HP7470A Plotter calibration with an HP-IL interface

[Richard L. Taylor]

Hi,

Does any one know how to calibrate the HP7470A plotter that has an HP-IL interface?

Thanks in advance

Rich

[Garth Wilson]

Are you missing the manual? I have the manual here for the 7475 which is almost the same thing but for bigger paper, with HPIB which should work the same way, and I don't find anything about calibration. If it were an analog machine, there would be trimmers inside for that; but it's not. It's all stepper-motor controlled, with gears and a toothed belt, so it cannot come out of calibration. We used one continuously for months at my last place of work around 1990, and I wondered about the rough wheels that control the paper movement wearing down, but I guess their carbide surface was so hard that it wasn't a problem. Otherwise, I suppose you could plot something, measure it, and crank calibration constants into your software to multiply the X and Y values by.

What we were using it for was plotting PC boards (2x or 4x actual size) on very tough, stable-based material, before the days of being able to just send your files to a board house via the internet, and the boards always came out perfect and screw holes and connectors lined up perfectly with what they were supposed to mate with. There was no discernable error. Ever.

[Richard L. Taylor]

Thank you for that info. I had no idea. I did buy a service manual on CD at EBAY for $10.00. One of the strange things on my HP7470a is I wrote a program to draw the Nevada county boundries and part of the joining boundries come out as double lines about 0.4 mm apart when I use pen 1. When I switch to pen 2 and draw the map again, the double lines are not in the same place. What do you think?

Thanks

Rich

[Garth Wilson]

Quote:

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part of the joining boundries come out as double lines about 0.4 mm apart when I use pen 1. When I switch to pen 2 and draw the map again, the double lines are not in the same place. What do you think?

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Is the tip of the pen split?