help with surf pi kit no sound

[langleylocator]

thanks guys another step nearer it looks as though we have some kind of life attached pic is on the scope from TP1. I have had the tester on the MPS A13 and have 12.46 on the collector 0 volts on the base and the emitter am i correct in guessing that this is not right and the transistor is Kaput defunct let out the magic smoke.
pic quality is also better used image re-sizer to make it fit better please let me know what you think thanks again for all of your help,Steve.

[porkluvr]

hi, working on that now
here is the fet cropped.but for some reason it keeps blowing it up to fill the page you can see the pins marked s 0 And A triangle on the fet but on the silk screen it seems to suggest it should be the other way around.

The "S" you're showing appears to be the Siliconix logo and should not be confused with a source pin designation.

[geoscash1]

Just make sure it has the writing facing up with the drain sink laying against the board like in this image.

http://www.geotech1.com/forums/attachment.php?attachmentid=30380&d=1403273753

Check Q6 and R34 along with your solder joints over the whole board. I believe R34/Q6 controls your audio so make sure R34 value is correct and
then check the transistor, if I remember correctly it should be the MPSA13.

[langleylocator]

hi, working on that now
here is the fet cropped.but for some reason it keeps blowing it up to fill the page you can see the pins marked s 0 And A triangle on the fet but on the silk screen it seems to suggest it should be the other way around.

[geoscash1]

Can you repost the image a little smaller or from a bit farther away, the pic is so large it is hard to see what's what..

[langleylocator]

Hi guys, thanks for all of the replies, However still no luck,and no sound( apart from a faint buzzing from the mosfet hope i haven't cooked it)
here is a photo. still not certain if it is the right way round though? also seem to have the very simillar voltage on the S & G Pins is this normal ?

[geoscash1]

Your welcome Langleylocator....

[golfnut]

sure Q2 is wrong way

[langleylocator]

Wow thanks for the quick reply i was not sure when i places it on the board i only saw the "S" and followed that pin lay out, will re solder back in the other way round. Have to take the kids to soccer now will report back when done .
thanks again !

[geoscash1]

FET backwards

Hi Langleylocator,
looking at your board pics, it looks like your FET (irf9640) is backwards or 180 degrees, you should have it so it looks like the one in the image below.
correct

Yours

[langleylocator]

noooob i need of help

As requested by some guys here I have taken some pics, can anyone spot anything i have cocked up so badly IE that i cant see it
pic's 1.2 3& 4 board

pics 5 & 6 scope signals from TP1
pics 7& 8 scope signals from TP2

[langleylocator]

still looking for help i have replaced the resistor 100k for the recomended 100 ohm but i still have no sound. i have a scope and seem to get a signal on T1 & T2. please help as im stuck in limbo.

[langleylocator]

Hi Guys, Yet Another NOOOOB to md'ing And electronics. I can solder quite well,and decided to make the PI 1.2. however i am another one with similar problems NO audio . I have tested the U1 U2 U3 U4 & U7 pins as suggested in an earlier post and have similar results yet still no audio or signal ( I have managed to score a scope {FREECYCLE IS A WONDERFULL PLACE} don't really know what i am supposed to be looking for with it) any HELP would be greatly appreciated.
I have also meterd out all of the resistors and found 1 that is the wrong rating namely R5 Is listed 100 Ohm but i have found that i have inserted a 100k (I have no idea where this came from as i counted all of the items in the bag And found the diodes missing. quick trip to maplins sorted that little problem) would this be the cause of my problems?
H-E-L-P.
DESPERATE of slough Uk.

[methanolcat]

OK, so I started probing U7 when I noticed that sometimes (whenever I put any kind of pressure on U7) I would get a tone, sounds like it is suppose to, loud. I kept messing with it and determined the socket was bad, it never would make good connection and stay, unless I put pressure on U7.

I changed the socket, put U7 back in and turned it on, was then getting a constant tone, it would not stop, so I get to messing with it and noticed that jiggling wires around the tone would stop and go, further investigation showed that I had a wire break going to P2, wire had broke at pot terminal (most likely from all this messing with it). I fixed the broken wire, then tried it out. It has erratic behavior at this point with no movement whatsoever, I can even leave the room and it will start going off, I even took it outside away from everything and no change.

U5 still heats up so something is not right with one of the IC's, I checked Tp2 and my waveform looks much different than when it was working right.

I can get it to work (detect metal) but only if I adjust P1 to a voltage around 4v+ and the detection distance is very short with large object.

If I take out U2 then U5 doesn't heat up so I guess what I am going to do is order some new IC's, they are cheap so I'll get several of each.

Thank you very much for your time and helping me, I appreciate it, I will get back to this once I get more IC's.

[Qiaozhi]

I did like you said and with the scope on TP2 the waveform changes in the presence of metal can, so that part seems to be working.

I do not get an audio tone from (point 3) with +5v applied, I do get a noticeable pop/ crackle when making connection but no tone.

Can you check whether the sample pulses are present?
Put channel 1 probe on U7b pin 13 (main sample), and channel 2 on pin 5 (Earth field sample).

Also, let's look at the output of the integator stage by putting the scope probe on U3 pin 1. Does this change in the presence of metal?