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-   -   Are these Revox tape heads scrap? (https://www.vintage-radio.net/forum/showthread.php?t=186682)

mole42uk 11th Dec 2021 9:46 am

Are these Revox tape heads scrap?
 
2 Attachment(s)
Here's a couple of Revox tape heads that have seen better days. The record head has a deep scratch to the lower right face and there is evident wear to both. They had both been cleaned with alcohol just prior to the photos, so the streaks are residue from that. Should I scrap them or will they stand a refacing?

Thanks for any guidance.

Restoration73 11th Dec 2021 9:56 am

Re: Are these Revox tape heads scrap?
 
Looking at the cost of new heads, I would seek a second opinion, as reprofiling if only
once might be worthwhile;

http://www.summertone.com/services/

stevehertz 11th Dec 2021 9:57 am

Re: Are these Revox tape heads scrap?
 
The proof of the pudding is in the eating - how do they perform? Do they 'work'? I wouldn't discard rare heads like that if they are working, even if it's below par. Also, pure alcohol shouldn't leave streaks, if streaks are being left, then clean again using IPA from a chemist on a cotton bud. It doesn't look as if the complete face of the heads has been cleaned 'properly' to me.

TIMTAPE 11th Dec 2021 10:45 am

Re: Are these Revox tape heads scrap?
 
Yes I would never discard partially worn heads of that calibre. They're expensive and becoming much harder to source new.

Revox used to say that if the wear "flat" was 2mm (?) or more wide (as it is on both these heads) the head should be replaced. But that was back when the machines were the best way of recording, and new heads were freely available off the shelf.

I've gently relapped many mildly worn Revox heads in order to restore a better radius, which is all they often needed. Since they had relief slots (gutters) machined at their edges, there's often no need to remove edge ridges, unless the head was poorly aligned when installed. The playback head in photo 1 was obviously installed incorrectly as the wear pattern is trapezoid in shape. Harder to tell with the record head.

There may be pitting in the head faces around the crucial gap areas. It's hard to tell from the photos. (Pitting often occurs after someone played a sticky shed tape, failed to clean off the muck and then left the heads in that state for some time. The water absorbing tape residue eventually corrodes the head face).

The scratching at the bottom right of the record head should be fine as it's way outside of the normal tape contact area.

Only the inner head unit needs replace or relap and reinstalled in the original two piece mumetal housing.

Ted Kendall 11th Dec 2021 10:52 am

Re: Are these Revox tape heads scrap?
 
Terry has been around for donkey's years and knows his stuff. I'd say a relap at this stage would be beneficial, together with careful setting up of the heads on re-fitting - the face tilt looks as if it may be out. The usual way of checking this is to use engineer's blue or felt tip pen to show the wear pattern.

Incidentally, I think the quoted breakpoint was at 4mm, although I did use one set of heads far further than that - I had to admit defeat when the gap collapsed on one side of the playback head - at all but 6mm! Curiously, the head showed no obvious deterioration before that. I wouldn't bank on that sort of luck, though.

TIMTAPE 11th Dec 2021 11:21 am

Re: Are these Revox tape heads scrap?
 
Quote:

Originally Posted by Ted Kendall (Post 1431567)
...Incidentally, I think the quoted breakpoint was at 4mm...

Thanks for the correction, Ted.

Quote:

Originally Posted by Ted Kendall (Post 1431567)
...although I did use one set of heads far further than that - I had to admit defeat when the gap collapsed on one side of the playback head - at all but 6mm! Curiously, the head showed no obvious deterioration before that. I wouldn't bank on that sort of luck, though.

Yes I think I read somewhere years ago that a playback head increases in HF efficiency right up until the eventual opening of the gap, then it's all downhill, whereas a record head needs a certain minimum of metal remaining in order to fully magnetize the tape.

Ted Kendall 11th Dec 2021 11:54 am

Re: Are these Revox tape heads scrap?
 
Quote:

Originally Posted by TIMTAPE (Post 1431576)
Quote:

Originally Posted by Ted Kendall (Post 1431567)
...Incidentally, I think the quoted breakpoint was at 4mm...

Thanks for the correction, Ted.

Quote:

Originally Posted by Ted Kendall (Post 1431567)
...although I did use one set of heads far further than that - I had to admit defeat when the gap collapsed on one side of the playback head - at all but 6mm! Curiously, the head showed no obvious deterioration before that. I wouldn't bank on that sort of luck, though.

Yes I think I read somewhere years ago that a playback head increases in HF efficiency right up until the eventual opening of the gap, then it's all downhill, whereas a record head needs a certain minimum of metal remaining in order to fully magnetize the tape.

Agreed. As the polepieces get thinner and the inductance drops, both output and HF should, theoretically, rise. In this case they certainly didn't drop until the day the gap went phut. I remember also having Terry make some heads for a Telefunken machine which originally had Photovox heads. These worked well, but were about 6dB down in output. Terry concluded that this was because he had used thicker polepieces than Photovox, the upside being that his heads would have a longer life.

mole42uk 11th Dec 2021 12:01 pm

Re: Are these Revox tape heads scrap?
 
Quote:

Originally Posted by stevehertz (Post 1431548)
The proof of the pudding is in the eating - how do they perform? Do they 'work'? I wouldn't discard rare heads like that if they are working, even if it's below par. Also, pure alcohol shouldn't leave streaks, if streaks are being left, then clean again using IPA from a chemist on a cotton bud. It doesn't look as if the complete face of the heads has been cleaned 'properly' to me.

Yes, the heads work but I haven't yet measured the frequency response.

The heads were filthy, really clagged up with tape shed and sticky stuff. I always use cotton buds and 100% pure alcohol (IPA), these images were taken after the initial wiping just to show the extent of the wear. They need taking out of the machine and properly cleaning now - I wasn't going to bother if they were scrap!

I have contacted Summertone to get them refaced - it'll make me happier to know that they have been properly treated!

knobtwiddler 11th Dec 2021 12:09 pm

Re: Are these Revox tape heads scrap?
 
Another vote for Terry. From seeing his work and chatting with him (he did my A810 heads, which weren't far off the condition shown here - and said that he believes they have about 75% of their life left), I've come to the conclusion that most heads can be lapped satisfactorily in the R-R world. I'm planning to send him some more heads soon.

Michael Maurice 12th Dec 2021 1:27 pm

Re: Are these Revox tape heads scrap?
 
Who and where is Terry?

ms660 12th Dec 2021 1:46 pm

Re: Are these Revox tape heads scrap?
 
Quote:

Originally Posted by Michael Maurice (Post 1431929)
Who and where is Terry?

http://www.summertone.com/

Lawrence.

Marotick 12th Dec 2021 5:54 pm

Re: Are these Revox tape heads scrap?
 
During use, the heads will be polished and the sound will improve.
It's about the air gap if it is dirty or scratched then it will be disappointing.
Use tires that are not contaminated and clean the heads with every tire change.

Jack Marotick

ButchJames 15th Dec 2021 2:36 pm

Re: Are these Revox tape heads scrap?
 
Quote:

Originally Posted by knobtwiddler (Post 1431593)
Another vote for Terry. From seeing his work and chatting with him (he did my A810 heads, which weren't far off the condition shown here - and said that he believes they have about 75% of their life left), I've come to the conclusion that most heads can be lapped satisfactorily in the R-R world. I'm planning to send him some more heads soon.

Terry done some cassette deck heads for me a while ago - great service.


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