How To Relap Tape Heads (With New And Improved Camera Angles!)
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- เผยแพร่เมื่อ 26 ก.พ. 2022
- Here's the second video on tape head relapping that I promised to make, and this time you can actually see what I'm doing. The first attempt at this video is here: • How To Re-Lap Tape Dec... , you should probably watch it before or after watching this one, as there is information there that is not in this video. Unfortunately, in that attempt I did not have my headcam aimed correctly and it's hard to see what I'm doing, hence this second video.
UPDATE: There have been a couple of comments about how my methods are "not precise" and how "Studer techs use precision jigs" to relap heads. First, my methods are far more precise than a worn head. Second, while I'm sure Studer techs were more precise, try getting Studer to relap your Tascam heads. For that matter, try getting them to relap Studer heads; Studer no longer exists except as a name owned by a company that makes mixing consoles. By the way, before you make some sort of negative comment about this video, you might want to click here: • Graphs Prove Relapping...
I had one commenter suggest that I should read the Nortronics head relapping guide. Where do you think I learned this from 40 years ago? Here's the last version (that I know of) of the Nortronics Head Relapping Guide, showing their now unobtanium home relapping kit. It has a great deal of good info in it. Click the link to download it. b2b022d1-70b1-4729-96b4-2b294...
www.redbankvintageaudio.com - แนวปฏิบัติและการใช้ชีวิต
Let me be clear about something that some commenters (including those who later deleted their own comments) apparently are not clear on, perhaps because the video does not show it clearly: *There is a piece of flat glass under the lapping paper at all times. I'm not lapping on the soft carpet on the bench.*
I’ve repaired and restored several hundred reel to reel machines but always just replaced worn heads. These days heads for older decks are harder to come by, so I was looking for information on relapping heads. This was just what I was looking for!
Back in the 1980’s I put myself through college and grad school as a tech at a local medium-high end stereo store. I loved doing it! I fixed between 30 & 50 units a week for 6 years and then more working for them part time because they couldn’t find a good enough tech to replace me.
It was a hard job to leave because I enjoyed it so much and because it took several years at a corporate job until I was bringing home the same salary. In hindsight the decision to leave was a good one because the consumer electronics repair industry has pretty much dried up since.
Now I restore & repair vintage audio gear, primarily tube based. It’s easy and enjoyable because I’ve done most everything before.
Thanks for the video!
Glad you liked it! I've been in the audio field in one capacity or another since 1977. I've always enjoyed it.
you've got a replacement 1/2 inch 16 track head for my fostex i presume then? >:3c
I love it Scott, fantastic education. I have wondered many times at how recording and playback heads worked. Great video. Thanks
Glad you enjoyed it.
I’ve struggled to find information on these topics on TH-cam in the past, thanks for making this, subscribed.
Great demonstration on head lapping , learned from watching now going to try it out ! Thanks .
Good luck! If you have some heads from a junk machine to learn on, that's best. Remember to follow the natural curve of the face of the head by rocking the head as you work.
Please be sure to like, subscribe, and comment. Help me grow my channel!
Wonderful video and good instructions
Thanks. Glad you liked it.
16:43 Well, I guess that is one up for the Teacs then as having the same record and playback heads means that when the playback wears down to the point it's unusable, it can then be swapped with the record head, doubling the combined heads' life and thus the deck's life.
I had never heard of 10000 and 22000 grit sandpaper until now. I think the highest I've used anywhere is 4000.
Good video.
Your idea would work except for one thing: The record and play heads wear at the same rate, so when one is shot, they're both shot.
The sandpaper is more properly termed, "lapping film," and it's made by 3M and others. 3M makes a lapping film so fine that each grain of aluminum oxide is only one micron (1/1,000 of a millimeter) across.
Ah yes,@@ScottGrammer, I forgot to mention the caveat that the deck is mostly used for playback than for recording. I guess, that's a fair assumption for a deck in home use.
These are very impressive materials indeed @@ScottGrammer, effectively allowing one to lap various pieces with relative ease and without equipment.
@@Stelios.Posantzis It is. But the tape passes over both heads, regardless of whether the machine is playing or recording, so the wear on the heads should be nearly identical, unless one has less "wrap" than the other, meaning that the tape is not held as tightly against it as the other head.
Right @@ScottGrammer. Thanks for pointing this out. I had always wondered if that was indeed the case and why decks were made this way (i.e. all three heads in contact with the tape at all times). I initially thought that maybe manufacturers were too chap to alter the tape path during playback just to save the recording heads That cannot be the reason though since they do have a mechanism to ensure the tape is not touching during fast rewind/wind. Maybe, from their perspective, if the two heads are different (unlike Teac that is), then why bother? If the playback head is ruined, then the deck is done unless a replacement can be found.
