Shoebox Comptometers - Repairing

Ah yes! Well, what did we expect? Did we really think these old workhorses would be in perfect operating condition after 60-100 years of service? Of course not! However, as Ray Mackay will tell you, they can be refurbished to operate like a clock. But it probably will NOT be a easy path. You'll need patience, care and, quite possibly, some parts. Read on...


Testing your machine...

The very first thing you need to do is determine if your machine is operating properly and, if not, exactly which keys and/or functions have gone awry. Click here to do so.

H-model repair manual

In February of 2001, Jay M. Goldman, an avid Compt collector, generously provided me with a copy of an official Felt & Tarrant repair manual for the H-model machine date Oct. 1919. It runs to some 50 pages plus 9 "figures" and was clearly intended for use by F&T repairmen. Should any doubts arise in the process of diagnosing a malfunctioning machine, this manual should be considered the "last word", allowing, of course, for applicable model differences.

Opening the case...

Prepare a table working area about 3 or 4 feet long and cover it with newpaper, a cloth or pad to catch the debris that will surely be present. Use a screwdriver that closely fits the head slots to avoid burring them should resistance be encountered. A small tap hammer will often help in stubborn spots. Have a cup or small box nearby to save screws and other loose parts while working.

Special Note... (case corner)
The four corners of the case have small screws holding the sidepieces together. Due to day-to-day twisting and stress over time, the original close corner fit will have undergone some distortion. Normally, there should be NO reason to remove these screws and you could find it virtually impossible to reseat them. Simply leave them alone! If you have a machine where one or more are missing, you'll need to do some very careful stressed-alignment to get them back, assuming you can locate suitable replacement screws at all.

The "clearing lever" should be removed first by unscrewing at its base and gently working it free from the inside mechanism. If your Compt has just been unearthed from some back office supply closet, this procedure could require some patience and careful back-and-forthing. Such machines are often corroded so take care not to mar or dent the case while performing this task.

Next, remove the 2 screws from the lazy-S "answer-shelf" at the front and gently tap upward under the front lip until the shelf separates slightly from the case. On B-models only (SN25000-34999), it will be necessary to remove the 5 or 7 screws just under the "1"s keyrow. The shelf can now be taken off by carefully working it forward first from one side then the other. Fitting this shelf back can be a bit trickey as the left and right sides must be coaxed to work together for the side positioning pins to seat properly.

Now the machine should be turned on its left side and the four bottom corner screws holding the main case to the underside of the inside frame removed. On most 10-column machines, there is a row of 4 screws across the center that hold a case stiffner. Do NOT remove those. You may note at this point the sorry state of the four rubber "feet" that typically are flattened, crumbling, etc. As a final step, you might wish to replace these with near-original feet.

Next, the mechanism with the keys and "keyplate" attached must be coaxed out of the case. Warning, it is VERY easy to get a finger or two pinched in this process! DO NOT attempt to pull the mechanism out from the top or lift the case off from an upside down position. Always with the case on one of its sides, work the mechanism back and forth gradually edging it free from the case. Carefully turn the assembly this way and that way with a nudge here, and a tug there. Bit by bit, the case should become free and can be set aside for later cleaning.

Replacing a key...

If your shoebox Compt has a missing keytop and/or bent keystem you'll need to be aware of how to approach the matter.

As Ray Mackay advises...

"NEVER fit a top with the key in the machine! If the error mechanism is locked you will break the hook that locks the segment lever from the lever itself or bend the segment lever locking hook retaining piece, It is also possible to damage the segment lever or keystop lever and then you have a long job to fix either.

"Keytops were fitted at the factory to keystems with a peened hammer so they would not work lose as the keys take quite a thrashing in normal use. Since tops could become brittle and shatter, repairmen were supplied with keytops prefitted to stems for replacement purposes."


Obviously, keytops alone are rarely available so the usual way to remedy the situation is to replace the combined keytop+keystem as Ray recommends above. While not exactly rocket science, this does require a learning curve which, depending on one's mechanical inclinations can be either inordinately burdensome or a piece of cake.

Except for the earliest wooden case models, most shoebox Compts look pretty much the same underneath. There are two pieces that need to be removed in order to be able to pull the keystem cleanly out of the mechanism and up thru the keyplate. With the machine resting on its left (non-lever) side, identify the two pieces by depressing the desired keystem from the top a few times. The spring action should be apparent.

