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Need advice on removing an SC503 broken vertical knob/shaft assembly


 

I accidentally pushed my lab chain into a rack mounted SC503, and sheared off the skirted part of the vertical knob/shaft assembly.
after much searching, I did get a replacement from a kind list member. at last, restoration is at hand!

The problem is that the plastic keyed shaft is stuck inside the attenuator rotating cam assembly, and I just can't get it out to replace it. A check
of the manual just says "pull the knob/shaft out. hah! if only I could... I can push it back a bit, but I can't pull it out. I can't see any kind of locking device to anchor the knob shaft in place, so I am baffled as to why it won't come out.

any suggestions to offer? I am SO close to restoring this beauty.
all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.


Wayne Rothermich
 

Hi Walter,
I had the same broken shaft problem with an SC504 that I recently bought on eBay. The retention mechanism for the hollow shaft is very strong indeed. After a bit of a struggle, I was able to grab one side of the broken shaft with very small long-nose pliers and pull it out. If that had not worked after several tries, my next thought was to find some way to push it out from the rear. Failing that, my recommendation would be to take the SC503 apart and disassemble the cam switch. Not fun, a couple hours of intricate work, but would certainly succeed.
Wayne Rothermich

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of walter shawlee
Sent: Wednesday, June 10, 2020 8:50 AM
To: TekScopes@groups.io
Subject: [TekScopes] Need advice on removing an SC503 broken vertical knob/shaft assembly

I accidentally pushed my lab chain into a rack mounted SC503, and sheared off the skirted part of the vertical knob/shaft assembly.
after much searching, I did get a replacement from a kind list member. at last, restoration is at hand!

The problem is that the plastic keyed shaft is stuck inside the attenuator rotating cam assembly, and I just can't get it out to replace it. A check
of the manual just says "pull the knob/shaft out. hah! if only I could... I can push it back a bit, but I can't pull it out. I can't see any kind of locking device to anchor the knob shaft in place, so I am baffled as to why it won't come out.

any suggestions to offer? I am SO close to restoring this beauty.
all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.


Wayne Rothermich
 

Hi Walter,
I had the same broken shaft problem with an SC504 that I recently bought on eBay. The retention mechanism for the hollow shaft is very strong indeed. After a bit of a struggle, I was able to grab one side of the broken shaft with very small long-nose pliers and pull it out. If that had not worked after several tries, my next thought was to find some way to push it out from the rear. Failing that, my recommendation would be to take the SC503 apart and disassemble the cam switch. Not fun, a couple hours of intricate work, but would certainly succeed.
Wayne Rothermich


John Gord
 

How about:
Drill
Tap
Insert long screw
Pull?

--John Gord

On Wed, Jun 10, 2020 at 08:50 AM, walter shawlee wrote:


I accidentally pushed my lab chain into a rack mounted SC503, and sheared off
the skirted part of the vertical knob/shaft assembly.
after much searching, I did get a replacement from a kind list member. at
last, restoration is at hand!

The problem is that the plastic keyed shaft is stuck inside the attenuator
rotating cam assembly, and I just can't get it out to replace it. A check
of the manual just says "pull the knob/shaft out. hah! if only I could... I
can push it back a bit, but I can't pull it out. I can't see any kind of
locking device to anchor the knob shaft in place, so I am baffled as to why it
won't come out.

any suggestions to offer? I am SO close to restoring this beauty.
all the best,
walter (walter2 -at- sphere.bc.ca)
sphere research corp.


Ed
 

I agree with the last post, I did this myself by using a large self tapping screw and just threaded it into the hollow shaft and pulled on the screw with pliers.

ed


 

I finally go that evil shaft out. I sprayed a bit of nu-trol down the shaft edge, to make it as slippery as possible inside the cam assembly.  I ground down a small pair of forceps to fit in the tiny gap on the side of the shaft and the hollow center, and locked on to the the shaft.  it took an incredible amount of force, but it finally popped out. I thought I had broken the shaft at first, until I say it was all out.

that screw idea sounds better to me in retrospect, but I was worried it would force the edges out, making it even harder to remove the shaft. In any case, I am just happy to be able to finish the repair.

thanks to everyone for advice,
walter

--
Walter Shawlee 2
Sphere Research Corp. 3394 Sunnyside Rd.
West Kelowna, BC, V1Z 2V4 CANADA
Phone: +1 (250-769-1834 -:- http://www.sphere.bc.ca
+We're all in one boat, no matter how it looks to you. (WS2)
+All you need is love. (John Lennon)
+But, that doesn't mean other things don't come in handy. (WS2)
+Nature is trying very hard to make us succeed, but nature does not depend on us.
We are not the only experiment. (R. Buckminster Fuller)


Ed
 

Glad you got it out. When I put the screw in , it did not go too far down so it did not affect the latching part.
I said large screw, but what I meant was a screw that was just bigger than the hole in the shaft so it would thread in and hold and therefore give me something to pull on.

ed