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Ok, after putting together the display and powering it up, it does its intro and displays 10.<=

Then, I put in R2 to calibrate and all I can get is Lo._
I hook up 1.4 volts (2x AA batteries and 20k pot) and it shows the same. Tried adjusting VR3 and VR2 fully both ways and even resetting after the adjustments. All it will show is Lo._
Checked the voltage on the sensor input and it is correct. Even tried 2.x volts as input. Can't get it to go off of Lo._

Everything is together including the modifications. It is now set up for dot mode, a/f, and unleaded. Won't go off of 10.<= or Lo._ in voltage mode.

Checked for misplaced components, shorts, and solder bridges. Wonder if my op-amp is bad. I used a ground strap when installing all the static sensitive parts.

Has anyone else had this problem?
 

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Slasher48 said:
Ok, after putting together the display and powering it up, it does its intro and displays 10.<=

Then, I put in R2 to calibrate and all I can get is Lo._
I hook up 1.4 volts (2x AA batteries and 20k pot) and it shows the same. Tried adjusting VR3 and VR2 fully both ways and even resetting after the adjustments. All it will show is Lo._
Checked the voltage on the sensor input and it is correct. Even tried 2.x volts as input. Can't get it to go off of Lo._

Everything is together including the modifications. It is now set up for dot mode, a/f, and unleaded. Won't go off of 10.<= or Lo._ in voltage mode.

Checked for misplaced components, shorts, and solder bridges. Wonder if my op-amp is bad. I used a ground strap when installing all the static sensitive parts.

Has anyone else had this problem?
Are all your trim pots located in the correct position according to their resistance as per the instructions? My kit was supplied with 4 trim pots, 3 of which are only used, and the resistance values weren't labeled on them. So of course I just threw any which trim pot in and expected it to work correctly. I had to desolder all the trim pots, test their values on my fluke and reinstall them in the correct positions.:mad: Other than that, I have not run into the problem that you mentioned. I suggest e-mailing Peter at [email protected] for advice. He said these displays aren't the best and they can be a headache sometimes. Maybe he can shed some light on your problem.
 
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All pots were tested before installing. I'll see what Peter says.

Thanks
 

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I was curious as to what are the specific advantages of DIY wideband A/f meter compared to say a Halmeter or a Lambda A/f meter. Also looking at the tech page it seems there are a lot of parts associated with the project, what is the cost of the total project and are all the parts available? Thanks
SH
 

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Slasher48 said:
Ok, after putting together the display and powering it up, it does its intro and displays 10.<=

Then, I put in R2 to calibrate and all I can get is Lo._
I hook up 1.4 volts (2x AA batteries and 20k pot) and it shows the same. Tried adjusting VR3 and VR2 fully both ways and even resetting after the adjustments. All it will show is Lo._
Checked the voltage on the sensor input and it is correct. Even tried 2.x volts as input. Can't get it to go off of Lo._

Everything is together including the modifications. It is now set up for dot mode, a/f, and unleaded. Won't go off of 10.<= or Lo._ in voltage mode.

Checked for misplaced components, shorts, and solder bridges. Wonder if my op-amp is bad. I used a ground strap when installing all the static sensitive parts.

Has anyone else had this problem?
Yep, I'm having this exact problem right now. Have you found a solution yet?
 

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Slasher48 said:
Not yet..
Found my problem. Hopefully your solution is as easy as mine. I was a big bonehead and with my messy workspace neglected to connect the grounds of the 12V supply with the 2 AA batteries for the test! DUH! Now everything works fine.
 

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Slasher48 said:
They're connected. Just get Lo._
On the site, they also mention trying to replace the 3.3K resistor with a 6.8K resistor. I wonder if this may help? Here's the quote:

Trouble Shooting (27 January 2002)
As with all kits, there are variations in the components supplied. We note that some people have reported being unable to set the lower calibration limit of 14.00 with 1.4 Volts across the sensor input, this can be "cured" (assuming there are no construction errors) by either replacing the 3.3 k resistor connected to VR3 with a larger value (say 6.8 k) or by replacing VR3 with the 20 k pot in the kit (though this will make adjustments to VR3 a little more "touchy").
 
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