Advanced CZ20 Surgery and Stuff

[gleaner1]

My CZ20 sens pot crapped out. Thanks to the folks at Fisher I have a new one in the mail cheap. Warning: Viewer discretion advised. One Valium, five wires to solder, three hours labor, and I'm good to go.

[gleaner1]

More to go...

[gleaner1]

Torn down.

[gleaner1]

The offending component. The steel shaft had a defective staking to hold it firmly into the plastic piece, it all came loose and so did I. Theoretically, I could repair this but the new switch is very reasonably priced and I will have it soldered in and going soon. My hope is to pull another silver before New Year's Day.

[gleaner1]

Final pics of the carnage. Okay, questions anyone?

[seeker41]

very, very cool!!!!!!!!!! thank you for taking the time.

[Prairie Prowler]

Thanks for posting the details ..I think my CZ 20 has a damaged coil wire at the box entry fitting .I'll need to do a repair ..H-Huntin..

[gleaner1]

When I get the new sens switch in the mail, I will post some more pics concentrating on the coil wire replacement procedure.

[Lowbatts]

Thanks Gleaner, haven't worked on mine yet. Since it still has that screw bouncing around inside thanks to the service center at FT I may take the time over the cold season to fix that now seeing how you've done it.

Since it still has the same housing I would assume the front panel upgrade they did has not changed the assembly from it's original CZ-20 configuration significantly.

[gleaner1]

Thanks Gleaner, haven't worked on mine yet. Since it still has that screw bouncing around inside thanks to the service center at FT I may take the time over the cold season to fix that now seeing how you've done it.

Since it still has the same housing I would assume the front panel upgrade they did has not changed the assembly from it's original CZ-20 configuration significantly.

Lowbatts, I had to send my original cz20 back to the factory in 1994 after 6 months use for a loose screw jingling around inside. The only screws inside the unit are the four screws that engage the two short standoff bars that hold the two boards together. I recommend a tiny bit of blue loctite on these. The way the unit is held together has not changed from 20 to 21. I would seriously consider not using your machine with a loose screw, the screw could easily short circuit something and then it will be kaput.

[Willee]

So the coil and headphone cable is terminated to a plug connector ... not soldered to the board.
Good to know.
My CZ-20 coil cable developed an intermittent right at the waterproof fitting.
The way the fitting clamps down on the cable I can see why it happened ... bet it is a common problem.
Fisher would not work on it unless it was upgraded to a CZ-21.
If I had this information available a few months ago I would have fixed it myself.

Some service tech's can fix things while other can only replace with new. (Hint Hint Wink Wink)

However, I was happy with the CZ-21 upgrade and would recommend it to anyone.

Willee

[gleaner1]

Hey Willee, the coil cable is soldered to the unit on the faceplate board, the battery and headphones connect with little plugs. I will show more pics of this sometime very soon, I just have to get going on it.

[gleaner1]

These are pics showing close-ups of the coil wire and other things. You have to fully tear down and be a good solderer to replace/repair the coil wires.

[gleaner1]

