PM2 suddenly show only zero

[kreutpet]

hi ,

i have been searching this forum to find some hints about trouble shooting PM2 monitor issues. I am aware that the PM2 to is already very old and most recommend to migrate to PM5.

Anyway, I am actually quiet happy with the PM2 and do have some electrical engineering background.

So i first replaced the pickup wire, which unfortunately did not changed the issue. The monitor still shows zero.

So i opened the PM2 and first saw some corrosion at the battery holders.
My board is a "Concept II Rev2.1Enhanced Pm II"
I removed and cleaned the battery holders. The board is still in perfect shape, only the battery holders had some corrosion. Everything looks fine so far and a checked the board for obviously defect components. Did not see any defect components.

I verified that the 3V voltages is received by the U10 max859 (DC-DC Converter) and the output of the pin 6, which is 3V

The U11 max1044 (switched-capacitor voltage converter) shows on pin2 1.5V and on pin4 -1.4V


My assumption is that the voltages are OK.

So i continued to follow to circuit to the U9 Comparator Max922, which i assume is for the signal coming from the pickup.
First i checked the pins on the wire pickup plug. It seems that the connectors of the plugs are good soldered to the board as they have good contacts.
I checked the supply voltage of the max922 and measured on pin7 3V and on pin2 0V.
On pin3 I measure 2.85V



Can anybody give a hint on how to verify the supply and pickup circuit on my PM2?

Thanks

[Citroen]

Put pictures on https://imgur.com post the BBCode links to your pictures on here.

[Carl Watts]

Send me a Private Message, I can help you fix it.>>>>> Use the contact on the right of the screen.

I'm not that keen on posting the fix on here, I make money out of fixing these but am prepared to help someone with an electronics background that clearly demonstrates they know what they are doing repair their own personal monitor.

Cheers,
Carl.