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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Sat 11, 2015 4:33 am 
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Remember the high voltage for that tube goes through the socket, so I think the main concern would be that whatever you use be NON-conductive.

Of course, you don't want to fill the base with adhesive. You just want a ring around the top of the base. If the glue isn't runny, it shouldn't be hard to not get too much.

Ordinary bathtub sealer type RTV contains acetic acid that is corrosive. This is what makes it smell like vinegar. There are grades of silicone rubber that don't contain it.

Jim Mueller

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Sat 11, 2015 5:01 pm 
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Location: Weimar, Texas
Jim Mueller wrote:
Quote:
Remember the high voltage for that tube goes through the socket, so I think the main concern would be that whatever you use be NON-conductive.

Of course, you don't want to fill the base with adhesive. You just want a ring around the top of the base. If the glue isn't runny, it shouldn't be hard to not get too much.

Ordinary bathtub sealer type RTV contains acetic acid that is corrosive. This is what makes it smell like vinegar. There are grades of silicone rubber that don't contain it.

Jim Mueller



I found some "electronic rated RTV", my words not theirs, on Digikey and Newark. I have some buck regulator IC's that I want to buy so I'll probably put in an order for the silicone too. Almost $8 for 3oz but at least I can get it in small quantities. A big tube is $50+ and I'd never use it. I guess I shouldn't say never. Right now I don't have any interest in restoring many things with CRT's. I'm finding out that may not always be the case. The oscilloscope was not on my radar until recently.

What do you think about using Permatex Ultrablack Advanced Formula Gasket Maker to replace the hardened "gasket" in the rear support bracket?

http://www.permatex.com/products-2/prod ... ker-detail

I paused the teardown until I can glue the socket. I have plenty of stuff to occupy my time until parts arrived and I don't want to risk messing up the tube. I wish I had a way to test it but I don't think my Eico 666 will test CRT's and that's all I have

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Sat 11, 2015 9:41 pm 
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To heck with it... I'm committed and I don't even have to wear a straight jacket (yet)

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Sat 11, 2015 10:03 pm 
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What do you think about using Permatex Ultrablack Advanced Formula Gasket Maker to replace the hardened "gasket" in the rear support bracket?

http://www.permatex.com/products-2/prod ... ker-detail

I assume you mean the rubber that goes around the base of the CRT. The Permatex looks like it will work but it also looks rather permanent. You may have problems if you need to remove the CRT in the future for some reason. I would choose something that is non-adhesive or adhesive on one side only.

As for the glue you choose for the CRT base, if you do much tube work that involves tubes other than all glass types (miniature, Compactron, etc.), you will find plenty of them with loose bases. The same adhesive is appropriate for them.

Jim Mueller

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Sat 11, 2015 11:01 pm 
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I'm thinking the OP means to put a layer of the permatex on the CRT holder and let it dry before inserting the CRT.

To toe OP. Don't worry about any internal wires breaking off the socket. I had one of those CRTs with a loose base liek that and I handled it quite awhile before re-gluing the base and it still works.


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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Sat 11, 2015 11:08 pm 
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Jim Mueller wrote:
I assume you mean the rubber that goes around the base of the CRT. The Permatex looks like it will work but it also looks rather permanent. You may have problems if you need to remove the CRT in the future for some reason. I would choose something that is non-adhesive or adhesive on one side only.

As for the glue you choose for the CRT base, if you do much tube work that involves tubes other than all glass types (miniature, Compactron, etc.), you will find plenty of them with loose bases. The same adhesive is appropriate for them.

Jim Mueller


Yessir, that's what I meant.

Good point on the glue.

The black stuff that is on the tube now is not going to be fun to get off. it's firmly attached and very glass-like. I haven't messed with it because the base is loose. I'll try to remove it once the base is glued on.

Tube Radio wrote:
I'm thinking the OP means to put a layer of the permatex on the CRT holder and let it dry before inserting the CRT.

To the OP. Don't worry about any internal wires breaking off the socket. I had one of those CRTs with a loose base like that and I handled it quite awhile before re-gluing the base and it still works.


Correct. I also thought about putting a piece of paper on top of the Permatex, setting the neck of the tube on it to form it, and then letting it set up a little. I've also got some Scotch Removable Mounting Putty.

There's a guy on YouTube (and here), bandersontv, that has a video where he desoldered the base on a CRT and replaced it. I guess they aren't so fragile as I was thinking they were.

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Sun 12, 2015 5:59 pm 
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The chassis didn't polish up as nice as I would have liked but I didn't expect it to. It had a layer of grime on it and it felt like something "crystal like" was growing on it. Probably corrosion artifacts. I hit it with a DA sander, 2 grits, and it smoothed everything out. Then I tried Simichrome but that didn't work very well. Next I gave Flitz a try and that was better. I followed it up with Metal Armor and that got it to where it is now. Considering that it's normally out of site I think it'll do

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Sun 12, 2015 11:14 pm 
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Quote:
There's a guy on YouTube (and here), bandersontv, that has a video where he desoldered the base on a CRT and replaced it. I guess they aren't so fragile as I was thinking they were.