Some final notes:
1. I forgot to mention, you must remove the two long standoff bars at the bottom side of the unit to dismantle the boards. These are the standoffs that have the white clamps and screws. I use a good set of vice grips and lightly clamp onto the standoff, then loosen it. Same to tighten.
2. I smear a small bead of silicone onto the bottom of the heads of the four screws that go in the battery box. These have little orange o-rings from the factory but they do not hold up to being disassembled, they tend to split and break. A good dab of silicone to cover the screw heads after tightening is good insurance.
3. A good little bead of silicone around the headphone wire, then tighten up the strain relief. This is factory procedure.
4. There is no silicone sealing the xxxheadphonexxx cable (correction, I meant the coil cable) the grommet does the work. Putting a small bead of silicone around the coil wire and grommet prior to putting on the strain relief nut is good insurance.
5. Use extreme caution at all times to not damage or contact any components on the boards. I wrap them in soft cloths while working. One slip and kaput.
6. I count 12 little yellow trim pots on the top board. That's a lot of crap to trim out.
7. The bottom board has five or six white trim pots.
8. The top board comes completely free of the unit, no wires attached.
9. The bottom board has four ground wires soldered to it from the switch board. I leave it all together to cut down on soldering, plus there is no need to separate the bottom board. I unsoldered the sens pot wires at the sens pot. It is very difficult to solder the sens pot wires directly to the switch board, not much room. I simply soldered the new switch wires to the old wires where I disconnected from the bad pot, which was much easier. Use shrink wrap everywhere.
10. The bottom board plugs into the faceplate board with a 15 or 20 pin/socket plug. Use caution when aligning all those pins with all those holes.
11. The top board connects to the bottom board with two 6-pin connectors, one at both sides. ***correction there is a third set of pins that engage the upward pins on the switch board******** see pics. Use caution when aligning.
12. Once all the pin/socket connections are started, CAREFULLY press the boards together until all the pins are firmly seated in the sockets. Take your time when pulling apart and pressing together the board pin connections.
13. tywrap the coil wire and headphone to the two short board standoffs as seen in pics to give some good mechanical pinning of the cables.
14. Take care when stuffing the grommet for the coil wire into the strain relief, its difficult and you will need soapy water. Fully seat the grommet. Do not damage the grommet. Take your time and work it in with a butter knife or screwdriver.
15. Use a bit of blue loctite on the board clamp screws. They have been known to get jingling.
16. Make sure you use insulation or shrink wrap on the two coil shield wires. You can see this in the pics, they used clear tubing.
17. Now, stuffing it all back together, this is more difficult than pulling apart. Put the desiccant pack on in original position. When stuffing the guts back into the housing, be patient, keep pushing everything in while lightly pulling the coil and headphone wires out, until the faceplate is up against the gasket. Make sure the paper clip is firmly on the shield paper. Keep your eyes on any wires that get in the area of the gasket, keep them tucked in. If the faceplate does not want to go all the way, do not force it, its the power wire getting pinched at the back end of the unit. Try to pull the power wire up and out toward the face plate and keep working, it will go together very freely if everything is in the right spot with no pinching or binding of wires. You will know when its okay, it goes all the way home very easily.
18. There is no need to remove the switch knobs to tear down, I did just to clean and inspect. Beware that sometimes the knobs will be very difficult to remove, they tend to be stuck on the switch shafts real tight. If you have to remove a knob and it wont come of, do not force it. Cut it off with a dremel and order a new one. I ream out the knob holes with emery cloth so they never get stuck.
19. The headphones can be separated with a butter knife and some patience, they snap together, but it's tricky.
20. The CZ21 upgrade is not for me. Too expensive. But that's just me.

[synthnut]

This is such and informative write up .....Thanks so much for sharing ....It sure makes this detector more impressive when you see what goes into it ......and the time it took to create it .....Nice job !!..... .....Jim

[Paul Brunner]

Just want to thank gleaner1 for taking the trouble to document this repair so well. I dropped my cz-20 about 6 mo.s ago, breaking the power switch with a direct hit. I have been reluctant to open it up blindly, and (knowing I can't afford to send it in to Fisher, yikes!) it has been sitting in the closet ever since. Gleaner1's thorough walk-through gave me enough confidence to take a look inside. I was pleasantly surprised to see that the switch shaft had caused the rear part of the switch to break free of the metal tab securing it. After re-seating the back, the switch worked fine. I am always amazed at the generosity some people show in taking time to post their experiences on-line for the benefit of strangers. Thanks again gleaner1.

[CoilFisher]

Well, I have to say, that is advanced. I am quite impressed Gleaner. Now, we know what you are doing in the basement.

One final thought we need to put to the test: Will it leak?

[gleaner1]

The leak points are the coil and headphone cable strain reliefs at the box, plus the faceplate gasket. I had mine submerged about two or three feet deep a few times with no problems. The units are notorious for a bulletproof, leakproof design. CoilFisher, I fix these things in my kitchen. You DO NOT want to know what goes on in my basement. If anyone wishes for more specifics on the application of RTV to the cables at the strain reliefs, let me know, I will do a quick graphic in MSPaint. No RTV on the faceplate gasket please.

[CoilFisher]

Ha ha ha! You got a laugh out of me gleaner.

Nice thread!!!

I wonder how much you saved doing it yourself? I heard they are expensive units to fix.

[gleaner1]

The last I knew, Fisher will not fix a cz20. But they will upgrade it for $500 or $600 dollars. Thank you very little Fisher. If anyone wants their cz20 coil replaced, I will do it for $489.72. Plus shipping. This includes the coil price. No, really, just pm me. It will take fourteen to twenty business days to get your unit back. But I guarantee my work. Call me at 1-999-TAKING ADVANTAGE OF THE FORMERLY AND/OR STILL LOYAL FISHER CUSTOMER BY SECONDARY PARTY VULTURE REPAIR CO. LLC. Hey, everyone has there price level. By the way, I love Fisher, just in case you did not know. I will post my cz20 finds soon.