Modification HP1663C to HP1662C, HP1661C and HP1660C

[GB97816]

Hello, I bought a HP1663C logic analyzer and disassembled the device. The capacitors in the power supply have been replaced. The first traces of leaked electrolyte were already visible. I noticed that the assembly of the acquisition circuit board is very similar to the HP16550A.
So I desoldered the components from an HP16550A and soldered them on the acquisition board according to the assembly of an HP1662C. With the addition of two 42R2 resistors at U21 and 31R6 for R61, this also worked fine. The device had 68 channels on it, corresponding to an HP1662C. For this I use a photo of the board of the HP1662C.

In high spirits, I then also assembled the remaining components for an HP1660C. However, I do not have a photo of the acquisition card for this device. Unfortunately, that didn't work, the device reports an error in the timing circuit of the additionally installed acquisition chips. All other tests pass.
The same problems also occur if only the HP1661C assembly is added. So a 64 CH update works smoothly, but something doesn't fit on 96 CH or 128 CH.
Apparently it is not enough to add the assembly of the clock lines and the (probable) chip enable signals. Does anyone have high res photos of the HP1660C's acquisition board (01660-69517; 01660-66517) or of the HP1661C's acquisition board (01660-69518; 01660-66518)?

Thank you for ideas and help.

Greetings Georg

[GB97816]

Hello,
a photo (from HP1661C or HP1660C) of the following areas would be helpful.