HP-19C print adjustment

[mareksaw]

Hi All,

I have recently acquired a working HP-19C with "untested" printer. It turned out that the printer is generally working but no print appears on the paper. So I opened the calc, there was some bad corrosion on the PCB which I cleaned and I tried to adjust print intensity potentiometer. After this it started printing. Wow!

But unfortunately the print was very unstable. Just after turning the calc on print was too wide. After a minute or two it was getting back to normal width but then after a few minutes it started to get smaller and smaller. Taking the batteries out and in usually solved the problem - for a few minutes. Sometimes even turning off and on helped. I suspected some more PCB problems regarded to corrosion.

So I opened the calc again, found some more uncleaned corrosion and I had to bypass one PCB trace which was almost broken by corrosion. I also did more cleaning on battery terminals. After this the print quality is good, the print is more or less stable and even after the calc is switched on for some minutes the print keeps its quality.

But now print is too wide - I can not get all characters to be visible on print. Surely I was trying to adjust it with the motor speed potentiometer but I am now in its max position and I get what you see below:



Is there any other way to get the print to fill the paper width correctly? Or maybe I have still problems with some signals due to damaged PCB traces? Does the print width depend on battery voltage?

Regard

Marek