Restoring HP25 S/N 1702S13138 - Very strange take a look

[albertofenini]

(05-30-2019 05:44 AM)teenix Wrote:  The 0168 is a replacement for the 0153. Maybe it was a code change.

Maybe the power supply had some modifications also. The PCB holes look filled with solder from the original assembly process.

cheers

Tony

Ciao Tony, we knew about the 0168 as a replacement for the 0158, so this doesn't surprise
However, the PSU modifications are exactly about where the Vdisp is generated and in this unit Vdisp is too high
We'll try to see if Ø1 and Ø2 are good, it's a test we have not done yet
The board looks intact, no previous attempts to be repaired so the modification looks original
What's your guess for a wrong Vdisp, where and what could we investigate ?
Take care !!