klem kedidelhopper wrote in message
...
On Jan 18, 6:59 am, "William Sommerwerck"
wrote:
You can make one if you have a high-quality tape deck, Just record
some of the higher frequencies in the range of 4K and above, and use
that to align your subject tape heads. Should be no problem if you
have a audio generator and a good tape deck to make the master
alignment tape.

This reminds me of the joke about the town that set its public clock when
the local fort fired its canon at noon. The fort, of course, fired the
canon
when the clock struck 12:00.

I have an old Yamaha that is a spare machine. It has always seemed to
sound "good" however I never really ran any tones through it to see
what playback looks like. I'll have to investigate using that one as
my "standard". Back in the 70's I used to align Ampex and Scully
professional tape recorders and could A B an output pretty closely by
ear. The last few years though the high frequencies have been rolling
off, (between my ears) and so now even 10KHZ is difficult to perceive.
So I really can't rely on "what seems to sound good" to me any more. I
thought that music sounded reasonably good on the faulty channel of
the Teac until I looked at the meter while running tones. I'd still
like to find a commercial alignment tape though. I have several old
reel to reel alignment tapes made by Ampex and Nortronics I think but
nothing for cassettes. Lenny

++++

For tape speed checking/adjustment I've used the following for the last
year, perhaps 5 repairs and no bounces from any of them, so presumably
perceived as correct speed.
(My speed test tape is old , slightly ruffled and maybe stretched )

I found a large quantity of salvaged capstans+spindles.
26 off on my mic (rather than callipers before) measure 1.99 +/-0.01 of
reading accuracy and 2 nearer 2.00
5 off measure 1.79mm
1 at 2.19mm
9 measure 2.49mm
(A sampling of these measured by a mechanical engineer measured at
62 degree F and agree with my figures, ie 0.01mm less than round number))
The machine in question uses 2.49. Either spindles or bearings would have to
be an off-size for free movement, so presumably sintered metal bearings
are (easier?) made round number size and spindles made 0.01mm smaller
diameter and
speed of rotation adjusted just as easily to that as any other speed.
Assuming it is actually 2.5mm then doing the maths and strobing with quartz
f-meter calibrated strobe then my test tapes are 0.4 percent out from
calculation via 15/8 ips etc.
spindle rotation speed of 6.05 rev per second with an error of about 0.4
percent , needs longer gate time or repeating more times to bring that
accuracy up (rounding errors? so probably longer gate time required than my
meter has).
If 2.49 diameter then 0.6 percent out.
Hopefully will revise these figures when I get a bit of cross-calibrated
engineering
accuracy but above is probably fairly representative and scale
for the different spindle diameters.
I used a white LED on a stable audio genarator coupled to f counter.
I found monitoring strobe at 6 Hz difficult but just painting
"tip ex" over about 1/4 circumf of capstan and monitoring for strobing
at 4 times frequency was much easier and better for the f meter gate time
also.
Not as obvious as exact strobing, you have to monitor the relative
flaring-up
and monitor direction/change of its drift.
Another possibility as a test tape - record some constant tone, any f, on a
few minutes of tape, pull out a long length and pass a small magnet over two
parts
a measured distance apart. retract, and then time the interval between dips
in play mode (not tried).
Where no rear access and have to strobe from the front , assuming enough
space for this
add-on. 12 or 16 or 20 pin smal plastic cog, Fit to a plastic cylindrer to
drill an
undersixe hole to the capstan spindle size. Mark one quarter segment black.
Cut into anyold
cassette casing to reveal the area that the spindle and pinch wheel goes
into. Unfortunately usually no more than 1mm
of free space over the pinch wheel. So a dot of hotmelt glue to hold well
enough to
test speed. Place this cassette in th edeck and deck in play and switch off
power , leaving pinch wheel
touching spindle , to stick this cog in place. Knowing the diameter of the
spindle
and scaling , eg for 2.19mm diameter then 27.52 Hz on f monitored sig gen
for
4 strobe "spokes" in use at x4 frequency.