(keystem spring assembly) You should note a thin but strong wire (the keyspring) which can be released by positioning the length of the spring under your thumbnail and carefully removing the end from under the bent lug on the frame. ALERT! When removing this wire spring, you should wear safety goggles as there is a danger of it "sproang"ing out of control.

With the tension removed from the keyspring, it could simply fall off or require some gentle wiggling. The similar-sized sheetmetal "lazy A" gismo to which the spring was attached (the keyspring retainer that I'll call an "A-frame") should now be loose enuf to be easily removed by finger. You can now gently work the keystem out of its seat upward thru the keyplate.

It is recommended that the first time you perform this operation, you immediately reinstall the keystem just removed, reattach the metal retainer and its keyspring and test that the key works as before. This should fix the procedure firmly in your mind. Then simply repeat the removal and you're ready to repair or replace that particular keystem.

For some time, I assumed that all keysprings (the wire thingy attached to the "A-frame" member) were interchangeable and that differences in keystem lengths required no compensation within the mechanism. Not so, it turns out as Tom Thorton of Morristown, NJ recently advised...

"...the keysprings (on the A-frame) are different tension depending on key number. I believe there were three different tension springs used but looking closely you could eye ball the difference. (wire size is different)"

...and, of course, we have Ray's confirming remarks...

"The lower keysprings were of a heavier guage than the higher ones. This is, of course, because the 9 key transits a further distance so the roll section of the spring develops more kinetic energy. I am not sure if the 3 different sizes are correct as I though there were four."

On H- and J-models there appears to be some trick to getting the keystem retainer pieces of 1-keys and 9-keys reseated due to the presense of top and bottom crossbars. If you encounter this, a slight bending of the "lip" on the frame member should allow the "ear" of the A-shaped retainer to be reseated. The lip should then be returned to its original shape if possible. Warning: doing this more than a couple of times risks having that lip break off.

If, by some chance, you locate a keytop and want/need to fit it to a keystem, we again turn to Ray Mackay...

"To remove the keytop put the keystem in a vise and gently ease the keytop off the key. It is wise to have soft metal guards on the vice so not to mark the keystem with jaw marks. You can now tap the new keytop onto the key."

There remains much more to be discovered about the inner workings of these dreadnaughts of yesterday's office and additional information will be posted as it becomes available.

Recently (late 2000), I had occasion to do a full keyboard replacement on my SuperTotalizer as I needed to replace all the light colored keys (they were of the "shrunken caramel" type and quite ugly). Things went swimmingly until I was halfway thru the job when suddenly a column with keys 5 thru 9 started jamming up after I'd installed the 4-key. After a couple of frustrating hours, I wrote Ray Mackay about the problem and here is his (somewhat edited) reponse...

"When cleaning out a machine, I always removed all the keys. This meant I could see what was happening as I slid shafts out to be cleaned with very fine wet and dry emery cloth.

Once the mechanism was out of the case, all the keys were removed and the keyplate also removed. We then removed the front registers (dial wheels), particularly if the machine had a rock-frame (H & J models) as the shafts on these could only be removed with the frame out of the case.

We had a bath which can be made out of half a kerosene can, (ours was a professional model). We mixed one gallon of kerosene and one gallon of Shellite. The machine was then dunked down and up until all the muck and grime was removed. Using the same bath, we next washed all the dust and grime residue from the keyslots on the keyplate. The bath was then allowed to settle and the gunk slowly decended to the bottom. The semi clean stuff was then poured through a nylon stocking filter back into the can for further use.

Using a set of follow-thru shafts, (you can buy lengths of about 30cm in various gauges from your local tool shop) we ground the end dead flat and removed any burrs. We then followed each shaft through, one by one, cleaning oiling and replacing them as we went. Some shafts have a fine spring on them such as the accumulator locking hook springs and the trigger springs. Each of these was carefully observed as we moved through the hole to make certain it had not dropped off. Particular care was taken with the bronze bearings in accumulators and the locking dogs in rock frames as these were extremely susceptible to gumming up.

After cleaning all the shafts, oiling and refitting them, we used an old nine 9-key cut off about 3 cm below the segment lever and keystop lever pertrusions (the offset "shoulders" on the keystem). This meant we could insert it between the segment lever and keystop lever and operate each column observing that all the trigger adjustments were correct.

