Subject:
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Re: Smoking serial/charger board...!!!
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Mon, 1 Dec 1997 03:34:24 GMT
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Original-From:
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Fred G. Martin <fredm@#avoidspam#media.mit.edu>
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Viewed:
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318 times
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Hi. This evidence pretty conclusively points to a power-ground short
on your board. Here is why:
* you are fairly certain it is not the RJ11 cable (the most common
cause of blown R11's).
* when applying charge pwr directly to the HB's charge jack, you get a
hot R14 and a too-bright yellow LED.
OK, now you have to find why your board is shorted. You can use the
hot R14 and too-bright charge LED as evidence.
Power-ground shorts are devilishly hard to find, but I can get you
started at least. Here is what to do:
1. remove all devices plugged into the HB.
2. remove all socketed DIPs.
3. make sure HB is turned off.
4. plug charge power into the HB charge jack.
Do you still get hot R14/too-bright yellow charge LED? If yes, it may
be the battery itself. Try removing that and see if the problem is
still there.
If not, turn HB power on and see if problem recurs. If so, pwr-ground
short is on the board, beyond the pwr switch.
I realize this is incomplete debugging info but hopefully you can get
started looking for the problem.
Fred
In your message you said:
> I am having a similar problem (see notes below) - R11 is burning on the
> serial/charger board. My HB had been on the shelf for a month or so, and
> it may have been left on AND I had made the motor-power hack (I tapped the
> center of the battery pack to supply the motors' power). This all reminded
> me of the note below on a problem very much like this.
>
> I checked the charger-to-HB cable and its correct (cable I have always used).
>
> I think the HB was on when I first plugged in the charger. I soon started
> smelling that electronic-burn smell we all hate so much!!! I quickly
> disconnected every thing and noticed R11 was brown.
>
> I checked the battery pack - its at 5V. If I try charging via the charge
> jack on the HB, the charge LED glows brightly, but R14 on the HB gets very
> hot in a few seconds. I also checked to be sure the HB power switch is off
> position and I was not connected to the serial/charger board.
>
> I remembered the note below of a similar problem. Oddly, I too had made
> the motor power hack. But thats been in for a long time with no problem.
> For good measure, I disconnected the jumper cable I had run to the HB's
> motor power trace from the center of the battery pack - but no change in
> symtombs.
>
> I did not notice any hot caps, as someone else suggested a shorted cap in
> response to the other posting of R11 burning.
>
> Any ideas???? Short somewhere?? I disconnect all motors, sensors and
> external connections.
>
> Keith
>
>
> > make sure you have a telephone-style and not network-style RJ11 cable.
> >
> > Here is how you tell if you have a telephone-style or network-style
> > RJ11 cable. Hold the two ends together, metal contact side up, as if
> > you were trying to plug them into each other.
> >
> > Then look at the wiring colors. On a telephone cable, each color
> > should line up with itself on the other end.
> >
> > On a network cable, the colors are inverted.
> >
> > See the diagrams for clarification. Again, please, please, PLEASE!
> > be careful about this and do not use network cables with your Handy
> > Board.
> >
> > -Fred
> >
> >
> > TELEPHONE STYLE WIRING
> > +---------------+ +---------------+
> > --------+ yellow =======+ +======= yellow +--------
> > + green =======+ +======= green +
> > + red =======+ +======= red +
> > --------+ black =======+ +======= black +--------
> > +---------------+ +---------------+
> >
> > NETWORK STYLE WIRING
> > +---------------+ +---------------+
> > --------+ yellow =======+ +======= black +--------
> > + green =======+ +======= red +
> > + red =======+ +======= green +
> > --------+ black =======+ +======= yellow +--------
> > +---------------+ +---------------+
> >
> >
> >
> >
> > In your message you said:
> > >
> > > Well,
> > >
> > > Today I dig up my handyboard which was working fine with the serial/sharge • r
> > > board and all the last time I used it a few months ago.
> > >
> > > After a fresh overnight NiCd charge using the onboad power connector
> > > (i.e. not using the serial/charger board), I thought I would play with
> > > it a bit. That's when the fun started...
> > >
> > > Upon plugging in the telephone cord between the handyboard and serial/char • ger
> > > board, R11 started to turn darker and literally started smoking... By the • tim
> > e
> > > I got around to disconnecting the cord, R12 and LED14 have started to do t • he
> > > same. I guess that R11(47 Ohms 1/2W) burnt out causing a domino effect on
> > > R12(47 Ohms 1/8W)...
> > >
> > > My question is, does anyone know why it's doing this? Right before I shelf • ed
> > > it couple month ago, I made the modification for using less than 9.6V moto • r
> > > (per instruction on the handyboard homepage). But, all was working fine
> > > after that (at least I thought so)... I should mention that the two motor
> > > driver sockets are empty because I'm still waiting for my TI 754410 (and
> > > have been for 2 months)...
> > >
> > > I have just replaced R11 & R12 and I thought I should ask before I try
> > > again... Any clue would be appreciated... Voltage across pin 3 & 4 of the
> > > modular socket on the handyboard read 10.2V. The charge rate switch was
> > > at normal.
> > >
> > > TNX
> > >
> > > --Ron
>
>
>
>
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Message is in Reply To:
 | | Re: Smoking serial/charger board...!!!
|
| I am having a similar problem (see notes below) - R11 is burning on the serial/charger board. My HB had been on the shelf for a month or so, and it may have been left on AND I had made the motor-power hack (I tapped the center of the battery pack to (...) (27 years ago, 28-Nov-97, to lugnet.robotics.handyboard)
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