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.
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!
Rough n ready demo.. Check the video.
Links: Geofex page about the technical side of oil can devices – Tel Ray Oil Can Addicts a very helpful group keeping the flame alive on these devices – Schematic Page of the Fender Dimension IV
Masuto's 
It needs 15ml of oil.
Richard, in charge of Oil Can Delay Addicts, told me he uses 1+1/2 tablespoonfuls to great results.
That’s usually the same as 15ml. However I met different tablespoons that’s why I prefer to measure in ml. 🙂
Congrats if it started to work!
My Gibson GA-4RE ’66 (the same Adineko can inside) works fine too about a couple of years after it arrived and was repaired by me in a close way you did now. I was afraid by condition of the “memory disk” but it turned absolutely fine when I opened the can.
More problem I was getting is some dead caps in the tube schematic of the unit and a ground problem with the RCA sockets plate to the oil can heads. But this is another Gibson part of the unit. I hope your one Fender made is simpler a bit and stayed more alive.
Yes as i’ve written, the electronic parts are kept to a minimum on mine.. that makes it even more of a desktop unit..
Very nice!!!
Thank-you!
I have an old Fender Dimension IV that I’m trying to get running. It works for several minutes, then it quits making the vibrato sound (just a dry signal), but the motor is still spinning. If I turn it off and let it sit for a while, it starts working again for a few minutes. Does that happen when it is low on oil? Or could it be the neon light? Or something else?
Check the belt first..