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Thread: Relapping Heads

  1. #1
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    Relapping Heads

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    I thought to start this thread to serve as a resource for those who are brave enough to give relapping a try.

    Nortronics has this guide to head wear and relapping:

    http://recordist.com/ampex/docs/repa...nortronics.pdf

    You might want to get a copy on your hard drive.

    This thread could serve as a forum for our success and failures.

    ----------

    Also, my tascam 38 has one good head (sync) and an older worn head on playback. I would like to get a new(er) 38 head to put in the sync position and move the current sync to the playback position. This would free up the worn head for relapping.

    Just gotta find that newer head at a price I could afford.

    Regards, ethan
    In Sunny Vancouver ..... (Washington)

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    I've not seen this guide before, but I have lapped a few heads myself, from my Otaro MX5050. I started with 600 grit wet sandpaper on an old bathroom mirror (the glass is for flatness), then moved to 15u and then 5u optical polishing sheets. Here's a few pics of the work... first one is before (of course), second one is after the 600 grit, and the final is all three heads (plus erase head which did not require lapping) mounting in the headstack after polishing.

    Any questions, feel free to ask!








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    Nice job!

    These are great photos for us all to look at when the question of head come up. On the worn photo you can see the difference between the flat and the unworn head area. Do you recall how much the head was worn away?

    The Noritronics guide says that the gap depth on typical heads is between 16 and 22 mils (1/1000") and that one should relap at 5 mils wear and at 10 mils wear.

    So not to selves. When asking if your head is good measure the wear depth. Assuming that it has not been relapped before if there is more than 15 mils wear your head is good for relapping practice.

    Regards
    In Sunny Vancouver ..... (Washington)

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    Quote Originally Posted by evm1024 View Post
    I thought to start this thread to serve as a resource for those who are brave enough to give relapping a try.

    Nortronics has this guide to head wear and relapping:

    http://recordist.com/ampex/docs/repa...nortronics.pdf

    You might want to get a copy on your hard drive.

    This thread could serve as a forum for our success and failures.

    ----------

    Also, my tascam 38 has one good head (sync) and an older worn head on playback. I would like to get a new(er) 38 head to put in the sync position and move the current sync to the playback position. This would free up the worn head for relapping.

    Just gotta find that newer head at a price I could afford.

    Regards, ethan
    Ethan why not just get the worn head relapped and then reinstall it? The turn around time is only about a day.

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    Prior

    The deck appears to have had the current sync head replaced at some point and the (bad) playback head appears to have worn through the gap length. I think that it is too far gone for a relape.

    --Ethan
    In Sunny Vancouver ..... (Washington)

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    Me and a 12 year old Scottish friend...

    ... Finely got around to trying my hand at lapping a few 8 track, 1/2" heads that I picked up a while ago. Not sure which deck they come from. The headstack base is like that of my 38. All 3 heads are brass based like the rec and repro. The wires go to phenolic PCB rather than a header like the 38. Anyone know?

    Here are 2 photos of the rec/sync head. A before and an after. Looks like a usable head. When I get the time I'll open up the 38 and pull those heads. I may build a header and try putting one of these heads in.

    OK here goes: I did this on the kitchen counter, rinsing the sand paper and head frequently. Starting with 400 grit wet I followed the Norinco instructions to remove the keystone and establish a nice profile. Once the flat spots were all gone and things looked good I moved on to 600 grit wet paper. This took much less time to remove the 400 grit marks. When I thought there was enough of the 600 (perhaps 10 minutes) I moved on to a 1500 grit paper. I took another 20 minutes or so with this. I took extra care to not mess up the work that I had already done.

    One thing tha I did do was to rotate the head 180 degrees at every rinse. THis was to make sure that my hand pressure was equal on both sides and top to bottom. I wanted whatever weirdness I was doing to cancel out.

    The last photo shows the side of the heads. You might notice that the brass/epoxy at the head face might show the gap depth. Not sure of the construction inside but it was about 20 mils before I started.

    Oh, I did use a caliper to measure the wear depth and came up with about 7 mils. It appears that theblown head on my 38 has a wear depth of 20 mils. This is consistent with the 20 mil gap depth figure that I've heard. wore later when I get it our and try a relap.

    Regards, Ethan
    Attached Thumbnails Attached Thumbnails head-2-initial-jpg   head-2-1500-jpg   head-jpg  
    In Sunny Vancouver ..... (Washington)

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    Very nice work! Hard to see the contour of the head in the first two pics, but the last one certainly shows off that beautiful curve.

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    I agree...nice work. Too scary for me yet, but I may have some spare heads here depending on what I do with my "parts or repair" 48.

    That head reminds me of a Fostex E16 head...no edge slots.

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    Quote Originally Posted by sweetbeats View Post
    That head reminds me of a Fostex E16 head...no edge slots.
    Edge relief slots are usually put in during lapping by JRF Magnetics to improve performance as the head wears again. They prevent the tape from lifting slightly at the edges.

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    I might even tackle that if there were no head slots but my deck has them so I'd be freaked about wrecking it. Nice work tho'.
    Tascam TSR-8

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