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Head Relapping

 

 

 

We are able to relap or recontour a tape recorder head so that the original performance of the machine can be obtained. This can be done on most makes of tape head provided the wear is not too bad. If the tiny vertical head gap is showing signs of breaking up then it will not be possible to recondition the head.

When a tape head is partially worn it may show as a loss of high frequencies giving a "bumpy" response and increased incidence of dropouts caused by imperfect tape to head contact. Often a head will display signs of uneven wear between tracks and it is usually the outer tracks that are most affected. The narrower the track width the worse the problem can be and the more benefit will be obtained by reconditioning.

Relapping requires a thorough knowledge of the materials used in head manufacture - mumetal - supermumetal - recovac - vitrovac - sendust - glass ferrite etc. and requires experience to identify the material a head is constructed of. The head is viewed under a stereo microscope to identify the material. Only when the type of material is identified can the correct method of relapping be determined. Different head materials require different specialist lapping compounds, this is why material identification is so important before relapping is attempted.

Relapping requires an in depth knowledge of magnetic head construction i.e. to identify telltale signs of gap depth and other parameters.  Otherwise a head can be destroyed by using incorrect procedures. Head profiles are important. All magnetic heads exhibit "contour effect" which is "humps and bumps" in the response curve, especially at the lower frequencies. The electronics of any particular recorder are tailored to correct this effect as far as possible. Incorrect relapping changes the profile and thus the frequency response. So when relapping the profile must be also be shaped. When correctly reprofiled and relapped a head is almost "as new". In fact it is better than "as new" sometimes, because as the gap depth has been reduced to remove the head wear, the gap losses are reduced and the head efficiency increased.

 

View from top of head showing original and relapped contour

 

When you send us your head for treatment we will inspect it to discover if it is suitable for refurbishing. If it is, the inductance of the head is noted and reprofiling can take place. This is done under controlled conditions to a very high accuracy and maintains the original contour of the head to ensure the tape path is correct. Final polishing takes place and a further final inspection is done. The inductance is again checked to ensure the manufacturer's specification is maintained.

If the head fails any of the tests then you will be informed and no further payment is due as the head will be disposed of. If the head passes all the tests it will be returned to you by insured post at the cost originally quoted.

 

The cost:

When you send us your head(s) we make a charge of 22.00 per shipment to cover our handling costs. Each successful relap of a single or two channel head* costs 50.00 per head. So if a two channel* record and a play head were to be refurbished, it would cost a total of 122.00. If the heads were not suitable to be worked on, then only the 22.00 handling charge would be payable.

* Heads with more than two channels are by quotation. A two channel head may be 2 or 4 track format but must have only two separate channels.

When you send us your head(s) be sure to include your address and telephone number. Do use an insured method of delivery and let us know when to expect delivery by using our Contact Form. We will contact you to collect payment by card when the work is completed.