Schematic for P.I. Hi-Power Goldquest

[nalag46]

I have one of these in non working condition. If anyone has the schematic or any technical data it would be most appreciated.

[kt315]

good start point for new project there. to sorry, big sorry, eric foster does not share the schematics. only guys here are able to help.
first. some photos of the PCB from you. please - hight resolution, at day direct light, no by mobile phone in a dark room. yours sincerely.

[Reg]

Hi Nalag46,

What is it doing wrong? Do you have a scope? If so, take a look at the TP connected to pin 6 of the NE5534. Do you see the typical pulse and decay? If so, then most of the detector is working. If you have no pulse signal, then do you have any signal at all?

You can use the CS 6 pi schematic as a basic schematic. The preamp is a different IC and a little different and many of the resistor values are different, but overall, the designs are very similar. There are a couple of CS6 schematics on this forum.

If you use the CS schematic, it will give you a lot to use for evaluation. Look at the outputs of the 4017 and see if they are there. If so, the 555 timer is working and the 4017 is probably ok. You can use the CS schematic to follow the signal through the unit. However, the CS schematic has one more IC stage not found on the GQ.

There are several TP's on the GQ so you can look at them also. Use the wire going from the pc board to ground the board to the mounting standoff as your ground connection.

Don't mess with any of the pots. If you have you will need a scope to get the output of the NE5534 correct. The first pot closest to the coil connector is adjusted to give you the best pulse decay when at 10 usec delay. The second pot is the one that you adjust to 0 the NE5534. This is done using a scope and looking at the output of the op amp at a very late time after the pulse. The opamp should decay down to 0V with no offset. The second pot sets this voltage at 0V.

Let us know more about what the detector is doing and not doing when you check it with test equipment.

Reg

[Qiaozhi]

I have one of these in non working condition. If anyone has the schematic or any technical data it would be most appreciated.

Do as I did with the Minipulse. Take photos of the top and bottom of the PCB; invert the bottom image; then scale and overlay the top and inverted bottom images. From there you can trace the layout and back-engineer the schematic.

[nalag46]

I have been asked to look at this detector by a long standing user who says the 3 pin power connector had to be replaced. He let his son do the soldering and apparently, got the wires crossed and after switching it on, the fuse in the battery pack blew up. He replaced it twice with the same results and that is all I have been told.
From the description, it should be a simple and straight job except that it is not. On the power board, I have found the 7912 and the 79L05 negative regulators both open as well as a BC214 tranny. I have sorted the wire connections on the power plug and replaced all the three dud components and the 14/15v from the batteries is now feeding the 12v regulator with the correct polarity but I can only measure a -2v at the output, which in turn is also the voltage feed for the 5v negative regulator.
There is also a 5v positive regulator that does not appear to have been affected but I am yet to fathom where the supply for this one comes from and this is as far as I have got to so far hence my request for an schematic.

[greylourie]

Here is a cs 6 P.I schematic. Although it does not appear to show a 7912 regulator. Perhaps the goldscan schematic might be of help. Eric Foster designs often share similar elements.

Let us know how you progress. A lot of people would be interested. Also if you could possibly post a Top and Bottom image of your board - would be so grateful.

[Reg]

Your description sounds more like you have a Goldscan than a Goldquest. Can you take and post any pic's of the unit?

The GQ is really a low powered unit. The Goldscan is a high powered unit.

Reg

[kt315]

Do as I did with the Minipulse. Take photos of the top and bottom of the PCB; invert the bottom image; then scale and overlay the top and inverted bottom images. From there you can trace the layout and back-engineer the schematic.

something like to knock in the closed door. no reply. I suggest to sell the GQ to somebody of geotechers. will be more a progress.

[nalag46]

The detector is definitely a Goldquest or that is what it says on the tin but I haven't seen one of these before.
Enclosed are pics. of the two mains boards. The diagram of the Goldscan IV power supply board is the nearest to this one but the Goldquest has two timers 555 ics.

[Reg]

You should be able to use the Goldscan 4 schematic to figure out what is going on. The GS 4 has almost an identical layout but has the two empty IC sockets filled.

As for your power supply board, one 555 is for generating a +voltage and the other is the audio like what is shown on the GS 4 schematic. So, basically, it is a GS4 with a few mods. I don't see a GB pot so that might be the difference.

Eric didn't deviate much in his designs. That is why you can use the GS 4 schematic and be close.

Reg

[nalag46]

Thanks for that. I think with the schematic supplied I will be able to sort this matter out now and will report back in due course as I am quite busy with other projects right now.

[6666]

Hey Reg did Eric hand make his MD's ?

[sinclairuser]

looking at your pics, and the schematics, it looks like your boards are fully populated, if the two designs are as similar as suggested, it may be possible to add the ground balance feature.

[Reg]

6666,

As far as I know, Eric hand built each detector.

Reg

[6666]

Thanks Reg.