Newb needs help with Surf PI Volume knob

[ronbyrne]

Got my kit this morning and dived in all excited, but i dont know a lot about electronics, How do i connect this external knob to the board, i just guessed this arangement but am just getting a constant whine on speaker, volume works ok. but i am not sure this is the correct connections.


Also , is there any test points that just require multimeter ? i did search for answers but just end up lost.

[Comp]

????? Sorry, I have given up...... {we really do need a Surf P.I. section, on the projects page, in my opinion!!!}

I (think!) you have wired up the variable resistor wrong,.. the two outer (unconnected) contacts are for the on/off switch,... I'm not too sure if the socket with no plug on is for the 'threshold' control,...... if so, it needs something connected to it!!!

I will go surf (?) the site, see if I can find more info on the new board...


Cheers, Fred

[ronbyrne]

cheers fred.

Yes i know about the power, its just the 3 center wires, are they correct going to the volume connector ?
eg. left, middle and right pins on board go to left middle and right on the pot ?

the empty socket is for the tuning knob

[Comp]

Sorry, hard to tell,... the board has been revised/tweaked recently,.. I cant tell you, to be honest what the pinouts are,...

does this thread (Post 186) help you any??????

http://www.geotech1.com/forums/showt...t=17121&page=8

The whole Surf section seems a bit disjointed to me, TBH,... and as that is where a 'newbie' is likely to start, perhaps needs a bit of work..

If that does,t help, contact Silverdog on here,... he will point you in the right direction, I have found him to be very helpful with info on his kits......


Cheers, Fred

[silverdog]

With your multimeter, you need to adjust the offset pot to give 0v DC on pin 6 of the ne5534

The Delay pot really needs a scope but trial and error will give you detection, if you can adjust it to detect gold then you are doing ok

What coil are you using ? The surf can be a bit fussy if you coil is way out spec

looking good so far though

[Comp]

Ok, rethinking,...(10.30 on a Friday night is not the best time to be asking questions!!! LOL!)If you are getting a constant whine out of the unit,.. the audio stages must be working something like,..... so they are probably wired up correctly..... to test the pulse generator/coil stages, put the coil near an old am radio switched on,.... that will tell you if the transmit section is working ok!!! Cheers, Fred

[Comp]

.. ok , you need to set the output of the NE5534 to 0 volts, as Andy says, with the preset, P1,....... and if the 'threshold' trimmer, {P2, 10K } is set wrong, it could give you a constant tone,.... try it in the middle of its range,.........

have you got your negative 5v line????

Cheers, Fred

[ronbyrne]

ok, i must have done something wrong. constant 4.47v on that pin (measure from tp2) i turned the trimmer a lot without any change. Where do i check for -5v ?

[ronbyrne]

ok, i have -5v on pin 5 of 7660

[woodbob123]

Check the board against pictures on the forum, easy to look at a mistake 100 times and not see it, electro caps are always a problem. preset pots to middle using a multimeter on or off the board, try and keep a note of how many turns so you can centre again.
as silverdog said check coil is close correct number of turns and dia.
Good luck it will work.

[ronbyrne]

Ok, i have been in denial a bit since ysterday. Time to come out with it ! lol.
On first powering up the board i connected to a bench power supply 12v current limited to 0.2 amp and powered it up with the wrong polarity !! so , what could i have damaged ?

thanks for all the help so far.

as for removing the trimmers and pre setting at mid. what reading am i looking for ?

Coil is mono 10" 20 winds of don't know what ! got it from degause coil from tv. measures 3.5 Ohm

[TH Jim]

3.5 Ohms sounds a little high, what size is the wire? Try and aim for 1.5 - 1.8 ohms, at least 0.5mm wire, that should be ok.

Having powered the unit with the wrong polarity ANYTHING could have happened - its not a good situation to try and diagnose remotely!

Really its best to set the delay using an oscilloscope, very difficult otherwise, then adjust the offset for best sensitivity.

A rule of thumb is: The shorter the delay - the higher the offset needs to be.

Good Luck,

Jim.

[woodbob123]

to set preset midway if it 10k, between 2 outer pins will be 10k from outer pin to middle pin set to 5k each side but when you turn pot you will see it change.

[silverdog]

There are a couple of links to make on the board, one above C6, one next to the ne5534
There are marked with white lines on the silkscreen

[ronbyrne]

There are a couple of links to make on the board, one above C6, one next to the ne5534
There are marked with white lines on the silkscreen

Thanks Silverdog, That was it, i had started to strip everything off when i saw your post, i would never had thought they were links, anyway i put all back togeteher with the links and am getting sound which rises as i put metal near coil, trimmer adjusts to 0v (ish !)Thanks a million, i can get to tuning now. For the coil, i have a spool of enameled 28swg (0.375mm) is that too thin ?