Hello.I'm out in San Francisco this weekend and somewhat busy. The email list I am talking about is 'elec-trak' <elec-trak cosmos phy tufts edu>. Good people, lots of information.
As for the specifics, that sounds really familiar. I know what it is: There is a thing called "card 4" over on the right side of the tractor where the relays are. It has a few transistors, and 4 diodes down on one corner in a 2x2 arrangement. Check these diodes; they provide the field power in forward and reverse. They are also very old now, and when the reverse ones fail you lose the field in reverse.
However since you have a compound motor, there is a small field in series with the armature, so it moves. When you floor it quickly, the back-emf trips the F/R relay and it moves forward.
Or you can contact Harold Zimmerman for a new card 4. Be very gentle with removing the card; the edge connector is also 30 years old and you do not want to break or crack it. Gentle.
Chris Bettye j Rockweiler wrote:
I just took emery paper and cleaned all the contacts in relays .Took it for a drive just one reverse speed. But if I floor it quickly it buzzes a little and goes forward!Any ideas?----- Original Message ----- From: "Christopher Zach" <czach computer org> To: "Bettye j Rockweiler" <rock mchsi com> Sent: Wednesday, June 07, 2006 1:59 PM Subject: Re: e20Bettye j Rockweiler wrote:I'm MICK not BETTY and I believe I can do any test you suggest .Model e20-D .It runs now.I'm waiting for a diode now for the charger.I'm mowing with now and I have all the speeds going forward.But only one speed in reverse .I don't believe it low speed. Some times mowing and I go up to a tree,I can't back up at all. I reverse some times goes forward.Oh ok, this is not too bad. Check your relays up at the top and you will probably find one sticking/not making contact. Fix that and reverse should be fine. My guess is it's not getting field power in reverse.Have you joined the EV list yet?Chris