Okay. Thanks for posting that. I wanted to verify two things:
1. You were using new tape and what type it was in case your heads didn’t have the key slots cut above and below the coil stacks, because…
2. Some heads have key slots cut above and below the coil stacks, and some don’t. It’s a good idea to have them because tape widths are standardized to fairly close tolerances for slitting, but some manufacturers did a better job of adhering to those standards than others. Okay. Everybody except Ampex/Quantegy did a better job. Ampex’s slitting equipment wasn’t as precise, and in order to avoid their tape ever being too wide, they slit their tape slightly more narrow than the standard so that when their slightly less precise slitters slit wider the width was still within the standard. This resulted in two things, #1 when you switched from some other brand to Ampex tape on a machine that had an established wear path, the Ampex tape would “country-lane” (wander) in the tape path, and #2 if you cut a wear path with Ampex tape it was often slightly more narrow and if you then switched from Ampex to another brand that was more precisely slit to the standard, the edges of the tape would lift or curl in the wear path, causing diminished response in one or both edge tracks. On the more narrow format machines like 1/4” 8-track this might even result in no response on an edge track…been there, done that. If the wear path was slight one could sometimes run a reel in fast wind over the heads with the lifters defeated a couple times to dress the wear path to the more precisely slit (wider) tape, problem solved. In other cases a relap was necessary OR reverting to Ampex/Quantegy tape. The key slots avoid all this because they effectively eliminate the edges of the wear path. I went through this with a 388 I used to have, and ultimately had JRF relap the heads AND cut key slots, which was not done at the factory on a 388. Again, problem solved. But this is not your problem, you have key slots cut in your heads, and you are using new tape. SO…
My next suspect is tape tension. When tape is pulled too tightly across the heads it causes the edges to curl up. OR you need to rotate your guides because THEY do not have edge slots and the edges of the tape might be curling in the guides and remain curled across the heads, OR, and I’ll have to look at the MS16 manual, but if the guide adjustment is like the model 58 (the 1/2” 8-track contemporaneous to the MS16), then you might need to adjust the guides because the more precisely slit RTM tape is wider than whatever tape was used when the guides were set.
Get a bright flashlight and shine it down along the tape in PLAY mode and then look from the other end to see if you can see the tape curling.
When I’m talking about Ampex being more narrow, I want to be clear we’re not talking huge amounts, but 0.001”-0.003” difference. And that’s enough to be problematic depending on the circumstances. I’m speaking from experience with this in 1/4”, 1/2” and 1” formats. Haven’t dealt with it in 2” yet but that is purely circumstantial.
