Joe, if you mean will I mark the blank gage face for the position of the needle with the 8.000 crystal I could do that no problem and send one to you and one to MinnGreenGT also if he wants one, Rob?.
Let me know if I understood your post right.
I wiil get some florescent blue spray paint and try the color change for the sidelit to see what happens.
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11:21 PM
Oct 18th, 2001
Joe Torma Member
Posts: 3485 From: Hillsborough, NJ USA Registered: Jul 2001
Well, this might open up a whole new can of worms, but...
Can anyone with an 85mph/140kph that's disasembled tell me what the number on the IC that's right by the crystal is? Also, what the frequency on the crystal is.
I want to figure out what the divide rate on it is. For the life of me, I can't find the damn number on that IC in my ECG guide! I'm starting to wonder if it's a custom IC or not.
For starters, mine has a 4.194304mhz crystal, and the IC is marked: AMI 8640MFE 6393 R CO4306
None of those numbers, or variations on them (with/without letters) show up in my somewhat old guide. Anyone have a new one?
I'm still planning on making custom gauges- like stock appearance 160mph or even normal whiteface gauges (backlit numbers, not face) for whatever application.
FieroHoho- I'd like the gauge face with the correct speed marked, I can use it to produce new faces
As to the questions about painting the back of the metal gauge pod/face- I've got two that I've been working on just painting white (and then repainting the black) so they look like "new". If doing that, you'll also want to pull out the plastic pieces from warning light surrounds, they'll need to be painted white also (takes a few coats to cover the bright orange).
Fierohoho, Here while back I wanted to change my speedo and tach. While I found plenty of info on the tach I did not find what I was looking for for the speedo. This thread kinda dwindled out https://www.fiero.nl/forum/Forum2/HTML/010985.html I'm not sure I understand which crystal changed the speedo toward the right degree to read the kph for mph. What I was wanting to do is find the right component to change to be able to read the kph for mph effectively changing the 85 mph speedo to 140 mph speedo. Therefore you could effectively use the face plate as is to be able to judge speed.
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Originally posted by watts: Can anyone with an 85mph/140kph that's disasembled tell me what the number on the IC that's right by the crystal is? Also, what the frequency on the crystal is.
I want to figure out what the divide rate on it is. For the life of me, I can't find the damn number on that IC in my ECG guide! I'm starting to wonder if it's a custom IC or not.
For starters, mine has a 4.194304mhz crystal, and the IC is marked: AMI 8640MFE 6393 R CO4306
None of those numbers, or variations on them (with/without letters) show up in my somewhat old guide. Anyone have a new one?
watts, My crystal is 4.194304 and the adjacent chip is AMI 8417CR 6393 R C04306 KOREA
Butter- that is exactly what fierohoho was trying for (he has a 140kph speedo face). But apparantly none of the crystals changed the speedo exactly to the 140mph. So we're basically planning on using the 8.000 crystal to make a 160mph... just making custom faces (which is the easy part).
Terry, Something was edited out of your message. I am sure you are the one that could clear this matter up since you are in the engineering field. You mention the variable resistor that is covered on Oliver's page, but that only refers to the Tach modification. Is the correct method of making this change the same method as the tach but using a 50K variable resistor on the speedometer pc board and then just adjusting the resistor until the speedometer face reads correctly regardless of what max MPH is being used?
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12:42 PM
PFF
System Bot
Joe Torma Member
Posts: 3485 From: Hillsborough, NJ USA Registered: Jul 2001
I haven't done this on a Fiero speedo, only a Ciera speedo and Fiero/Ciera tachs, but I don't see why it wouldn't work on the Fiero speedo since it's nothing but a frequency to voltage converter like every other GM speedo.
Look on the Fiero speedo circuit board for a 25544339 (or something) like that chip. I know the last numbers are xxxx4339. This is an National meter driver chip. GM did change to a different chip at some point, but it works and is wired the same.
Pins 5 and 8 should go to a resistor pack (white 14 or 16 pin IC looking chip with some black lines on the top). Also, there is a capacitor across pins 5 and 8.
These pins go to a resistor on the pack that sets full-scale. If you change it to a 50k pot (cut the traces), you should be able adjust the speedo to read whatever you want.
Sorry, to be so vague, I'm in Huntsville,AL and not near a speedo to look at.
This change will leave the odo and trip reading correct and only change what the face of the speedo reads.
The higher MPH you adjust it to, the more accurate it will be.
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03:43 PM
BRIAN CORNELIUS Member
Posts: 86 From: APPLE VALLEY, USA,MN 55124 Registered: May 99
Thanks Terry. This will sure make it a lot easier than trying to get the riht crystal. If anyone does the mod it would be great if a picture could be posted like Oliver did for the tach mod at his site: http://home.t-online.de/home/O_Scholz/fieroidx.html
