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richard morantz
09-18-2007, 11:39 PM
I have been having trouble with my previously fine E20. One day it ceased to have faster motor speeds in forward, fine in reverse. When I check the voltage across the 1A coil it goes to 36V in reverse, but only to 12V in forward when it should be charging the coil to close the switch and bypass the resister. Any suggestions where the problem could be? The usual series of clicks heard as the relays throw and the motor speeds up are not there. It goes forward, but only in the first speed.
Thanks for any help.
Richard

mfrerking
09-19-2007, 12:25 PM
What model E-20 do you have? If it is one of the older models, you may have a problem in card #4.

richard morantz
09-19-2007, 02:24 PM
Thanks for the reply, my E20 is the AA model, probably 1970, definately old with the card #4. How does one check for problems with this? Just buy a new one and install it, hoping that will do the trick?

What about taking this opportunity to buy the new solid state control system from Altrex (?, I think that's the name) and upgrade the system. I realize it will not be the origional any longer, but I want to use this machine, not just collect to restore. The new speed control electronics cost about $500 to purchase and install, but a few $80 parts for repair of the old system adds up and the new system could solve all of these problems.
Richard

FarmallMan
09-19-2007, 03:11 PM
Have you gone through the troubleshooting section in the homeowner's service manual yet? There's a fairly easy to follow proceedure in there that would be worth following before you buy a new card. Harold Zimmerman offers new cards, but chances are pretty good that the old card can be fixed. Look for burned components, etc for clues. There's a schematic for the card in the service manual. The SCRs are fairly common problems, from what I've been told.

The alltrax will definately solve the problem, but is not an "easy" fix. It will involve some rewiring, and re-fabbing of the speed control, etc. If you do want to go that route, you can buy an alltrax through the Electric Tractor Store (see commercial vendors).

Nick :cool:

richard morantz
09-26-2007, 12:01 AM
Farmall man,
thanks for the tips. i do have the homeowners service manual and have gone through their troubleshooting guide. This situation is not one covered specifically, there is one about failure to go into the higher speeds and the solution, if it's not something simple like a bad connection, is to replace Card #4. I have looked at mine, I see no burnt areas,but I see how easy it would be to replace components of the card. The diagram in the service manual gives the value for the resistors, but only numbers the diodes. I couldn't find a guide to these numbers, and don't know the specs on the diodes. How do you test these? with a multimeter?

I understand the alltrex conversion problems, I wouldn't consider it unless I needed to replace a couple of hundred of dollars worth of parts. I think the altrex part is $400 and the new throttle setup another $100. If there were ever a problem with this circuit it would be necessary to replace the whole thing. If the electrak original parts are kept they can be repaired or replaced, as needed (if ever) for less.

Richard

mfrerking
09-26-2007, 02:48 AM
I am not very knowledgable on how to test diodes. I do know the better meters have this capability. I have spent some time studying diagrams in a copy of a Simplified Troubleshooting Manual (not sure why it is called that, dosen't seem "simplified" to me) to see if I could determine the why the variation in voltage at 1A. The manual does not show a flow pattern through Card #4. So, determining exactly where the faulty card component is, if that is the problem, is beyond me.

From the information you have provided, your machine functions properly in reverse. This means, to me, the contacts and switches are functioning properly. The start and 1A switches are closing to get 1A contacts to close. If you have speeds 3 & 4, the related switches and contacts are functional as well. Because the resistor diode assembly and Card #3 are involved in this process, I would think they are fine.

You might check the wire continuity and connections related to 1A. If no problem there, with everything else ruled out, then a problem w/Card #4 is the likely problem.

Not sure if I have stated anything you hadn't already figured out. Maybe a concurring opinion will help. Best of luck.

Mark

FarmallMan
09-26-2007, 02:49 PM
I've been looking at the schematic on page 6-21. I would say that the problem is probably in the portion of card 4 that's on the left side of the schematic. Line 16 is lower in forward than it should be. There could be a couple of things that it could be....

Helpful troubleshooting info for you and us: wire 16 feeds coil 1A, which you have already identified as only having 12 vdc in forward, and 36 in reverse. Wire 16 goes to terminal 16 of card 4. In forward, there should be +36 VDC between terminals 19 and 17 of card 4 with the meter's pos lead on terminal 19 and neg lead on terminal 17. Putting the tractor into reverse should reverse this voltage. Please verify these voltages.

In Forward, CR 402 and CR 414 should be conducting. That is to say, you should have +36 volts between terminal 16 to 17 and from terminal 18 to 17. In reverse CR 413 and CR 403 conduct, terminal 17 becomes the "positive" and 19 becomes the "negative". Check terminal 16 to 19 and from 18 to 19 in reverse. Let us know what you find out.

Any diode should work, as long as it has a voltage rating of at least 50 VDC and current rating of say 5A or so. The higher these numbers, the "safer" you'll be. You can test diodes using a resistance setting on a multimeter, they will conduct one way, and not the other (will have very low resistance one way - with the black lead of the meter on the striped or dotted side of the diode - an high when the leads are reversed). You should disconnect one side of a diode before testing, otherwise the rest of the circuit may fool you.

Nick :cool:

Robbie Robinson
09-27-2007, 10:10 PM
I've been looking at the schematic on page 6-21. I would say that the problem is probably in the portion of card 4 that's on the left side of the schematic. Line 16 is lower in forward than it should be. There could be a couple of things that it could be....

Helpful troubleshooting info for you and us: wire 16 feeds coil 1A, which you have already identified as only having 12 vdc in forward, and 36 in reverse. Wire 16 goes to terminal 16 of card 4. In forward, there should be +36 VDC between terminals 19 and 17 of card 4 with the meter's pos lead on terminal 19 and neg lead on terminal 17. Putting the tractor into reverse should reverse this voltage. Please verify these voltages.

In Forward, CR 402 and CR 414 should be conducting. That is to say, you should have +36 volts between terminal 16 to 17 and from terminal 18 to 17. In reverse CR 413 and CR 403 conduct, terminal 17 becomes the "positive" and 19 becomes the "negative". Check terminal 16 to 19 and from 18 to 19 in reverse. Let us know what you find out.

Any diode should work, as long as it has a voltage rating of at least 50 VDC and current rating of say 5A or so. The higher these numbers, the "safer" you'll be. You can test diodes using a resistance setting on a multimeter, they will conduct one way, and not the other (will have very low resistance one way - with the black lead of the meter on the striped or dotted side of the diode - an high when the leads are reversed). You should disconnect one side of a diode before testing, otherwise the rest of the circuit may fool you.

Nick :cool:
I have had this same trouble with my E20BA model, but found problem in tghe little pins inside the plug take time and look there, and careful in bending them back into place. Also after a few month trouble came back and this time I find that the plug is crack on the back side, seem that when I would put a lite touch on it it would work just find, this is how I found the crack. Now I'am looking for a new plug. if anyone has or knows where I can get one let me know.

Thanks Robbie

FarmallMan
09-27-2007, 10:47 PM
I'm a little fuzzy about which plug you're referring to. Do you have a picture of it, or can get a pic of it?

Nothing especially custom was used on these machines. It's all pretty ordinary stuff. Maybe I could point you in the right direction......or suggest an alternative.

Nick :cool: