On 2025-08-21 17:58, Abe Kornelis wrote:
All,
If it works, don't fix it.
We also had cases of "if it doesn't work don't fix it".
On our computer, the card reader and card punch both had
a peculiar fault that was present for at least two-and-a-half years,
and which had probably been present since the machine was installed
7 years before.
These devices were capable of being turned off and re-called
in quick succession. If the card reader was turned off,
it could be recalled within 20 milliseconds,
and the reader would continue without stopping.
Unfortunately, this did not happen. It could not even be
re-called after 0 milliseconds. The reader stopped
and missed a cycle, running at half speed.
Concerted efforts to fix it by studying the logic diagram
could not account for it.
In the end, it needed a "finger test".
While the reader was operated in this manner
(stopping and recalling), relays in the reader mechanism were
observed. In turn, the armature of each relay was pressed.
One was found that cured the fault.
When the relay was examined it was discovered that the relay
arm (which carried the electrical contact) had been bent.
When this was straightened, the fault was fixed.
The relay arm was not bent by accident; someone had done that
intentionally.
The fault contributed to undue wear on the clutch.
Exactly the same procedure was carried out on the card punch.
This fault also caused undue wear in the clutch mechanism, and
resulted in repeated fracture of the pin holding the clutch's
gear wheel to the rotating shaft.
