Surf PI Pro

[Tepco]

Voltage change is good but lack of response is not. Assuming for now timing circuit is good, check pin 6 of 5534 input amplifier, and response to offset adjustment, should be around 0V and responding, with some very small change for large metal near the coil.

[sentella4d]

Sorry Tepco;my mistake.
The reading from pin 7 of 358 can be controlled with delay pot,from -.93 to .71volts or so.If i put any metal on the coil there is no change in voltage.

[Tepco]

Not 7660, measure at pin 7 of 358 chip

[sentella4d]

Hello Tepco;
I measured the voltage from pin 7 of the 7660 and the voltage is around 1.45v with and without metal.THe delay pot has no effect on voltage.The sensitivity pot is wired correctly.
Thanks

[Tepco]

Hello forum members;
My name is Angel, I am new to the forum.I bought this surf pro pi kit already assembled: http://www.ebay.com/itm/231202148661...84.m1497.l2649

I have wound the recommended coil; 21 turn, 9.1 inch, 24 gauge coated enamel wire, set up the offset to 0 volts and the r2 trimmer to 3.3k but the coil will not detect any metal.I have tried setting r2 to between 2.3k and 3.6k to no effect. I am using 4 feet of RG-58u to connect the coil to the board,and i am not close to nay metal.No matter what r2 setting all i get is a constant threshold sound,no metal detection.I am able to control the volume level and threshold with the pots,but the pulse delay and sensitivity pots seem to have no effect.

I measured the 5v and - 5v rails and i get +5.1 volts and -4.84 v.
I have tried t check for any solder bridges or loose welds but none were found.I have tried changing the component configuration according to these forum posts:

http://www.geotech1.com/forums/attachment.php?attachmentid=24310&d=1365551799

I also tried these suggested modifications:

http://www.geotech1.com/forums/attachment.php?attachmentid=24368&d=1365944910

.,I also tried a 125 mm id, 30 turn flat spiral coil wound with 24 gauge speaker wire as suggested but no change,just a constant threshold.
I have very limited electronics knowledge.No matter what I try it does not work,I have no oscilloscope I am stumped,I do not know what to do...Please Help!!!

Angel

Reading this post I came to conclusion that your problem is probably minor one, most probably related to wrong sensitivity pot connection. You now have threshold tone adjustable, this part of the circuit works, most probably timing too. Lack of detection can be result of two most common causes: wrong delay adjustment (too short delay for given coil) but then increasing delay will make detector to work. In this case more probably sens. pot. To check this, measure voltage at pin 7 of U6B (first part of 358 after analog switches, there are many schematics and PCBs in circulation). You should get something around 0V without metal, rising in presence of it to some 3.8V. If you already have 3.8V here (not responding to delay adjustment), or voltage not changing at all problem can be elsewhere, but if this is OK check sens pot connection. One end of pot goes to GND, another opposite end to C17 (1uF cap from pin 7 of 358 chip), middle pin to pin 3 of 358. If this is not connected properly you can get audio turning the pot but no response to metal.

[geoscash1]

Yea, that's the same as mine...

[sentella4d]

SMP3 files

SMP3.pdf

[sentella4d]

Hello Geocash;
my brother took my camera right now,he is on vacation.Anyways i did verify that all the components installed on the board were the correct ones.I my board version is SMP3.I checked to make sure that the weer no cold solders,short circuits and that all the correct solder bridges were installed.I will post a parts list and electrical schematic that came with my detector.

[geoscash1]

Can you post close up clear pictures of the top and bottom of your board?, Maybe someone will spot a component problem or something else, There are some very knowledgeable guys here and have helped me out with just pictures.

[sentella4d]

Hello Geocash1;
Both the Pulse delay and Threshold pots rare 10k,I had already noticed that they were inverted,so i switched them.All IC chips are presoldered,no sockets.

[geoscash1]

sentella4d,

The volume, sensitivity and threshold pots have 3 wires and the delay pot only has 2 wires, is that how yours are or were setup?, if so you may have had the pots mixed up. If they are mixed up or the wires wrong it will work in weird ways or not work correctly. Make sure the wires are correct in the wafer plugs.. Also I found that the chips/IC's may need to be removed and put back, make sure they are pressed all the way in to their sockets.



R19 - 10K - Threshold - 3 wire
R24 - B1K - Volume - 3 wire
R30 - B20K (might be a 10K) - Delay - 2 wire
R31 - B100K - Sensitivity - 3 wire

[Qiaozhi]

Dear Qiaozhi;
I have a multimeter,but I currently do not have access to a scope

Without a scope it will be very difficult to debug.
One of the members here had a non-working Surf-PI kit which he sent to me to repair. This was after a long exchange of posts where we attempted to identify the problems. There were so many faults it would have been highly improbable that I could have got it working without a scope.
Although this is a relatively simple circuit, it's just not possible to monitor the sample timings without the correct equipment.

[Nupi]

Dear Qiaozhi;
I have a multimeter,but I currently do not have access to a scope

Maybe you have enough to a software scoop ?
You can ask Qiaozhi?

[sentella4d]

Dear Qiaozhi;
I have a multimeter,but I currently do not have access to a scope

[Qiaozhi]

Hmmm ... seems to indicate that the board was completely untested, let alone tuned.
Can you get access to a scope?