29 Jul
2013
29 Jul
'13
11:36 a.m.
The original LDR seems to be unavaialble. I do
have what I believe to be
the part number for it, I can look it up if you want. I believe it was
made by a company called 'Quantarol' or something similar. No, this is
not in any HP manual that I've seen, but a very similar mechanism was
used in a thing called a Racal Thermionic Digideck P72 and I have the
component-level manual and parts lists for that. In the absense of
further information it would be reasonable to use that as a starting
point.
However, I did try looking up tyhis part number on google and various
data sheet search sites and came up with nothing.
So, since these LDRs do fail, finding suitable substitues which need only
minor modifications to the circuit would be a Good Thing. That is waht I
am asking about
How did I wrote the article..
At some moment I had 3 drives with problems, not running fast at seek and
rewind. I searched for the LDR on part number and on family,
and found out HP used
CDSe LDR's which are primarily sensitive for IR and not for visible light.
The Racal manual I mentioned describes the LDR as :
'Photocell Quantroll Q130B'
I ahve never man anged to find any data one this, if anyone knows the
specs I would be interested.
This is why the bulbs in HP 98x0 machines burns on low
light level, from an
engineering view this understandable less change for trouble with leaking
light etc..
And a much longer bulb life, of course.
[...]
So I replaced the bulb with a 3.5mm white LED and
resistor, it didn't work
As an aesthetic point, I don't like using a white LED here. White LEDs
came out about 30 years after the machine, so I would rather keep the
original bulb if at all possible.
I wonder if an IR photodiode of phototranssitor could be used with minor
modifications to the circuit?
-tony