Are there any common mistakes when building a max232 cable? - Third Generation F-Body Message Boards

87tpi7749 · 02-11-2005, 07:05 AM

I don't know. I've built seven cables. I would rate my soldering ability & understanding of schematics average. I use all the right parts. I heat sink when soldering sensitive electronics. Not one of my cables will pass tts's cable check program, or even link to the car. This has been verified on three computers. My 2 transistor will work. I have finally given up on the DIY cable idea & ordered parts from a cable manufacturer. Problem is; I spent more than twice what I would have in the first place. And burned my fingers a thousand times for nothing. Just wondering is there a common mistake that is often made?

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AlexJH · 02-11-2005, 11:46 AM

Do you have bypass capacitors from the power to ground pins? As close as you can get to the two pins?

327_TPI_77_Maro · 02-11-2005, 11:47 AM

Hey there. I can't answer your question, but can you point me to the cable check program you are using? Will it check a 2 transistor cable? Thanks!

87tpi7749 · 02-11-2005, 07:38 PM

Quote:

Originally posted by AlexJH
Do you have bypass capacitors from the power to ground pins? As close as you can get to the two pins?

I guess? I never really paid much attention to "how close" they were to pins. Most of the ones I've done are within an inch. Does this make a difference?

87tpi7749 · 02-11-2005, 07:40 PM

Quote:

Originally posted by 327_TPI_77_Maro
Hey there. I can't answer your question, but can you point me to the cable check program you are using? Will it check a 2 transistor cable? Thanks!

The program is from tts power systems website, click down loads then aldl test, it should be easy to find. It is only for max232 cables, so no on the 2 transistor.

Craig Moates · 02-12-2005, 03:09 AM

It'll work on the 2-transistor cable as well.

87tpi7749 · 02-12-2005, 09:30 AM

Craig, Is that true? My 2 transistor works flawlessly with freescan but fails every test I run with the aldl test program. All the max232 cables that fail the test also fail to cummunicate. It would seem I am running the test correctly (cable only) no coonection to ecm. Now I am really confused, but happy I bought a cable.

stuckatcuse · 02-12-2005, 09:41 AM

watch the polarity of the capacitors. Some of them are wired in reverse.

87tpi7749 · 02-12-2005, 03:19 PM

I regard the (-) symbol on the side of the cap as negative. Is there a way to check poalrity with a meter?

Craig Moates · 02-12-2005, 07:26 PM

You're correct, - = negative. No, no way to tell. Hook em up backwards and give em enough juice and BAM! It's cool...

AlexJH · 02-14-2005, 07:49 PM

Quote:

Originally posted by 87tpi7749
I guess? I never really paid much attention to "how close" they were to pins. Most of the ones I've done are within an inch. Does this make a difference?

It can make a difference. When I put a circuit together, the bypass caps from +V to GND are as close as possible to the IC's pins.

How much electronics equipment do you have? Have you checked that the right voltages are on the power, ground pins?

87tpi7749 · 02-14-2005, 09:17 PM

I got it working. With some help from a professional cable manufacturer, I discovered that my version of aldl test was the problem, I had to use the old version, all boards work! Thanks everyone for the tips, it makes DIY feel like you're not on your own, it should be more like DIWTGO (do it with thirdgen.org).