DIY-WB LED problem

[Crescent Kao]

Hey Phil,
  Much appreciated for your assistance... I just performed the test you
described. With IC1 removed and pin 1 and 2 jumped on IC2 (IC2 still in
place), when I vary VR3, I get a voltage range of 0.63v - 0.85v
 With the jumper removed and pin 1 jumpered to the sensor input, when I vary
VR3, I get a voltage range of 1.97v - 2.65v

This was performed with 12v power and the 1.8k ohm resistor in place from
pin 9 on IC1 to REG1 as described in the testing procedure.

The results are kind of odd as they somewhat overlap the voltage range you
listed for each test. Perhaps I have the trim pots at VR2 and VR3 wrong? The
pot at VR3 is currently labelled 502 and VR2 is labelled 254.

Thanks.

Crescent Kao
Director of Marketing and Sales
www.c-speedracing.com


----- Original Message -----
From: "Phil Hunter" <ilphayunterhay at yahoo.com>
To: <diy_efi at diy-efi.org>
Sent: Sunday, January 20, 2002 2:21 PM
Subject: Re: DIY-WB LED problem


> Looking briefly at the schematic, here's my suggestion: remove
> IC1 from it's socket, nothing to the sensor input, on IC2a short
> pins 1 & 2, this will make it a unity gain buffer where pin 1
> follows the voltage on pin 3. Vary VR3 from end to end, pin 1 should
> vary from about 1/4 to 1/9 of 2.5V. Remove the short and jumper pin 1
> to the sensor input, this will turn it into a 3X amplifier, now
> varying VR3 should have pin 1 varying from 3/4 to 3/9 of 2.5V. This
> should give you confidence that all the input circuitry (with the
> exception of VR2, the 3.3K & the 560K ) is correct.
>
> HTH,
> philh
>
>
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