[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: (ET) Card 4 status, might work, hm.
I had to replace both transistors on my card 4 when I got my E20 last summer. I got the replacements at Radio Shack. Both replacements had the pins in a different order than the board
calls for, so I had to twist them around to get them in correctly. Q401 was replaced with a 2N222 (from a 15-pack of generic NPN transistors) and Q402 was replaced with a TIP31.
And they do work... I kept getting bumped out of the higher speeds until I cleaned up the shunt connections.
On Sat, Sep 11, 2010 at 10:55 PM, Chris Zach <cz alembic crystel com>
Ok, so I took card 4 out, replaced the blown resistor, cleaned it up, and put it back in the tractor. Decided to check to see if the shunt was showing 0 ohms resistance.
The sense wires showed 64k. Oh brother.
Took off the plate, turns out when I assembled the shunt a few years ago I used 10 gauge crimps on the cables (now melted), spaced the lugs with copper bolts (all overheated) and the sense wires were far away from the shunt (and covered with carbon).
So I cut off all the crummy crimps, cleaned up the shunt and bolts, then put new screw-down 8 gauge copper lugs on all the main wires. Instead of putting things between copper bolts everything is right against the shunt on the bottom and top.
Fired up tractor, moves faster, go figure. However speeds 6,7,8 are still out.
Checked the shunt, it's ok now the strip of metal gets hot under heavy load but the lugs are cool. Which is good. However why does that metal strip insist on getting hot? The E-15 doesn't have a stupid shunt, why does the E20 have one?
Anyway, checked the voltage on the relay output of card 4, it's only putting out 9 volts or so. I think the first amplifier transistor is shot. So does anyone know what types of transistors they used, and if Mouser has a replacement?
Overall this has been one of those "clean up a lot of things" type of project. In the meantime I bypassed the relay so I can have the higher speeds (and be able to stop cruise control by blipping the throttle). I'll get back to this next week.
On a side note: I noticed my MOV was once again blown to bits. This time it looks like it might have caught fire as well. Just how big of a MOV does one need to provide surge supression on the motor armature? Should I put 3 or 4 of them in parallel?
Elec-trak mailing list
Elec-trak cosmos phy tufts edu