Noise on 5V rail? Weird problems?

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wagon
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Joined: Sun Jul 17, 2005 4:10 am
Location: Toowoomba, QLD, Australia

Noise on 5V rail? Weird problems?

Post by wagon » Mon Jun 06, 2011 3:18 am

Hello ladies and gentlemen!

I have been having weird problems, made most noticeable recently with the transmission shifting strangely, especially at WOT. I changed the TPS, checked/replaced solenoids, etc. all to no avail. Finally, out of desperation, I pulled the MS to bits and had a bit of a look-see.....

When I built it about 6 years ago I saved about $2 and used ordinary electrolytic caps around the 5V reg, instead of the specified tantalums. Bad move! It finally bit me on the backside! I changed the cap on the 5V output to a 22uF tantalum and lo and behold : the transmission now shifts properly (WOT gearchanges at 4900, 100 shy of the limiter) and it seems like the WOT flooding problem has disappeared.

The funny thing is everything worked fine for years although the WOT flood problems only started about 18months ago. When I did the 4-speed transplant it worked OK too, but about a month ago it started to misbehave.

Moral of the story : use tantalums if they're specified ; don't be a tightwad. :)
1984 Ford Falcon 250ci inline 6 MS'd of course!

Now improved the way Ford should have built it with a 4speed automatic.

Also with 3.45 LSD for added goodness.

If you are hitting your head up against a wall it always feels better when you stop.

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