View Full Version : Black Screen of Death and the CW Computer. Matag Repairman Edition

07-01-2014, 08:19 PM
CW Computer & Black Screen of Death

I had the Black Screen Of Death the other day with the LCD freezing up on change bit followed by a re boot and the Death Screen.... A row of black blocks on the top row of the LCD.

The quick fix was a replacement computer after changing cards and checking connections.

So tonight I pop the cover off the CW Computer and I was shocked being a Circuit Board Electronic Guy finding the Computer with lots of SAWDUST inside.... That is like putting a blanket over your computer and not letting it properly cool.... So likely, HEAT Overload was the reason for the Black Screen Of Death....

I took it to the shop and slowly and gently blew the dust out of the top part of the computer. Remembering a Sony Tech in San Diego showing me a LP Air hose with something on it to prevent STATIC that was used in the Cell Phone Referb Lab. He said normal LP Air can FRY the Circuit Boards... with static. So lesson remembered....

At the Philly Sony Service Center I would replace the postage stamp size chips using a sharp knife to cut the traces along the chip then with flux clean and remove the pieces.... Then the re soldering in careful strokes like combing hair... We had a heat air gun too for chip removal.. but many times it blew off other small components and then you had a mess.... I miss the Sony days....

I wanted to point out the 3 Servo Drivers that are mounted to the case as a heat sink... When you get a Servo Axis Failure, this is the most likely component to fail.... a 7 leg chip....

I believe I will add opening my other computers and inspect for dust too.... BE WARNED.... NO Vacuum Cleaners... that will kill the computer.... And at your own risk blow the sawdust out....

For this computer I will carefully remove the Servo Heat Sink Hardware, the Plug Hardware, and finally the nuts holding the circuit board securely to the metal case and remove it... I will wear my Circuit Board Grounding Wrist Strap then using Circuit Board Cleaner wash the board. Waiting a day for the Cleaner to fully evaporate from under the chips.... Then give it a SHOT... It might work again..... I will post the results in a few weeks.... Busy here in the shop....


Servo Drivers 5206-2 http://pdf.datasheetarchive.com/indexerfiles/Datasheet-075/DSAE0010669.pdf

32 Bit, 25 Mhz Microcontroller http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=MC68332

$7 Bucks, the right equipment, and luck.... :) http://www.digikey.com/product-search/en/integrated-circuits-ics/pmic-motor-bridge-drivers/2556626?k=5206-2&stock=1&pbfree=1&rohs=1

07-01-2014, 09:42 PM

That is a lot of dust. I am very surprised to see that much inside the computer box.

07-02-2014, 10:44 AM
Wow that is a lot of dust is this a fire hazard?

07-06-2014, 02:15 PM
Good Question.... But in my opinion the dust inside the Cut Motor is more of a problem with the heat of the motor and the air flow from the sparking brushes through the motor and out into the muffler...

New Problem today that makes me scratch my head and wonder....

Running the last of 60 sheets of plastic today and the first bit was the 1/6th circuit board end mill. I hear on the intercom the machine stop and wait for last bit change. I walk into the shop and the machine starts up.... The bit is going to the position for the 2nd bit cut and I open the cover and stop the machine... I NEVER changed the Bit to Bit 2 and I never hit ENTER.... The Machine did it by itself.... The wrong bit would have given me the wrong size holes......

I re booted and the keypad and LCD look normal but shut down until later when I can make a holes only fix....

I did blow the plastic dust as the machine started the first bit cut and the cut was normal up to the "Auto Bit Change" without me... The machine and dust collector are grounded in a few areas... I am betting it was a STATIC Charge that caused this.....

More Later...


Gary Koval
07-07-2014, 07:41 AM
I don't know if you remember, but, several months ago I called you with this same problem on my "B" machine. Heard it stop for bit change and then start up again without any intervention on my part. Even had a video of it happening, short maybe 30 seconds. Per our conversation I contacted LHR via email, weekend day but couldn't figure out how to upload the vid because of size. Didn't hear back, and discarded the video. If you figure out why this happens, I'd be interested in the fix...

07-07-2014, 08:57 AM

Yes, I now remember.... my thinking was a pinched wire at the time... Now with my adventure I believe it was Static Electricity as I used LP air to blow down the machine as it was starting to carve the first part and it was a big fine plastic cloud cleaning the rails... Normally I have been blowing with the power off... Interesting to note that I did the same thing when I got the Black Screen of Death.... So in my opinion it was a static charge made by the moving plastic into the dust collection hood... Again machine grounded and dust collector grounded....


Gary Koval
07-08-2014, 06:44 AM
Thinking back, I remember that I would push the stop button, and the machine would stop momentarily then start up again. Only lifting the cover stopped the machine. Still happens occasionally on long days (8+) hours of say, 1 hr carves. I do have filtered downdraft but it does get a little dusty, but cleaned after each carve with a grounded shop vac, where the stranded ground wire runs down the length of the hose,again per your suggestion.