Mono In-Stereo Out boingy greatness from Germany in a rack, possibly related with the similar Vermona spring reverb unit.
Some pics:
My second hand unit has been repaired before (burned resistor..)
This tells us the reverb tank is specced at IN 10 ohms OUT 2575 ohms
Accutronics tank
Driver circuit
Input/output/ac in board
Gutshots show this is a fairly simple unit, its driver circuit consisting of a few ics (TL072, LM380M, LM833N) some jumpers, low noise high precision resistors, OEM capacitors. Maybe its simplicity speaks for its quiet operation.
The reverb tank itself is a Fender Reverb amp compatible model, Accutronics model 9AB2C1B, medium delay (Length: 42,5cm. 3×2 springs, input impedance: 10 Ohm / DC: 0,8 Ohm, output impedance: 2575 Ohm / DC: 200 Ohm).
The Fender Dimension IV is a unit that has been manufactured for about a year (1968-1969) by the CBS acquired guitar staple (along with other musical devices) in an effort to break the pedals/effects market.
It is a slapback+vibrato box, cometically similar to a mini amplifier, tolex covered, the metal front panel fashioned to suggest a motion effect. At the back, 4 RCA male plugs allow to connect the device to the spring reverb loop of a guitar amplifier.
Front plate
Facing the front plate, we find an on/off switch with dedicated pilot lamp, and a commuter to choose either the vibrato effect or the amplifier’s own spring reverb. Inside, there is a 2 Megs pot that sets the effect strenght over the dry signal.
The unit uses an oil can as its core “memory” device-this fascinating electro/mechanical invention was created by Tel Ray (later Morley) and licensed to a few other brands, used internally in organs and amps, as well as guitar pedals.
How does it sound? Like a very haunting, fast revolving Leslie. my guitar playing friend told me it’s very surf-y, another guy who’s into electric blues told me hit sounds eerie-like something out of a Halloween kids’ record!
How does it work? Let’s break it down very easily: inside a can theres a spinning disc that gets “written” by means of a special oil, and three (sometimes four) heads read and cancel the data stored.
As you can tell from the very simple schematic above, the electronic components are very few, basically just a resistor and a lamp to take care of any input overload (the lamp is described as a generic, 120v neon lamp) but the mechanical side can be tricky to restore: the disc is irreplaceable, and it can get damaged if it spins or moves in a dry can. Shipping these units is not recommended.
How much oil should you put in the oil can? Two teaspoonfuls of the special oil are needed (it’s called Ucon LB-65) to make it work. 15-20 ml to be exact.
In my case, there was some oil residue that looked brown! I drained the bad oil using a syringe, and using a clean cotton rag i wiped the can dry-in a slow and very careful manner to avoid touching the disc.
Mine had issues, as it arrived can dry and needing help from a seller in South Carolina that assumed, it would be working with a bit of oil.. good grief.. The motor was running but the small spindle and the larger wheel’s treads were a bit greasy, a common fault considering most of these units are stored upside down or sideways up-a position that can potentially damage the innards by oil spill.. mine had a saggy, worn rubber belt so traction was sloppy-i used cotton tips and toothpaste to restore the grip of these metal parts.
I swapped the rubber belt with a 7cm one i found on one of those assorted diameters Amaz*n tape rubber belt packs-all i had to do was to carefully remove one side of the pulling spring, slide the new rubber belt in, and screw the spring back in, keeping in mind its correct angle.
The 22K resistor was way off so i soldered a new one in.
Since i dont have a Fender Reverb amp handy, i used the preamp of my Fisher Space Expander to drive the Dimension IV..
It’s a great effect, i can only suspect Fender came too late in the game-this wet, surf guitar effect must have sounded a bit passé by 1968!
Update: the Cembalet healed itself and now it works great. I did not have to do anything to it, it just works again, magic, bang.
A friend who’s an electronic repairer said that the most important part to watch out for is the inductor (Spule in german), as it’s custom wound to specs for this instrument.
This must be a very early one, word has it that Jimi Hendrix tried one of these boxes for its big muff-like forced sustain. It is one of the earliest electro harmonix effects.
It is powered by TWO 9v batteries and so much for it “being distortion free”, it is very hissy and noisy, and colours the tone. The compression is VERY apparent and squashed.
Transistors: FS36999, the same as early 70’s Big Muffs.
The tube version Black Finger is a much different, more reliable item.
Tabletop machine, self oscillating AND from past internet auctions and reviews it is apparent, nobody knows how to determine if theirs is in working order (😂), because it is very temperamental and does a lot of different things.. But when it behaves, it’s magic!
Echo, reverb and has a very weird chorus.
Amazing and beautiful, nothing like a tape echo or a memory man.. Far less predictable!
Masuto's 