Re: (ET) E20 problem in forward, quickly resolved.

Here's another E20 quirk that bothered me for some time and recently I stumbled upon the problem and the fix was easy. While in motion occasionally the tractor would just slow down to a slower constant speed, and the fuel gauge would drop to "E", then seemingly without any change the tractor would again speed up to the speed the foot pedal had been at all along and the fuel gauge would register again. I couldn't logically figure out what was going wrong with the E20's speed control system. Then, recently as I was backing the tractor out I smelled burnt plywood. Huh? As a bit of back story, I got this tractor with batteries that have the stud terminal on top of the automotive post (EHPT style) and holes had been drilled into the plywood under the seat lid to accommodate those tall terminals. Bouncing on rough terrain over the years had caused the terminals to work their way through the plywood and come in contact with the sheet metal seat lid. Several terminals had actually burned a hole in the sheet metal (and heated up the plywood). This of course had been sporadically depriving the circuit of full power while in motion . A heavy vinyl blanket now covers all the rear terminals.

From: Christopher Zach <cz alembic crystel com>
To: "elec-trak cosmos phy tufts edu" <elec-trak cosmos phy tufts edu>
Sent: Saturday, June 1, 2013 12:31 PM
Subject: (ET) E20 problem in forward, quickly resolved.

So my E20 was mowing away today, and suddenly I lost all speeds other
than 1 in forward. No problem in reverse. Wait a few minutes, everything
goes back to normal.

Odd.

I sat down to take a look at it and figured the problem was in card 4.
Replaced the two field diodes since one of them (upgraded years ago)
looked a bit burnt. Still same problem. Issue was not field, but power
to 1a,2a,3a coils.

Which goes from the armature through CR402 or CR403 on card 4. CR402 was
the most likely culprit, but diode looked fine. Checked voltage, only 9
volts on either side of the diode. Odd.

Checked the connector next. Sure enough one of the two fingers had
broken off, and the other finger was not making proper contact. Bent the
other connector slighty, cleaned up the pads on card 4, put it in, all
is now well again.

So there you go. If you lose speeds 2 and up in one direction but not
the other check around CR402.

C

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