Commodore MPS 803 printer, cleaning

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I recently recovered an old one Commodore MPS 803 dot matrix printer, abbandonata in cantina. Le sue condizioni non erano proprio ottimali, ma, per fortuna, funzionava. Ho quindi deciso di procedere ad un'accurata pulizia e lubrificazione.

Commodore MPS 803 Printer Features

The Commodore MPS 803 printer is a dot matrix printer, produced since 1985. It can print on single sheets of A4 paper, but also on continuous form paper, using an optional cart.

I caratteri, già presenti in ROM, sono composti da una matrice di 7x6 punti. La densità è 10 caratteri per pollice. Relativamente alle prestazioni di stampa, la Commodore MPS 803 può stampare in maniera bidirezionale (sia quando la testina avanza che quando ritorna), con una velocità di 60 caratteri al secondo.

Printing method: dot matrix printing (Impact Dot Matrix).
Character dot matrix: 7 (height) x 6 (width) dots.
Dot size: 0.3mm.
Print speed: 60 characters / second.
Character size: 2.4mm (height) x 2.2mm (width).
Text line width: 80 columns.
Printing method: bidirectional printing.
Paper transport: single pages or units (tractor) for optional continuous paper.
Type of tape: KMP tape, black nylon.
Paper width: A4, Letter and optional continuous paper from 102 mm (4 inches) to 254 mm (10 inches) wide.
Copy / carbon copy: original + 2 carbon copy.
Graphic printing: 7 vertical dots, 480 horizontal dots, per line.
CPU: NEC µPD7811G, 128 byte di RAM, 10 MHz.
ROM 4 KB (EPROM 2732).
Power Consumption: 8W idle, 30W printing.
Weight: about 2 Kg.

Internal and external cleaning of the Commodore MPS 803 printer

Per smontare la stampante e pulirla internamente ed esternamente, ho dapprima rimosso il carrello per il modulo continuo (tractor), poi il coperchio superiore, infine il nastro dell'inchiostro. Per questa operazione non sono necessari attrezzi specifici.

Ho quindi svitato le due viti che fissano il secondo coperchio. A questo punto si può rimuovere anche questo secondo coperchio, che protegge l'interno della stampante.

Pay attention to lift the cover, because the cable for the button and the LED is present, which must be disconnected from the motherboard.

After releasing and removing the cover, you can move on to removing the printing unit, which contains the roller, head and motors.

Here too, it is necessary be careful not to tear the electric cables. First you have to move the head all the way to the right. The head flex flat cable can then be pulled out of the motherboard.

After unscrewing the two fixing screws of the printing unit, disconnect the rear connection cables (those of the stepper motors and the micro switch).

The printing unit is equipped with some adjustment levers. I recommend consulting the service manual, attached at the bottom of this page, for further information.

As can be seen from the service manual, the printing unit can also be disassembled by removing the roller, gears and other components. If you are not experienced, I do not recommend disassembling the printing unit.

In the lower part of the printing unit, there is the microswitch that aligns the head to the left: I recommend deoxidizing it.

Once the printing assembly is removed, you have access to the motherboard.

Per rimuoverla, bisogna svitare le viti che la fissano, le viti dei cavi di massa, nonché allargare delicatamente i gancetti di plastica. Anche gli altri componenti possono essere rimossi, per procedere ad un'accurata pulizia della parte inferiore del case. Rimuovere la scheda madre e gli altri componenti è un'operazione è un po' delicata: I only recommend to those who have a good dexterity to do it.

Dopo aver spazzolato e pulito accuratamente (ma delicatamente) tutte le parti, è possibile procedere a lubrificare le parti in rotazione (ingranaggi, alberi, ecc...) e la guida (barra metallica) che sorregge la testina di stampa. Come suggerivo prima, it is advisable to read the service manual (attached at the bottom of this page) to clean, lubricate and adjust the printing unit.

Anyway, avoid using too much lubricant! The quantity must be minimal and, above all, the lubricant must be carefully positioned, without dirtying and mixing the other parts.

After having cleaned and lubricated everything, it is possible to reassemble the Commodore MPS 803 printer. To reassemble it, simply retrace the steps described above in reverse! Remember to reconnect all the cables (including the 4 of the printing unit and that of the button / LED) and to gently screw all the components back on.

As you can see, the result is excellent and the printer, reassembled, looks really good!

To test the printer, I used the Easy Script word processor. I made a video with step-by-step instructions for using Easy Script and printing with the Commodore MPS 803 printer.

Documentation

In support of this article, I attach the Commodore MPS803 printer service manual.