johnny5 Posted January 1, 2009 Report Share Posted January 1, 2009 So I burnt up the holes at j3 when trying to desolder the sil header, to replace it with a polar header type. So I tried j4 as a 15v input. It seems that these connectors are the same? Well I powered it up and at pin 4 I'm getting +17.77? And at pin 11 I'm getting -12.7? I recheckex my psu and it was at 15v? Now I'm completly baffled? How could this be possible? When the aout is run off a 12v supply you should get +12/-12. Any help would be great! Quote Link to comment Share on other sites More sharing options...
seppoman Posted January 2, 2009 Report Share Posted January 2, 2009 J3 and J4 are the same, J4 is only for convenience, e.g. to supply a VCF module like the ssm2044. You can use it as an input, too.Your strange voltage levels are still about 30 V in total so I guess you've got a problem with GND reference level. Did you connect the GND of your bipolar supply, too? As long as bipolar and "regular" core GND are both connected to the NG (i.e. are interconnected), the voltage levels should be alright. Only question is why there's a difference of a few volts between the GNDs, so maybe you should make sure that there's no current flowing between the two GNDs (to check, disconnect one of the two GNDs from the NG, set your multimeter to current mode (A) and make that connection via the two probes).BTW, if you intend to use some CV outputs in bipolar mode while powered from +-15V, you should read this:http://www.midibox.org/forum/index.php/topic,10907.msg84344.html#msg84344S Quote Link to comment Share on other sites More sharing options...
stryd_one Posted January 2, 2009 Report Share Posted January 2, 2009 That's what I thought: +5V is connected to analog ground somewhere. Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 2, 2009 Author Report Share Posted January 2, 2009 J3 and J4 are the same, J4 is only for convenience, e.g. to supply a VCF module like the ssm2044. You can use it as an input, too.Your strange voltage levels are still about 30 V in total so I guess you've got a problem with GND reference level. Did you connect the GND of your bipolar supply, too? As long as bipolar and "regular" core GND are both connected to the NG (i.e. are interconnected), the voltage levels should be alright. Only question is why there's a difference of a few volts between the GNDs, so maybe you should make sure that there's no current flowing between the two GNDs (to check, disconnect one of the two GNDs from the NG, set your multimeter to current mode (A) and make that connection via the two probes).BTW, if you intend to use some CV outputs in bipolar mode while powered from +-15V, you should read this:http://www.midibox.org/forum/index.php/topic,10907.msg84344.html#msg84344Sthanks for all the info! first i should mention that im slipping and had my ng interconected to the core via core j6 that is used for the mbsid. i originally had it hooked up through j10 and my lcd or the ng wouldnt light(i honestly thought that maybe i had old documents). then for some reason i seen the mbsid interconnect diagram and thought that it was ok for the mbcv(i cant remeber why i thought that was a good idea?). so all testing was done with j6 from the core. ok with that out of the way, i do have GND from the analog psu connected at j4 to the ng. Im currently away from home till tomorow. but im almost sure that there is a GND from j6 of the core. anyways im going to make a new interconnect cable for j10 of the core to j1 of the ng and hopefully it will light light up! so after i re do my interconnects correctly im going to recheck my voltage at pins4 and 11, hopefully that will do the trick. if not i will be disconnecting the analog GND and measuring MA across the 2 GNDs. i will report back with the progress!!and thanks for the link about bipolar mode i actually dont have any gear that use negative voltages yet but im sure it will be in the +5v/-5v range. what really stinks is my desoldering skills and to beat up these really nice boards its such a shame. wish i had read that before i assembled my board! Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 3, 2009 Author Report Share Posted January 3, 2009 ok so I just got the chance to take a look at it. Now I'm powering up fine with 5v from j10(I must have made a bad cable the first time). But I am still reading +17/-12. So I first tried to disconnect the dinx1 just to make sure the short wasn't there. Then again +17/-12. So I disconnected the analog gnd from the ng board set my dmm to current at 200ua and measured in between gnd on my analog psu and gnd at j6 of the core, and I came up with -115ua. Ugh so I guess there is a short some where? Dose anyone have an easy way to narrow this down? Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 4, 2009 Author Report Share Posted January 4, 2009 i havnt been able to stop thinking about it, and i am thinking that i need to pull the ng print the schematic highlight all components and connections dealing with +5v on the ng then look for continuity across them and analog gnd. Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 8, 2009 Author Report Share Posted January 8, 2009 ok so while checking continuity across vcc at j1 of the ng board to all GND and AGND connections, i did not find a straight continuous path any where. but i did notice that at most points my dmm would want to make a sound and it was reading 520? so i tried an ohm reading (not really knowing if this matters) i found that there is 41.6k resistance from the vcc at j1 to all AGND and GND on the board? this is racking my brain. ??? Quote Link to comment Share on other sites More sharing options...
