1 year on, a problem

alexander · Post by **alexander** » Wed Jan 20, 2010 3:55 am

hi, this is quite a similar problem to the previous thread.
symptoms:
*MJ V3.0.0 board
*a few months ago, tacho signal lost (on my digital dash) and car in limp mode. wiggled the wires on the box near my leg. seemed to do the trick. now seems to have been a coincidence..
*very recently, car went suddenly into limp mode. no tach signal. came and went a few times, now permanantly in limp.
*PIP signal to MJ confirmed with a scope
*software shows proper readings for MAP and tach, but i am getting an error reading the map, or a couple of times the map has appeared with a hugely large rpm scale
*cant write to the mj either.
*visual inspection of the board shows light, white corrosion around some of the pins of the microprocessor in the socket, and the socket in the board. also around T2. i think some drips of water may have entered the case on one occasion, which i imagine explains the corrosion.

so, what to do?
obviously, seems i need to trace voltages etc where i can, so i will take that as a given, but i have a couple of questions for now:
*i dislodged the microprocessor from the socket but have had my fingers all over it. is it the sort that can be damaged by that?
*it would be prudent and simple to buy a replacement anyway, and stick it in, but i cannot find any referece to its serial no. except on autosportlabs documentation. so how do i order one?
the documentation refers to it as MCHC08KX8, and also as MC68HC908XK8. the one i pulled out says MC908KX8CPE.
none of these yields anything on the Net beyond autosportlabs. brent, can i buy individual ones from you, or is there some other way of identifying these things locally (australia)?

thanks all
alexander. warm, sunny, sydney.

Post by **brentp** » Thu Jan 21, 2010 12:20 am

Alexander,

I would hold off suspecting the processor chip, yet. Almost always, the processor will either work, or not work at all.

If the MAX232A chip is socketed as well, I would remove that device, and plug it back in, which will "re-seat" the device, which will help clean off accumulated corrosion. Re-seat the processor chip as well.

While your at it, clean the back-side of the board with some alcohol (regular isopropyl is fine). let it dry, then re-flow all of the solder joints.

then, double check the power connections into the V3 molex connector. If the connections are marginal or intermittent, it will also cause the problems you described.

Try these steps and report back

NITROPIXIE · Post by **NITROPIXIE** » Sat Jan 23, 2010 9:14 pm

Obviously the inside of vehicles can get a bit damp too. Would it not be advisable to protect your circuit board by using something like http://www.jaycar.com.au/productView.asp?ID=NA1002 Maybe this could be mentioned in the kit assembly guide??

alexander · Post by **alexander** » Sun Jan 24, 2010 7:35 am

not a bad idea, but when i manage to reverse the damage i have inflicted on the insides of the MJ during my 'inspection', and then actually figure out what is wrong with it in the first place, i think i will be repositioning the box where water cant drip directly on it!

Salamander · Post by **Salamander** » Thu Feb 04, 2010 2:11 am

change the max232, this is the problem

BRUCEROE · Post by **BRUCEROE** » Sat Apr 10, 2010 3:11 pm

My experience is, tin plate connections at logic levels will fail some day. My fixes are to either solder things, or use gold to gold connectors. A chip can be placed & soldered into a "carrier" with gold plated pins. That may be plugged into a connector with gold plated pins. One processor built here in 1984 is still functioning fine, its tin plate predecessor failed in a few years. Bruce Roe