I've wanted to have one of these scopemeters for a long time but they are not cheap specially if you are in Canada. Finally I got this nice looking but dead 199C for a good price and I thought with service manual and schematics I can fix it
The unit is in pristine condition with 2017 CAL sticker and inside is untouched but it does not power on
I don't have the battery yet but with connecting the adapter, I hear a weak beep and that's it. Also by pressing and releasing the power key OR by pressing the ^ + > and power on , the same thing, a faint beep.
So I went through the steps in the service manual and did extra tests of my own based on the circuit operations and schematics and here is the result:
The 3V3GAR voltage that supplies the D-ASIC and all the memory chips is alive and solid. All three clocks (32KHz, 3.68MHz, 40MHz) are alive
Voltages and signals around the P-ASIC are all fine except that the POWERON (H) signal does not come from the D-ASIC thus the Flyback converter does not start so all power supplies are down.
The power on key functions properly (bit goes down with pressing)
There is a triangular 416.5KHz waveform at MS3603 (ROW1) which according to the manual is generated by the mask ROM. However, it is not 3.3V but 0.4V peak
There is not activity on the WDI pin of the watchdog IC
So, I still believe the mask ROM is running and perhaps something happened to the memory module flash (corrupted, cleared, etc...) but the beep and 416.5KHz give me some hope that the D-ASIC is ok
Do you have any further suggestions as to how to proceed from here? Am I right about the D-ASIC? Is there any way to fix this?
I don't have the IR serial adapter but the actual serial TX/RX pins (3.3V) are available on the board.
I was thinking maybe I could connect them via a FTDI adapter and do the RAM check which is in the manual and maybe even flash the eeprom with new firmware?
I am new to this kind of thing, so any help, even with the very basics, is highly appreciated
there are so many of these scopemeters with similar symptoms being sold on ebay all the time and I thought people must have found a way to fix them but repair reports/diaries are non existent!