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Equipment Discussions >> ATM, Optics and DIY Forum

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whirlpoolm51
professor emeritus
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Reged: 01/05/12

Loc: pittsburgh,pa
Does anyone have any knowledge on circuit boards?? new
      #5513272 - 11/10/12 02:36 PM

Still looking for some help on these 2 celestron single arm mount motor boards please!! it is driving me crazy tha it worked one minute and now it doesnt

I have 2 boards and with one i plug all the motors in and only one runs and never shuts off until i unplug the controller

The second on i have worked perfectly and now it doesnt!! is it possible to burn out or short out these boards???


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glennnnnnn
sage


Reged: 10/20/09

Loc: San Diego, CA
Re: Does anyone have any knowledge on circuit boards?? new [Re: whirlpoolm51]
      #5513485 - 11/10/12 05:43 PM

A board can not act like it should if it has been handled without ESD precautions having been taken. It is possible to burn out a board, but if you have the standard motors and standard power supply, then is is more likely the board has been damaged somehow in a physical way or through Electo Static Discharge, which can ruin logic circuits easily.
Get a magnifying glass and examine each board for cracks or broken solder connections. If you put these boards in and took them out repeatedly, there could have been some stresses involved that caused a malfunction.
You could mess up the board by over tightening a mounting screw, for instance. Some devices are designed without any margin for error, and if you don't handle it right, it fails.
Sometimes, though, what you think is the problem isn't.
Are both motors good?
Is the power supply working correctly?
Is each connection to the board free of damage and clean?
EDIT: I just read the OTHER post on the same subject and Dan h is right. (Or as right as its possible to be in this case!) You didn't mention you plugged it in wrong. When the board gets hot that's bad, so I'd guess that you burned something out. The power requirements are 9 volt to 12 volt, and depending on your source the "12 volts" you are using could be more than that. But if you got it plugged in wrong anything could happen. I'd use a 9 volt battery next time.

Edited by glennnnnnn (11/11/12 03:23 AM)


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ZeroID
sage


Reged: 04/21/10

Loc: Auckland, New Zealand
Re: Does anyone have any knowledge on circuit boards?? new [Re: glennnnnnn]
      #5514984 - 11/11/12 07:38 PM

Electrostatic damage is normally internal to chips etc. Be nothing to see but erratic operation would point to that being a good possibility.
Hard to diagnose, even harder to fix. Start repacing chips and hoping. Boards are normally robust enough to not be affected.


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Wes James
Postmaster
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Reged: 04/12/06

Re: Does anyone have any knowledge on circuit boards?? new [Re: ZeroID]
      #5515860 - 11/12/12 11:50 AM

The key to avoiding electrostatic damage in the first place is to keep yourself grounded to the circuit board's groundplane. At any given time, you can have several thousand volts of static charge on your person... and a chip may only be rated to a maximum voltage of 50 volts. Not hard to understand why just the simple act of touching a circuit board can result in damage. One of those things that if you don't know what you're doing can cause way more damage than you had to begin with!

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gpelf
sage


Reged: 12/28/11

Loc: Kentucky
Re: Does anyone have any knowledge on circuit boards?? new [Re: Wes James]
      #5517561 - 11/13/12 09:39 AM

For what its worth, ESD is much more of an issue if the component is not mounted (Chip is off the board). Once in the circuit it is not as likely to have ESD damage. Although very high in resistance the board insulation itself helps to discharge high transient surges. +1 on burning something up if a cable is hooked up wrong.

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DAVIDG
Post Laureate
*****

Reged: 12/02/04

Loc: Hockessin, De
Re: Does anyone have any knowledge on circuit boards?? new [Re: gpelf]
      #5517693 - 11/13/12 11:13 AM

I've repaired a number of telescope electronics over the years and have designed and built CCD cameras from scratch.
When it comes to the these GOTO system, 9 times out of 10 the problem is that someone used the wrong the polarity on the power supply and/or jammed one of the motors so it draws too much current. With either of these conditions what it does is fry the voltage requlator on the board. They use a surface mount regulator that is designed for less then 1 amp of draw. So the first place I would check is what was polarity of the power supply and then check the input and output of the regulator.
One the Meade ETX systems the regulator is listed at 500ma and is not reverse polarity protected. The fix has been to cut the traces going to the regulator and install a LM7805 regulator that cost $1.50 at Radio Shack and can easily handle over a 1 amp of draw and is reverse polarity protected.

- Dave


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Gene7
scholastic sledgehammer


Reged: 06/10/10

Loc: Mid Ohio, USA
Re: Does anyone have any knowledge on circuit boards?? new [Re: DAVIDG]
      #5518264 - 11/13/12 04:42 PM

The most likely thing to happen is a crack in the circuit board, very hard to see. Use an ohm meter to check continuity from one end to the. Also use the meter to check each solder connection. In fact,you best re-solder all joints using flux. Gene

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bob71741
Pooh-Bah
*****

Reged: 02/16/08

Re: Does anyone have any knowledge on circuit boards?? new [Re: Gene7]
      #5519590 - 11/14/12 02:13 PM

As mentioned above, hard to damage ICs with ESD when installed in PWB.

Would be difficult to troubleshoot PWB w/o schematic unless something is smoked, but would still need schematic to determine what was smoked.
My advice is to return to factory for eval/repair before you do any real damage to the unit by resoldering joints, replacing SOT package regulators w/ TO-5 regulators, etc.

Not sure how you would have damaged a 3 terminal regulator as all types have thermal shutdown, and how would you have applied reverse power?

Try the factory or someone that works for a living repairing electronics.


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whirlpoolm51
professor emeritus
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Reged: 01/05/12

Loc: pittsburgh,pa
Re: Does anyone have any knowledge on circuit boards?? [Re: bob71741]
      #5519752 - 11/14/12 04:07 PM

pretty sure i burned out the second one i had by not paying attention and missing a pin when connecting the motor,

But and this is a big but!! the first one works still but only one motor driver or leg should i say works and the other leg doesnt.

Circuit boards are sure fun to learn about but are very very delicate hahaha i bought an arduino motor shield and the atmega365 and i have had so much fun writing the codes and programs for it


so this is a learning process for me , although the 2 boards i burnt out i needed for my drive system i am learning from my mistakes


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