Re: 1502 chart recorder
If the belt still remains on the drive gears, you might remove it and closely inspect the nylon gears as well. They have a propensity to develop cracks and eventually fail.
If you are working on the electronics, be advised that there were a few versions of the PWB used in this item with around three in this series with some noticeable changes in circuitry. If you can obtain the Tek a500 series instruction manual, document number 070-2554-00, it will have all of the different rev level schematics. The board rev level is usually indicated by a tiny label located in the upper right hand corner of the board when looking at the rear of the recorder. Rev 6 was the last version of this unit.
In addition you might have noticed that there was a change in the drive motor used in these recorders. I believe that it happened at rev 4, when Tek moved to an external speed control board and new motor. The board is located in the motor area.
When picking these up off of eB, I try for the rev 6 recorders since these are the newer ones and may have less wear and tear. If you are lucky, you might come upon a seller who is offering a batch of them at a reasonable price. I keep a couple spares around for my 1502 and 1503 units as parters.
Another issue is the chart paper. If you are looking for the real thing, Graphic Controls Corp
is, from what I can find, the only supplier of the paper these days. But be prepared for sticker shock. I checked on the prices of this stuff last year and it has risen to around 33 dollars per roll, minimum 10 roll order. A check just now shows a price of 34.80 a roll. The last I purchased was around 5 years ago and at that time it was a little over 15 dollars a roll. This is probably because they have to set up and print the paper for the order when it is requested.
When searching on their site, simply type in the Tek part number 006-1658-01 in their search field to find it. Occasionally there will be some rolls come up on eB at a more reasonable price.