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Stuff that Drives You Nutz!!!

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Several months of Torment just ended. It started innocently enough. I bought a Wacom Intuos graphics tablet, thinking that I’d learn to cartoon. Problem was, this top of the line pad never worked well enough for me to get started. The mouse worked OK but the pen was jerky sometimes and sometimes not. The mouse, even when it worked, had a highly variable speed and acceleration threshold. Impossible to do precision movement. I query to Wacom about a new driver got me the usual corporate crap.

My USB connection to my camera would work really well one day and then sputter along the next. The 13 (!) port hub that drives everything except my tablet and my 56k modem would work really good most of the time but lousy sometimes.

My modem would not work on the hub but worked fine on my 4 slot USB cardbus adapter.

USB 01

The ancient USB 1.1 port in this ancient Dell had long since given up the ghost so I got this no-name ChiCom 4 port card for the princely sum of $11. In fact I got two. It has worked well for years.  The fat grey cable feeds the 13 port expansion box

The modem worked great most of the time, getting 49kbps out of this 25 mile long mountain line but sometimes it would generate Microsoft Mysterious Error Message 777 (really. Maybe Gates trying to out-do the devil) and other times it would only connect at 14.4 or 28k.

The USB bus powered hard drive that I clone my machine to worked great most of the time but sometimes it would have a write buffer error or something similar.

The little SD card reader always works fine, as does the USB interface to my Archos Jukebox music player.

The intermittent part was what drove me crazy. Most of the time everything worked well, though just often enough, something would screw up. What was really baffling was that usually when something malfunctioned, moving it to a different hole in the 4 port adapter fixed things.

Today my graphics tablet quit completely. The little blue “I’m alive and connected” light would blink just a little and then the tablet became inert. In an attempt to put some ert back into it, I opened the back which involved taking out about 147 tiny Phillips head screws that I had to use a stereoscope to see.

The first thing I did was stick a DVM on the power leads on the USB cable. 3.6 volts. Hmmmm, that didn’t seem quite right. Just to make sure that they hadn’t changed the spec to 3.3 volts or something, I got on the net (using the touch pad built into this machine) and verified that yes, 5.0 volts is still the standard.

I unplugged the tablet, got some tiny probes and probed the card socket. 3.7 volts. Damn! Card must have gone bad. I got out my brand new backup card. 3.7 volts. Maybe a bad port. I unplugged everything and checked. 3.8 volts on all 4 ports. I’m starting to see a pattern here.

This card uses an external 5 volt, 1 amp wall wart, the remains of which are here

USB 02

I checked the barrel plug. 3.8 volts. I looked at the nameplate. Sure enough, 5 volts, 1 amp rated. When I popped (literally) the case, the remnants of blue smoke wafted out. My several months’ tormentor had been uncovered.

I couldn’t really see anything blue-smoke-less but it stank anyway. I plugged in the wart to a variac and the output voltage varied roughly with the input. Hmmm. An unregulated regulated switchmode power supply.  What’ll those ChiComs think of next? Da Pricks.

I now realize what was happening. At the end of this 25+ mile long power utility feed, the voltage varies significantly, depending on how much load is on the system up here. Today it went below 32 degrees for the first time and most of the RVs around me use electric heat. Coincidence that everything quit working today? I think not.

In fact, after glancing over at my high-zoot Westinghouse switchboard voltmeter, I noted that it was reading 116 volts instead of the usual 122 volts. At the unregulated regulated switchmode power supply, that dropped the “5” volts to a level at which almost nothing worked.

To its credit, my $5 no-name USB bus drive enclosure was and is working fine. The drive is probably 3.3 volts inside so it didn’t matter much.

I rummaged around in my computer bone yard (hurray for bone yards), found another USB supply, hooked everything back up and things worked perfectly.  I think that I bought a dozen of these little adapters at a buck a pop at a swapfest.  Hurray for cheap ChiCom parts.  The inert one had been in service for several (probably more than 4) years so I can’t complain for a buck!

Moral of the story #1: When all sorts of “unrelated” things start going wrong with your computer setup, check the power supplies.

Moral of the story #2: Make sure that you put ALL your computer stuff, even your little wall warts on your UPS.

Moral of the story #3: make or install a full time UPS instead of a standby one. My standby UPS never triggered that first time. It simply passed through that variable line voltage. My full time UPS (high current power supply, battery bank, inverter) IS regulated and WILL stop this problem from happening ever again.

Now back to my cartooning lessons. The world won’t be safe if I ever master this art :-)

Posted by neonjohn on November 17th, 2008 under Computing, Cool Stuff, Power Generation


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