Once we knew everything was right we put the newly cleaned keyplate in place, donned goggles, sat the machine on end and replaced all the keys. Starting with the 9-key and the 2-key assures that the opening between the four levers is maintained. Even so it was still very easy to get a keystem hooked between the levers and one had to take care. The whole process would take about 1 hour; so you can see you built a kind of proficiency.

Since everything was checked before refitting the keyplate, we then knew that if things didn't work properly we had either knocked a spring off or put a key in incorrectly; although incorrectly fitted keys usually revealed themselves after one or two other, incorrectly installed, keys were fitted.

NOTE :- Not all keystems are the same length so it is important to check them before fitting them. It is also important to keep the keys in the original columns especially if a key had the segment lever or keystop lug peined to compenate for wear and tear."


To continue with my own full keyboard replacement experience:

Except for colors of course, all F-, H- and J-model keystems in the same row are identical (note above that Ray takes exception to this) so there is no need to keep them separate to guarantee getting them back where they came from. Same is true for all the A-frames and wire springs (I generally let the springs just hang onto the A-frames after removal but if they fall off, thats ok, too).

Removal should proceed column by column starting from the pennies column and working to the hi-order column (because of the overlay of one of the A-frame "tits" on its neighbor). Which key within a column to remove first doesn't much matter but you should pay special attention when removing the 9-keys and the 1-keys. These are partially under cross-bars and therefore a bit trickier to remove.

Please note that Ray Mackay prudently recommends wearing safety googles while removing or replacing keystems to minimize the risk of one of the wire springs flying into your eye. I cant argue with the logic as one simple misstep could be a disaster but I confess that I dont do it because I cant see well enuf thru the googles. But I'm *VERY* aware of the danger whenever I'm releasing a spring or rehooking one and, once I've positioned my thumbnail and the spring is close to being seated (or unseated), I look away until the deed is done (or must be re-addressed).

When it comes to putting all the keystems back, I've found that its best do it column by column reversing the removal sequence; that is, hi-order column first, pennies column last, again, because of the overlap of the A-frame "ears". Within a column, restore the 9-key thru the 5-key first and then the 2-key, followed by the 4-key and 3-key, leaving the 1-key for last. Take care to be certain all stems come down between the dual segment levers and not outside of one. Also, check the key's operation after installing each. The 9-keys are quite tricky to get back in so expect it to take a bit of time and care to get the first one properly installed. Again, its those pesky crossbars that get in the way. The 1-key replacement is likewise no "piece of cake" so take your time there as well.

And when you've reached the final pennies column you'll have an especially tricky time with the 9-key there since the A-frame left "ear" must hook under a matching "lip" on the machine frame and there seems to be no way to both get it under there and deal with the crossbar restriction as well (you'll have a similar problem with the 1-key in that column). I've reached the conclusion that the only thing to do is gently pry the "lip" on the frame member up a bit, get the A-frame "ear" under it, seat the A-frame with its keystem and then restore the bent frame member "lip" back as best you can (whew!). Perhaps there is a better way to do this but I have no idea what it might be. Here is where you will need patience for sure. Oh yes, the other keys in that last pennies column should be no more trouble than with the other columns just completed.

When you have all keystems out of the machine is a good time to give them a thoro cleaning. The keytops are easiest but the stems are often corroded and always grimmy to the nth. I use fine emory cloth soaked in water (Ray Mackay's preference) but other ways should work just fine. And, of course, after installing the mechanism back in the case, inserting the bottom screws, fitting the register cover and clearing handle, you'll want to give each keystem its drop of light machine oil to insure trouble-free operation over the next century.

Before considering the job done, you should run all the normal tests just to be certain nothing has gone awry. In addition, Tom Thornton, of Morriston, NJ, advises the following special tests:

Using both hands, press all 9s ten times continously & rapidly to insure that the carries work properly. Hold down the left hand 9, then strike each 9 to right 3 times, (each will hang) thru the 1st column. Then let go the left to insure that all delay & carry over properly. Do a partial keystroke on each 9-key and 1-key to assure that they lock the machine as intended. Also, insure each sub lever cuts off its carry (hold lever in, hit 9 three times).


Return to Comptometers Home Page
21007
eMail