help! prbs bldg ALDL interface

[Eric Deslauriers]

Anyone out there who is an electronics guru, I can use your help. I know
enough electronics to fill Thumbelina's thimble, most of which I've
learned on this project. Oh, and let me thank you in advance. FYI, I've
tried TKM, but he was having problems building his cables to do this, so
I've decided to go try it on my own (maybe that's why I'm having
problems?).

I'm trying to build the circuit shown at
http://www.techedge.com.au/vehicle/aldl/160/aldl_hw.htm so I can
diagnose my Blazer's lean code (should be a lean condition with the new
cam). I THINK I have it all done right, but I have a few questions.

Q1: I used a 2N2907A rather than a BC557 or a 2N2907 as detailed in the
schematic/notes. According to the electronics guy, it was the same.
According to one website I found, they are interchangeable, but one is a
PNP and the other an NPN. From what I could tell, the only difference
was the material it was made of. Let  me know where I'm wrong and what I
missed please.

Q2: Looking at the schematics, the Collector ties into the 12v/LED wire
and the Emitter into the CTS/DTR line - right? I'm basing this on
holding the tab @ 7:00, staring at the ends of the pins and making the
Base 12:00 and the Emitter 9:00, the collector 3:00 as detailed on
several web pages I found.

Q3: The LED has the positive side closest to the 12-volts lead (H),
right? And that's the side WITHOUT the flat spot (and was the longer leg
before I cut it off if I remember rightly).

Q4: Will having 12V at the CTS/DTR pins nuke my serial port? 'Cause
that's what I'm getting and it makes me nervous to plug 12v into a 5v
port.

Q5: Does anyone have a better ALDL pinout? The one on the page seems to
differ from mine since my 12v  is pin C, not H. My wiring diagram
supports that. A and B are correct  since I short those with a paperclip
to read the blinking light. How can I tell which is the data line
(that's not clear on my  wiring diagram)? This has to be for a non-8192
baud, TBI ALDL.

TIA, TIA, TIA, TIA

Eric D
88 K30 Blazer

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