Re: TDS 500 600 700 series calibration

Dan Fish
 

Roy,

Yes, I agree, this is common. You'll see it in pictures on ebay. Some have been happy with removing the gel, some not. I think it helps with light transmission and parallax. But you can remove it as long as your tube still has some life in it. But that is a problem with these scopes with the color shutters, they turn up the tube intensity to get through the shutters and the tube life is shortened.

If you try this, get the tube out. All along the front edge of the black sealant you can peel it back to see the edge of the glass and the start of the layers of the shutters behind. Don't go further than you need to. Just expose the gap between glass and shutters, avoiding the small gauge wires running around the shutters.

Once you see the gap you will see that the edge is sealed with RTV, yellowish white. That's the hard part because you have to pry with tools/blade to pick it out to expose the gel. Once most of the RTV is gone you can get the gel to separate and get the glass off. I did it with a couple feet of 18AWG insulated wire. Start at a corner in a sawing motion until you pull through. The glass should come off easily, don't force it, I broke the first one I tried.

It's a bit of a nasty clean-up to get the gel gone. I didn't try a strong solvent like acetone, although tempted. A good 99% alcohol and plastic scraper gets it. Then put the glass back on using the same gap. There will be enough nubs of RTV to set the gap. I sealed it up with a bead of black RTV.

Good luck!
Dan

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Roy Thistle
Sent: Monday, February 4, 2019 5:16 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] TDS 500 600 700 series calibration

Hi Dan:
I have a TDS540, that has not been powered up in a couple of years (maybe more!).
When I look from the side, in the right light, I can see some crazing or some wrinkling on at least the top half of the screen (looks like the surface of the plastic, in front of the crt screen, has been damaged by cleaning with a solvent; but, its not the plastic... it's below the plastic.).
Given what I am seeing, I am assuming it is the gel that has degraded?
Regards
Roy

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