The wires are relatively stiff. They will take some bending and pulling but too much will break them. The break will probably happen right at the glass where it may be impossible to fix. Glue the base on as soon as you can.

Would it be possible to just leave the old rubber in place and wrap it with a layer of fresh stuff? That would save a lot of work.

Another consideration, you have to be able to rotate the CRT to get the trace straight with the front panel.

Jim Mueller

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Sun 12, 2015 11:34 pm 
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Mike6158 wrote:
The chassis didn't polish up as nice as I would have liked but I didn't expect it to. It had a layer of grime on it and it felt like something "crystal like" was growing on it. Probably corrosion artifacts. I hit it with a DA sander, 2 grits, and it smoothed everything out. Then I tried Simichrome but that didn't work very well. Next I gave Flitz a try and that was better. I followed it up with Metal Armor and that got it to where it is now. Considering that it's normally out of site I think it'll do

Image


Looks nice.

If you really want it to be more polished you might try some #000 steel wool.


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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Mon 13, 2015 12:58 am 
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Jim Mueller wrote:
The wires are relatively stiff. They will take some bending and pulling but too much will break them. The break will probably happen right at the glass where it may be impossible to fix. Glue the base on as soon as you can.

Would it be possible to just leave the old rubber in place and wrap it with a layer of fresh stuff? That would save a lot of work.

Another consideration, you have to be able to rotate the CRT to get the trace straight with the front panel.

Jim Mueller


The rubber was soft when it was originally installed. It kind of wrapped around the brackets but not so much that I couldn't get them off. It's about 1/4" thick and hard as glass.

I did not think about having to rotate the CRT. I'll have to think on that one. The way it was installed there wasn't going to be any rotation...

Tube Radio wrote:
Looks nice.

If you really want it to be more polished you might try some #000 steel wool.


I used an ultrafine 3M Scotchbrite pad on it. The chassis was pitted so I feel like it's about as good as it's going to get without a lot of polishing and metal removal.

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Mon 13, 2015 7:40 pm 
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I did not think about having to rotate the CRT. I'll have to think on that one. The way it was installed there wasn't going to be any rotation...

Sure there could be. Loosen the clamp, rotate the tube to align the trace, tighten the clamp. That's another reason to not use an adhesive.

Jim Mueller

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Mon 13, 2015 7:50 pm 
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Jim Mueller wrote:
Quote:
I did not think about having to rotate the CRT. I'll have to think on that one. The way it was installed there wasn't going to be any rotation...

Sure there could be. Loosen the clamp, rotate the tube to align the trace, tighten the clamp. That's another reason to not use an adhesive.

Jim Mueller


No sir, the black stuff is hard as a rock and molded to the bracket and tube base. it's going to be a pain in the neck to get that bracket off and remove the "rubber" from the base.

Like so:

Image

Image

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Tue 14, 2015 5:24 pm 
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I'm having a hard time finding tube sockets for the two chassis mount tubes and I'd like to replace the socket on the CRT with something a little better. Preferably at least bakelite construction on both cases. The sockets in the circuit boards are fine.

The CRT socket is 12 pin. The chassis has one 7 pin and one 9 pin. Both have 1-3/16" spacing on the mounting holes. 6X4 and 1V2 tubes. If I have to I can drill new holes obviously but I was hoping that someone made a tube socket that would drop in.

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Tue 14, 2015 6:17 pm 
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Here's the CRT socket.

http://pacifictv.ca/socket.htm#crt

The second CRT socket shown.

Same socket I used in my Heath oscope, although I didn't buy it from them.


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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Tue 14, 2015 6:24 pm 
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Location: Weimar, Texas
Tube Radio wrote:
Here's the CRT socket.

http://pacifictv.ca/socket.htm#crt

The second CRT socket shown.

Same socket I used in my Heath oscope, although I didn't buy it from them.


This one? 14 pin Diheptal (B14A) tube socket

It says it can be used for the 12 pin socket too.

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Tue 14, 2015 7:10 pm 
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You need the New production 12 pin Duodecal (B12A, B12-43) ceramic tube socket


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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Tue 14, 2015 7:22 pm 
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Tube Radio wrote:
You need the New production 12 pin Duodecal (B12A, B12-43) ceramic tube socket



Of course... I see the tube model. Their site is a PITA to deal with. No ordering from the site... I sent them an email requesting availability, etc. Considering that a Google search turned up a lot of nothing I guess I shouldn't b.. complain...

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Tue 14, 2015 8:53 pm 
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I think that socket might also be available on Ebay.


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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Tue 14, 2015 8:56 pm 
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Tube Radio wrote:
I think that socket might also be available on Ebay.


It is. From Canada or China. Shipping is prohibitive from Canada and it takes forever to get here from China. It's like the road from here to there is washed out or something...

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 Post subject: Re: Knight Wideband Oscilloscope
PostPosted: Apr Tue 14, 2015 10:15 pm 
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Location: Weimar, Texas
Tube Radio wrote:
You need the New production 12 pin Duodecal (B12A, B12-43) ceramic tube socket


Bummer...

Quote:
Sorry we just recently sold out of the B12A tube sockets and it will be several months before we receive more. I will update the web site shortly.

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