seppoman Posted January 8, 2009 Report Share Posted January 8, 2009 i found that there is 41.6k resistance from the vcc at j1 to all AGND and GND on the board?that should be fine - I didn't measure how high the resistance across the supply is but if you'd get a continuity there you'd have a short on the supply rail and the LED wouldn't light up.Also, a current of some uA (micro-A, not milli-A, right?) between both grounds is nothing to worry about.Do you get symmetrical (analog) voltages if you connect only J4, i.e. without connection to the core?S Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 9, 2009 Author Report Share Posted January 9, 2009 ugh >:( I have a short from + to - somewhere can't beleive I didnt notice this already. Wish me luck finding it and I will report back with the progress. Quote Link to comment Share on other sites More sharing options...
stryd_one Posted January 9, 2009 Report Share Posted January 9, 2009 I have a short from + to - somewhere can't beleive I didnt notice this already.Especially since you've been told at least twice ;)+5V is connected to analog ground somewhere.you've got a problem with GND reference level. Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 9, 2009 Author Report Share Posted January 9, 2009 :o ok so it wasnt as bad as i thought. i was checking mta cables i had made up with a old analog meter i have. then 20 mins later there i am checking my ng with the same analog meter, and i noticed that i was continuity from + to - on my analog input. i honestly thought i had checked that already but i cant really remeber now. so anyway i went crazy reflowing joints checking continuity all over the thing and just when i was about to bash my head into the wall my old analog meter breaks. the cable pulls apart from the probe. i was about to chuck it against the wall and take some time away from the whole thing. then i calmed down and grabbed my reliable dmm. come to find out i was not getting full continuity across + to -...any way long story short all voltage test afterwards read fine. leson learned never trust a analog meter reading close to 0 for continuity. sad part is i will never really know exactly where the short was. :Pthanks for the help fellas much appreciated!!! Quote Link to comment Share on other sites More sharing options...
stryd_one Posted January 9, 2009 Report Share Posted January 9, 2009 Awww poor meter :( What a stress!Glad it's behaving now. Do the dance! Do the dance! Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 15, 2009 Author Report Share Posted January 15, 2009 ok so like i said all was good....pins 4 and 11 of the 2 ic sockets where both reading +15 -15.(by the way im constructing a new +/-12v supply as we speak instead of changing resistors for 15v bipolar operation) i dropped in 2 tl074's powered it up rechecked power everything was fine for a minute then i was getting -30v at pin11 and .5v at pin4. thinking maybe the tl074's where bad i switched them out and tried some fresh ones, and the same thing. only this time i bumped pin10 there was a tiny visible short i powered down. pulled the tl074's and tossed the one. then rechecked voltages everything was fine. i was still reading 'ready' on my lcd then it began to flicker.new little problem one of my wires broke on my ribbon-cable to lcd(led+). no biggie quick re-solder, power on, core is 'ready', connect to ng to core i get no display. i mess with the contrast and i get top row blocks? i have searched all over the board for info but most info on the top row of blocks is pre bootstrap? now im scared i fried my DAC? maybe i still have a short somewhere on my aout? i might have another 20mins in the next hour to take a look at it i hope. Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 16, 2009 Author Report Share Posted January 16, 2009 LCD issue solved I think it was becuase I didnt have my pannel strapped down to GND. Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 16, 2009 Author Report Share Posted January 16, 2009 ok latest test dropped in two new tl074's and I read 0 on pins4 and 11 and my regulaor at the core got alittle warm. Nothing else is though. :P Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 21, 2009 Author Report Share Posted January 21, 2009 so i had some time today gave another once over.... what i noticed was that pin3 of ic3 is shorted to the flood somewhere? i removed all the solder from ic3 joint and the connected jumpers joint? i couldnt find any other shorts to the flood anywhere? Quote Link to comment Share on other sites More sharing options...
seppoman Posted January 21, 2009 Report Share Posted January 21, 2009 IC3 pin 3 comes directly from the DAC when the jumper for channel 3 is set to unipolar mode (one jumper horizontally). You mean there's a short to GND, right? Is it present if you remove IC3 and the channel 3 jumper? If not, maybe the short is located around the DAC. If yes, maybe while soldering you've damaged the green protective laquer somewhere and made a connection with a large tin blob? If you don't find the short yourself, maybe you could post some hi res pics of your board?S Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 22, 2009 Author Report Share Posted January 22, 2009 IC3 pin 3 comes directly from the DAC when the jumper for channel 3 is set to unipolar mode (one jumper horizontally). You mean there's a short to GND, right? Is it present if you remove IC3 and the channel 3 jumper?Swith ic3 and the jumper removed i was getting continuity from ic3 to the bottomside copper flood surround section.If not, maybe the short is located around the DAC. If yes, maybe while soldering you've damaged the green protective laquer somewhere and made a connection with a large tin blob? If you don't find the short yourself, maybe you could post some hi res pics of your board?Sif the short is under ic3 or the header maybe? i could probally get better photos and also keep in mind as of right now the board needs a once over (removed alot of solder for trouble shooting), solder and cleaning. Quote Link to comment Share on other sites More sharing options...
