How to Open (and repair) an Ampex/Lear Jet Cartridge
by Abigail Lavine
NOTE: Here's some e-mail from Edward Lawrence on opening Lear 8-tracks. He's a technician who actually worked on the original design!
Why is it that Ampex, the absolute last word in audiotape for the serious professional, consistently produced 8-track cartridges with pinch rollers which turn to gummy goo? It's true. 9 out of 10 Ampex/Lear Jet cartridges have dangerous and unusable melted rubber pinch rollers. And on top of that, the carts are especially difficult to open in order to replace the roller. But with a little bit of work and foresight, you can create a kit which will make opening them oh so much easier. I learned the secrets I'm about to share from 8-track repairman extraordinaire Joe Wally, of Wally's Stereo Tape City in New York City. The man is a professional. Literally. He's been repairing 8-track tapes as part of his job since before some of the people reading this were even born. Joe Wally uses an ordinary kitchen knife, a hex screw driver or socket set, and two specially prepared hex head screws. The first step is to force the kitchen knife into the seam between the two sides of the cartridge shell at the top, near where the tape is exposed and the pinch roller is visible. Pry the two sides apart a bit. Now turn the cartridge over, so the label is face-down and you can see the five little holes on the back. The middle hole is slightly larger than the others, and this is the one to attack first. You'll need to have a hex head tapping screw which is just slightly larger than the middle hole. When you find the correct size screw, hacksaw the sharp end off of it. While you're at it, find a slightly smaller screw, one that's a little bit bigger than the four smaller holes, and saw the end off that one too. Now screw into the middle hole until the two sides of the shell begin to separate. Move on to the four smaller outside holes one at a time. The two sides should spread apart. At the end, you can remove the screw in the middle. Before you completely pull the two sides apart, BE SURE TO TURN THE TAPE OVER ON THE TABLE SO THAT THE LABEL IS FACING UP. That way the spool of tape inside will stay in its path. Change the pinch roller and do whatever other repairs may be necessary. In the end, the two sides should go back together with a little effort, or a few raps from a mallet, or with great care in a workbench vise.
NOTE: Tracker KenGAce@Aol.com has some comments to add to this discourse:
"AMPEX pinch rollers are the worst! The problem with AMPEX tapes is you can't just use a roller from another cartridge (NO!). The hole diameter and outer diameter are unique to AMPEX tapes. AMPEX tapes only use a taller sized pinch roller. Therefore, you have to replace the rubber by removing it from the plastic spool (a real mess. Ammonia dissolves this well. Watch out for the fumes though). The problem is finding the rubber replacement. It is essentially a short piece of rubber hose pulled over the plastic spool. Exact inner & outer diameters are critical for proper operation as well as the smoothness and elasticity of the material.
I found an ideal substitute for the the gooey rubber washer. Your local hardware store may sell a power tool called an oscillating spindle sander. It's used for sanding down the inner edges of holes. The sandpaper tubes fit over rubber hose-like tubes (usually available in various diameters). The smallest diameter is 3/4" (important) and the length is 4 1/2". Ryobi makes such a spindle sander (P/N 4610810) and sells these rubber spindle replacements as well (about $3 to $4). You have to wrap about 2 to 3 layers (evenly) of masking tape strips around the plastic cart wheel to widen the diameter for better tape contact; and trim it accordingly. Next, cut the rubber spindle with a sharp razor EVENLY to the correct length of the wheel. Slip the rubber tube section over the plastic wheel and clean it off. Make sure the rubber tube is on the wheel evenly and not riding on the raised plastic edges! You can repair about 5 to 6 tapes with one rubber spindle.
"A cool thing I did to repair some Ampex rollers. First, ofcourse, I used every
method possible to open on up, then I got the sticky rubber crap off of the plastic inner
part. I then took a piece of garden of regular 1" garden hose, cut it to the correct
height of the inner roller and ripped off the green part of the hose. I took the rubber
inner part and put it around the plastic part of the Ampex roller. (Glue the part of the
hose to the plastic inner roller, so it doesn't hover around it) I then wrapped a piece of
Scotch tape around it, and put it back in. Works fine. Crude, but works fine." :)
"Since hex head self-tappers are hard to get, I used Spax wood screws with the
points cut off. These are cylindrical and have a more widely spaced spiral than metal
self-tappers. The Pozidriv head gives more or less the same grip as a hex head
would." Andrew Lowell - lovelinf@NOSPAMpop.algonet.se
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