Turbocharged Rimatron 7MX

[Qiaozhi]

I think that you should proved the different link around pins: 3, 13 and 9 of circuit LM13700.

Hi Luc,

I do not understand your reply above. The wiring for the LM13700N is correct. This arrangement allows the detector to operate with a single 9V PP3 battery, without the need for a circuit to generate a negative supply voltage. It's not ideal, but seems to work quite well. The original Rimatron circuit has poor depth capability when compared to the Bandido for example, but the turbocharged version has improved performance that is much closer.

The Rimatron was only back-engineered out of curiosity, and I never really expected anyone to build a clone. However, if you come across one on eBay, then it may be worth doing the modifications. My purpose for posting the back-engineered details was purely for learning purposes.

I guess you're saying you didn't get the copy to work.

[Legaucho]

Turbocharged Rimatron 7MX

Hi Qiaozhi,

I came back from my professional displacement for some days. I acquired an inductancemeter which is very useful to determine the coils of the detector which will be to construct.
I decided to stop the tests of Rimatron, I will try to start one of detector which are nowadays under discussion on the forum. In fact I think that the time crossed to perfect Rimatron is not worth trouble of in its weak characteristics of detection compared with other detectors

I think that you should proved the different link around pins: 3, 13 and 9 of circuit LM13700.
At the next time and Best regards. Luc

[Legaucho]

Turbocharged Rimatron 7MX

Hi Luc,

You are probably correct about C21. Looks like this needs to be connected to SCR, but connecting to GND shouldn't make a big difference. The RX and TX coils should both be 29 ohms. Note that the TX coil is center-tapped, so the two halves are each 14.5 ohms. The inductance is the important value, not the resistance, but you will need an inductance meter to test this. If you do not have an oscilloscope then you have a big problem. You were lucky with the Bandido and the Hammerhead, but this is unusual. Many others here end up using a big hammer and starting again.
If all else fails, then you can send me the PCB and I'll get it working free of charge. We are both in Europe, so the postage cost will be small.

Qiaozhi

Hi Qiaozhi

Thank you for your proposition and information, I still will try to control the circuit and to realize the DD head of detection and to get an inductance meter. I must stop the tests in the next days because I must leave for a professional trip to South Korea. I have note your proposal for controlling my circuit, I keep your proposal but before coming to this possibility I would realize a second PCB because the first starts to suffer from the modifications and many weldings. Thank you again, I will keep you informed of the possible projections of my tests. With the best Luc

[Qiaozhi]

Hi Qiaozhi,
The PCB is finished, the components were assembled, and a first test was made but without result. I do not have an oscilloscope. I already built a TESORO Bandido uII max and also Hammerhead and these two circuits function perfectly.
I waits to receive the audio cable screened ( cable between coil and box ) to finish the head of detection. Is the resistance of each reel of 25 or 29 Ohms? Because I initially tested with a winding of 29 Ohms but I did not have a result. I reverified the circuit, the weldings as well as the connections as well as the values of the components, but it seems that something does not go. I saw that the C21 capacitor was to be connected to the SCR and not to the GND.
Can you take other photographs of the original on other angles of view. If you have some ideas, don't hesitate.
My best regards.Luc

Hi Luc,

You are probably correct about C21. Looks like this needs to be connected to SCR, but connecting to GND shouldn't make a big difference. The RX and TX coils should both be 29 ohms. Note that the TX coil is center-tapped, so the two halves are each 14.5 ohms. The inductance is the important value, not the resistance, but you will need an inductance meter to test this. If you do not have an oscilloscope then you have a big problem. You were lucky with the Bandido and the Hammerhead, but this is unusual. Many others here end up using a big hammer and starting again.
If all else fails, then you can send me the PCB and I'll get it working free of charge. We are both in Europe, so the postage cost will be small.

Qiaozhi

[Legaucho]

Turbocharged Rimatron 7MX

Hi Legaucho,

How is your project going?
Have you build the coil yet?

