500-series knobs are plastic over a metal insert.
Dave Wise
________________________________
From:
[email protected] <
[email protected]> on behalf of stevenhorii <sonodocsch@...>
Sent: Thursday, February 15, 2024 8:02 AM
To:
[email protected] <
[email protected]>
Subject: Re: [TekScopes] Tek 576 Curve Tracer repair
Have you worked on any high-rel or military equipment with knobs? They
usually used knobs that may be plastic (sometimes bakelite) but the knob is
molded over a brass or aluminum insert. The set screw hole is usually
threaded through both the plastic and metal insert. The metal insert takes
the stress of the tightening of the set screw. Some have two set screws.
The shafts that they mount on often also have a flat milled on them. Even
if the set screw is slightly loose, it will still allow the knob to turn
the shaft. I have seen these knobs broken, but it¡¯s usually from impact to
the knob, not stress failure of the plastic part.
These knobs are more expensive than the all plastic ones though.
I have some recollection of this type of knob on some Tek instruments. Did
the 500-series scopes use them? I don¡¯t recall ever having a 500-series
scope with broken knobs. Missing ones, yes (my 500-series scopes were all
bought from surplus stores or the old US DoD surplus sealed bid sales - I
miss those).
Steve H.
On Thu, Feb 15, 2024 at 07:02 Jean-Paul <jonpaul@...> wrote:
Bo brave on progress.
All the decades old knobs suffer as the plastic is stressed by the design
and ages to crack.
Even if set screws are tightened carefully the knobs tend to split at the
hole of the setscrew.
No way to repair, only solution is find a like new exact knob replacement.
Thus I operate ANY old TEK equip with detent switch rotary and high torque
VERY carefully and slowly.
Same for old HP like HP8640B RF gen
Jon
