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Professional reconditioning of magnetic heads
- Thread starter krellmk
- Start date
about cassette deck's heads...
if we exclude the nakamichi heads on their 3 heads models, which have slots at the edge of the tape and are designed to get good tape-head contact until the gaps are totally worn-out and then such heads don't benefit from a relap because when their performance starts to suffer it means they are totally worn out... of course, because of the slots, no wear groove does develop on such heads.
for the other cassette deck's heads, relapping is useful only BEFORE the heads are totally worn out at their gaps.
point is that, even with some wear groove (but with the gaps which are still good), the tape-head contact starts to suffer... this happens, i.e. , because the head surface area which is outside the wear groove works like a pressure pad lifter on a deck which was designed to work fine WITH the help of the pressure pad. So, lapping the head by removing the wear groove will simply make the pressure pad into the cassettes pressing the tape against the head gaps area properly again.
another reason why a relap would be needed even on a head with a light wear groove is if, for whatever reasons, you need to realign the head (in example, if the previous alignment wasn't right and, in such case, also the existing wear groove was developed with the head not well aligned and now you wish to align the head properly)...
So, moving the head alignment when there is just a wear groove is, in general, a very bad idea... this way, the existing wear groove will be misaligned with the tape travelling path and then it would badly affect the performance... also, the tape would easily be damaged. In fact, a wear groove acts like sort of tape guides parallel to the tape travel (and the deck was not designed to have such extra guides/constraints)... now, if you don't touch the alignment such extra guides will be well aligned with the tape travelling path and the tape will run straight inside the groove... but if you go and touch the head's alignment then you'd get such extra guides which are misaligned with the tape travelling path and the tape would be forced against the "walls" of the wear groove or it might also run on top of the borders of such misaligned groove.... in both cases, the tape might get easily damaged.
So, if (for whatever reasons) I need to realign heads which show also a light wear groove, I first relap the head to get a smooth surface with no grooves at all and then I can safely realign it as needed.
yet another reason to relap heads, even if they show little wear, is when there is surface corrosion (hoping the corrosion didn't really affect the gaps in depth)... like, i.e., on this sendust head I've recently relapped and which now works just like new again.
Of course, there are also situations where the only true solution is to replace the head with a new one.
if we exclude the nakamichi heads on their 3 heads models, which have slots at the edge of the tape and are designed to get good tape-head contact until the gaps are totally worn-out and then such heads don't benefit from a relap because when their performance starts to suffer it means they are totally worn out... of course, because of the slots, no wear groove does develop on such heads.
for the other cassette deck's heads, relapping is useful only BEFORE the heads are totally worn out at their gaps.
point is that, even with some wear groove (but with the gaps which are still good), the tape-head contact starts to suffer... this happens, i.e. , because the head surface area which is outside the wear groove works like a pressure pad lifter on a deck which was designed to work fine WITH the help of the pressure pad. So, lapping the head by removing the wear groove will simply make the pressure pad into the cassettes pressing the tape against the head gaps area properly again.
another reason why a relap would be needed even on a head with a light wear groove is if, for whatever reasons, you need to realign the head (in example, if the previous alignment wasn't right and, in such case, also the existing wear groove was developed with the head not well aligned and now you wish to align the head properly)...
So, moving the head alignment when there is just a wear groove is, in general, a very bad idea... this way, the existing wear groove will be misaligned with the tape travelling path and then it would badly affect the performance... also, the tape would easily be damaged. In fact, a wear groove acts like sort of tape guides parallel to the tape travel (and the deck was not designed to have such extra guides/constraints)... now, if you don't touch the alignment such extra guides will be well aligned with the tape travelling path and the tape will run straight inside the groove... but if you go and touch the head's alignment then you'd get such extra guides which are misaligned with the tape travelling path and the tape would be forced against the "walls" of the wear groove or it might also run on top of the borders of such misaligned groove.... in both cases, the tape might get easily damaged.
So, if (for whatever reasons) I need to realign heads which show also a light wear groove, I first relap the head to get a smooth surface with no grooves at all and then I can safely realign it as needed.
yet another reason to relap heads, even if they show little wear, is when there is surface corrosion (hoping the corrosion didn't really affect the gaps in depth)... like, i.e., on this sendust head I've recently relapped and which now works just like new again.
Of course, there are also situations where the only true solution is to replace the head with a new one.
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I am not in the relap everything camp in fact very much the opposite. Cassette heads have to be put on right at the start. If they are not then all the tapes you made on that deck are off and now you want to change the head? While the concept of a pad lifter might be good on paper, I don't think it works that way in the real world. Keep in mind the pads are felt usually and they will conform to shape. If they are not and some hard substance then you have a low grade tape. I have worled on a lot of decks in 47 years to find that the left channel often is upset due to incorrect tilt or that there is contamination on the head that pushes the tape away from the gap. This is why even just recently I used Nu Finish car polish on a head and the level and high frequency came up almost 3 dB just from doing this plus the head that looked real foggy was a very shiny one after. Some heads with deep wear are done life wise and a $60 lap job is not going to get you a new head. The heads for cassette decks are those sitting at places like mine as the Onkyo service where Teac heads were suppose to go never have any stock anyway- Like Jim said they threw away a lot of parts and wrote them off like Sony did. This seems to be a very common business practice in these big companies which I call poor management.