Update again - I do now have voltage at slot 9 on card 1 when putting it in reverse (there was a loose connection), but there's still something amiss with card 1. With the reverse relay not connected to card 1 (slot 9, I think wire 38... not sure offhand), slot 9 goes right up to full battery voltage when I move the speed control to reverse. So, I connected in a new relay (one without a short across the coil), and now slot 9 (and hence the relay) only goes up to about 4V, not enough to trigger the relay. So, there seems to be something amiss with card 1, although I haven't found it yet. All of the components in the involved parts of card 1 *look* fine (yes, I know looks aren't everything, but usually you can spot a blown resistor or cap visually - I've blown up my fair share :) ). The problem with testing individual components is that they're soldered into card 1, so I can't just measure the resistance or capacitance of an individual piece (without unsoldering them and removing them from the card). I guess I'll just have to start tracking the voltage around the related circuit on card 1 (if I can tell from the schematic which pieces are involved :) ), to try to find why the full voltage isn't getting through.
Could just be that these relays suck.
Mike
--
--------------------------------------------------------------
Michael S. Briggs
UNH Physics Department
(603) 862-2828
---------------------------------------------------------------
On Sat, 5 Aug 2006, Michael S Briggs wrote:
To answer my own question about jumpering pins 8 and 9 on card 1 together,
and what card 1 actually DOES as far as the reverse relay control - from
the card, it looks like it's a time delay circuit, so that if you flip
from forward to reverse (or vice versa) too quickly, while the motor is
still spinning one way, you don't suddenly reverse the field to point in
the opposite direction. Is that correct? So, the reason I shouldn't just
jumper 8 and 9 together is so I don't go and reverse the field too quick,
which would probably give me a big induced current in the field winding,
presumably frying a connection somewhere - probably on the relay.
Seems like I could do that as a temporary fix (if I need to wait
for some part to arrive so I can fix card 1), just making sure I give
plenty of time between going from forward and reverse, to avoid frying
relays left and right.
I'll check though to see if I can determine what part on card 1
fried, to see if I can get it working without jumpering across those
terminals (we have gobs of resistors and capacitors at work, so if that's
all it is, I can "borrow" a 3 cent resistor or cap to fix it).
Mike