On the Wurlitzer 120 Service Manual

By the time the 120 was released, the Wurlitzer electronic piano had been available for several years. It is, in the words of the service manual’s Introduction, “lighter weight, smaller, more attractive, and contains a number of other improvements over former models.” We’re not sure if the 120 is in fact “more attractive” (the 112’s cool-toned splatter finish is amazing and we could never pick favorites), but the 120 definitely has a smaller form factor. And although it has a lot of similarities with the 112, it definitely warrants its own service manual.

Wurlitzer 120 Service Manual Readers’ Guide

Instructions on regulating and otherwise servicing the mechanical action of the 120:

Preparation of the Model 120 Wurlitzer Electronic Piano for Sale (3) advices what to do if debris bridges the reed and the pickup.
Checking the Bar and Reeds on page 10 advises that the reed bar fasteners should not be screwed down too tightly.
A general description of Key and Action Regulation starts on page 11. It has the same verbiage as the 112 service manual, declaring that the electronic piano is regulated “like the conventional piano,” but goes further to say that regulation should “only be attempted by a tuner-technician or a trained service man.” We mention this as an interesting historical note; if you’re regulating your own Wurlitzer, carry on.
In the regulation section of the 112 manual, it includes photos of the actual keyboard being regulated. In the 120 manual, there are photos of some sort of amazing, single-key demonstration assembly, which gives you a clear view of all the mechanical parts and how they fit together.
Adjusting the capstan screw is on page 11 and the section on let-off is on page 13. Let-off goes into somewhat more detail than in the 112 manual. The butt spoon and how you can tell whether it is properly adjusted is on page 14. Damper adjustment is covered on page 15. There is a discussion on the hammer strike point on page 15, and how to determine whether or not it requires adjustment.
Troubleshooting blocking hammers and tones not produced by a light touch are found on page 16.

Connecting external devices. As seen in the 112 manual, we have some risky advice on connecting headphones and external speakers on page 18. Connecting external devices that are too low-impedance stresses the power tubes and output transformer. Although this may have been acceptable when the amplifier was new, our recommendations on speaker impedance can be found here.

If you are looking for information on the amplifier, the service manual doesn’t have much other than schematics. If you would like to examine the schematics, we recommend downloading the Schematics & Diagrams PDF. The text in the main manual is searchable, which distorts the schematics a little bit. The Schematics & Diagrams version is also high-res, printer-friendly, and reproduces the manuals clearly.

Our favorite details:

The page titled Removing the Fall Cover (4) has drawings of an important new feature of the 120: the spring-loaded latches that keep the outer lid attached. For some reason, it is incredibly rare for a 120 (or 140-series) Wurlitzer to still have all of its latches. The 112 had drawbolt-style latches, which never fall off, but are not as convenient as the spring-loaded latches.
“The pilot lamp, located on the left key block, is Neon and should last indefinitely. It is a normal characteristic of this type lamp to light up and go out rather slowly.” (7) “Indefinitely” is certainly a bold claim, but the slow turn-on of the 120’s indicator light is an important part of its charm.
The Model 920 is described on page 18 as “a specially constructed external amplifier…which contains an 18 watt amplifier driving a 12” concert speaker.” The 920 also included tremolo and tone controls. Wurlitzer had a very ambitious plan for including tremolo from the beginning: you can find it in the 112’s patent. The 920 came one step closer, but Wurlitzer never truly fulfilled their earliest visions for tremolo, which went way beyond the simple one knob found in the 140- and 200-series models. More here.