Author Topic: Chrystal Tester Build  (Read 2297 times)

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Offline k7rmj

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Chrystal Tester Build
« on: December 13, 2016, 06:14:39 PM »
Buddy inspired me with his posting of the Chrystal Tester that Alan posted. So, I dove into it head first. Home brew equipment is not real easy. I think the hardest part is laying out the parts on the circuit board. I used an old board from years ago when I was first learning to etch my own boards. I don't recommend etching your own boards unless it is for a really special and easy project that you will need to duplicate many times over.

I used what some call the "Manhattan style" board construction. In one of the photos you will see the little island circles. They are cut out of scrap, single sided, circuit board material. You just figure out where you want them and glue them to a blank or like I used, the bare side of an old left over board. You can see them in the photos. I used very slow drying super-glue to glue them in place.

Figuring out where to place the islands is the hardest part. One tip to making it a little easier is to basically lay out the parts just like they are on the schematic diagram. Wherever you have multiple parts to attach at a common point is a good place to put an island. Be careful though, you can get an island with too many connections on it and that makes it difficult to solder them all in place without messing up the other connections on the same island.

Before you start gluing the islands on the board you should lightly sand the side of the board you are gluing them to. Just rough it up a little. This gives the glue a good surface to stick to.

You don't have to use the perfect round islands like I did. I just happened to have a bunch of them in my junque box that I picked up at a ham-fest some time ago. After you glue all the islands in place it helps to tin all the islands before you start soldering parts to them.

I mounted most of the resistors vertically so they would take up less space. The capacitors I used are all from the junque box and that is why the .02 caps were disc ceramic and the 470 pf are tantalum caps. They are all the right value but just different in size. I wasn't too worried about using NPO caps for this oscillator circuit because it is for testing crystals which are inherently stable.

At first I was going to install the board in an Altoids tin. But, even though it would fit okay, it was just too small to fit all the connectors and such that I want mounted on a front or back panel. So I am using a small clam-shell case. Another item from my junque box. The difference between Junque and Junk is that the items in the junque box are much more fancy. LOL.

Well, there you have it. I am really pleased with this little circuit and test box. It works on the bench. Now all I have to do is get out the drills and make holes for the power, and output connectors and the crystal socket. I'm not real happy with the connectors I have for the crystal socket. They are the small, probe type connectors. I think something with a little better holding power would be much better.

Let me know if you have any questions, suggestions or corrections.

73 Frank   de K7RMJ

Offline RJ

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Re: Chrystal Tester Build
« Reply #1 on: December 13, 2016, 06:26:08 PM »
Looks really good! Thanks for sharing this with us.

Offline k7rmj

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Re: Chrystal Tester Build
« Reply #2 on: December 13, 2016, 10:19:30 PM »
Thanks for the kind words RJ. It was a fun build although it sure took me a lot longer than I thought it should. I guess my age is catching up with me LOL. Any suggestions about what to use as a crystal socket? I'm tempted to just install a couple of alligator clips on the front panel but that would not be real elegant LOL.

73 Frank   de K7RMJ

Offline The Radio Shop

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Re: Chrystal Tester Build
« Reply #3 on: December 14, 2016, 05:07:59 AM »
Very nice job Frank. Well Done.  Does not matter how it is done as long as you have fun doing it.  I like the island approach. Most of the time the islands are glued to the copper foil side so you use the ground plane of the board. Good to see how you repurposed and old board and made it work.

As far as crystal sockets look around for old cb radios for parts. Also computer board headers make for nice sockets to set them in.
Buddy kc4umo

Offline k7rmj

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Re: Chrystal Tester Build
« Reply #4 on: December 14, 2016, 11:37:48 AM »
Hi Buddy and thanks for the kind words and good tips.

I was originally going to use the foil side of that board but it wasn't flat enough due to the etched surface and the little islands did not stick very well. So I used the other side of the board to glue the islands to. I got a much better contact for the glue to stick to the board that way.

Yes, old CB radios or computer headers would be a great source for the crystal sockets. Unfortunately when I moved down here to Arkansas I lost a lot of the small parts during the move that included anything useful for the sockets. The good news is that it gives me a good reason to start collecting new parts LOL. I think for now I'll solder a pair of alligator clips top a piece of circuit board and use the alligator clips instead of a socket. That should work for immediate needs until I get the collection or parts built back up.

I still need to solder the DC and the output connections from the board to the panel mounted jacks inside the case and it will be ready for use.

73 and thanks again
Frank  de K7RMJ

Offline k7rmj

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Re: Chrystal Tester Build
« Reply #5 on: December 30, 2016, 09:19:41 PM »
Here are some pics of the finished tester
Here you can see the inside of the box with the BNC connector and the RCA connectors. They are in parallel for the output.


Next is the inside from the other end of the box. You can see the 12V DC input and the "crystal socket".


I used an 8-pin IC socket for the crystal socket and mounted it on the front of the tester box. I used some small 6-32 nuts as stand-off spacers to keep it from shorting to the case. There is lots of room on that circuit board to add an amplifier and buffer in case it is needed in the future.

Here is the box all buttoned up and ready to rock. Both front view,


and back view


It's a neat little test device. To use it I just connect the 12 volts, and plug in a crystal to the IC socket then connect my old Heathkit frequency counter IM-2410 to the BNC connector.

Now I am ready for step #2 of designing crystal IF filters.

73 DE K7RMJ  Frank

PS: I hope you all have a safe and Happy New Year