Turbocharged Rimatron 7MX

[Qiaozhi]

Again me, what is the type of transistor Q1 in Turbocharged Rimatron 7MX
Merci d'avance
Luc

The markings are unclear, but any general purpose npn transistor will be ok.

Sometimes these Smart2 M6 detectors become available on eBay, but make sure you buy the correct model. It must be the motion detector version that contains the Rimatron 7MX PCB. See pictures below.
Otherwise you can build one from scratch, but you will need to construct your own coil.

[Legaucho]

NPN transistor

Thanks a lot
Luc

[Qiaozhi]

Hi Sean,

I think this may be the one ->
http://www.maplin.co.uk/module.aspxI...&doy=29m1#spec
although the dimensions (160x103x43) seem to be slightly smaller. In my case the 43mm dimension is more like 53mm. This might be a mistake on the website (and in the catalogue) but it could also be a newer replacement. Also note that the end panels are each secured by 2 screws instead of the original 4. Later this week I'll visit the shop to check for myself.

Hi Sean,

The Maplin's number is N85AL. There's a mistake in the catalogue, and the correct size is 160x103x53. It's actually made in Canada by Hammond Manufacturing -> http://www.hammondmfg.com/1455.htm
Costs £9.99 inc VAT.

[Qiaozhi]

Again me, what is the type of transistor Q1 in Turbocharged Rimatron 7MX
Merci d'avance
Luc

I took another look at this transistor today. It's an MPSA13 - darlington NPN silicon.

[Qiaozhi]

Dear QIAOZHI,
Can you tell me what is this component labelled F1 on your drawing
sorry for my english language ( I'm french )
best regards
Luc

I tried shorting out the small filter (F1) and there was no change in the operation as far as I could acertain. If you're planning to build a clone, just leave it out.

[Legaucho]

F1 on Turbocharged Rimatron 7MX

I tried shorting out the small filter (F1) and there was no change in the operation as far as I could acertain. If you're planning to build a clone, just leave it out.

I will do it, thanks for your answer.
I'm still working on the PCB in this moment.
Best regards
Luc

[Qiaozhi]

I will do it, thanks for your answer.
I'm still working on the PCB in this moment.
Best regards
Luc

One other small point. I recently did some hand calculations regarding this design, especially around the integrating and differentiating stages. As a result I changed C14 (in the feedback path of U4A) from 102nf to 22nF, which has improved the discrimination somewhat, and reduced the chatter in trashy areas.
U4A is the differentiator in the DISC channel. Normally the cutoff frequency Fc is set higher than the break frequency Fb, but for some reason it's the other way round in this design. Lowering the value of C14 gives a higher frequency cutoff of 18.5Hz (was Fb=7.2Hz and Fc=4Hz). Since Fc is now higher than Fb, the gain of this stage is also boosted as a consequence, which improves the ability to reject bad targets at greater depths. i.e. less chance of digging a big hole and finding a nail!

[Legaucho]

Turbocharged Rimatron 7MX

One other small point. I recently did some hand calculations regarding this design, especially around the integrating and differentiating stages. As a result I changed C14 (in the feedback path of U4A) from 102nf to 22nF, which has improved the discrimination somewhat, and reduced the chatter in trashy areas.
U4A is the differentiator in the DISC channel. Normally the cutoff frequency Fc is set higher than the break frequency Fb, but for some reason it's the other way round in this design. Lowering the value of C14 gives a higher frequency cutoff of 18.5Hz (was Fb=7.2Hz and Fc=4Hz). Since Fc is now higher than Fb, the gain of this stage is also boosted as a consequence, which improves the ability to reject bad targets at greater depths. i.e. less chance of digging a big hole and finding a nail!

Thanks again about your observations and modifications. When my detector was finished I will send some pictures and try results.
At the next.
Bye Luc

[Legaucho]

Turbocharged Rimatron 7MX

One other small point. I recently did some hand calculations regarding this design, especially around the integrating and differentiating stages. As a result I changed C14 (in the feedback path of U4A) from 102nf to 22nF, which has improved the discrimination somewhat, and reduced the chatter in trashy areas.
U4A is the differentiator in the DISC channel. Normally the cutoff frequency Fc is set higher than the break frequency Fb, but for some reason it's the other way round in this design. Lowering the value of C14 gives a higher frequency cutoff of 18.5Hz (was Fb=7.2Hz and Fc=4Hz). Since Fc is now higher than Fb, the gain of this stage is also boosted as a consequence, which improves the ability to reject bad targets at greater depths. i.e. less chance of digging a big hole and finding a nail!

