Whites Surfmaster PI

[keith777]

Hi all.
i was wondering is anyone in the UK has this PI detector and can tell me what in air depth that they get on a copper 2p coil. i bought this machine for £20 last week. it needed a good clean as the person i got it off. the detector had been in a shed for quite some years. i did have to get a new battery holder and replace the battery terminal cable with the plug end on, as they both had a lot of green corrosion on them. also there was a small part on one of the traces on the circuit board that had corroded away that i had to bridge with a wire. the machine seems to be working now, but with not owning one of these machines before. i don't know if the detection depth on it is correct or not. it seems a bit on the low side to me. i get at a push 7" with the 2p coin in air.
thanks in advance.....

[Qiaozhi]

I have the same detector, except that it has the yellow control box. I think your detector is a slightly newer model.
A copper 2p coin is loud at 7", definite signal at 10", and faint at 11".
A copper 1p coin is load at 6", definite signal at 7", and faint at 8".

[keith777]

I have the same detector, except that it has the yellow control box. I think your detector is a slightly newer model.
A copper 2p coin is loud at 7", definite signal at 10", and faint at 11".
A copper 1p coin is load at 6", definite signal at 7", and faint at 8".

so mine is defiantly under preforming. i wonder what the problem may be. i couldn't see anything by eye that may be coursing any problems other than the corroded small part of a trace line that needed bridged up.
anyone any thoughts on this please.

[GeoMax]

Hi,

I would first check if you are having issues with timing and proper coil damping.

[keith777]

Hi,

I would first check if you are having issues with timing and proper coil damping.

my electronic skills are limited. i wish i new more than i do.
timing and proper coil damping are above my pay grade.lol

[Qiaozhi]

so mine is defiantly under preforming. i wonder what the problem may be. i couldn't see anything by eye that may be coursing any problems other than the corroded small part of a trace line that needed bridged up.
anyone any thoughts on this please.

It's difficult to say off hand.
If you have an oscilloscope, then you could check the calibration. Perhaps someone has messed with the DISC trimmer. That's the one in the middle of the PCB, and it affects the sample delay.

[keith777]

It's difficult to say off hand.
If you have an oscilloscope, then you could check the calibration. Perhaps someone has messed with the DISC trimmer. That's the one in the middle of the PCB, and it affects the sample delay.

not my board, but do you mean this one.

[Qiaozhi]

not my board, but do you mean this one.

That PCB looks different to mine. The one I have has 3 trimmers.
One is next to the NE5534 (preamp) to adjust the null offset.
The second is next to the MPSA13 (audio output transistor) to adjust the volume.
The third affects the sample delay. It's labelled DISC on the schematic, and should be near the 4093B IC that controls the main sample and EFE pulses.

[keith777]

That PCB looks different to mine. The one I have has 3 trimmers.
One is next to the NE5534 (preamp) to adjust the null offset.
The second is next to the MPSA13 (audio output transistor) to adjust the volume.
The third affects the sample delay. It's labelled DISC on the schematic, and should be near the 4093B IC that controls the main sample and EFE pulses.

i will take out the board in mine and take some photos......

[keith777]

here is two photos of the board.....

[Carl-NC]

The pot on the right adjusts the offset of the preamp (NE5534). It's halfway which is about where it should be. Messing with this is unlikely to affect depth at all, until you go too far and you lose a lot of depth.
The pot on the left sets the minimum sample delay. What you might try is to set the user control for the sample delay to minimum, and then adjust this pot and see if you can squeeze out a little more depth.
The pot on the back side adjusts the volume.

[GeoMax]

Hi,

the IC chip in the top right corner of the PCB looks a little damaged... Maybe there is a problem there too. The three capacitors in the top right corner also don't look "healthy" or it's just the angle of the picture. I would check them too.

[kt315]

what type transistor you see in TO-220 enclosure? thx for pics, it is 505-0194 board.

[kt315]

schematic with mods.

[keith777]

i have came across a person selling the same machine. who has shown photos of the board inside there case. the board in there case is actually different to mine, even though the rest of the machine is the same.
this is what they have written in there advert.

White’s Electronics Surfmaster P.I. Metal Detector
This is a high-performance Pulse Induction metal detector, which allows it to ignore wet salt or mineralized ground. It features fully automatic tuning (S.A.T.) and the audio tone increases when a target is detected. It is ideal for use on beaches or for relic hunting.
The detector runs on 8x AA batteries (supplied) giving 25 to 35 hours of continuous operation.
This unit has been refurbished as follows:
• New battery pack (alkaline batteries included).
• New camlock on detector shaft.
• TX oscillator IC replaced.
• Voltage converter IC replaced.
• Pulse Delay and Tuner controls replaced.
• Some internal wiring renewed.
• Calibration checked.
This detector now works as good as when it was new.
Please note that, due to the proprietary nature of the original Tuner control, the battery test function no longer operates. However, this does not affect the normal operation of the detector. In fact, it is immediately obvious when the batteries are getting low. Many DIYers have made their own copies of this popular design over the years, and (AFAIA) none of these have ever included the battery test circuit.
Please see the attached photos to check the physical condition of the detector. Obviously there are some marks as you would expect, but generally the detector is in good condition for its age, and is a very good working example.
£250.00