Full m/lab SD2000 schematics

[Andrei]

Compare N12 and N14 to the output of the second 5534(n50) and post the result, I will tell you if it looks ok.
Cheers Mick

[Mechanic]

On the 200v cap is 183v


much detail possible

183v is perfect! I think it operates from about 170v to 195v.

Compare N12 and N14 to the output of the second 5534(n50) and post the result, I will tell you if it looks ok.

Cheers Mick

[Andrei]

Nice! If the gate voltage is working like that then the coil must be doing good things as well.
Just check that you have 180v approx on the 200v cap and it should be safe to hook up the receive if you haven't already.

On the 200v cap is 183v

Then you can check the output at the second 5534 and compare to the first(earliest) sample to make sure your coil has settled to gnd(or very close to) before the first sample is taken.
If not, you can try adjusting the 65pf cap(transmit page) as this controls the gate timing. You could also probably fiddle with the 47k resistor. Cheers Mick

much detail possible

[Mechanic]

Hi Mechanic! 4093 is serviceable, replaced only N fet VN2410L on IRFU210A. Now I have voltage at the gate vb- to 5+.
[ATTACH]48986[/ATTACH]

Nice! If the gate voltage is working like that then the coil must be doing good things as well.
Just check that you have 180v approx on the 200v cap and it should be safe to hook up the receive if you haven't already.
Then you can check the output at the second 5534 and compare to the first(earliest) sample to make sure your coil has settled to gnd(or very close to) before the first sample is taken.
If not, you can try adjusting the 65pf cap(transmit page) as this controls the gate timing. You could also probably fiddle with the 47k resistor.

Cheers Mick

[Andrei]

75pf NP0

I suspect the V2 has an ad797 preamp vs the lm394 on the original version. Could be a few other differences as well.

The voltage at the gate for the N fet should swing from vb- to 5+.
If it has been hit with high voltage it has probably failed and taken out the 4093 as well.

Cheers Mick

Hi Mechanic! 4093 is serviceable, replaced only N fet VN2410L on IRFU210A. Now I have voltage at the gate vb- to 5+.
oscillogramme-Model.pdf

[Mechanic]

75pf NP0

I suspect the V2 has an ad797 preamp vs the lm394 on the original version. Could be a few other differences as well.

The voltage at the gate for the N fet should swing from vb- to 5+.
If it has been hit with high voltage it has probably failed and taken out the 4093 as well.

Cheers Mick

[au1]

Hi Andrei,
The voltage should fluctuate. As long as the fet isn't getting hot and you see "some" voltage it's probably ok. Are you getting any sound?
The pdf you posted is what comes out of the gates of the 4066's.

Mechanic,
I'm having difficulty verifying what the value of the capacitor is in the drawing.
Best I'm able to see is "67p polarized".

Also, do you know what the difference is between a SD2100 and SD2100 V2?
I found this for sale today. Says it's a SD2100 V2. Show's no signs of wear and has 2 coils, and everything that came with it from factory.
Asking $600.00.

[Andrei]

oscillogramme-Model.pdf
what is the voltage should there be gate VN2410L?

[Mechanic]

Hi everyone and my best wishes for the year 2020,

Mechanic,
I was looking for litz wire to build the search coil, I found this one (attached pic.),please can you advice?
[ATTACH]48978[/ATTACH][ATTACH]48978[/ATTACH]


Thx
J.Anis

Hi, it is hard to say. It has been a long time since I looked at coil wire. From memory it was 28 or 32 strands of .2mm diameter strands.
If you have made your detector, perhaps see if you can find yourself a second hand coil to suite as building a good coil is quite hard. After you find some suitable wire you then need to find a suitable "coax". The one used by Minelab, Nugget Finder and Coiltek is specially made for coils, not commonly available. It is litz core and fine litz screen, low capacitance, not able to be detected by the coil.

Fortunately the old 2000 is a little more forgiving with coils than the later models.

Cheers Mick

[Anis]

Hi everyone and my best wishes for the year 2020,

Mechanic,
I was looking for litz wire to build the search coil, I found this one (attached pic.),please can you advice?


Thx
J.Anis

[Mechanic]

Yes it does and the 2.7k resistors, the 150nf and 150r.
I'd also replace the 1k resistor with 470r and the 22r with 10r.

Cheers Mick

[au1]

Mechanic,
You posted this diagram previously showing how to replace the LM394 and one of the 5534's with an AD797.
Does this eliminate the BC850 and the 3 electrolytic caps also?

Thanks

[Mechanic]

The SBYV28-200 diodes do work, but in my testing I found the byv28-200 to be better.

Disconnect the receive wire from the coil. There is a chance your front end receive fet is no good and this will just confuse things too. Then once the transmit is behaving properly move on to the receive.

Cheers Mick

[KingJL]

Hi All, I'm sorry for responding so late.

KingJL,

Please below is answer to you question:
Parts used for circuit:
-Diodes: SBYV28-200
-Mosfet: BUK455-600, IRF710, BS170,
-IC: TL271CP, CD4093BE, DC40106BE, LM393N or LM393P
- chemical 100uF capacitor/250V...

Also (again I don't mean to indicate that this is the source of your problem), The SBYV28-200 is not the same as the BYV28-200 Sintered Glass Avalanche Diode (especially reverse current leakage specs which are critical to this application)... I have used and had experience with the BYV28-200 (actually have 10 in my parts box), have not with the SBYV28-200!

[KingJL]

Hi All, I'm sorry for responding so late.

KingJL,

Please below is answer to you question:
Parts used for circuit:
-Diodes: SBYV28-200
-Mosfet: BUK455-600, IRF710, BS170,
-IC: TL271CP, CD4093BE, DC40106BE, LM393N or LM393P
- chemical 100uF capacitor/250V

-The Remove test of Diode between TX and 100uF/200V: condition is the files names
[ATTACH]48686[/ATTACH]
[ATTACH]48687[/ATTACH]
[ATTACH]48688[/ATTACH]
[ATTACH]48689[/ATTACH]

-100uF/200V polarity:
(-)Pin connected to ?VB, (+) Pin connected to Diode SBYV28-200& 68ohm & 110K resistors.

When no diode:
(-) Pin=-6.8V
(+) Pin=-6.8V

When diode set:
(-) Pin=-6.8V
(+) Pin=-1.14V

...

I had to ask about the components used as it gives us a confidence factor to begin with.
First , I don't mean this to be the source of your problem, but I believe the correct BUK455 for the SD2000 is the BUK455-200a.

The screen shots of the TP with coil indicate that a problem ( I don't mean to indicate that this is your only problem) is in the path of the diode that was temporarily removed (note the shortened duration of the flyback with the diode removed... with diode removed the actual flyback voltage is probably also excessive ). Taking your re-affirmation that the polarized cap is correct and correctly connected, the signal is being shunted to VB- even though the capacitor has not reached the 180 V level (you may need to verify that the cap is not faulty). You need to verify the voltages at the IRF710 gate and closely recheck the IRF710 connections. I don't recall you answering Mick's question/warning about the IRF710 mounting/tab. But you have a definite problem in this path (the 180 V regulation).

Also, there may be a problem with the status of the front end blocking MOSFET's as it appears that the signal at TP is being limited to within the +-5V rails... although that could be because you are using a 1x probe to veiw the voltage at TP (which will be 180V or higher) with a low voltage oscilloscope system. When viewing TP, I would recommend at least a 10x probe. The flyback should be much higher (especially with the diode removed)... it appears as if it being clipped!