[QuadList] Dropouts at fixed intervals

[Dale Lamm]

[snip]
I never could figure out how these little bits of magnetic fields would get 
on the transport.  Does anyone have the knowledge of the cause?
[end]

First heard an explanation in the early 70's at an ABC affiliate. When we 
saw them on playback we were told they were scratches. Maint supervisor got 
curious, mounted some junk tape on a TR-70 and hit play. Took a demagnetized 
greenie and poked it into the tape's oxide side upstream of the headwheel. 
Could not make a so-called scratch.

Same screwdriver when slightly magnetized would make the diagonal speckles 
every time. He concluded that small oxide particles shedded from some tapes 
would stick on mechanical components in the tape path, and magnetically 
"scratch" any tape that would pass by later on. This included syndicated 
programs destined for other stations down the line on a tape bicycle.

Folklore was that the front erase head was a prime suspect in holding these 
little magnetized headaches. Guess that's why they came out with back erase 
heads. We were told to religiously clean all path components every time the 
heads were wiped, which was after all 30 min shows or a couple times a shift 
if just playing spots. Remember the Tex-Wipe lint-free cloths and liquid 
Freon?