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Re: (ET) new relay in - now no reverse



Here is a good example of how theory, as shown in the books, and practice
as shown by someone with experience in the same subject diverge to the
point that the problem cannot be solved by the theory alone.  Most
'tradesman's problems are such.
   Always listen to the man who has a bit of age and grease under his
fingernails as to the solution problems applying to his specialty.  His
livelihood depends not just on theory, but the practical application of
it. And that man likely has more diverse application books on the subject
at home than are available in the college library.  His knowledge and
experience go to his fingers.  Which get results.

The melding of the two areas of thought is also a good example of why we
have this board.

Dave
Weymouth MA
(retired, Northeast Institute of Industrial Technology,  electronic lab, 
Boston) 


On Sat, 5 Aug 2006 10:56:58 -0400 (EDT) Michael S Briggs
<msbriggs alberti unh edu> writes:
> 
> 
> RJ,
> 
> On Fri, 4 Aug 2006, RJ Kanary wrote:
> 
> >       Prove out all the voltages that SHOULD be present with an 
> ANALOG 
> > VOM.High impedance sand based DMMs will lie to you especially at 
> these 
> > voltages.
> 
> I don't see why a DMM should be inaccurate on voltage. Don't you 
> *want* a 
> voltmeter to have high (very very high) impedance? Otherwise when 
> you 
> connect it in parallel with some circuit element, the combined 
> parallel 
> resistance of the voltmeter and the element you're measuring voltage 
> 
> across can drop some, so the voltage you would read wouldn't be the 
> voltage it normally sees. So, I don't see why you would want a lower 
> 
> impedance on your meter.
> 
> >     Verify that voltage AND current is available at Pad 8 {Wire 
> 41} of 
> > Card 1 when Reverse is selected. If this proves out move to Pad 9, 
> {Wire
> 
> Alrighty. I'm assuming it should have the full 36V (or 38V, or 
> whatever 
> the pack is putting out) at those points.
> 
> > 38}. If voltage and current is present here, now you can suspect a 
> 
> > wiring error at the other relay terminals.If voltage and current 
> is NOT 
> > present here, you are about to embark on one of the finer 
> adventures of 
> > owning and repairing an AA model E-15, repairing Card 1.  :(
> 
> D'oh. I'll check it in an hour or two - need to finish making some 
> biodiesel for our cars and furnace first. Given that I thought I 
> heard a 
> "pop" noise when I first put it in reverse after putting in the new 
> relay, 
> I'm unfortunately thinking it's not going to be a simple wiring 
> issue. :( 
> But, if it's just a case of a  blown resistor or cap on card 1, that 
> 
> shouldn't be too bad - I've done a fair amount of electronics work 
> in the 
> past. Well, it shouldn't be bad if it's obvious which element blew. 
> :) 
> Chasing down a bad circuit element can be a pain in the tuckus.
> 
> Thanks,
> Mike
> 
> 
> >
> > ----- Original Message ----- From: "Michael S Briggs" 
> > <msbriggs alberti unh edu>
> > To: <elec-trak cosmos phy tufts edu>
> > Sent: Friday, August 04, 2006 9:35 PM
> > Subject: (ET) new relay in - now no reverse
> >
> >
> >> 
> >> So I finally had time to put in a new relay in place of the blown
> >> forward/reverse relay. Forward works fine now - even took it out 
> for a
> >> spin around the neighborhood. When I then went to back it into 
> the garage,
> >> I discovered that when I try to go in reverse, it goes forward. 
> D'oh!
> >>         My first thought was that I had hooked up the 
> forward/reverse
> >> relay wrong. I checked, and nope, it's fine. The problem is that 
> the relay
> >> isn't firing when I move the switch to the reverse-neutral side. 
> I hear
> >> the reverse microswitch click, but the relay doesn't move. 
> Checked the
> >> power connections on the relay, and it doesn't seem to be getting 
> any
> >> power when I move the speed lever to reverse.
> >>  Now, I suppose I could have just knocked something loose while
> >> fiddling with everything in there, but I'm wondering if there 
> could be
> >> some greater problem going on that I'm overlooking (considering 
> all the
> >> failures that I've had - while mowing last week, it stopped 
> running - the
> >> control fuse had blown, and took out the fuse block in the 
> process.
> >> Put in an inline fuseholder in place of the fuse block, with a 
> fresh fuse,
> >> and found that I couldn't go forward due to a blown 
> forward/reverse relay.
> >> Put in a new relay, and now the relay isn't getting voltage to 
> fire. It
> >> seems like each time I fix one thing, something else breaks).
> >>  After putting in the new relay, the first time I moved the speed
> >> control lever to reverse, I thought I heard the sound of 
> something blowing
> >> - wasn't sure though if it was just the reverse microswitch 
> clicking, or
> >> if something did in fact blow. It looks like control of the 
> reverse relay
> >> goes through card#1 somewhere (still need to look over the 
> schematics to
> >> figure out which "port(s)" on card 1, so I can see if something 
> is just
> >> loose, or if something did in fact blow). I should be able to 
> troubleshoot
> >> it ok, but what I'm concerned about is if there might be some 
> greater
> >> problem underlying these little annoying problems. There have 
> just been
> >> too many failures one after another for it to just be a 
> coincidence, I
> >> think.
> >>  Actually - if I had wired the power connections to the reverse
> >> relay backwards, what would that do? From looking at the relay, I 
> assume
> >> it just uses a current through a solenoid to control a switch. If 
> the
> >> current goes the wrong way, the B field would point in the 
> opposite
> >> direction - but since I'm not sure exactly how it controls the 
> switch, I'm
> >> not sure if that would be a problem or not, or if it could blow 
> something.
> >>  So, any tips anyone can offer (again) would be appreciated.
> >> 
> >> Thanks,
> >> Mike
> >> 
> >> -- 
> >> 
> >> --------------------------------------------------------------
> >> Michael S. Briggs
> >> UNH Physics Department
> >> (603) 862-2828
> >> ---------------------------------------------------------------
> >> 
> >> _______________________________________________
> >> Elec-trak mailing list
> >> Elec-trak cosmos phy tufts edu
> >> https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak
> >> 
> >
> 
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