Groma Kolibri - platen removal
This machine is loved by many due to its beautiful design and near cult status after playing in movie The Lives of Others.
My machine had a problem with line advance mechanism: it was not engaging reliably, resulting in squeezed lines or no line advance at all. Serious problem if one wants to use the machine for fast, frantic typing like I do.
I suspected that the dog which catches the ratchet is misplaced or dirty but to get there I needed to remove the platen. Like many others I could not find, at first, screws which lock platen axle. On almost all machines they sit somewhere near ends of the platen cylinder but not on Kolibri. Engineers building this machine tried to make it as compact as possible - any unnecessary width extension was avoided, resulting in very compact “Macbook Air” of that era.
It turned out that two plunger screws sitting just behind the platen ratchet are these “droids which we are looking for”.
Removing them makes the platen turn freely on its axis. Thin, knurled knob at left platen’s end is, as expected, ratchet release for turning the platen in step-less mode. It acts as a simple, friction clutch, pressing the ratchet tight against the platen assembly.
After removing left platen knob and this friction knob the left end of platen axis is free. I removed also chromed masking plates on both ends of the carriage, to better see what I’m doing. Carriage back panel followed.
Before attempting to lift the platen it is necessary to unscrew line guide plate, otherwise it is too narrow for the platen to pass.
Leaving the right platen knob in place I lightly tapped (wooden or plastic mallet, to protect thin threads on platen’s axle) the axle towards the right. Once it started to move I pulled it out.
To avoid ratchet mechanism falling into parts it is a good idea to directly follow the axle with something of similar diameter, pushed into opening hole when the axle is being pulled out. I used threaded rod which I had at hand. It keeps the mechanism in place well enough to test its function while troubleshooting.
Before lifting the platen it helps to lock paper rollers assembly in back position. Since the arm operating this mechanism is being removed together with pulled out axle I used a screwdriver tip to lock the spring-loaded mechanism in position. It removes tension from the platen and makes life easier.
Once the axle is removed it is now straightforward to lift the platen out of the carriage. Line advance ratchet will fall apart so be prepared for that.
It turned out that on my machine it was just dried and gummy grease which hindered the dog to engage the ratchet. After degreasing and cleaning it started to function again.
Putting things back together. I started with ratchet wheel. It is being kept in tension by spring-loaded roller so one needs to pull back the roller with one hand, place the ratchet wheel with the other hand and the third hand can then push in a rod which will hold it in place for coming platen. Pay attention which side you mount the wheel - as this is a friction mechanism the side facing the platen is the one with extruded rim.
While all your three hands are occupied you use your fourth hand to make sure that dog’s steering hand (red arrow) is placed on top of the small metal tab (green arrow) - it will steer the single/double line spacing. It is easy to miss it at this point and it falls naturally below this tab or is pressed by the ratchet wheel in locked position.
It should look like this:
With all this in proper orientation we mount the platen. Paper table (or a miniature of it, really) has a metal tab beneath which holds the table steady in place. Most other machines use springs for that but on this Groma they simplified this - and it works very well.
When mounting the platen first drop its right side into the cavity and then place its left side ABOVE this tab, like this:
And Bob’s yer uncle!
Just squeeze in the platen into position. Pressing in the platen’s axle secures all parts in place.
Now there are just a few details which need to be taken care of.
The axle has flat spots which should land in proper position for plunger screws to hold firmly.
Observing through the screw hole will tell you if you are in proper orientation to secure the axle. It should look like that:
If misaligned it will look like that:
On the right side there is a spring-loaded (green arrow) arm which activates/deactivates paper rollers assembly. There also sits loose spacer cylinder (red arrow) - don’t lose it!
When the platen axle sits in position the spring needs to be hooked onto its notches. State “before” usually looks like that:
We want to mount the spring as shown with yellow arrows below. For better access I unhook the carriage release spring and move it back.
Hooking the carriage release spring back into position the final assembly should look like below:
And that completes the job. Last step is to screw back side and back panels and mounting the guide plate.
To hold these tiny screws on screwdriver tip I use a small trick: when I form my screwdrivers (grinding to remove wedge-shaped tip and make it parallel instead) I also slightly bend the tip (sideways) so it holds the slot screw by tension in place. There are very fine screwdrivers out there which accomplish it more elegantly by spring load but I cannot afford them so I use this dirty trick instead.
Photo session of this beauty follows.
Ribbon reverse lever discretely hidden on the bottom-right.
Bottom plate - evolution after Groma Gromina - keeps the mechanism enclosed, protecting it from dirt and keeping your clothes safe if you decide to type with the machine on your lap. Which is very convenient with Kolibri!
Referred as MacBook Air of these times the machine is indeed very low profile.