I need teacher for that
Can you give me some information's about the way of SCR and GND ( it's two separate way or can be connected together.
Luc

[Qiaozhi]

I need teacher for that
Can you give me some information's about the way of SCR and GND ( it's two separate way or can be connected together.
Luc

SCR and GND must not be connected together. I probably should have called this net "Screen" rather than "SCR". It is connected to the screen of the coaxial cable that goes to the search head, and is also connected to the negative terminal of the battery. GND is ground (0V). If you find it easier, think of SCR as the negative supply rail.

[Legaucho]

Turbocharged Rimatron 7MX

SCR and GND must not be connected together. I probably should have called this net "Screen" rather than "SCR". It is connected to the screen of the coaxial cable that goes to the search head, and is also connected to the negative terminal of the battery. GND is ground (0V). If you find it easier, think of SCR as the negative supply rail.

It's much clear for me now, I can finish my board. Good day
Luc

[Legaucho]

Questions about Turbocharged Rimatron 7MX

One other small point. I recently did some hand calculations regarding this design, especially around the integrating and differentiating stages. As a result I changed C14 (in the feedback path of U4A) from 102nf to 22nF, which has improved the discrimination somewhat, and reduced the chatter in trashy areas.
U4A is the differentiator in the DISC channel. Normally the cutoff frequency Fc is set higher than the break frequency Fb, but for some reason it's the other way round in this design. Lowering the value of C14 gives a higher frequency cutoff of 18.5Hz (was Fb=7.2Hz and Fc=4Hz). Since Fc is now higher than Fb, the gain of this stage is also boosted as a consequence, which improves the ability to reject bad targets at greater depths. i.e. less chance of digging a big hole and finding a nail!

I have built it, and I find some mistake on the electronic diagram( e.i: Pin 12 of the IC LM11730 in place of Pin 13, D1 and D4 inverted.
Can you check in the original board the different connection of the U2A, U2B,U2C,U2D with U1A, U1B and U4A, U4B, because when I look on your pictures: PCB top and PCB bottom there is some difference
( Some tracks of the circuit are hidden by the components, but it seems that those will not be connected there or had put them to you ).
Concerning the layout of the circuit for L-RX1, are you sure that it does not miss a track? .
I am sorry to put to you at contribution, but having in your possesion the original cuircuit, it is easier for you to control these remarks or interrogations.
Best regards
Luc

[Qiaozhi]

I have built it, and I find some mistake on the electronic diagram( e.i: Pin 12 of the IC LM11730 in place of Pin 13, D1 and D4 inverted.
Can you check in the original board the different connection of the U2A, U2B,U2C,U2D with U1A, U1B and U4A, U4B, because when I look on your pictures: PCB top and PCB bottom there is some difference
( Some tracks of the circuit are hidden by the components, but it seems that those will not be connected there or had put them to you ).
Concerning the layout of the circuit for L-RX1, are you sure that it does not miss a track? .
I am sorry to put to you at contribution, but having in your possesion the original cuircuit, it is easier for you to control these remarks or interrogations.
Best regards
Luc

Hi Luc,

There does indeed appear to be a mistake on the schematic for U2B (LM13700N). Sorry about that. The inverting input of U2B should be pin 13. The schematic currently shows two pin 12s on that device.

I think the wiring for the other devices is correct. Please can you mark on the
PCB pictures where you think there's a problem.

I'm certain that the diodes D1 and D4 are the correct polarity, as these devices did not exist in the original. I added these to the turbo version.

Can you explain more about the problem with L-RX1? Where do you think there's a missing track?

[Legaucho]

Turbocharged Rimatron 7MX

Hi Luc,

There does indeed appear to be a mistake on the schematic for U2B (LM13700N). Sorry about that. The inverting input of U2B should be pin 13. The schematic currently shows two pin 12s on that device.

I think the wiring for the other devices is correct. Please can you mark on the
PCB pictures where you think there's a problem.

I'm certain that the diodes D1 and D4 are the correct polarity, as these devices did not exist in the original. I added these to the turbo version.

Can you explain more about the problem with L-RX1? Where do you think there's a missing track?

Hi Qiaozhi,
Thanks for your reply,
Please find hereby the PDF attached file with on it my observation, can you check if I'm right.

Concerning L-RX1, there is no problem.
See you
Luc

[Qiaozhi]

Hi Qiaozhi,
Thanks for your reply,
Please find hereby the PDF attached file with on it my observation, can you check if I'm right.

Concerning L-RX1, there is no problem.
See you
Luc

Hi Luc,

The location of C22 is correct in the original schematic diagram. If it was connected as you have shown then U6A would be disabled. Also, there is no problem with D1. The purpose of the U6A/D1 combination is to switch off Q1 in the presence of any discriminated target.

I have some questions:

1. How have you constructed the coil? The Rimatron uses a Double-D. The TX and RX coils are identical (9.5mH, 25 ohms) but the TX coil is centre-tapped.

2. How much of the detector do you have working so far? Try running it in All-Metal mode first.

Qiaozhi