Minelab Sterling schematic

[wam]

Hi, I have faulty Minlab Sterling - is anyone having schematics for this unit?

[Melbeta]

Do a search for "sterling".

I read some posts yesterday in this forum, a fellow posted many photos of his Sterling unit, including pcb, but no schematics. But if you do a search for sterling, there may be a schematic in here.

[wam]

I have started to re-draw TX side from PCB, if anyone can do RX side we could exchange schematics.

[joecoin]

Sterling is the same as the Musketeer X (I think).

[wam]

Hi, I have repaired my Sterling and got it worse again.
The original problem was simple:

• The ON/OFF switch had about 50 R when ON – I got it fixed with WD40 sprayed via two holes on the pot..
• After while I had intermittent problem with battery power – The wire for battery clip was breaking connection – I have soldered it to terminal and no problem.

Additional exercises:

• The output amplitude on the coil is 20 Vpp sine wave and it will not change if supply vary between 9.6 and 15 Vdc.
• When I have made quick check it looks like that the “largest” range for detection was when voltage is between 9.6 and 10 Vdc.
• I have checked it with crystal 3.6 MHz – it did work but TX signal was distorted in lower part. The amplitude was smaller but over 10 Vpp 3.6 kHz.
• I have checked it with 7Mhz crystal – it works and responds with higher audio,

signal had several Vpp. 7kHz.
5. I have taken 10kHz signal from the oscillator U7 (instead 5khz pin) and it was working but coil was out of resonance so amplitude was 4 Vpp and shape was triangle type.
In all above conditions detector was working and responded with audio changes but I did not have time to evaluate how good or bad. Unfortunately I had power on board while replacing crystals and it resulted in burning transistor Q3. It looks like that Q3 burns out when crystal oscillator is not running. I did not have replacement type so I have tried some others. All other transistors gave me 17Vpp signal so to make it bigger I decided to connect 220k on top of SMD R44 (100k). It changed signal back to 20 Vpp. Then I have connected 220k on top of R58. and it increases output signal to 23Vpp. The detector was working and taking 50 mA (before this the supply current was 40 ma). At this stage I gave up and decided to stay on 20 Vpp output and get ready with some conditions to measure accurate effects of this variations.
My concern is how much it is possible to rise output power (and how to do it).
I do not mind to drive this detector with 500 ma for 4 hours on one battery charge if it will improve detection by 20%. Please let me know if there is any data in this matter.
Regards.

[wam]

Output signal from Minelab Sterling or Musketeer

Now I have original output transistor Q3 BC368 fitted in my Sterling. The output sine signal is 17.4 Vpp. Finally I am thinking that may be it is the right amplitude. Is anybody able to confirm my observation base on the signal from other Sterling or Musketeer?
The measurement was taken with 8 inch coil.
Regards.

[wam]

Minelab Musketeer Advantage Sterling Tribune Colt

Hi,
it looks like all of Minelab below have similarities in electrical circuit.
Models: Sterling, Tribune - are identical in appearance.
Musketeer, Advantage, Colt - they could have the same circuit but the PCB layout may be different.
Please let me know If anyone drowned some partial schematics.
Regards,