Interesting video - thanks for posting. I'm curious about something. With the 600-grit paper, it looked like you laid it directly on what looks like a bench pad or rug on your benchtop. When you moved to the higher grits, you placed what looked like a thin piece of plastic or glass underneath the paper. Why the change? And would it make sense to use the hard backer under the 600-grit as well, or do you want the soft backing at the start for a specific reason? Thanks!
Glad you like the video. The glass was there at all times.
Thank you for this very useful video. I see you polish the heads in a « flat » way, without taking into account the curvature of the head. Should one not apply a slight curve to the movement when sliding over the dry wet sandpaper?
I do, although it may not be apparent in the video. I need a better camera for such things. As I lap the heads back and forth, I also rock the head against the direction of travel with each stroke, following the original curve of the head, until the wear groove is gone and the flat spot from tape wear vanishes.
It's not really possible to achieve the original hyperbolic curve of the head, if that's the curve it had to begin with. Not all head faces are hyperbolic. But it is possible and relatively easy to get to a shape that restores full frequency response and reliable tape contact, provided that the head is not too worn to begin with.
Thanks for your comment!
i have a cassette deck and it is so worn out, you can see the insides of the wear groove (probably about 0.1mm - 0.2mm deep) and the gap in the head is about 0.5mm wide, very visible. You can actually see inside the head. Oddly, the head does play some tapes almost perfectly but only on side A, side be on any tape (prerecorded or home recorded) sound seriously muffled. I would love to replace the head and wouldn't really care if it wasn't 100% perfectly adjusted but i dont have a soldering iron :(
One way to possibly improve the precision of the lapping would be to put the head against a square block while moving it on the paper.
I see what you mean, but I'm not sure how to make that work. Besides, I don't take a lot of metal off because once the wear groove gets to be about a half-millimeter deep, the head is pretty much worn out, so I don't relap unless the wear groove is much less than that. And I only remove enough metal to get rid of the wear groove.
@@ScottGrammer Well, I did that lapping against a block. And I was working on a flat surface plate. What happened was that since the head was always in the same place, some waviness resulted across the head, as the head position on the paper was never changed, and the paper is not perfectly flat.
A way to avoid that is to use a smaller square block that you can move with the head, thus allowing the head to move around on the paper and be cut
more randomly.
scott this is amazing to watch but aint nobody in this plane of existence doing this in their home
Perhaps some of my viewers exist in a different plane?
The head on my machine doesn't have any sort of lip or anything that catches your nail, but it does have some slight visible corrosion, which has a very slight texture (not enough to catch). Would starting with 600 still be necessary, or would starting at 1500+ be acceptable?
What concerns me is that corrosion is not merely a surface defect, but rather it etches into the metal of the cores and the surrounding metals. It may have already eaten too far into the head to be repairable. Corrosion creates pores of varying depths, and you would need to get though them all. This might mean going too far, which will result in a ruined head. I have added a link to the description above where you can download the last version of the Nortronics Head Relapping Guide. I suggest you take a look at it.
Relapping is not really intended to go into the cores of the head, but rather to bring the unworn surfaces around the cores down to the level the cores are presently at, get rid of any flat spots on the cores, and then bring the entire face of the head to a high polish. Wearing the cores deliberately (to get rid of corrosion) is not a great idea because the cores can only be worn so far before the backs of the head gaps are reached, at which point the gaps widen suddenly, the inductance of the head drops, and it ceases to perform within acceptable limits. You did not say what machine you have, but if the rest of the machine is working well, it may be worth looking for a set of heads for it.
As always, I would not suggest removing the heads unless you have the necessary knowledge and tools (including professionally-made alignment tapes) to put the heads back and align them correctly.
I have alignment tapes, but that's the answer I was afraid of. I have another machine I can get one from (head is same make and part number). I was just hoping I could save this one. Thanks anyway.
Nice video, very helpful. Gives me confidence to try it. BTW- Crown used plastic connectors that plug into the heads, no soldering to the head. Why wouldn't every mfg use a removable connector? It makes service so much easier.
Any chance you could do a video on basic re-alignment of the PB head, after lapping? I have a calibration tape from a quality lab house, but I think they are recorded in full track mono, or perhaps 1/2 track mono, so not sure if maximizing the playback amplitude on a both channels of a 1/4 track, stereo PB head would actually be optimizing the head height, since the recorded signal is wider than a normal 1/4 track, stereo track width? Almost thinking a commercial pre-recorded tape would be a better tool for setting the tape height, and then go back to the cal tape for the azimuth and zenith adjustments? Thoughts?
