And how it differs from the “A” model.
In my last three posts I have described in detail my restoration of an early ca. 1951 Kenwood Chef A700 mixer. From what I’ve learnt, these first “Chefs”, up until the “D” model in the late 1950s, were all much the same in design, albeit with several small changes along the way. However, at some point in the evolution of these first pre-D model Chefs we arrive at what is now called the “B” model, with the very first machines now referred to as the “A” model. At the time, both A and B models were just labeled as an “A700” model on the machine itself (the D model was labelled as an “A700-D”). I don’t know if “B” was an official Kenwood model designation, perhaps only used in service manuals, or a more recent categorization? If anyone can enlighten me on this please leave a comment. The main externally obvious feature that identifies a B model is a change in the motor air vent design from the single slot of the first machines, to two smaller slots as shown in the picture below.
Another feature introduced with the B model (or at some time during B model production) was the option to have plastic parts in colours other than black! I’ve seen photos of later D models with different colours (green, yellow, blue, red etc.), but I’ve only seen B models with black or red plastic. I thought that maybe these were the only B colours offered, but recently I came across an image of an old Kenwood advertisement showing a B model and headlined; “The Kenwood Chef, Now in COLOUR!” (curiously, the machine illustrated has a black speed knob). The advert helpfully lists the colours available as: Signal Red, Apple Green, Pastel Blue, Rose Pink, Jasmine Yellow, Dove Grey and, Cream and White. From the surviving machines I’ve seen, I would assume that Signal Red was by far the most popular colour, apart from black (I’d love to hear from anyone who has a B in one of the other colours). Indeed, not long after restoring the A700-A model described in my previous posts, I saw a fine example of a red B model, with all its plastic parts intact, for sale on a local auction site. I couldn’t resist, and managed to buy it at a bargain price.
And now I’ve finished restoring my lovely red A700 B. I found a few differences to my A model, particularly in the wiring, so I though I’d write this post, highlighting the differences for those who are interested.
The only external differences, compared to my early A model mixer, are the change in the design of the motor vent holes as mentioned above, and the use of a rubber grommet where the power cable exits the body. My A has no grommet, but I note that later A models did have a grommet. Otherwise the body shape is identical, and the external parts are the same and interchangeable with the A model (the speed knob, plastic parts, screws, bowls, bowl springs, attachments, feet etc.). Another difference to my particular A machine is the logo. My A has an early “Kenwood” only logo, whereas this B has the “Kenwood Chef” logo. This meant that I needed a new logo for the restoration, so once again I photographed the logo, drew it up in Adobe Illustrator, and got the good folk at Grizzly Decals to reproduce it in black glossy outdoor vinyl (hint: make sure you tell them not to scale your artwork – assuming you’ve drawn it at exactly the right size). Once again, the result was awesome.
Gear Train and Planetary Hub
Again, there are no significant differences in the gear train. There was, however, one difference in the brass bearing for the planetary hub drive shaft. My A machine has a fixed brass bearing, whereas this B has a screw-in brass bearing. To remove, first remove the planetary drive shaft and gear, then remove the two thin brass nuts which lock the bearing. Finally, unscrew the bearing out through the gearbox.
Motor and Electrics
The motor was essentially the same as my A model, as were the fan and wishbone assembly, the hinged governor switch, and the design of the metal shroud. The wiring and electrical components were different however. Differences are listed below:
Two inductors have been added to the circuit by mounting them under the small paxolin terminal board. The inductance values were not given on the parts, but kits sold online use 22uH ferrite-core inductors. These are available from RS components (stock number 213-1881), which is where I got my replacements.
The circuit has a 4.7nF line-to-ground suppression capacitor as well as a 0.1uF across-the-line suppression capacitor (my A model had a 50nF across-the-line capacitor only). When replacing these, make sure that the 0.1uF cap is X2 supression class, and the 4.7nF cap is Y2 supression class.
The radial snubber capacitor for the governor switch has a value of 0.22uF, up from 0.1uF in my A model. I actually found a direct replacement polyprop radial snubber capacitor to mount on the governor switch. This part is RS stock number 871-7034.
The resistor in series with the snubber capacitor is implemented as a 5.4 ohm tap of the external wire-wound resistor, rather than a discrete resistor soldered to the capacitor as in my A model.
Here is the wiring diagram:
Once again, I designed and etched a small circuit board for the inductors and suppression capacitors. This time I reused the external wire-wound resistor, which was in good condition. This saved me having to find room for a 5.4 ohm resistor. Also, I intend to put this mixer to regular use. The smaller ceramic encased resistor I used in the A has not been sufficiently tested under load for me to be confident enough to use it here. It’s an option if the original resistor ever fails.
So those are the main differences. To finish I’ll leave you with some images of the restoration. Thanks for reading.