adn6244 0 Report post Posted March 29, 2008 (edited) I have just finished the cmoy from Jaben but strange thing is the amp only sound "normal" when I press the 2 pins in the yellow box with my finger. Otherwise the vocal will disappear and the music will also like not in tone or very vague. Appreciate help from the sifu here!! [attachmentid=3968] my digicam is down at the moment so the photo was taken from ahkang website...heady...apologise for not asking in advance. Edited March 29, 2008 by adn6244 Share this post Link to post Share on other sites
feesh 0 Report post Posted March 29, 2008 you mean jaben sells cmoy pcbs? Share this post Link to post Share on other sites
heady 0 Report post Posted March 29, 2008 I have just finished the cmoy from Jaben but strange thing is the amp only sound "normal" when I press the 2 pins in the yellow box with my finger. Otherwise the vocal will disappear and the music will also like not in tone or very vague. Appreciate help from the sifu here!! my digicam is down at the moment so the photo was taken from ahkang website...heady...apologise for not asking in advance. Hi adn6244, No problem re: the pic. Those two pins are pin 3 and 4 of the opamp and is one of the input and the V- pins respectively. Since I am no electronics guru, I can't tell you why touching them makes the amp works. My advice will be to check and check again that the components used are correct and placed in the right position. You need to also test if the supply voltage is correct in the opamp socket. Also after checking everything is correct, try to melt and solder at each joint again so that the solder looks shiny. Try it. And feesh, yes, Jaben sells CMOY kit, including casing. Share this post Link to post Share on other sites
feesh 0 Report post Posted March 29, 2008 I have just finished the cmoy from Jaben but strange thing is the amp only sound "normal" when I press the 2 pins in the yellow box with my finger. Otherwise the vocal will disappear and the music will also like not in tone or very vague. Appreciate help from the sifu here!! my digicam is down at the moment so the photo was taken from ahkang website...heady...apologise for not asking in advance. adn6244: i myself am new to this field of amp building, but i do have some knowledge on opamps when i was studyiong physics. haha. i may not know the exact problem you're facing but it seems like your V- is not properly grounded. if you look at the cmoy schemetics, V- is connected to the ground after R3, 1Kohm resistor. and since touching the pins = grounding, that could be the problem. try just touching the V- pin, if it solves the problem, then thats probably the reason. Probably try using a wire to connect it to your enclosure if its made of metal. hope this helps. forgive me if it doesnt. Share this post Link to post Share on other sites
adn6244 0 Report post Posted March 29, 2008 feesh..I got the whole set of cmoy pcb, components, casing all in from Jaben. feesh and heady, thanks for the reply but I am going to ask a really stupid question here...which one is v-pin? I have interest in diy but I have limited knowledge in electronics but will try to pick up as much as I can along the way!! Share this post Link to post Share on other sites
alamakazam 0 Report post Posted March 29, 2008 schematic, front component photo and opamp datasheet is useful for troubleshooting Share this post Link to post Share on other sites
blippster 0 Report post Posted March 29, 2008 adn6244, I found the same problem with the vocals disappearing on one I assembled on a bare board. Managed to solve it by grounding the input/output jacks properly. Just a thought, you might want to check those areas especially, out of everything heady mentioned. Share this post Link to post Share on other sites
feesh 0 Report post Posted March 29, 2008 feesh..I got the whole set of cmoy pcb, components, casing all in from Jaben. feesh and heady, thanks for the reply but I am going to ask a really stupid question here...which one is v-pin? I have interest in diy but I have limited knowledge in electronics but will try to pick up as much as I can along the way!! V- pin is the one on the right in the yellow box. (: Share this post Link to post Share on other sites
adn6244 0 Report post Posted March 29, 2008 has to touch both pins in yellow box to get the "right" output will try to desolder-resolder the input/output jack tomorrow.. the battery wire broke when i was trobleshooting and just managed to rewire it after spending few hours to remove the residual.... will try to post photo later... Share this post Link to post Share on other sites
heady 0 Report post Posted March 29, 2008 has to touch both pins in yellow box to get the "right" output will try to desolder-resolder the input/output jack tomorrow.. the battery wire broke when i was trobleshooting and just managed to rewire it after spending few hours to remove the residual.... will try to post photo later... I don't think it is due to the input/output jack, if touching pin 3 and 4 makes the amp works. The amp should work without problem, IF you have used all the correct parts in the correct positions. And the soldering is ok. BTW - what opamp are you using? Regards Share this post Link to post Share on other sites
adn6244 0 Report post Posted March 29, 2008 opamp 833...not sure if this is the problem. I thought this opamp should have been changed by jaben but I was given this opamp when I bought the unit approx 2 weeks ago. I don't have other opamp to test so not sure it is giving the problem. I tested the voltage, it's less than 20mV so it didn't blow my cheap earphone. Although this test is not conclusive of whether the opamp is working or not!! Share this post Link to post Share on other sites
adn6244 0 Report post Posted April 21, 2008 I spend some time troubleshoot desolder and test and test until one fine day...... I wanted to force out the Dip socket and resolder...and pull out 2-3 small rings on the pcb Went jaben and bought another set and spend few hours to prepare and finally soldered the working cmoy Now will move on to the m3 soon ...very soon .. Share this post Link to post Share on other sites
heady 0 Report post Posted April 21, 2008 Now will move on to the m3 soon ...very soon .. I salute you man. From cmoy to M3. That's quite a jump. Share this post Link to post Share on other sites
alvin1118 0 Report post Posted April 21, 2008 agreed with heady, big jump from cmoy to M3! Share this post Link to post Share on other sites
adn6244 0 Report post Posted April 22, 2008 Oh...I made a mistake it's Mini3 Me not ready for M3 yet!!! I also ordered the jdslabs cmoy to test but they are still with vpost now Share this post Link to post Share on other sites
