Re: strange electrical issue - anyone have any knowledge of what to do.


Christopher Erickson
 

Most likely some kind of failure in the rectification and filtration electronics of the power supply.  Probably a cold solder joint or a bad filter cap.  I would offer to fix it for you if you sent it to me but I doubt you would want to send it to Hawaii.  However I AM very curious about its behavior and what is causing it.
 
 
-Christopher Erickson
Observatory engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com
 


From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, October 19, 2017 2:56 PM
To: ap-gto@...
Subject: RE: [ap-gto] strange electrical issue - anyone have any knowledge of what to do.

This is beginning to sound similar to a problem I have with a "new" (two years old, but never used) 12v Pyramid 10a regulated power supply. 
 
When I use this PS, any DC power cable hooked up to a DC output (screw terminals or the front cigarette lighter socket) heats up very quickly to the point where I can't touch it.  And the back of the PS where there are two external transistors mounted, gets hot very quickly too. 
 
And when I attempt to plug the DC end into something (such as a video monitor or video camera), there's a little spark between the plug and socket when I first plug it in. 
 
I didn't catch any of this the first time I used it -- and it apparently fried one of my monitors.  I've also melted two DC power cables in testing.  No fuses have ever blown.
 
When I do simple tests for voltage and continuity, everything checks out OK.  No shorts, no reversed polarity, and the voltage is 13.89v DC.
 
But there's most definitely something wrong with the PS.  I'm thinking that testing for the problem is beyond my skills.  So I've put it in the tub for electronic recycling.
 
But I do have an old Fluke 77 and a brand new Fluke 115.  So maybe I have the proper tools, just not the knowledge to use them to figure this problem out. 
 
I've already purchased a new PS, but I haven't yet put the suspect PS in electronic recycling.  If there are some relatively simple tests I can perform with either of my Fluke instruments, maybe I can get to the bottom of the problem and "save" the otherwise brand new PS.
 
Woody
 
 

-----Original Message-----
From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, October 19, 2017 4:54 PM
To: ap-gto@...
Subject: RE: [ap-gto] strange electrical issue - anyone have any knowledge of what to do.

 

Use a voltmeter to measure what voltage difference exists between the laptop's chassis ground and the CP4's chassis ground.  NOT the ground pins of the AC power cords.
 
However spurious ground differentials will only exist when the CP4's power is connected and disconnected.  They will probably be fast and only detectable by a O-scope, analog meter or a digital meter with an analog scale, like a Fluke model 77.
 
Running the CP4 from a battery will isolate the CP4 completely and guarantee that a spurious ground differential can't come from the CP4.
 
I still say the CP4's external power supply is the #1 culprit.
 
 
-Christopher Erickson
Observatory engineer
Summit Kinetics
Waikoloa, HI 96738
www.summitkinetics.com
 


From: ap-gto@... [mailto:ap-gto@...]
Sent: Thursday, October 19, 2017 8:16 AM
To: ap-gto@...
Subject: Re: [ap-gto] strange electrical issue - anyone have any knowledge of what to do.

But how to test it? My only test destorys laptops? 


Try running your CP4 off a 12 volt battery. That would confirm that something is flaky with your Dc power supplies.

Rolando

On Wed, Oct 18, 2017 at 3:24 PM, chris1011@... [ap-gto] <ap-gto@...> wrote:
 

Try running your CP4 off a 12 volt battery. That would confirm that something is flaky with your Dc power supplies.

Rolando




-----Original Message-----
From: Ron Kramer ronkramer1957@... [ap-gto] <ap-gto@...>
To: ap-gto <ap-gto@...>
Sent: Wed, Oct 18, 2017 2:13 pm
Subject: Re: [ap-gto] strange electrical issue - anyone have any knowledge of what to do.



I have gone to 3 prong with ground, that actually was in use with the 2nd laptop. (before it died).
Laptops don't display anything or even beep. They just come up with power light and fan.  That's all.

Battery on the first new laptop was fully charged and if power is disrupted, the battery takes over.  (like if I pull the AC or turn off the power strip, the laptop would stay running). 
What puzzles me is why they go blank when the 12v connector is applied into the cp4? 

no bios message or anything else (ACER splash screen is ever seen, just black).
I'm quite good with computers... I've never seen one power up with fan and nothing else.  I don't know if I can wait - I think I might have to move a extra desktop out there
but the 1.5 days of software install and configuration is getting old. 

I'm more concerned with why power drops when plugging in the CP4. 
NOTHING else shuts down.  

On Wed, Oct 18, 2017 at 11:03 AM, 'Joseph Zeglinski' J.Zeglinski@... [ap-gto] <ap-gto@...> wrote:
 
Ron,
 
    Could it be that you have flakey power from the AC outlet at the “gate”?
 
    Unexpected glitches could cause Windows to crash – without a formal shutdown. That might be corrupting your Windows boot partition. When you try to reboot, the laptop can’t find a proper boot record, so it stays black ... usually a text message says to insert a bootable device.
 
    I would suggest installing even an inexpensive small UPS in the dome, so that the unexpected power dropouts are carried through for upto 10 minutes. Some,  even small UPS (like from TrippLite), have a USB cable talking to Windows, and when it senses a switch over to its battery, it issues a formal Windows Hibernate or shutdown, when its battery nears being drained, or by your specified shutdown period.
 
    However, the battery in the laptop should have already handled this  – and the power option in Windows is normally set up to shut down Windows when its battery reaches 10%. Check your power option plan to confirm.  If for some reason, there is no grace percentage in your power plan, it would also crash Windows, possibly irrecoverably without user Win boot record repairs. So, this may still not account for your problem.
 
    Finally, very many, if not most telescope device electronics seem to be meant for battery operation, so the circuit board LOGIC ground wires are tied directly to Chassis (Earth) ground. Without that green ground wire, there is no place to dispel a short except the DC supply, via whatever other circuit boards traces “conveniently” share that common  Earth/Logic connection. Since you haven’t provided one in the power cable, everything else is at risk.
 
    I may be possibly overstating the latter case, but I wouldn’t chance not using at least a properly grounded power cord from the mains.
 
    In any case, you should have a UPS – fed by a proper 3-wire power cord, since UPS’s complain and probably won’t function without a safety Earth Ground connection to the main AC supply.
 
    Have you tried booting to laptop BIOS, to see if it is just a boot record damage or the laptop really is fried? The former can be fixed by yourself, with some time and effort. Worth investigating before returning more laptops for electronic repair. Possibly a software tech at the local PC store, can get the laptop booting again – quicker than shipping it to the manufacturer.
 
Good luck,
Joe





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