lost in modifications 4A

[1024MAK]

The transistor on top of the Z80 is the spider mod and is official.

Any extra connections to C27 would have been to a reset button (push to make switch).

The various capacitor, resistor and diode changes around the area of the right hand keyboard connector / speaker area are the DC-DC mod. However, as you have an issue 2 board, this may be an earlier version of the mod. Hence it may be worthwhile checking what has been done and comparing it to the last version (as on my blog).

The DC-DC mod is an official mod, but both this and the spider mod may be done differently (physically different, not electrically different) depending on who did the work.

It’s unusual to find the DC-DC mod done on issue 2 boards, as they were sold well before Sinclair developed the final mod. So only boards that were repaired or serviced would have had this work done.

Mark

[RobG]

Thank you for your answer.
Yes, it appears this board was fixed at some point, it has the latest ULA (6C001E-7,) which unfortunately is bad, D5 pin is not working