Hi Rob,

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Many thanks for your further reply and, yes, what you used are what we call circlip pliers but there's no way the pliers I've got?here?would be strong enough?to use with these fittings.

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I still don't know if our fittings are identical, they might differ perhaps in just the detail, or whether Tektronix may have used serrated spring washers of varying strengths over the years but there's no taper on the latch plate on these and there's no way the latch plate?would line up with the slot in the pin without compressing the spring washer 116, which is under the countersunk head of the pin 115, and that was my whole problem.

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It was easy enough to get the various items into position?but?significant pressure was needed simultaneously on the countersunk head of 115 and the latching plate 118 before the plate would even begin to line up with the slot.

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My eventual solution was to use a pair of wire strippers, the old fashioned sort that have two overlapping sections with V grooves cut into them and at right angles to the main arms,?in this instance a pair intended for fairly heavy duty, with some plastic cup washers, the type used under rack fixings, to protect the?fittings either side of the cover, plus?a couple of plain washers to delay the mangling of the cup washers.

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This arrangement allowed me to apply pressure both to the countersunk head of 115 and also to the plate 118, due to the V groove which straddled the inner end of 115, in order to compress the cupped spring washer 116.

However,?although the spring washer compressed ok to start with there came a point where it seemed to bottom out but with the latching plate and slot still not quite lined up, if I hadn't removed these fittings myself I would have had very serious doubts at this stage as to whether or not they were what was previously fitted!

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Perseverance and?curses,?plus a?few scraped and bloodstained fingers:-), finally saw each plate in turn sufficiently engaged that it could be driven home with the assistance of a small hammer, but it certainly wasn't a case of just "sliding everything together".

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Oh well, rested and spry I were, and the new attempts did pay off, but it sure ain't something I'd want to try too often:-)

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Regards, and thanks again,

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Nigel

GM8PZR

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Howdy back Nigel,

<<<“but I suspect the 7000 series fittings are different”>>>

Quite the contrary it appears that they are identical. The trick is not compression of the 115 and 116 but rather the taper and getting 118 to slide into/underneath ?the ?tabs on 115. I use a small nut I taped to prevent scratching in case I slip. I place it on the bench aligned on 115 (just so that it is well seated against 116 and the case. with the inside of the case facing up. ?I then use the snap ring pliers to get 118 sliding into position. The fit is quite tight so trying to get it to slid on with just a screwdriver (or other implement) is difficult at best. The pliers at the following link are the kind I use/have. I modified them by grinding (with a Dremmle and file) ?one of the pins (more or less flat) flat so that it holds on 118 better sliding it onto/under 115. With the pliers as wide open as they are at first there is a slight alignment issue.

Anyway it worked “ok” even without grinding the pliers pin on the first few. Once you do one or two it will be obvious as to the modification.

I, as you; have become convinced that Tektronic's had some kind of a “jig” for doing these. ?However my conclusion was that it was likely a set of pliers of some sort that held onto the tabs of 115 making/trivial it easy to slide 118 into place.

Finally it does make a difference on what part of 117 you are on. Basically you want to slide everything together as if 118 is in the locked position.

Again, hopefully helpful and that you are reading this well rested and spry for the new attempts.

Rob

From: TekScopes@... [mailto:TekScopes@...] On Behalf Of poldhu1901@...
Sent: Tuesday, February 26, 2013 7:03 PM
To: TekScopes@...
Subject: Re: [TekScopes] 2901 Time Mark Generator Case Fixings

?

Hi Bob

Many thanks for your reply, the pliers you describe are what we call circlip pliers in the UK but I suspect the 7000 series fittings are different as those pliers wouldn't work for what I'm trying to do.

I've created an album in the group photos area called "2901 Time mark Generator" and have uploaded a drawing?to that showing the 2901 covers and fittings.

On this version of the drawing, item 115 is the countersunk securing pin, item 116 is the dished serrated spring washer, item 117 is the plastic index plate, and item 118 is the locking plate that I need to latch into a groove?at the end of the pin.

My problem is the amount of force that's required to compress item 116, I've tried supporting the head of the pin and pressing?down on the locking plate with a nutdriver that fits over the inside end of the pin?but it just won't press down far enough to allow the locking plate to slide into its groove and I'm concerned that the amount of force I'm having to apply is going to damage the cover around the fitting, especially if I slip.

Next up I'm planning to try?a couple of nutdriver heads from a socket set, one pressing on the outside of the countersunk pin and the other over the inside of the pin pressing against the locking plate as before, but this time I'll try compressing them either in a vice or using a G-clamp, which hopefully will allow better control and reduce?the risk of applying pressure to the cover.

It's just getting really silly, I keep thinking I'm missing something but what I've got exactly matches the drawing and there must have been an assembly tool for this, there's no way these latches could have been assembled in a production environment without one.

Regards

Nigel

GM8PZR

In a message dated 26/02/2013 18:00:37 GMT Standard Time, rgwood@... writes:

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I am on the road and cannot provide pictures until the weekend. The case rings/locks on 7000 series boxes sounds very similar to what you describe. ??

In that case, I modified a standard set of “snap ring” or “C-ring” pliers *at least that what I learned to call them *. They are pliers that in one setting the jaws compress the c-ring to place it internal to a shaft. The other position they expand to open the ring on the outside of a shaft.

In any event they work good to push the tab under the slot with very little if any downward force. I’ll send pictures this weekend if needed, Hopefully the description gets you started.

Hopefully helpful

Thanks as always for the bandwidth.

Rob ?

From: TekScopes@... [mailto:TekScopes@...] On Behalf Of poldhu1901@...
Sent: Tuesday, February 26, 2013 5:37 AM
To: TekScopes@...
Subject: [TekScopes] 2901 Time Mark Generator Case Fixings

?

I'm sure this is?could turn out to be a very silly question, BUT.......

Some time ago?I bought a 2901 that was?quite grubby and?removed the top and bottom cover "twist to lock" fixings in order to clean?beneath them.

So far so good, and all cleaned up nicely, but I've yet to find a way of getting them back again that isn't likely to cause damage to the covers!

The fitting method is simple enough in principle, the locking "lever" drops over a slotted shaped end to the locking "screw" and then slides into place to hold the whole thing together against the tension of?a dished serrated?compression washer?that sits under the countersunk "s crew head", but there's so little give in those compression washers that any attempts so far have risked putting sufficient?pressure on the quite thin aluminium covers to damage them.

This is a similar sort of arrangement to the cover fixings on the old 500 series scopes etc but I recall those as being bigger and never causing this sort of aggravation. I'm sure there must have been other small TEK cases with these fasteners, and there has?to be a quick and safe way of fitting them, but I'm wondering now if there was some kind of shaped tool that compressed the fitting from either side without putting pressure on the surrounding metalwork.

Any thoughts would be much appreciated.

As an aside, for anyone who might be interested, I found some nice internal photos of the 2901 here....

Regar ds

Nigel

GM8PZR