[Solved] Screw will not come out of Tektronix 2230 case

[BlownUpCapacitor]

I have stumbled into a very bad problem.

I was trying to disassemble my Tek 2230 to replace the RIFA caps inside, however, as I was doing so, the screw underneath the case kept on spinning with no end.

This is very problematic because without this screw removed, I can't service the scope.

What I think happened is the stand-off that this screw is screwed to is screwing itself out of the sheet metal. So the stand-off is spinning WITH the Torx screw, making it near impossible to unscrew the Torx screw from the stand-off.

I don't want to keep using a scope that could die any moment I turn it on.

[mc172]

Grind the head off with a Dremel (or angle grinder).

[BlownUpCapacitor]

I don't have either of those. Do you think a drill with a TCT bit would work?

Edit: The screw would spin too though...

[bdunham7]

That sounds like fun.  Below that screw there is a hexagonal standoff going to a PCB, then on the other side of that PCB there is another hexagonal standoff going to yet another PCB, then a nut.  At least that's what I see on similar models.  You can try putting a 1/8" or so flat-blade screwdriver into that hole and prying either up (not too hard) as you try to turn the screw or prying sideways on the flat side of the hexagonal standoff to keep in from spinning as you turn the Torx driver.

If all that fails, grinding it off is another option but you'd need to use masking tape and plastic to totally seal the scope up--including the exposed part of that little hole--to keep filings out of your scope.  Metal dust and high voltage are an exciting but unprofitable combination.

A third option would be to see if it tightens back up and then overtorque it until it snaps.  That seems risky to me because those standoffs go into vital PCBs.

[BlownUpCapacitor]

I tried number 1 and that only bent the case. A closer look at the construction reveals that a lot of the screw thread is exposed meaning I'd have to go deeper to engage the hex shape.

Number 3 I already tried. Maybe the standoff snapped off?

Now I'm trying number 2, grinding it off... with a file because I don't have any other tools to do so. I can proudly say that I've ground off about 1mm of metal after nearly an hour.

[bdunham7]

Now I'm trying number 2, grinding it off... with a file because I don't have any other tools to do so. I can proudly say that I've ground off about 1mm of metal after nearly an hour.

Great excuse to go to Harbor Freight and get a cheap Dremel tool replica.  I'm not sure exactly how much faster it would be though.

[electronic_guy]

Try adding a little bit of WD-40 to it. You need to take care not to add too much in case it seeps into the main board. Do it very carefully. I once tried to repair a Tektronix 2230 and opening that little bugger wouldn't have been possible without the magical WD-40.

[themadhippy]

with a file because I don't have any other tools to do so.

no pliers and electric drill?grip the screw head with the pliers and drill the head  out

[jpanhalt]

Be sure to put tape on the case to protect from the inevitable scrape you will make with the file or grinder.  Anything will help.  Duct tape or vinyl electrical may be better because of their thickness.

With that type of head, grabbing it and using a drill will probably be easier.  I use a small pair of vise-grips.  With that screw, a 1/8" drill will probably work.   Once the serrations for the driver are gone, it will be easy to increase the size, if needed.

[fmashockie]

That screw connects to a little hex stand off on the underside of the mainboard.  But the hex stand off then connects to a shielding plate that is on top of the mainboard (between the A2 attenuator board and A4 timing board. see pics attached.  Sorry I can send you better pics tomorrow in the morning if you think that would help).  That hex standoff is attached to that shielding plate via a hex locking nut.  That nut is probably loose.  So trying to overtighten it is not going to work. 

That screw is not very long.  I'm not sure how far you can pull it out with pliers in its current state, but if you could get it out at least 1/4" (5-6mm), I would do what someone else suggested and cut the head of the screw off with a dremel tool while pulling it up with pliers to hold it in place. 

A dremel tool is a good investment if you are in repair business (like myself), if you like to restore as a hobbyist, or if you own any kind of old equipment.  They are the easiet way to remove a stripped or stubborn screw.  And they aren't that expensive (relatively) and can be purchased from a variety of different places. 

[wasedadoc]

Should the case lift off straight if that screw is removed?  If yes, have you tried pulling the case away from the body while unscrewing? 

[Jwillis]

Wedge a thin screw driver under the head and keep upward pressure as you turn the screw slowly. This sometimes works if the threads have become malformed or a nut is spinning on the end. By keeping upward pressure it might create enough friction on the offending nut to allow unscrewing.

I've used an item like this Pry Barfor similar problems. Just a little pressure is all that is needed usually.

[BlownUpCapacitor]

Thank you everyone for your help!

Yesterday I managed to file off the head of the screw and was able to remove the case.

What appeared to have happened was that the hex nut that was connected to the standoff unscrewed itself, making the whole thing loose.

In the first image, you can see the thread of the standoff poking through the PCB.

That screw connects to a little hex stand off on the underside of the mainboard.  But the hex stand off then connects to a shielding plate that is on top of the mainboard (between the A2 attenuator board and A4 timing board. see pics attached.  Sorry I can send you better pics tomorrow in the morning if you think that would help).  That hex standoff is attached to that shielding plate via a hex locking nut.  That nut is probably loose.  So trying to overtighten it is not going to work. 

That screw is not very long.  I'm not sure how far you can pull it out with pliers in its current state, but if you could get it out at least 1/4" (5-6mm), I would do what someone else suggested and cut the head of the screw off with a dremel tool while pulling it up with pliers to hold it in place. 

Looks like my scope is a little different. Mine's of the later version with a high serial number. I think it was the last serial version Tek made of the 2230. My scope's serial number is B028699. This one has a longer screw thread for that.

I could immediately tell the difference as older similar models such as the 2235 didn't have one this long.

Edit: Can someone maybe tell me the thread pitch and size of this screw? I assume it's in the imperial measurements because it's American.

[fmashockie]

Awesome glad you got it off! I suppose you right then: my 2230 S/N is B024587.

I honestly don't know if that screw was even in place on mine when I bought it.  The previous owner who tried to repair mine left more screws missing than intact!    Whoever they were really did a number on it!

[jpanhalt]

It is probably a 6-32 or 8-32.  Without a size reference it is hard to tell as the pitches are the same.    My guess is 6-32 from the picture of the  PCB..  I believe Tek used B serial numbers for stuff made in Beaverton, OR.

[Chris56000]

Hi!

. . .Tektronix usually quote the sizes of screws in the Mechanical Parts List, including the length and thread size – their descriptions are usually a bit cryptic but you can usually work out what it days if you think about it for a few minutes !

Chris Williams

[fmashockie]

. . .Tektronix usually quote the sizes of screws in the Mechanical Parts List, including the length and thread size – their descriptions are usually a bit cryptic but you can usually work out what it days if you think about it for a few minutes !

Very good tip here by Chris.  I just checked the manual and almost all the little screws are #4-40.  I can't find that specific screw though in the exploded diagrams.  The hex stand-off and hex nut are listed (13 and 14 on pg 10-10).  But I would assume it is a #4-40.