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**Pepe LeMiau** · 01-07-2011, 03:06 PM

I have reasons to believe that the detector is either Apollo 2 or Apollo 3.
I read some of the manuals available on the White's webpage and the Apollo 2/3 both fit very close to description: there's a wink light, full transistor design (not a single IC, well maybe except something that looks like optocoupler), analog meter, 10-turns tuner knob (with weird bearings inside) and an old type of coil connector with yellow dots on both the coil plug and coil socket.
However, I'm still not sure, so I need confirmation.
This detector might be easily 30 years old (or more), I'm looking for someone who has seen it and could confirm that's an Apollo.... It's hard to find any info on the net about these detectors, I couldn't even find a single picture.

**Carl-NC** · 01-08-2011, 05:33 PM

I would need to see a photo of the complete unit, but it looks like a late 60's Coinmaster 3. There should be an ID tag inside the battery door. The Apollo's I've seen are brown, and have no "White's" marking on them.

- Carl

**Pepe LeMiau** · 01-08-2011, 06:34 PM

Unfortunately I have only the front panel, the rest of the case is missing, so are the batterry packs and battery cases.
I've read the manuals for all Coinmaster "3" series on White's webpage, my detector could be Coinmaster 3 TR or Coinmaster 3 TR MM as they both have the wink light and 10-turn tuning knob.

**Pepe LeMiau** · 01-08-2011, 10:18 PM

Is the Coinmaster 3's schematic (even a basic one or similar unit) available somewhere ? I need it really badly because the unit simply doesn't work. There's only a strange 12kHz 2,6Vpp (at max volume) noise at the speaker out, other than that it's completely dead.

**Pepe LeMiau** · 01-27-2011, 06:39 PM

Hello again, I'll refresh the topic a bit.

Since I couldn't find schematic, I drew one myself. I made mistakes here and there but when I posted it on Polish forums, someone pointed me to GoldMaster 66 schematic, which is very similar to my unit, the transmitter side is almost identical, so is the receiver except that mine has 10-turn tuning knob and the audio amp is a bit different (doesn't matter):

http://www.geotech1.com/pages/metdet...ldMaster66.pdf

Theoretically it gave me enough info to rebuild the coil, but first test with prototype didn't go very well

I made a typical T/R coplanar coil and modified the design a bit to feed Q1's base, unfortunately the transmitter runs at frequency way higher than I expect it to do, around 48-50kHz, and the receiver is deaf

Does anyone know at what frequency should this device operate, or maybe what type of coil it used ? I believe that it was a 4B multicoil but that's just my guess. I'm desperately looking for any info.

**Pepe LeMiau** · 01-30-2011, 11:59 PM

I got the detector partially running. The receiver is tuned to 2.1-2.4kHz, I measured it using audio generator. It's just deaf below 2.1 and above 2.4kHz. So the transmitter obviously has to be working in that range.

The transmitter works fine, except I have serious problems getting it work at right frequency. At first it ran at 50kHz and as soon as I added any capacitor as shown on the schematic, oscillations stopped. So I took a break to refine my knowledge about Hartley's oscillator.
I made a second coil set, this time I abandoned the coplanar design and I decided to try DD coil. Without the feedback coil it's easier to guess the inductance.

I wound a 12cm transmit coil which has 4 sections at 70, 70, 30 and 40 turns, so it allowed me to test various configurations. This time finally I got it running at 2,2kHz (I got the right inductance by shaping the transmit coil), however below ~10kHz the waveform starts to deform, at 2,2kHz it looks pretty bad, far from sinus.
I ignored the waveform for now and did basic tests to check if the device works. I set up the coils to get very quiet signal (it turns out that sensitivity is higher that way) and checked various metal objects.
For a first run the test wasn't bad, it detects larger objects from decent range, however for small things, like coins and rings the detection range was extremely low.

RIght now I have two questions:

- Is the DD type coil suitable for low sensitivity detector like this one, or should I try again to make a coplanar, similar to the original one ? I might buy the original 4B multicoil from ebay sooner or later if I'll find a cheap one (and if I'll find confirmed info that this detector is compatible with 4B); but for now I'll have to build a replacement.

- Perhaps someone familiar with LC generators could explain, why the output waveform is malformed at lower frequencies ? I think that it has something to do with the ratio between Collector and Base sections of transmit coil; however I have no idea how to fix it. If required, I can capture the waveforms and post it here.

**Qiaozhi** · 01-31-2011, 09:35 AM

Are you sure the TX frequency should be as low as 2.1-2.4kHz?
The Whites Coinmaster 5000, for example, runs at 5130Hz +/- 20Hz.
Is this the schematic of your detector?

Attached Files

Whites_Coinmaster2D.gif (76.2 KB, 2753 views)

**Pepe LeMiau** · 01-31-2011, 09:53 AM

Well, I can't be sure since no one has identified the model (yet). I'm checking ebay auctions every day, hoping that I'll see a photo of identical, complete unit. So far no luck.

