U4 (v2.2) optoisolator schematic pinouts needed, resets...

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242ATL
Experienced MS/Extra'er
Posts: 191
Joined: Thu Feb 16, 2006 4:21 pm
Location: Central New Jersey

U4 (v2.2) optoisolator schematic pinouts needed, resets...

Post by 242ATL »

Hey everyone,

I need the pinouts for U4 of a v2.2 board....I already have the schematics from http://www.bgsoflex.com/v22/megasquirt_ShemV2.2.pdf but the pinouts for U4 are not listed.

I am trying to diagnose a reset problem with my system. (msns-e, 029q) running wasted spark using an error daughter card, with 2 vb921's firing a DSM coilpack... on a volvo b230 (with a b234 16v head).

I am getting resets (a lot of them) with just 12v power applied in the car, with the car not running.

I'm a bit of an electronics newb, but I'm learning as I go. To the experienced, I'm sure this post will seem a bit elementary, thus my request for pinouts instead of a "fix this" post :)

The reason I ask, is that one solution I found for the reset problem is:
(from http://www.msefi.com/viewtopic.php?t=20 ... eset+power)
I was getting many resets also. A wise man told me to remove the XG1/XG2 jumper, run a wire from XG1 to pin 6. Pin 6 is the sheld for the IGN input. Ground the sheld at the distributor input or wherever you got your IGN signal from. I did this and my resets went away. If you have already grounded that side of the shield you have created a ground loop, by grounding the MS in two places. By removing the jumper and grounding the sheild, you give the IGN ckt a seporate ground. I was getting 51 resets at idle over a 3 minute time span. ALL my resets went away after this mod.
However, I already have a wire connected to Pin6 of U4 going to T3 of the error daughter card (it is my understanding that T3 supplies the conditioned output to U4).

How can I ground pin 6 of U4 AND have a wire connected to the error card?

Thus my asking for the U4 pinouts.... I think if I see them, then I can reason/learn my way around how U4 works.

many thanks.

Mike
subie4me
Experienced MS/Extra'er
Posts: 177
Joined: Sat Jun 19, 2004 2:20 pm
Location: southern California

Post by subie4me »

just google 4n25. You'll get nore info than you need.
242ATL
Experienced MS/Extra'er
Posts: 191
Joined: Thu Feb 16, 2006 4:21 pm
Location: Central New Jersey

Post by 242ATL »

thanks for the suggestion.

Glen's garage had a schematic.
http://www.glensgarage.com/catalog/4n25 ... -p-68.html

but now, according to the schematic and chip orientation... and U4 orientation on the MS board, I have apparently soldered my LM1815 output to pin 3 of U4... which if it is oriented according to the schematics, pin3 is bottom left, pin 6 is top right on the v2.2 board with the board oriented with the LED's to the left.

and indeed, I am more confused....

does anyone know the correct pinouts of U4 on the V2.2 board?

thanks.

Mike
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