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Hugo Holden
February 18th, 2017, 04:09 AM
There is an IC in these monitors labelled IC101 in the IBM documents with another number 221-88 or 86. The actual IC is a Horizontal sync processor & oscillator for the H scan circuits. The IC in these monitors I have, had their original labels deliberately inked over and a sticker applied on top. Looking under that, the IC has numbers printed on it that are 221-141 and L8420 which was probably the date and not a definite commercial part number. But, after a bit of research, I have concluded that this IC is definitely the Motorola MC1391P. This information might also help others repairing these vintage monitors.

modem7
February 18th, 2017, 04:45 PM
Thank you.
I have added that useful bit of information to minuszerodegrees.net, specifically at [here (http://minuszerodegrees.net/5155/crt/5155_crt_unit.htm)].