Tuesday, August 1, 2023

Getting a Mignon to write again - feed rollers and adjusting the type

This rusty old Mignon index-typewriter needed some repairs to make it functional again. From browsing online, a fairly common issue with Mignon typewriters is that the feed rollers are 'gone' and glued to the platen. This made that the platen didn't just not feed paper, but it couldn't even be turned - blocked solid.

Removing (and putting back!) the carriage on a Mignon is easy, even simpler than it is on an old Oliver typewriter. Place the left margin-stop between two positions - this will keep the lever of the margin-stop in the up-position.

Then press down on the space-key and/or the carriage-release and simply slide the carriage off to the right. (The space-key and the carriage-release are actually the same function, a 'press' on the carriage-release will space the carriage.)

With the carriage off, unscrewing the plates at the front-sides of the carriage allows the margins-bar and ruler to be removed. Take care to catch the little springs that press the ruler agains the platen. This then gives access to the feed-roller springs that can be removed using pliers - note that these are spring-steel and the forked ends are genuinely sharp!

Temporarily loosening the brackets that hold the feed-roller assembly then allows the complete feed-roller assembly to be wriggled out to the front of the carriage. (I.e. no need to remove the platen; platen is held with pins, pins may not be without rust, etc...)

The feed-roller assembly is held together by double M2 nuts on all axle-ends. When these are removed, it all comes apart. Note that the centre pivot-axle is not symmetrical - there is a left and a right end! Note that also the four connecting brackets are all different and need to go back on their correct position in the assembly.

The feed rollers (now unstuck from the platen) had indeed become 'triangular' and beyond repair. To replace with new rubber, the old rubber was cut away from the core tubes of the feed rollers. Messy.

The 3 front-rollers and 2 rear-rollers reduced to metal tubes, can then be re-covered with a few layers of heat-shrink tubing. The front rollers to approximately 8mm diameter, the rear a bit larger to about 9 or 10 mm. (The Mignon is not very critical on roller diameter :-)

The feed-roller assembly is then put together again - and manoeuvred back into the carriage from the front. The assembly pivot-axle is clamped/held by the side brackets. 

The two curved-springs can be placed back with pliers, to lock behind the notch on the carriage-frame. Ruler and margin-bar replaced and side-plates screwed on to complete the carriage. (And paper-table put back, had taken that off for convenience and to reduce the risk of damage.) Scraping and light sanding of the platen to remove remnants of the feed-roller rubber sticking to the platen, and the carriage again feeds paper!

The carriage then placed back into the machine (easy), it turned out that only the top-halves of characters would print. This must've been an issue for some time, because this machine had the type-cylinder propped-up with a scrap of paper when it was bought. Instead of messing-about with scraps of paper jammed under the cylinder, the type-rod can be adjusted on the machine. This again is fairly easy on a Mignon.

Remove the single screw and remove the cover; press down the two keys to allow the cover to move forward and away with ease. This reveals the core of the mechanism of the Mignon, in all its brilliant simplicity. The large lock-nut holds the large central set-screw that captures the horizontal rod. If needed, adjust this set-screw to make the pointer move freely (yet not too freely). 

The 'flower-wheel' behind the lock-nut adjusts the position of the type-rod and thus the vertical alignment of the type. The little tab behind the rod needs to be pushed back to unlock this wheel, then this 'flower-wheel' can be rotated left/right to move the type up/down relative to the platen. The tab-plate springs back and locks the wheel in position to prevent drift of the vertical alignment during use.

A bit of fiddling and experimenting finds a decent spot for all platen-positions, so that the full character height is again printed. Still a bit top-heavy, but acceptable for now.

With the vertical alignment adjusted and paper feed working too; a new ribbon fitted and this Mignon can write again :)

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