Rohde & Schwarz CMS-50 input Ceramic substrate burned and "DSP Time out"

[BH3TXW]

Hi all,
Recently a friend acquired a CMS-50 with nice shape and appearance. But input attenuator/power splitter on white ceramic pad is burned, and DSP Time-out keep appearing on screen.

For input attenuator. I suppose it is a Y shape power divider on ceramic substrate. There are 3 arms of this Y shape. The one connected to relays' board looks good, we checked it out with DMM which shows 16 Ohms. The one connected to front panel N-type I/O is apparently burned. The last one connected to detect diode side is also broken by crack across of it. We decide to restore this by adding chip resistors to make the machine at least capable of measuring hand-held radios. But we just can't figure out how much ohms should be on each broken arm.

For DSP Time-out. We have extender cable attached. On Measuring Section, D500 DSP56002 is replaced, electro caps are replaced, all Vcc and Gnd are checked, and 20 MHz on EXTAL is also checked. On Digital Unit, D33 74HCT244T and D34 74HCT245T look like part of DSP interface, are replaced too. However, the error message "DSP Time-out" remains showing up and modulation and AF output are still crippled.

Service manual we have is only for CMS52. Now we got no clue to sort it out. My friend doesn't speak English and I wonna help him out on this.

Any suggestion or any input is appreciated!
Thanks!
Regards,
James - BH3TXW