Jaycar Digital Air/Fuel Ratio Meter, Boags..! help!

[sabretooth]

Can you verify the input voltage with a multimeter?

[Astroboysoup]

yes i can

power source says 12.0 and multimeter says 12.05, close enough id say.

First step was to test the power regulator circuit. see if 5v was passing through the IC1. tested pins 4 & 14 with the multimeter and pretty much spot on 5v +- 0.0 V which i didn't think mattered too much.

inserted the IC and then the display board., checked for shorts.. soldering was pretty much spot on and perfect so that was all good.

next was to adjust the dimmer and the display. attached the sensor to earth or negative and go the L for lean and adjusted VR1 in the dark for the display to just appear and then again with a bright light to get a good overall adjustment.

now this is where im having problems adjusting trimpots vr2 and vr3.

solders the 1.8k resistor to the board between IC1 pin 9 and and earth source. tested the source voltage and still 12v which is what you;d expect.

now i hooked things up and the display went to the - . as expected so i adjusted trimpot vr3 as described and turned fully clockwise and the display didn't change. thats where im stumped!!! it should go to zero

so ignoreing that test step i moved on leaving the trimpot fully clockwise

next i connected up a 5v power source and the 1v source as stated in the instructions. to try and adjust vr2 but seriously no luck there

the highest the thing will go up to is 1.6... instead of 10.. grrrrr

i give up... anyone want to have a crack at it?