LGP-30 Memory Drum Update

[allison]

On 01/04/2017 09:56 PM, Jon Elson wrote:
> On 01/04/2017 05:24 PM, Cory Heisterkamp wrote:
>>
>> I'm far from an expert, but it certainly looks like an oxide coating
>> to me. I'm reminded of the folklore when IBM was developing the RAMAC
>> and finally had success with a magnetic paint mixed up outside of
>> house. In that case it was easy to apply...just spin up the disc and
>> pour!
>>
>>
>>
>> http://www.radar58.com/temp/drum.jpg
>> http://www.radar58.com/temp/drum2.jpg
> Yup, that looks pretty "oxidey" all right!
>
> Jon
>
Based on more than a few drums and disks i've seen its oxide, not plated.
I'd also say if the scratches are not deep a little polishing may be the
trick.

I'D do nothing until it can be run up (remove all dust and gunk) and
then look
at the output of the heads.  Likely you don't have to write clock tracks
if there
is mechanical (tone wheel).  If so that means the clock is created there
so its
always in sync with drum rotation.  That's one less headache.

I have a hunch that the data/instruction tracks are not pre-recorded and
can be
over wrote and replaced at will but there is where the manuals and a
thorough
understanding of the machine and its logic is needed.

IF the data tracks are created by other timing (clock and logic) then
erasing
a track is safe (check manuals) and then you can write a track with F and 2F
and see if it reads out uniformly if it does that head is good and the
media
under it is.  Step and repeat, any that fail or have to many drop outs
or other
errors need care, relocate first and try again.

This is about what old school tricks need to be found out about and
relearned.
The closest analogy is how to steam and repair a coal fired locomotive. 
There
is hand me down knowledge that will be needed and learned or even
regenerated.

A very interesting project.

Allison