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Old 06-28-2006, 10:14 PM   #1
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ALDL circuit - MAX232 vs 2 transistor

For those of you with 8192 baud ECM's..... How are your experiences with your interface?

I had connection problems with the 2 transistor one, but I might have screwed it up or something... Just wanted to get some input. Please post your experiences with either the 2 trans or the MAX232 circuit (whether bought or built)!
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Old 06-29-2006, 11:18 AM   #2
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A max232 circuit will always be better then a 2-transistor. The reason is that it creates the proper voltages for the rs-232 interface. A 2-transistor setup doesn't always provide the proper voltages to the laptop serial port. This is one of the reasons it may work on one laptop but not another.

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Old 06-29-2006, 11:48 AM   #3
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excellent point. Just makes me curious how others can get by selling the 2 transistor interfaces?

eg - http://www.aldlcable.com/
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Old 06-29-2006, 12:20 PM   #4
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My homebuilt MAX232 has worked perfectly on both 7730 and 7749 ECMs.
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Old 06-29-2006, 04:17 PM   #5
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Ive tested my 2 transistor cable on 3 different ecms no problem. 165, 730, and a 93 S10 TBI ecm no problems. It was a total of like $3 in parts from radio shack.
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Old 06-29-2006, 05:31 PM   #6
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Quote:
Originally Posted by shaggy56
Ive tested my 2 transistor cable on 3 different ecms no problem. 165, 730, and a 93 S10 TBI ecm no problems. It was a total of like $3 in parts from radio shack.
have you tried it on different computers?
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Old 06-29-2006, 06:09 PM   #7
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My notebook was specifally bought to scan so no. Its an IBM thinkpad with a pentium 266 processor. It works great for my needs so I have no reason to use any other computer.
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Old 06-29-2006, 06:56 PM   #8
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I'm finishing up MAX232 as we speek

I always had problems with the 2-transistor type, even when used on a buds car, so Im using the MAX232 chip configuration. Using software, I designed my own printed-circuit-board. I bought the raw materials for the board and built my own. Looks very professional and like a commercial product. Not like the crappy pre-drilled boards at Radio Shack. Everything is in place, just waiting on my capacitors so i can finish it.

Also, the MAX232 works with either 160 or 8182 baud without having to change components. You can also incorporate a switch to change between 10k resisotr, a short, or an open from A to B at the ALDL.

Oh, for those wondering what it costs.

15 3" by 4" copper clad boards---$8
30 sheets transfer film---$10
Software---FREE
Schematics---FREE
Iron---FREE Everyone should have one of these already
#66 drill bits, pack of 20---$8
MAX232 chip---80cents
Diodes---1 cent for 100 Thanks eBay!!
Transistors---10 for $2
Capacitors---$12 for 400 variety pack
Already had the resistors


I bought in bulk so I can make more if needed, and for future projects. So when considering costs per board Im looking at right around $4 if you include shipping for everything.

Last edited by Phatfiddler; 06-29-2006 at 07:05 PM.
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Old 06-30-2006, 10:09 AM   #9
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The crappy predrilled stuff at radio shack seems up to snuf besides its in a black enclosure and you cant tell its home made anyhow. Ive used it on a few of my buddys cars and they seem more amazed at the dataloging coming from my notebook rather than the looks of the actual cable. I dont even think they realize the box even exists. I never had to do anything special to make it work so I dont know what the big deal is. Linked up to my 165 the first time i hooked it up. I have a few datamaster uni files saved at home from the S10 TBI unit.

Last edited by shaggy56; 06-30-2006 at 10:14 AM.
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Old 06-30-2006, 10:09 AM
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