Hi Qiaozhi,
The PCB is finished, the components were assembled, and a first test was made but without result. I do not have an oscilloscope. I already built a TESORO Bandido uII max and also Hammerhead and these two circuits function perfectly.
I waits to receive the audio cable screened ( cable between coil and box ) to finish the head of detection. Is the resistance of each reel of 25 or 29 Ohms? Because I initially tested with a winding of 29 Ohms but I did not have a result. I reverified the circuit, the weldings as well as the connections as well as the values of the components, but it seems that something does not go. I saw that the C21 capacitor was to be connected to the SCR and not to the GND.
Can you take other photographs of the original on other angles of view. If you have some ideas, don't hesitate.
My best regards.Luc

[Qiaozhi]

All seems working, the next step is the coil.

Hi Legaucho,

How is your project going?
Have you build the coil yet?

[Qiaozhi]

102nf capacitor ????? is there such a thing

Oh yeh! Forgot to mention that...
C14 (102nF) and C27 (103nF) should both be 100nF.

This back-engineering lark is a real bugger!
Thanks for reminding me.

[Delbert grady]

funny

102nf capacitor ????? is there such a thing

[Qiaozhi]

I made a typing error in my last reply.
On your PCB, R2 is connected between U2C pin9 and GND, but it should be connected between U2A pin 2 and GND. That is the only mistake I could see.

I must get rid of this dyslexic keyboard.
This should have been: "but it should be connected between U2A pin 3 and GND".
U2A pin2 is NC (not connected).

Hope you haven't made any changes yet.

[Qiaozhi]

Hi Qiaozhi,
Can you specify what you want to say about R2. its position on Pine 3 is it that really raised on the original card.
Thanks also for the testing informations.
Luc

I made a typing error in my last reply.
On your PCB, R2 is connected between U2C pin9 and GND, but it should be connected between U2A pin 2 and GND. That is the only mistake I could see.

[Legaucho]

Hi Luc,

I've looked at the PCB layout fairly thoroughly.
The only problem I can spot is that R2 is connected to pin2 instead of pin 3 of U2A. I think you may have commented on this earlier, but the original schematic is correct. It was a little difficult to trace out this design from the original PCB, as some of the tracks were obscured by the components. Many parts of the circuit had to rechecked using a continuity tester to confirm the correct wiring.

Good job!

To help with your testing:
The coil gave a residual reading of about 100mV pp. You should be able to improve on this figure by careful balancing, and therefore get better discrimination than the original.
TX amplitude was about 12V pp.
V+ was 5.16V, and GND sits 2.6V above SCR.
TX frequency was 3.48KHz.

Hi Qiaozhi,
Can you specify what you want to say about R2. its position on Pine 3 is it that really raised on the original card.
Thanks also for the testing informations.
Luc

[Qiaozhi]

Hi Luc,

I've looked at the PCB layout fairly thoroughly.
The only problem I can spot is that R2 is connected to pin2 instead of pin 3 of U2A. I think you may have commented on this earlier, but the original schematic is correct. It was a little difficult to trace out this design from the original PCB, as some of the tracks were obscured by the components. Many parts of the circuit had to rechecked using a continuity tester to confirm the correct wiring.

Good job!

To help with your testing:
The coil gave a residual reading of about 100mV pp. You should be able to improve on this figure by careful balancing, and therefore get better discrimination than the original.
TX amplitude was about 12V pp.
V+ was 5.16V, and GND sits 2.6V above SCR.
TX frequency was 3.48KHz.

[Legaucho]

Turbocharged Rimatron 7MX

Hi Luc,

Forget my last request. I've downloaded the free viewer. Although it's looking for a bitmap file called "plan fond", it still loads ok.
I'll take a look and get back to you.

In case, please find this file.gif
Best regards
Luc

[Legaucho]

Turbocharged Rimatron 7MX

Hi Luc,

Forget my last request. I've downloaded the free viewer. Although it's looking for a bitmap file called "plan fond", it still loads ok.
I'll take a look and get back to you.

In case, please find the .jpg file of Rimatron PCB
Luc

[Qiaozhi]

Hi Luc,

Forget my last request. I've downloaded the free viewer. Although it's looking for a bitmap file called "plan fond", it still loads ok.
I'll take a look and get back to you.