seppoman Posted January 22, 2009 Report Share Posted January 22, 2009 did you also measure with the jumper completely removed (not only turned sideways)? With Jumper and IC3 completely removed, the marked trace should not be connected to anything.which place of bottom gnd pour did you measure against? the gnd pour on the analog side (right) is normally not even connected to anything, so the problem can only be on the bottom side if more than one solder joint makes connection to it. Make sure that none of the solder joints touch it (normally that's no problem but maybe you've damaged the laquer somewhere). Especially resolder both joints on that marked trace.A problem on that trace occurring on the top side isn't very likely, the tin normally doesn't go through the holes in large amounts.J3 also looks dangerous. I can't really see what's happening there due to image resolution, but try to remove all solder on top and bottom side, looks a bit like you have some interconnection there.S Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 22, 2009 Author Report Share Posted January 22, 2009 did you also measure with the jumper completely removed (not only turned sideways)? With Jumper and IC3 completely removed, the marked trace should not be connected to anything.this is exactly what i did. i put the jumper in sideways just to 'mark it' after testing. which place of bottom gnd pour did you measure against? the gnd pour on the analog side (right) is normally not even connected to anything, so the problem can only be on the bottom side if more than one solder joint makes connection to it.i was measuring against the right side/analog. actually when you said that it is a GND pour i got really worried its not connected to anything except pin3 of ic3 and the connecting jumper pin.. Make sure that none of the solder joints touch it (normally that's no problem but maybe you've damaged the laquer somewhere). Especially resolder both joints on that marked trace.this is exactly what i was worried about so i checked continuty across all solder points and the right pour and only found the short at ic pin3. i may have went alittle fast at it maybe i need to go over again...J3 also looks dangerous. I can't really see what's happening there due to image resolution, but try to remove all solder on top and bottom side, looks a bit like you have some interconnection there.Sj3 is a complete mess im ashamed of myself :P one of these days i need to go pickup a real desoldering tool. i will go into it with the wick some more and try to get everything out of it. if this is the spot where the laquer is damaged and the traces are interconnected i hope i can get around it. i would just like to say thanks for taking time in helping me with troubleshooting this. Quote Link to comment Share on other sites More sharing options...
seppoman Posted January 23, 2009 Report Share Posted January 23, 2009 i was measuring against the right side/analog. actually when you said that it is a GND pour i got really worried its not connected to anything except pin3 of ic3 and the connecting jumper pin.What I meant to say was: the "gnd pour" on the bottom side, analog section (right hand on your pics), shouldn't have connection to ANYTHING, i.e. including GND, it's just there for a little shielding but has no function. But if you damaged the solder mask laquer and made connection to it on more than one occasion, it could be responsible for a short, too.Anyway, maybe try to resolder a few things and carefully inspect the whole area around the jumpers and IC3 under a good light and maybe a magnifying glass. Keep trying to solve that problem with removed jumper and IC3. If you can't find anything, you could try removing the IC socket or the jumper headers, although desoldering on double sided PCBs is never easy and your J3 doesn't exactly make you look like an expert in that field ;). A way to check at least one place from above without risking to damage the PCB is to remove only the black plastic from the jumper headers. Normally you can move that plastic if you're patient and maybe heat up the pins a little.S Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 23, 2009 Author Report Share Posted January 23, 2009 haha... you know whats funny is i learned this on j3. i tried to remove the sil header to put in a mta type header. brutalized it then figured i could just pull up the plastic and replace it with the snap in type. the only thing is the pins are still alittle small. goes to show live and learn or take some time out think and re think... Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 29, 2009 Author Report Share Posted January 29, 2009 ok had some time to go over stuff today and..... :Pc5 is shortedc4 shortedc3 shortedi guess this is why i have +5v to GND? im really curious if my dac is fried? i never left it on for over 5 seconds. Quote Link to comment Share on other sites More sharing options...
johnny5 Posted January 29, 2009 Author Report Share Posted January 29, 2009 also what could have shorted all of them at the same time? Quote Link to comment Share on other sites More sharing options...
seppoman Posted January 29, 2009 Report Share Posted January 29, 2009 how did you test that? If the caps were desoldered for the test - no idea. if you're measuring continuity on them while they're still on the PCB that means you've got a short between 5V and GND.S Quote Link to comment Share on other sites More sharing options...
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