White's Coinmaster 2 TR D, service info needed

[AF7U]

Hi everyone, I’m glad I found this forum, I saw it mentioned in another forum I believe. This is my first post so I'll include a bit of Bio. My wife and I enjoy detecting in our spare time and have since my first White’s Goldmaster – Forty Niner (49 TR). Later I picked up a 6000/Di, then a Classic-I. I’m due for a new model but this Coinmaster caught my eye, its an older model but I just can’t leave these things alone. It is a White’s ‘Coinmaster 2 TR D’, from an estate sale. This is the first time I’ve seen a Whites detector DOA. I have many years experience working in electronics, component level, with a fully equipped service bench, but zero time working on a metal detector. I’m sure this is just a controlled oscillator of some sort.

I don’t like to just jump in and post so I’ve done a lot of searching in this forum but can’t seem to see any resources for this model, either that or I need to learn more how the forum works. The only thing which works on this guy is the test mode which shows battery condition, so the meter works <Grin>. I’ve tested the speaker and cleaned the controls. It’s all discrete components with only one IC, a MC3360P, in the audio out circuit. I would REALLY like to see a diagram if anyone (hopefully) has reversed this. I have photos of the PCB and case if it would help with ID. I’m assuming the TR means ‘Transmit/Receive’ and the D means ‘Discriminate’ but that’s just a guess.

Actually any experiences with or thoughts on this would be much appreciated~!~
~Michael – AF7U

[Qiaozhi]

I don't have the schematic for that model in my archive. All my Coinmaster schematics seem to have different ICs, or are completely discrete.
Unless someone else can post the correct schematic, you'll have to reverse-engineer it from the PCB.

If the supply voltages are ok, the next thing to do is check that the TX oscillator is running.

Can you post some photos of the PCB (both sides)?

[AF7U]

Thanks for your thoughts, so far I am at the cleaning stage, I thought I would wait and see if I heard from anyone on the forum before I dive into it.
Let me know how this uploads... This is the component side and the mask side of the PCB.
Let me know your thoughts and I'll rig it up with a power supply and see what's going on.
Regards,
~M

[FatBob]

Here's a Coinmaster 5 it's the only one I have that's all transistors.

[AF7U]

Many thanks for the diagram, it gives me some idea about how things work... I do have a question... are the loops similar to each other? Would the 5 be similar to the 2 and so on? I see a 'Loop Calibration' variable resistor in what appears to be internal to the loop. Are these really inside the loop? I wonder how they are calibrated... My loops appear to be sealed.
~M

[AF7U]

Hi again, I always like to follow up and post to what ever forum I'm dealing with what I found after putting something on the bench. After some quick checks the problem turned out to be an open capacitor in the output line of the audio amp (MC3360P) preventing anything to reach the speaker. Apparently I hadn't had the controls in a position which wouldn't show any indication on the meter so the unit appeared to me to be DOA. I didn't need to go very far into the unit but a cursory observation showed an appx 67khz pulse spaced about 3.2m/s apart. I'm clueless as to what the signal was for or how it was applied, just thought I'd toss it out for what it's worth. Whenever I got the scope probe 'close' to to the PCB, that signal appeared.

Now I need to figure out how to use it... So far all controls work, the 'Tuner' and the 'Discriminator' controls appear to be 10 turn pots, this was a surprise to me as I don't recall any 10 turn pots on my 6000/Di but... memory fades. It senses metal objects and they show up when when 'Passed' (as in motion) under the loop. I guess I'll read the operations manual... as if any 'real detector men' needed to do that. <Grin>

Thanks Qai, and Bob for your thoughts.
~Michael