If the NEC P8000 printer complaint was missing lines across the printout then we immediately suspect the printer head, the ribbon, or sometime the mask. There are many brands of dot matrix printing machines, but this one has one fault: the printer head and printer driver ic’s damaged.
You can replace the printer head by replacing the main board without checking for short circuits or checking the printer driver. The chances are that the printer head will immediately fail again if you turn on the printer.
It is best to check the six printer driver Ics on any printer you come across. The printer head can be replaced or sent to a specialist for refurbishment. How do we verify or test the printer driver’s ic’s? You can simply remove the mainboard and see six ic’s with the same part number, which is the STA476A.
One of them will shorten the printer head pin if it is short. Each printer driver ic controls 4 pins, so six printer ics would manage 24 pins! It is also known as a 24 pin matrix printer.
Huntron tracker is what I use to check the signature of a good and bad ic. When you have the ability to compare the signatures, it is easy to pinpoint the culprit. You can also use an analog meter to find the culprit. Compare the resistance of the entire printer driver’s ic’s legs. If any are shorted, the meter would register that reading and normally the needle would kick at the most far right.
Sometimes there may be more than one shorted ic. Once you’ve determined the ic that failed, you can solder it out and then replace it with a new one. You have completed a printer repair job.
You can check the NEC P8000 printer, or any other brand of dot matrix printers by following the above procedure. This will save you time and money as it won’t cost you to replace your mainboard.
