That thought had crossed my mind but I daren't mention it.not everyone will agree with me but sewing machine oil is virtually identical - at least in function
electrically - these machines are super easy to work on. i've done three PR99's so far ... feel free to ask if you have any questions. those heads look very good to me - i'd say no more than 20% wear as opposed to fifty ...
That thought had crossed my mind but I daren't mention it.
I tried measuring the width of the flat spot with a transparent ruler but couldn't get it near enough for an accurate measurement, however I reckon it's about 3mm give or take. Some say performance begins to degrade when wear gets beyond 1mm, others say it's fine with 4mm or even 5mm of wear, - so much for consensus!
The wear guide at the top and bottom of the head is the clear indicator of flat or rounded wear. IMO on this head the wear is flat and and is the same width and depth as the wear guide, the head gaps are opening as well so for me that head is toast.THIS one is quite a bit more worn than yours (and in a similar way - rounded wear, conforming to head shape, like yours) but this one could probably also 'clean up well' with a quick polish and not even need a lap ... possibly
https://reverb.com/item/6583367-rev...MI9q-88ZiI6wIV8R-tBh035QuqEAQYASABEgJjE_D_BwE
The wear guide at the top and bottom of the head is the clear indicator of flat or rounded wear. IMO on this head the wear is flat and and is the same width and depth as the wear guide, the head gaps are opening as well so for me that head is toast.
Totoman your heads are approx the same as every deck I have worked on and will calibrate up fine
If you cant get the last few marks out with Acetone you can try some polishing compound (Peak or Autosol) on a strip of microfiber cloth
I wouldn't touch a head with a demmel either If a head needs re-lapping, send it to Terry at Summertone, its actually not expensive
http://www.summertone.com/services/
Alan
Yes that’s how I’m seeing the aforementioned heads that were posted ... (shrugs)Below is a couple of pictures of a heads with what appears to have wide wear in the first picture but as you can see the the middle of the head is still well clear of the bottom of the wear grove, so in this instance the wear was rounded. The second picture is after cleaning and polishing, they look like new
Head 1 by Alan Towell, on Flickr
Head 2 by Alan Towell, on Flickr
Alan
I guess you could use Audacity’s frequency analysis or whatever its called to look at some Audacity generated white and pink noise, then record it to tape and back into Audacity and see if it looked much the same. Not a proper calibration method by any stretch, but it should tell you if there is much loss above your hearing range. Again this won’t tell you about the head condition (which now looks fine to me), only about the overall performance and calibration of the tape deck as a whole, e.g. it will likely be more about electronic calibration to tape type as the heads.
PS If it is a nice tidy example I’d actually be inclined to get it properly serviced.