The Sinclair QL Forum

I have six QLs and just wanted to categorize them.

How can I recognize the revision of a motherboard without dismounting micodrives to flip the board (I've seen revision once on the backside of the board).

Issue 5 boards have a number of zero-Ohm resistors to the bottom right of the ROMs (JU1-JU6) to set up the ROM/EPROM configuration. You won't find them on issue 6 boards. Also, they have a MOLEX connector for the upper case LEDs instead of the fiddly connector on the issue 5.
From the outside, it's even easier: Provided your board has never been changed, any signs of "Samsung" and "Made in Korea" are strong clues towards issue 6 inside.

Tobias

Many thanks tofro. The hint with resistors did the trick. Additionally I have just found this tremendous site about QL's motherboards: http://www.sinclairql.net/build_standards.html