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

[David C Robie <mycroftxx1 juno com>]

Re: that voltmeter bit at the end.

The world is full of 'whoops'.  In this densely populated area you can
hear them at night, like peeping frogs. Some whoops are expressed
differently, colorfully and at length.  Volume and style vary. Some are
male, some female and I suspect some to be animal.  Some are mine.
Welcome to the world of whoops.

Dave
Weymouth MA


On Sun, 6 Aug 2006 19:27:53 -0400 (EDT) Michael S Briggs
<msbriggs alberti unh edu> writes:
> 
> On Sun, 6 Aug 2006, RJ Kanary wrote:
> 
> >       Since the time delay is likely inoperative, just using the 
> Reverse 
> > switch in the throttle eliminates more things to go wrong.I 
> suspect your time 
> > delay isn't working, since you have experienced reversing relay 
> issues.
> 
> It's definitely not working right now :) - but that's almost 
> certainly due 
> to the surplus relay with a short across the coil, that fried 
> something on 
> the time delay circuit (now that I managed to mow the lawn (without 
> reverse), I'll pull card 1 out and take a look at it). I guess the 
> question is whether to try fixing the time delay circuit, or just 
> bypass 
> it - which would mean I'd need to remember (uh oh) in the future to 
> never 
> switch between forward and reverse quickly. And if I do bypass it, 
> should 
> I jumper the wires that go to pins 8 and 9 with them also connected 
> to the 
> card, or just pull them off the card and jumper them off of it? 
> Reason 
> being that from the schematic, it looks like the line coming in from 
> pin 8 
> (from the reverse switch) also connects to some of the other stuff 
> on card 
> 1 - not sure what those parts are for though.
>       I'd *like* to get card 1 working I think. Hopefully the 
> only 
> problem is that a trace at the beginning of card 1 burned up, and I 
> can 
> just make a new solder trace, or solder in a wire jumper over the 
> burned 
> trace. If that SCR is fried, then my question becomes - what should 
> I 
> replace it with? I'm not all that strong on transistors and 
> rectifiers and 
> such, but it seems that a PNP (or NPN, crap, I always have trouble 
> remembering which is which... I think PNP is the normally open one 
> that 
> closes when you have a certain current coming into the gate?) 
> transistor 
> would be a nice replacement, if I understand the time delay circuit 
> correctly.
>       Is this how the time delay works? : when you move the speed 
> lever 
> into reverse neutral, the reverse switch closes, connecting pin 8 of 
> card 
> 1 to 36V (or whatever batt voltage is). Pin 8 feeds into the anode 
> of the 
> SCR, which seems to be functioning essentially like a PNP transistor 
> in 
> this circuit. There's a little RC circuit connected between pin 8 
> and the 
> gate of the SCR, such that the gate doesn't have enough current 
> coming in 
> until the capacitor in that RC circuit has charged up to a certain 
> point - 
> which is creating the time delay. Once enough current is going into 
> the 
> gate, the SCR closes (which I think is how PNP transistors work?), 
> and pin 
> 8 then becomes connected to pin 9, which powers the reverse relay, 
> causing 
> it to flip the direction of the current in the field coils in the 
> drive 
> motor.
>       Is that essentially how it works? If so, if I want to 
> replace that 
> SCR with a more modern PNP transistor, I'd need to pick one that 
> would 
> trigger with the "right" current coming into its gate (which means 
> I'll 
> need to analyze that circuit some... unless someone else has?).
>       Anyway, I managed to mow the lawn by putting in the old, 
> original, 
> fried relay, just rewiring it so I only have forward instead of only 
> 
> reverse. Mowing with only one direction is kind of a pain, but 
> easier with 
> no reverse than no forward. :)
>       Overall it was a rough day for the E15, mostly due to my 
> carelessness. After installing the new capacitor, I was topping off 
> the 
> tractor this morning, and wanted to see what voltage the charger was 
> 
> putting out. Being lazy and careless, instead of putting the 
> positive end 
> of the voltmeter to a well chosen spot such as the + terminal of the 
> most 
> positive battery, or where it connects to the power disconnect, I 
> chose to 
> put it on the spot on the Landis controller where the red wire 
> connects to 
> the PC board (the red wire that connects to the power disconnect, 
> and 
> hence is connected to the uppermost battery + terminal). Of course, 
> those 
> solder traces are really close together, and the probe of my 
> multimeter 
> shorted across the solder spot where the red wire connects, and the 
> trace 
> connected to the 47 uF capacitor, shorting across them, and making a 
> nice 
> "pop". Right now I'm trying to assess whether it only took out 
> solder 
> trace, or if it also fried anything else.
>       Bah!
> 
> Thanks,
> Mike
> 
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