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Old 3rd May 2009, 03:33 AM   #1
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Default You know that you are having a bad day when.......

I started laying out a PC board for my "universal driver" design while I was sitting around a hospital in Pittsburgh waiting for my mother in law's chemo treatments (late December).

I finished the lay out in a hotel room in Georgia on my trip home (December29).

I made two "home cooked" PC boards right before I had to go back to work in January.

I started populating one board in early January. Then Sherri had to go back up north, tasks started piling up, my job started demanding long hours, so the board sat on the shelf unfinished.

Today was the first day that I have had a few hours of spare time this year, so I got the unfinished board off of the shelf and started soldering.

I put all of the parts necessary for testing on the board. Everything looked OK so I hooked it up. Nothing, NADA, zip, not even heater glow. I had 6.5 volts right on the pins of the tubes, but nothing. This sickening feeling came over me. When I realized what had happened, I strongly resisted the temptation to throw the board into the trash, or worse!

Back when I made the board, I had swapped the top and bottom transparencies. The board is a mirror image of what it is supposed to be. Which brings me to one of the first rules of laying out a PC board. ALWAYS put some text on the board somewhere on EACH layer. I was in a hurry when I laid out this board, so I left the text off. Text would have made it obvious that the board was mirrored.

So now I can toss the board in the trash, nuke it in the microwave, run it over with the truck, or try to salvage it. If I had to choose right now I would nuke it, but that really stinks up the house, so I cracked open a Bud Light instead. I may have some time to deal with it tomorrow. It may be possible to remove the tube sockets and semiconductors and put them on the back side of the board.

I have about 10 days until I must travel back to West Virginia to help with Sherri's mother. I will be gone for about 10 days which will put me behind again, so tube time will be limited. On the bright side if I time it right, I might get a day or two to hit the Dayton Hamfest. It is the biggest electronics flea market in the world (or so they say).
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Old 3rd May 2009, 04:57 AM   #2
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On the upside:

1. You only populated one board.

2. You cooked them at home, so even if you destroy one, you're not out 75-100 bucks for someone else to proto the board for you.

3. You get to go to a big Hamfest. I've never been to one, not even a small one.

Don't get too frustrated. I'm pretty sure everyone that knows you realizes that you're dealing with a family illness, and that they need your support.

Jeff
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Old 3rd May 2009, 10:48 AM   #3
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I've had a few bad days, too. I used to lay out boards using rub-on resist pads and rub-a-dub marker (it works if the PCB copper is 1 oz or thinner - otherwise you get pinholes). I went all the way through the process of laying out and etching the board (a hybrid amp using the UA739 IC), then realized everything was mirror imaged. Duh...
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Old 3rd May 2009, 11:12 AM   #4
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My board maker will not accept any layout unless there is text to identify the layers. Guess they learned the hard way as well...

Jan Didden
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Old 3rd May 2009, 06:54 PM   #5
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Hey, don't worry - we've all done it.
I've laid out 100's of boards always at 2x or 4x full size and always put two accurate dimension lines with "reduce to [whatever dimension]" on the film. One day I got back a very odd sized PCB from our manufacturer - I put the wrong size on the film. Good job it was a prototype and not a production run!
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Old 3rd May 2009, 06:55 PM   #6
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you could hard wire the one .....................maybe
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Old 3rd May 2009, 07:37 PM   #7
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Last night I was rather disapointed by my stupidity and almost tossed the board. Today I had to prepare our 8 year old vehicle for a 2500 mile trip. While I was underneath the car I was thinking about the board and two blonde brain cells must have got together and ignited a spark. I didn't need to rip the board apart, I didn't even need to take the tube sockets out. I could just tack solder two more sockets on the back of the board. The CCS chips have 3 pins. The center one is the input and the other two are tied together through two resistors. I just need to swap the two resistors. All of the other parts have two leads, they don't care which side of the board they are on. I left the car half finished and came inside to try this out.
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Old 3rd May 2009, 07:39 PM   #8
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After dealing with a few of the typical things that surface with a new board (mostly wrong guesses at resistor values and a non cooperative scope), it is ALIVE.
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Old 3rd May 2009, 07:42 PM   #9
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Don't forget to finish the car
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Old 3rd May 2009, 07:46 PM   #10
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Does it work? There is no PowerDrive circuit yet (those parts might wind up on a piece of perf board due to another really blonde idea), but does 400V peak to peak of drive from a 550 volt supply sound like enough to make some screen grids glow?

I reduced the input level to make the picture fit the scope screen. This picture is only 350 volts peak to peak. Now I must go outside and put some oil in the car engine before I do something else really dumb!
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