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Just a quick one today, we’ll be looking at the Card Star Thermodrucker thermal printer, a low cost parallel thermal printer, I wonder how old the design is as it has a parallel port. I picked it up on Ebay about 2 years ago now to use for address labels when mailing out items. There seems to be low cost USB thermal printers for not that much more.

With the printer I got a parallel to USB cable and an overseas AC adapter rated for 9V AC at 300mA, I’ve been wanting to change the adapter for something else, so we’ll have a quick look at doing that too.

A few clips later and we’re in. We can see the thermal print head and motor sit above the PCB, held in place by 2 screws/risers, the print head connects via a flat flex cable and the motor just through some wires. There are some decent sized capacitors, Richey 1000uF 25V and Richon 1000uF 6.3V and we have zener diodes on some of the parallel port data lines. The PCB date code is 03/97!

Once we remove the print head/motor, we can see the main chip is the Siemens SAB-C501G, an 8-bit 8051 MCU which can run at 12/24/40 MHz with 256B of RAM, 8Kbit ROM, 4x 8bit ports, 3x 16bit timers and USART to name a few features. For an MCU like this back in the day, it wouldn’t have been too bad at all. The PCB says Digitronic and so does the MCU, I guess they had them programmed at the manufacturer.

There are 2 other chips as well, the Motorola 14069U Hex Inverter and the ST ULN2804A Eight Darlington array which looks to be driving the print head directly.

Lets take a look at the power supply side, they are re-using an RJ11 connector to feed in the power which goes to an bridge rectifier and gives 14.7V out and the 1000uF capacitor is connected to this too. An ST L4941 LDO gives out 5V to all the components. My only concern was the motor, perhaps it needs a specific voltage. I connected 8V to the 1000uF capacitor and everything worked then I reduced it to 5V and it’s still all good, so now I can change the AC adapter to a 5V DC one.

One Response to “Inside the Card Star Thermodrucker Thermal Printer”

  1. Matt says:

    Something mildly interesting: Thermodrucker is just german for thermal printer.

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