The schematic of my detector is very close to the GoldMaster 66 which I linked above

There's only one IC, very old 0.25Watt audio amplifier.

There are just minor changes, for example the the metal-mineral knob is missing on the schematic and the audio output stage is a bit modified. The transmitter is almost identical, except that the C5 connecting transmit and receive coils has fixed value.

Here's the only proof I have to backup my theory about ~2.2kHz freq, audio generator connected to the receiver http://www.youtube.com/watch?v=rRE8Ecwn0jI

**Qiaozhi** · 01-31-2011, 12:02 PM

Originally posted by Pepe LeMiau View Post

Here's the only proof I have to backup my theory about ~2.2kHz freq, audio generator connected to the receiver http://www.youtube.com/watch?v=rRE8Ecwn0jI

What exactly are you doing in your test?
Is the coil connected, or are you simply injecting the audio signal into the pre-amp without using the coil?

**Pepe LeMiau** · 01-31-2011, 12:27 PM

On the video, the generator output was directly connected to the coil socket, marked as "5" on schematic.
I repeated the test later using both coils, however the transmit coil was connected to the generator output instead of the detector's transmitter.
The result was more or less the same, only the audio signal was clearer.

When using the built-in transmitter, receiver is not completely deaf above 2,5kHz and below 2,1, probably just because the signal input level at the receive coil (when not balanced) is way higher than generator's output (I got it around 4,5Vpp). Still, this frequency range gives the loudest signal.

**Pepe LeMiau** · 02-01-2011, 07:55 PM

This is my best result achieved for now: http://http://www.youtube.com/watch?v=atJXFkBqI1Y excuse me the ugly "coils", they were modified a couple of times.

Detection range for coins and small items is almost non-existent.
There's no need to null the coil with the oscilloscope, because with properly nulled coil the sensitivity is even lower. With minimal signal left overall sensitivity goes higher.
During the last test I managed to tune the transmitter to around 2500Hz by adding more turns to the coil, with 122nF total capacitance parallel to the transmit coil. The coil schematic looks like this:

The collector section has 160 turns. Base section 100 turns.

I'm going to tune it again to get around 2200Hz and then I'll check again, right now I'm still outside of the receiver's maximum sensitivity.

**Pepe LeMiau** · 02-02-2011, 10:49 PM

I finally got the transmitter running at 2.18kHz by adding another 30 turns of wire.
At 2,6kHz the receiver sensitivity (point at which it started signalling anything) was 16mVpp on receive coil.
At 2,18kHz the sensitivity went up to 10mVpp, so it looks like it's around the right frequency.
However, that 10mV seems to be a lot, because if I null the coil to 2mV idle, I need like 0,5kg of iron near the coils to get the 10mV needed for the detector

So right now I have a couple of questions.
What's the RX coil voltage I could expect on properly build set of coils ? On the transmit coil I got around 7Vpp and I thnk I'll try to raise it a bit by changing R13's value.
I guess I could gain a bit by winding more turns on the RX coil (right now I got TX:RX ratio around 1:1).

Second thing. I guess right now I could calculate/estimate the inductance needed for TX coil with reasonable tolerance, it could be fine-tuned with capacitors easily.
So theoretically I could build the "final" DD coil.
However, since I got very poor results with the "trial and error" DD coil, I think it may not be a good choice for such an old detector. That's why I'm thinking again about coplanar coil or this one (how is it called?):

The problem is, that coplanar (and probably this strange coil also) both have feedback/bucking coils.
Since the bucking coil is wound in opposite direction, it affects the inductance of the transmit coil. In my first trial and error design the effect was so bad, that the generator simply didn't oscillate. So the question is: is there any (easy) way to estimate the inductance of the TX+feedback coils ? It is very important with this design, since the inductance directly affects oscillator frequency.

Also, could someone explain me why the original transmit coil had 3 sections, and receive coil two ?

BTW, on ebay someone is selling Coinmster 2TRDX which looks almost identical to my detector, only the tuning knob says Mineral - Metal while mine says Metal - Mineral.
It comes with this coil:

Does anyone know what coil type it is (hopefully the seller won't sue me for borrowing his photo) ?

**porkluvr** · 02-03-2011, 02:19 AM

<snip>

edit: My answer did not fit your question.

**Pepe LeMiau** · 02-04-2011, 12:42 PM

I'm almost sure that my detector is a Coinmaster 2TRDX. There are 3 of them on ebay at this moment and one of them looks identical. It comes with 4B multicoil. Two others have different coils: one marked "TR" and the second one "TR2D deep detection doublet" (is it a DD?). Are these 3 types of coils compatible ? I guess that the coil marked "66TR" also would work, as the board inside is almost identical with GoldMaster 66.

For now my detector seems to be working, however I'm still looking for confirmation that it should run at ~2,20kHz freq just to be sure that it's not broken.

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Looking for info about vintage White's detector (Coinmaster?)

Looking for info about vintage White's detector (Coinmaster?)

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