3 Jan
2017
3 Jan
'17
4:09 p.m.
On Jan 3, 2017, at 2:22 PM, Klemens Krause wrote:
On Tue, 3 Jan 2017, Cory Heisterkamp wrote:
> For kicks, I tried to use a piece of
cheap (=thin) (0.004?) notebook paper
> as a feeler gage to see if I could identify the offending heads prior to
> support removal. This was a no-go as clearance was too tight. So, is it
> true these ride 0.001? off the surface?
The (german) maintenance manual whose
scan is on our website speaks
about 12 micro.meters.
There are 64 data tracks, 4 timing tracks (including the main clock
at the rightmost position) and 3 tracks for the registers. Most problematic are the
timing tracks. If they are faulty, there is no
simple solution to change the heads, because there is no provision
to write them in the machine.
If there are only few tracks defective,
and not exchangeable, I
would try to get most of them in the lower adress-room of the
machine, and at least the last track. The first 3 tracks are
used by the "operating-system", program 10.4, and the last track
is used by the initial loader, that loads 10.4 itself.
But timing tracks S1, S2, S3 and the registers themselves must
be functional.
If this is not, a semiconductor drum-emulator ist indeed the
only solution.
If you lift all the head bars 1 or 2 mm, then the drum can
rotate even with this fake.
Klemens
Lots of great ideas guys! After work today I cleaned the 64 track heads and made temporary
0.004 spacers using paper strips and a hole punch. This puts all the head assemblies in
the clear for now so nothing can get damaged. Using Klemens suggestion of tinfoil, I made
up the perfect 0.001 feeler gauge and set the gaps for the short registers. Adjusting
these is a little tricky since you first have to break loose the head securing screw, then
adjust the height screw. However, the securing screw can take what is an acceptable gap
down to a drum contact once torqued. A little 'back and forth' while stationary
and that's resolved but perhaps there's a better way to adjust these while the
machine is running (as has been suggested while watching the waveform on a scope). I
don't think I'm that brave.
Anyhow, my next move is to spin the drum up on the machine (when it arrives) with just the
clock and short register heads and then see how much expansion we're looking at. I can
then bring in the other tracks heads assembly by assembly once I'm comfortable with
the runout and expansion. Spinning it by hand reveals quiet bearings and a nice tight
assembly.
In the interim I'll start work on the Flexowriter. Something I'm much more
comfortable with. -C
What I?m wondering is if anyone is familiar with the setup/adjustment
procedure for getting the heads set correctly. There *might* be a couple of
We
relocated some of the heads on our second LGP-30. This is not difficult. We put 3 or 4
layers of 3 micro-meter kitchen aluminium
between head and drum. If I remember right, the distance is 12 micro-
meter. Maybe, that we made a fine adjustment 3 or 4 layers with the
oscilloscope, to get the same output voltage at the head, than the
other heads. Maybe that 3 layers of 3 micro-meter Al have something
more than 9 micro-meters.
unused tracks I can relocate heads to, but my
thought is that if half a
dozen heads were already in contact, then the rest may be perilously close
as well (swelled drum?). My odds of setting 71 heads perfectly on a 50 year
old worn drum is?well?not great.
If I counted right on every head bar are 3 unused positions as spare
tracks.