COMPASS COIN PRO II SCHEMATIC

[kt315]

[kt315]

[Melbeta]

Hi Melbeta
i was told that these compass pcb's are three layer type so harder to fix...the resin is a real handicap in trying to fault find...i did think about rubbing the bottom of the pcb across some abrasive paper or maybe using a file to remove resin...its strange cause the detector normally works from cold on for a couple of mins...maybe a thermal problem with the solder connections..as the circuit warms up then maybe a dry solder joint causes the fault problem.....when i was in the television repair trade we used a can of freezer to locate thermal problem so maybe useful to locate the area

DaveRave,
Yes, I know about the can of Freon, then later they stopped the cans of Freon here in America, and came out with different kinds of coolant. I did that myself. They also have a electronic unit, that can sense differences in the heat on the parts of the board. But the spray cans of coolant work better. From what you say, it sounds to me more like a part is getting hot and then it goes crazy. When the part cools down, it begins to work good again. You need to use something to find the thermal defective part. Ask the guys in the TV repair business what they are using today. If it is that they should find the thermal defective part. And you can experiment with various chemicals to dissolve the resin on the parts. It could be a dry solder part, but in order to re-solder the trace side pins, you need to remove the resin.

The problem is most likely a defective thermal part, and I would look at the electrolytic caps first. They go bad, leak and they give thermal problems. So replacing them would be my first priority.

If you are going to go the route of removing all of the parts, better read the test pins first with a oscilloscope, and take voltage readings of adjustable pots. It is better to try and find the defective dry joint and/or thermal part in my opinion.

RonC told me he found a strange inside trace, so he abandoned the reverse engineering project that KT315 posted photos from. He could have been right and it could have been a triple layer PCB. But you have the schematic and from that KT315 can come up with a new board. Removing all of the parts is only necessary if one wants to replicate the original board. With SMT parts today, one can make the PCB smaller.

You could test it with a fan blowing onto the PCB. If it works great then you know for sure there is a thermal defective part somewhere on the PCB. One could make a small tube, and blow cooler air through the tube then and find the bad thermal area.

You could get some Acetone and see if it softens or dissolves the resin.
Melbeta

[Melbeta]

DaveRave
You are in the England area, do a search for a THERMAL SENSOR or a THERMAL PROBE. If you find one, it could find the bad part.
Melbeta

[aothunterpl]

KT Your version PCB , has 3 Tone mode audio ??

[kt315]

this is not detector matter. although last time i think about so popular crowfaunding way. this board must be desoldered and info given to people.
then people will have schematic, part list, gerber files. i am not so rich man to buy detectors from USA, shipping price kills any idea.
we must go by other way.

[dbanner]

its very difficult probing on the pcb as both sides have a resin coating....the fault causes auto notch/multi tone/meter ID to fail together...but sometimes the fault clears for a couple of mins and all works correctly then the unit go's back into its fault condition...maybe a capacitor but im not sure ??? PLEASE CAN ANYONE ADVISE

I just had a look at some compass coin scanner circuitry, my goodness, some braniac designer for sure. Anyways, not sure if your detector matches the scheme that I looked at but here goes.
The tones are divided by 4024 chip, then by means of a complex series of CMOS logic, finally gated through typical 4016 switches, including the meter. That's as simple as I can describe it without putting my foot in my mouth. If you are having intermittent failure of multi-tone and meter at same time, they both have one thing in common, that is they are both switched via the same 4016 chip. Look for this chip on your pcb, there may be more than one. It could be the cause of the problem. Make sure the soldering isn't dry on it.
Beyond that, you'll have to clean up the PCB and begin some serious troubleshooting.

[Melbeta]

I recently acquired a Compass Coin Pro II metal detector, so far the meter needle moved to the right when I turned it on, beyond that, no audio or no response to target.

Anyone got a schematic so far? And any suggestions? Mine appears to be a brand new unused version, no scratches on it including the coil...
Melbeta