bent metal levers and not too weak springs.) On the bakelite keys are many scratches; I guess that someone incorrectly stored the collapsed stand upon the keys when he transported the organ in its wooden carry case.


The tone generator modules contain dozens of of more or less rotten "explosive candy" paper capacitors those reliability is very questionable. As a safety measure I already replaced the ones in the power amplifier, because the previous owner said that the amp crackled and smoked a bit when he plugged in the HV connector of the organ during operation, and because the EL12 power tubes are expensive to replace and a short in the wooden cabinet could cause a fire. But to replace all of them in the organ would be a tremendous lot of work. Unfortunately I not even have schematics to determine the proper cap values for a replacement; the writing on the cracked and dirty capacitors is partly badly readable. But I bought already new capacitors and will repair this thing when I find time in future. This strange thing is like a piece of ENIAC, and feels like repairing the tube operated time machine in the movie "The Time Travelers" from 1964.

I am still not sure if the registers and tone generators sound like intended, because they use filters made from the same old capacitors, of those some may have a short, but replacing all "explosive candies" would be quite a horror job and may take at least a month since it would be extremely awkward to de-solder and dismantle the 12 tone generator units. My Tuttivox currently sounds somewhat similar like a harmonium or plain Hammond organ tones with almost no distortion (and no Leslie). The vibrato turns slower and stutters/ gets a hiccup after 15 minutes of warming up; possibly the ECC81 tube is broken.

The previous owner told me that the instrument once had been owned by a church organist (?). I bought it used for 50 EUR. Because it had stood at an attic for decades and according to the rusty/ calcium crusted top of amplifier and carry case it seems to have rained upon it many times, the instrument smelled very musty. After removing dust and cleaning it with humid toilet papers I therefore treated the loudspeaker cloth with fragrance- free Febreze (textile deodorizer based on a corn starch chemical) to remove the smell, which worked quite well.
Behind the keyboard is a row of 3 pre- punched openings those likely were intended for an expansion unit (with a 2nd keyboard??). Also the case shape looks like designed to place another device upon it, although on the internet I also found info that the similar shaped case of the Clavioline was designed to be mounted with its rear end under the keyboard section of an acoustic piano. For a size comparison you can see here my 1980th Yamaha PortaSound PS2 in its carry case on top of the 1950th Tuttivox amp.
My amplifier unit has the serial number 516 and the organ itself the number 455C. On the internet I found info about a similar, but earlier (?) released dual- keyboard instrument of the name Multimonica, which was also built by Harald Bode, but even this one contained only a monophonic tube organ and to play polyphonic sounds it had simply an additional accordion- like reed organ/ harmonium built-in as its 2nd keyboard. There are still many tube operated radios, amplifiers and also TV sets and oscilloscopes around, but I never heard about portable polyphonic tube organs before. I could well imagine that when the first lightweight transistor organs came out or at least with the arise of Yamaha PortaSound many people threw the last small tube organs away because these were neither a decorative furniture and versatile to play like a Hammond, nor remotely as portable as a modern, lightweight plastic keyboard.

A monophonic and technically way less costly variant of this instrument was released as Jörgensen Clavioline.

 removal of these screws voids warranty...    
back to tablehooters collection