I always re-align the heads after relapping. I align the height visually, using a magnifier and clear leader tape. Azimuth is set with alignment tapes from MRL, and then zenith is set by marking the face of the head with a wax pencil, running a few feet of leader tape past it, and evaluating how the wax is worn away. Head depth, or wrap, is set by consulting the service manual. If the manual does not speak to this, then it is set to match the original settings by referring to photos taken before the heads were removed. Full-track alignment tapes are fine for use on heads with other track formats, so long as the alignment tapes are fringing compensated. You really can't use an alignment tape to set head height.
It depends on which heads Crown was using at the time. They used many different kinds of heads on the same machines, over time.
Can you lap a cc casette decks head? Like a laser amorphous sony head?
I suppose it could be done, but I do not relap cassette heads.
Is there a second companion video of the frequency response testing of the heads in action?
No, I did not do that, but it's a good idea that I may well use next time I relap heads. I can tell you that I did this for two identical model 32's, both belonging to the same client, and both were easily able to exceed the factory frequency response specs after aligning the playback levels and EQ using an MRL 15IPS IEC test tape, and setting the record bias, EQ, and levels for RTM LPR35 tape. I have my own personal Otari MX55N whose heads I have relapped similarly, and its response is outstanding on both the 1/2 track and 1/4 track heads. I recently relapped the heads on a Pioneer RT-707 and an RT-909 for a client, and those machines were restored to fine performance with that same tape, albeit at 7.5 and 3.75 IPS and using the NAB EQ curve, of course.
Yeah I think you’ll find that the before and after frequency sweep will tell you how good a job this is. Personally I don’t think this is a DIY job. Way too many things can go wrong, and then you have the issue of getting proper alignment after the fact. Unless you’re using some kind of optical alignment block, you’re going to be having lots of errors. And I doubt you’d get it aligned properly.
Regardless, thanks for the attempt. However I think you should warn viewers of the risks involved attempting this.
On a different note, happy to see more tapehead videos out there. Not sure why the algorithm waited 2 years to show it to me!
where can i buy sony tape heads for 242d
Look on eBay for a seller called Joeoldaudio. You can message him through eBay with your parts needs and if he has the parts, he will create an auction and send you a link to it.
Scot Grammer. Heads if i want to buy give me advise
Hi. I don't know of any source of new tape heads for consumer tape decks, with the exception of the Pioneer RT-701, 707, 901, and 909. There is a fellow who is rebuilding 1/2 track heads and modifying them into the 1/4 track heads needed. You can find them by searching on eBay. I have used these heads and they work, although the playback EQ circuit of the deck will need to be modified to correct a rising high frequency response.
2:34 and a fostex E2 apparently! still have no idea how teac got that so wrong
It was a cost-saving measure.
Very nice video but what about demagnetize?
th-cam.com/video/tv4wbc3QPTo/w-d-xo.htmlsi=MQLEE8u0Y3ylDkmr
This is a very informative video, but it could have been much more so if it had had hi-resolution images of the heads' surfaces at each stage of the process. Head realignment needs to be a
v e r y precise process to get it right. So my thought is that relapping & realigning is best done
by professionals, not by individuals at home.
True on all counts.
You should have close-ups of the head so viewers can visualize what exactly you're describing
I've actually tried to do that two or three times but I've never had good results. It seems that it's very hard to photograph such a shiny surface. Perhaps I need to invest in a polarizer.
Studer tech's use a micro jig to ensure very high tolerance. Freehand relapping is not precise.
Neither is a worn head. And Studer will not relap your Teac heads for you.
Of course a proper jig which maintains the original contour and radius is ideal but skillful hand relapping using a proper rigid abrasive surface, as per the original Nortronics instructions, has been a tried and proven method for many decades. But as always the real proof of the work is in the relapped head's playback response to the test tape.
@@oldgoody1 No way hosay, freehand will never be proper. Impossible.
@@miss.wright3035 Didnt say it would be. Please read my post. Better is not best, but it's still better.
unprofessional ! That's not how you treat magnetic heads. I worked for 43 years in a company for professional magnetic heads. Applied Magnetics Corporation. You destroy magnetic heads, we polished the magnetic heads on special lapping film from 3M lubricated with isopropanol and the magnetic head was in a special holder so you didn't distort the gap material ! This video shows how to destroy a magnetic head.
I have an awful lot of happy customers who would disagree with you. And my Otari MX55N, which I use on an almost daily basis, would also disagree with you. But thank you for your comment. The film I use is from 3M, although I use water instead of isopropanol. I use water because isopropanol, which is alcohol of course, evaporates much too quickly to use. th-cam.com/video/9krRzG0zm_M/w-d-xo.html