If the complaint for NEC P8000 printer was a missing line across the printout, immediately we will suspect the printer head or the ribbon or even sometime the ribbon mask. Among so many brands of dot matrix printers, only this model has one common fault which is the printer head and the printer driver ic’s spoilt.
If you just replace the printer head without changing the main board or checking the printer driver ic for any short circuit, then chances are high that once you switch on the printer, the printer head would immediately breakdown again.
Thus it is wise for you, if you ever comes across this type of printer, besides replacing the printer head, you must check the six printer driver ic on the main board. As for the Dubai printer head, you can buy a new one or send to a specialist to refurbish it. Now the real question is, how do we check or test the printer driver ic’s? It’s simple, remove the main board and you will observe that there are six ic’s that have the same part number which is the STA476A.
If one of them shorted, it will short the printer head pin. Each printer driver ic control 4 pins thus six printer ic would take care 24 pins! That’s why in the market, they called it as 24 pin dot matrix printer.
Normally I would use huntron tracker to compare the signature between a good and a bad ic. It is very easy to find the culprit when you can compare them. Using an analog meter also can do the job. Compare the resistance of all the printer driver ic’s leg, if there are any shorted printer driver ic, the meter would register the reading and usually the needle would kick to most far right.
Sometimes it could be more than one ic shorted. Once you have determined which ic that gave way, solder it out and replace with a new one and you have just completed a printer repair job.
Whether you are checking the NEC P8000 printer or any brand of dot matrix printers, use the procedure above to test out all the printer driver ic before you switch on the printer. This not only saves your new printer head, it will save you money of not having to buy a new mainboard