Jackson 648 Tube Checker Rolls

I like the tube checker and after using it I noticed the paper rolls that contain the test settings did not wind properly and after a while the right portion of the roll could not be read. So how do you keep the rolls on track and drifting to the right? I took a look inside the checker and saw a guide on one side of the roll and not the other.

I am guessing at this,

but if the roller is even off a fraction of being straight you would get chart creep. The same if the chart is exactly even at the beginning of the roll chart. Is there a slot on the rollers that the chart fits into? It could be that the paper chart is wound too loose or too tight and could cause creeping??????

Chart creeping, and, jamming seems to be the nature of the beast of all tube testers with roll charts.
They are simple. Two pieces of cardboard tubing on gears.
One on top has a thumb wheel that you turn by hand.
As you roll the chart, it either rolls onto top tube, or, bottom tube.
The paper is simply taped accross each tube at the end.

I think it's a combination of things, including warped paper, un even tubes, non crittical gearing, and, face it, not much bearings for those shafts, either.
Hope this helps.
Bill Cahill

If you get tired of using the roll chart you may want to get a Jackson 648 manual from Vacuum Tubes Inc.
http://www.vacuumtubesinc.com/Products/BooksPamphlets/TheJacksonModel648Manual.aspx

I found it much easier to look up a tube plus it has all the tubes that are not listed on the chart and calibration methods. I also really like my Jackson 648 but I hated going back & forth with the roll chart plus half the ones I looked up weren't even on the chart. The manual made it much, much easier and was well worth the $25.00 investment.