kenshinz 0 Report post Posted November 1, 2003 Eh... as in can I connect the (-) on 1st batt to the ground, and (+) on 2nd batt to ground, instead of connecting them together 1st, then use another wire to connect them to ground Share this post Link to post Share on other sites
tropicalrips 0 Report post Posted November 1, 2003 jason yes i connect (+) of batt 1 & (-) of batt 2 to ground i also tried the one battery layout both had the same problem (hissing) but i solved that now by using the same resistor value for R3 (op-amp audio output) & R2 which is the op-amp's own ground i think everything was ok liao, i tested it with the volume pot and it works, no more hissing then i finish the case and put everything in...turn on the power...hear only silence... it went dead, going to do another board tonight, i think i re-soldered the first one too many times, but it did live for abt 20mins Share this post Link to post Share on other sites
jtfoo 0 Report post Posted November 1, 2003 I guess that the voltage of your batt1 and batt2 are different(usually the case), thus giving out uneven positive and negative volatge. That's why it's better to at least use matched resistors to divide the voltage. Share this post Link to post Share on other sites
tropicalrips 0 Report post Posted November 1, 2003 (edited) done up new board...still no sound... i think the op-amp is KAPUT anyway to test the amp? i hear a split second of audio when i switch it on then its gone, total silenca again i measure the (+) to ground at 7.8v and the (-) to gound is 1.2v this is not normal right? went back to the 2 batt layout and it works, but something very funny, i pull out one of the 9v and it still works is it normal, it works with (+ 9v) to ground and (- 9v) to the cap now i'm lost liao i hav double check all the resistors and they r correct, so can't figure out why it worked the first time i manage to to get it to work with 1 batt (very soft volume) just now using 1k as voltage divider, the other 4 around the op-amp is 4.7k, 2 10k as R4 based on Kenshinz drawing Edited November 1, 2003 by tropicalrips Share this post Link to post Share on other sites
jtfoo 0 Report post Posted November 2, 2003 i measure the (+) to ground at 7.8v and the (-) to gound is 1.2v this is not normal right? THis is bad. For 9V, should roughly be +-4.5V. Varies within 10% still acceptable. went back to the 2 batt layout and it works, but something very funny, i pull out one of the 9v and it still works is it normal, it works with (+ 9v) to ground and (- 9v) to the cap Very weird. I think your wiring is wrong already.. Can post a good closeup picture on your wiring? Share this post Link to post Share on other sites
ckng 0 Report post Posted November 2, 2003 done up new board...still no sound... i think the op-amp is KAPUT anyway to test the amp? i hear a split second of audio when i switch it on then its gone, total silenca again i measure the (+) to ground at 7.8v and the (-) to gound is 1.2v this is not normal right? went back to the 2 batt layout and it works, but something very funny, i pull out one of the 9v and it still works is it normal, it works with (+ 9v) to ground and (- 9v) to the cap now i'm lost liao i hav double check all the resistors and they r correct, so can't figure out why it worked the first time i manage to to get it to work with 1 batt (very soft volume) just now using 1k as voltage divider, the other 4 around the op-amp is 4.7k, 2 10k as R4 based on Kenshinz drawing You can build a circuit to test the op-amp. Tangent's site has full instructions. http://www.tangentsoft.net/audio/opamp-tester.html Regards CK Share this post Link to post Share on other sites
tropicalrips 0 Report post Posted November 2, 2003 i think if i build a test board it would make me more blur i hav trace my wiring base on the pic on tangent's test site everything looks ok, all my in & outs r in the correct place, the ground is also correct, but i'm still not 100% sure abt the values of the resistors to use, the list is confusing... what should the voltage divider resistors be? & also the (+a,-a) & (+b,- around the op-amp, the only resistor i'm sure is the R4 which is 10k Share this post Link to post Share on other sites
ckng 0 Report post Posted November 2, 2003 Can you post a pic of the under side as well? Regards CK Share this post Link to post Share on other sites
kenshinz 0 Report post Posted November 2, 2003 From the tangent site, the voltage divider resistors should be 4.7K BTW, what type of wires are you using ? The ones I got(AWG 30) keeps breaking apart, think they're too thin, and inflexible Share this post Link to post Share on other sites
tropicalrips 0 Report post Posted November 2, 2003 i'm using 3.5mm electrical wires for the jumpering, strip away the insulation and just use the copper wire, they fit nicely into the board Share this post Link to post Share on other sites
jtfoo 0 Report post Posted November 2, 2003 It seems you're using 5% carbon resistors, brown color. Your next upgrade you can try using the 1% metal film type, which is blue color. Your voltage dividers resistor appear to be correct, both 4.7K. From the picture can't tell much.. Maybe take a picture showing how your battery is connected to the board.. Share this post Link to post Share on other sites
tropicalrips 0 Report post Posted November 2, 2003 thanks Jtfoo, what abt the resistors around the op-amp? i'm using 100k, is it correct? the voltage side i'm quite sure its correct, + on the left - on the right, following the caps, both the caps and the dividers r connected to ground as well with the 4.7k dividers, i get very soft volume, almost none, tried it with 1k, volume increase, can i use 0.5k ? there is also a voltage difference between the left & right side, 2v & 7v on the other, is the op-amp causing this? Share this post Link to post Share on other sites
tropicalrips 0 Report post Posted November 2, 2003 here is pic of the under side, don't know if this can help Share this post Link to post Share on other sites
tropicalrips 0 Report post Posted November 2, 2003 (edited) here is a better pic of the front the jumpers are following the pics on Tangent's site Edited November 2, 2003 by tropicalrips Share this post Link to post Share on other sites
jtfoo 0 Report post Posted November 3, 2003 Couldn't see the color band on the other resistors. Sorry, can't tell is the layout is ok, though it looks about right. Share this post Link to post Share on other sites