Check out the new Tape Project website at tapeproject.com, now with online ordering. Inventory is updated every week, so stop by often to see what we have in stock.

Author Topic: How Long do Heads Last?  (Read 7360 times)

Offline jdcolombo

  • Full Member
  • ***
  • Posts: 32
    • View Profile
How Long do Heads Last?
« on: September 26, 2007, 05:30:09 PM »
Hi folks.

I'm curious - does anyone have an estimate of how long heads last in terms of hours of usage.  I realize that it differs with speed - twice as much tape travels past the heads for an hour of recording at 15 ips than at 7.5.  But, pick a speed.  So at 7.5 ips, how long would heads last in terms of # of hours of use - 1000?  2500? 500?  I realize it also varies with head design and material; ferrite heads supposedly last longer, but most of us are using pro or "prosumer" decks that don't use ferrite heads, at least not for R/P use.  I also realize that heads can be relapped once or twice before the gap opens and they are completely shot.  But even with the head material variable, does anyone have an estimate?  Techs who cared for these machines at radio stations and studios must have had an idea how long heads would last before replacement was necessary.  So how long?

The reason I ask is that as time goes on, parts for R2R recorders are going to get scarce.  I think you can still get parts for a Revox PR99, for example, but for how long?  If two years from now I need a new set of heads, will I still be able to get them?  If not, maybe I should go ahead and buy replacement heads for my Revox and Tascam while they are still available and just store them for that day when . . .

Thanks!

John C.
John Colombo
Savoy, IL

Offline slbender

  • Jr. Member
  • **
  • Posts: 12
    • View Profile
Re: How Long do Heads Last?
« Reply #1 on: January 12, 2008, 11:56:44 PM »
Hi RTR' Tape Users,

I think I remember answering a question like this once, so here it is again, the surface of a permalloy tape head is good if no uneven wear, until your fingernail gets "stuck in the groove the tape makes in the head surface. The amount of wear and tear it takes depends on several different factors

Factor #1 - Head surface material, ferrites can be several times header than permalloy and in general last longer, but bare ferrites as used in Sony and others tend to be very hard and also very prone chip off on a straight surface edge, so the thin gaps will develop chips making it wider and less uniform in areas, which worse then uniform wear causes anomalies in frequency response.

Factor #2 - Torque, the tape pressed against the head causes wear from friction, the combination of reverse-torque applied from the supply reel and the kg of pounds applied between the capstan and pinch roller results in an applied pressure against the heads. This physical system sees the head as the immovable force, and the tape as a fine sandpaper with iron oxide or other materials in contact with the head surface.

In the old, old days, the 1960's they used pressure pads, sometimes even into the 1970's, but most modern machines (1970's-80's) used the reverse torque, which applied more uniform pressure across the heads than did individual pressure pads on springs. Some sets applied a higher reverse torque (the  Pioneer RT-909 immediately comes to mind) which when aligned and set to factory standards has almost double the back-torque found on many other sets of that quality. The RT-909 therefore wore out heads about 50% quicker than an equivalent set would otherwise.

Factor #3 - The tape surface, mostly since it is a very fine emery cloth of sorts with paper or plastic backing instead of cloth, the tape if it looks dull and blotchy is fairly rough, but if it has a shiny mirror like surface, it is smoother and more refined. Clearly older tapes in the 1960's, like Scotch 111, Sony PR-150 are rough on the surface, while TDK GX, Scotch 207, or Maxell UD-XL have mirrored surfaces and all other things being equal would produce less wear. But some tapes like the 1980's EE tapes which have a splendid mirrored surface, but in actuality is a chrome tape, may induce more wear since it is a very hard surface.  Since true metal particles (as used in DAT and 8mm video tapes) was never used for reel to reel machines.

So, now to answer the question finally!!! The permalloy heads generally under typical conditions will last about 1500 hours (+/-) before the wear is serious enough to be measured on test equipment, and maybe 2000 hours before a user will hear or notice it.  Ferrite heads might last up to 5 times longer but due to head gap edge chipping effects, which probably require a microscope to see... they get worse with frequency response anomalies; however, if a ferrite chip gets knocked off and ends up stuck inside the head gap, I suspect it effectively shorts out the head and I could see that as a distinct failure mode...

Dokorders had a Molybdenum surface head which was claimed to last forever,  I have no idea... And some Diamond surface heads existed, mostly in some cassette decks I think.
 
Lastly, the single crystal glass covered ferrite heads supposedly the type all Beta and VHS video heads were made of, also found in later Akai GX RTR sets were quoted as lasting over 150,000 hours, but I kinda doubt those numbers, especially when using EE tape. So lets say they probably last about 5 times as long as bare ferrite heads, and never suffer the anomalies of edge chipping. 

So its from 1,500 hours typically for sets without pressure pads and less for the RT-909 and up to about 50,000 hours for some Akai sets depends on the actual products in use, YMMV.

Lastly, head relapping. Hmmm. The gap would have to be deep and uniform without widening in order for that to be effective without changing every electrical characteristic that makes the head, "the head".  Might be OK done once, not so sure about additional times.


-Steven L. Bender, Designer of Vintage Audio Equipment


Hi folks.

I'm curious - does anyone have an estimate of how long heads last in terms of hours of usage.  I realize that it differs with speed - twice as much tape travels past the heads for an hour of recording at 15 ips than at 7.5.  But, pick a speed.  So at 7.5 ips, how long would heads last in terms of # of hours of use - 1000?  2500? 500?  I realize it also varies with head design and material; ferrite heads supposedly last longer, but most of us are using pro or "prosumer" decks that don't use ferrite heads, at least not for R/P use.  I also realize that heads can be relapped once or twice before the gap opens and they are completely shot.  But even with the head material variable, does anyone have an estimate?  Techs who cared for these machines at radio stations and studios must have had an idea how long heads would last before replacement was necessary.  So how long?

The reason I ask is that as time goes on, parts for R2R recorders are going to get scarce.  I think you can still get parts for a Revox PR99, for example, but for how long?  If two years from now I need a new set of heads, will I still be able to get them?  If not, maybe I should go ahead and buy replacement heads for my Revox and Tascam while they are still available and just store them for that day when . . .

Thanks!

John C.

Offline rbwtapeinterlink-Bob

  • Sr. Member
  • ****
  • Posts: 300
  • For The Love Of Music
    • View Profile
    • Power Telecommunication for business & the church!
Re: How Long do Heads Last?
« Reply #2 on: January 16, 2008, 06:12:49 AM »
Hello Steve,

Thank you for this very easily understood explanation regarding tape head wear. Actually, this suggests to me that as soon as I purchase a tape recorder the heads should be replaced. By the way, did you have a brother by the name of Walter Bender who lived in Virginia many years ago? I ask because I've not run accross to many Benders and I purchased a Magnacord 1024 recorder from him. Just asking. Thanks again.

Bob Williams
Bob W. (African American) VPI, Ref Standard Grado, Denon 103r, Threshold, DecWare tube pre and Classe pre amp, Jolida tube phono pre amp, (Peter Gunn) modified Magnapan 1.6, Tascam 32-2B & 42B tape decks, Parasound belt drive CD transport, Pacific Valve tube DAC, VPI  TT, various upscale cables.