[Dave A]

The quad head had four heads spinning on a drum mated with a vaccum guide (canoe). The horizontally travelling tape was sucked in to the canoe by machine vaccum to be read by the vertically spinning head assembly. Transverse recording I think they called it.

As there were four heads at any given time there were four bands of video repeated four times in a frame. It did spin fast.

It would take just a small bit of oxide fluff to sluff off and usually clog one head. It was too fast for the fluff to continue on to the next head.

Usually you got just one head clog repeated four times every fourth line. If the head was clogged, there was no RF for the machine to process and the missing RF went to full snow if bad or snowy if a partial clog.

Freon was usually sitting by in a restaurant plastic mustard squeeze bottle ready to shoot directly in to the head assembly. Most of the time it worked. If not, the next trick was to take your fingernail and lightly press it to the exposed part of the spinning drum. Either one of these would cause the tape speed/drum speed to momentarily change and break up the pic. If it worked, the tape would re-lock in a few seconds and the show would go on.

The Freon evaporated so quickly that it was not a factor as it was about 20" of tape travel until the tape hit the takeup reel. I have to wonder how much Freon was gassed out and burned a hole in the atomosphere later on. We went through gallons of the stuff in a year.