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How can you establish how worn the record & play heads are on a reel to reel. I've seen ads where people say the heads are 60% worn etc, etc.....do they really know this or are they just guessing.
Any help much appreciated as always
cheers, Eric
If you send your heads to JRF for work, or just for evaluation, he sends them back with a written report showing the remaining head life as a percentage. I would trust a report from him (or from Sprague Magnetics or Flux Magnetics) but a number from any other source is meaningless.
Actually, the percentage of wear is determined by the depth of the remaining material at the head gap. This is *usually* determined optically. A secondary method to determine wear is to make precision inductance measurements, however; this is only valid when the original head inductance is known. Also, contrary to popular opinion, the high frequency response will actually INCREASE *just* before the head "gap" begins to widen. When the gap begins to increase, high frequency response will take a nosedive.
It isn't *that* much of a "guessing game", however I wonder how many people who state a percentage of head wear *actually* measure the depth of the gap. I would bet that MOST people just take an "educated guess (which is totally useless.)
Just some thoughts.
Bill
Gnerally there is reduced output in mv and high frequency fall out as the head wears and on a pro recorder, a record is kept of it's alignment and a dbv record of frequency fallout as measured on a RMS AC voltmeter like a Gen Rad 1840 or an Eico 250 with an alignment tape. Also, there is a wear pattern on the face of the head where the tape has cut into the resin and case. It generally takes a tech who know what he is looking for. Sometimes if the wear pattern is irregular due to mis alignment and has not eaten in to the magnetic core stack of laminations and widened the gap, the head can be re-lapped (re-ground with a new hyperbolic face).
"I think the journey should be just as enjoyable as the destination." GRH
It could be that the machine has a method of keeping track of the hours that it's been used.
It could also be that a tech has measured the high frequency response of the heads and made an educated guess on how much more life the heads have before they need relapping or replacement.
Hi, IB:
Many years ago, I picked up one of these nice fancy hourage meters, the type with rotational numerals showing up in a window, cut through the face.
I used it to track hours used on my Marantz tube amplifier, an 8-B.
Then, I finally just put it away.
But, those devices, many of which are still being offered through various surplus electronics outfits, can be inserted in-line with the power cord of any device and will inevitably keep track of total hours used when the device is operated, that is.
The URL below just shows a couple of more modern versions of the hour meter, some of which can be panel mounted, some not. Check it out!
Of course, it will not differentiate winding time "off-the-heads" from hours "on".
And, one further little observation: on the Panasonic SV-3700 and SV-3800 DAT recorders, there once were hour meters on the back of the recorder, so one could more or less determine total hours on the rotational heads. I think Panasonic may have removed this feature on their later models, but it was on the SV-3700.
And, ask yourself why high-end tube amplifier manufacturers never built these devices into their products? Why, it would make the user nervous and apprehensive about the longevity of the tubes in their gear!
There you go!
Richard Links
Berkeley, CA
Thanks for the link, and it's a good idea. But they would have to be wired in at some other point in the circuit, rather than into the line cord. The specs say they have a 3.0 watt power rating, and almost any component I'm aware of draws more than three watts.
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