Re: HP 2225A Thinkjet Printer not printing Message #13 Posted by Tony Duell on 3 Aug 2005, 3:55 p.m., in response to message #1 by Ronald
Firstly, I have the Thinkjet _service_ manual with full schematics. If you contact me at the above (unmunged) e-mail address I can look stuff up for you. This manual is not alongside me at the moment, so I am working from memory.
One thing confuses me. You mention that the battery is fully charged, but the Subject line refers to the 2225A which IIRC is the mains-powered HPIB model. There are significant internal differences mostly due to the different PSU (which leads to the motors being different!). What are you working on?
I think you've done the first test. The flexiprint cable to the PCB is the printhead connector. One of the tracks -- I think it's the middle one -- is obviously different to the others, it's the common connection. The others are the drives. With the cable disconnected from the PCB, check for resistance between the common connection and each of the others in turn. If any are open, suspect the printhead or the flexiprint. Be warned that ink leaking from the cartridge often corrodes the flexiprint at the carriage end, and AFAIK the flexiprint can't be repaired. I have dismantled a carriage to replace it, but getting the part is presumably next-to-impossible now.
The printhead drivers are ULN2803-like things (maybe 2003's). They take 12 outputs (IIRC) from the processor chip (the big one, the other 2 large ICs are the font ROM and RAM, they communicate with the processor by something that's remarkably close to Saturn bus :-)).
In the battery-opperated Thinkjet (2225B and 2225P IIRC) there's a little switching converter to step the battery voltage up to drive the printhead. I think you should be able to measure something in excess of the battery voltage at the common connection to the printhead when the thing is printing. I can see if the manual gives a voltage for this point.
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