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Old 13th Oct 2018, 11:27 pm   #10
1100 man
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Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 1,377
Default Re: Cleaning video heads etc

Usually clogged heads are as a result of a damaged bit of tape that sheds it's oxide rather than accumulated dirt on the tape path.

I still use VHS Hi-Fi machines to play old music compilations which have been played many many times over the years. I get occasional head clogs when a damaged bit of tape goes past- you can hear as the chewed bit of tape physically goes past the heads. Sometimes the Hi Fi sound will disappear, sometimes the picture.
It takes two heads to play back one complete frame of picture (each head plays one field). If one head clogs, you will get a picture that flickers at 25Hz with a complete screen of noise over the top. ie one field of the picture followed by the next field of snow.

To clean them, I use a clean finger moistened with IPA (isopropyl alcohol)held against the head drum with the machine in stop. The drum is rotated back and forth keeping the finger absolutely stationary. Each head on the drum is done in turn and then allowed to dry. That's vital, as if the machine laces up with a damp drum, the tape will stick to it and be pulled out of the cassette rapidly until the whole thing turns into a big tangle!!

Obviously, the finger used needs to be in good condition and similar to a chamois pad and keep the nail away from the head tip!

I've been servicing VHS machines since the mid '80's and then timelapse ones during the '90's, although we did used to use chamois sticks. Fingers, though, tend to always be on hand and seem to work just as well!

IPA is the safest solvent to use. Usually though, for most head clogs, the above method with just a dry finger works fine. Only for stubborn problems do I get out the IPA.

As has been pointed out, NEVER use any vertical motion as you will break off the head tip. Also NEVER use anything with fibres that will get caught in the head tip- I learnt that lesson with a cotton bud and a N1700 head when I was a kid!

The visual effects of clogged heads on the screen will vary depending on the machine. Some machines display snow, some strange patterns or vertical blocks of moving shapes. If only one Hi Fi sound head gets clogged, there will be a 25Hz flutter on the sound.

Hope that helps
Cheers
Nick

Last edited by 1100 man; 13th Oct 2018 at 11:33 pm.
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