ieatmumble Posted February 3, 2010 Report Share Posted February 3, 2010 (edited) Hey everyone, so i finished soldering my sammichSID about two weeks ago and after soldering everything and the voltage tests (everything was perfect) i had to take a break from it. This might be important so i have to say that after the tests i installed the ICs and then left it alone for two weeks. Today i got some time so i set up everything and when i turn it on so i can upload the firmware..bam..nothing happens, not even the LCD or anything. So i check the voltages again and everything is dead in the water. I'm not very good at this but my instincts tell me there's something wrong with the bridge rectifier as i get these voltages: Any ideas? Should i check something else and if the bridge rectifier is broken can i replace it with a 1,5A/1000V peak one as i couldn't find an identical one on the local online shops i found these which seem to be pretty close. Thanks a lot for everything, Dan. Edited February 3, 2010 by ieatmumble Quote Link to comment Share on other sites More sharing options...
nILS Posted February 3, 2010 Report Share Posted February 3, 2010 Everything was fine until you put the ICs in - that hint towards an IC put in the wrong way around. Do you get the correct voltages when you remove the ICs again? What PSU are you using? From your measurements it looks like 12VDC. Are you _sure_ you haven't changed _anything_ else? Quote Link to comment Share on other sites More sharing options...
ieatmumble Posted February 4, 2010 Author Report Share Posted February 4, 2010 Everything was fine until you put the ICs in - that hint towards an IC put in the wrong way around. Do you get the correct voltages when you remove the ICs again? What PSU are you using? From your measurements it looks like 12VDC. Are you _sure_ you haven't changed _anything_ else? I removed the PIC and the ICs and i still get no readings except on the bridge rectifier from what i see. And i triple-checked the position of the ICs and the jumpers so i really don't think there was something wrong there. The PSU i use is a regulated 12VDC one indeed. Quote Link to comment Share on other sites More sharing options...
nILS Posted February 4, 2010 Report Share Posted February 4, 2010 Since you have voltage problems, you do NOT put any ICs back on the board until you have fixed them. The bridge rectifier is really hard to kill, so I am not sure how you'd break that. Check for shorts between GND and the supply rails. Quote Link to comment Share on other sites More sharing options...
Wilba Posted February 4, 2010 Report Share Posted February 4, 2010 I don't think the bridge rectifier is dead. Compare your measurements: with mine: The fact that you're getting "around 12V" on the ground pin of the bridge suggests your black lead of the multimeter is not also on ground, which it should be so you can actually get meaningful results. I can't tell now what "around 12V" means because it's "around 12V" above something. Take measurements again with the black lead of the multimeter on the ground pin always.... EXCEPT when you want to check polarity/voltage of the input power, then measure with black lead on "input (-)" and red lead on "input (+)"... with power switch on, it should be the same as measuring it from the plug. Note also that the 0.22V value suggests you also have not put shunts in JBP, which you need to do if you're using regulated 12V DC and want to use 6581 SIDs. If you are not using 6581 SIDs, then you don't need shunts in JBP. As you can see from my pic, adding the shunts will short two of the diodes inside the bridge rectifier, so that you don't lose 1.6V and thus the SIDs will get the full 12V coming from the input. HOWEVER for that to work, the input power needs to be tip positive (+) otherwise the other two diodes will be used to reverse the polarity and you will only get 10.4V. Send more measurements and I can help you more. Quote Link to comment Share on other sites More sharing options...
ieatmumble Posted February 6, 2010 Author Report Share Posted February 6, 2010 (edited) Hello, sorry for the late reply. First of all i'm planning to use 6582A SIDs so i have no header in JBP. So..i edited the image in the build guide to illustrate my measurements (all measurements in this image were made with the black lead on the ground pin at the bottom near C4) : green is 0V orange is 0,39 to 0,47 (it increased in about 20 minutes but all the orange values were the same at a given time. i took another measurement after about half an hour and it was 0,6V) Regarding the bridge, i made 2 measurements. One with the black lead in the ground point near C4, the other with the black lead on the output (-) pin marked in the picture in the post above. Here are the values: A thing that i find weird is that after 15 minutes of measurements i removed the power supply and now after 20 minutes i still get the orange values with the switch button in either of the two positions (by this i mean with the switch on and off). Another thing that i find worrying is that when measuring the voltage of the power supply, i get 12,7V. Thanks a lot for everything, Dan. Edited February 6, 2010 by ieatmumble Quote Link to comment Share on other sites More sharing options...
Wilba Posted February 8, 2010 Report Share Posted February 8, 2010 I'm a little bit puzzled by the second set of bridge rectifier measurements, since if the black lead is on ground near C4, then it should be the same as the first set. The first set of bridge rectifier measurements look OK. What I also don't understand is how you are not seeing the 11.96V at the "orange" dot positions, since the bridge rectifier "+" output should be directly connected to the 7809 voltage regulator input (where you marked with orange dot) and also the other places you marked with orange dots. These should all be roughly 12V (i.e. what the bridge rectifier outputs). Maybe you have a short to ground somewhere around the bridge rectifier or the "12V" pins... maybe even heatsink compound or the heatsink is shorting pins of the 7809 voltage regulator. Without ~12V going into the voltage regulator, you won't end up with 9V or 5V, as the voltage regulators can't work. So... first check if the bridge rectifier "+" output is connected to the 7809 input (you can see the trace going between them on the top side). If it's connected (~0 Ohms resistance), then it's maybe a short between 12V and ground. I don't want to suggest taking out the 7809/7805 just yet, but it might be required as part of working out where it might be shorting. Can you please retest the values on the bridge rectifier with black lead on J2:GND (near C4), and ALSO J20:GND (near 7809) and take care to put the lead on the correct pin, they are the ones without a dark circle around the pad, since the pad is connected to the ground plane. Check also the resistance between the 12V pins (aka. "orange" dots in YOUR picture) and various GND pins. Quote Link to comment Share on other sites More sharing options...
ieatmumble Posted February 10, 2010 Author Report Share Posted February 10, 2010 Ok..so i retested the values: Step I (power supply not connected): Step II (power on): as you can see on step II the voltage on the bottom right pin already started increasing (it's not a difference between J2 and J20 ground). Eventually after 30 minutes or so it was going around 0,7V. The voltage in the orange dots is the voltage that i measure on the bridge rectifier's output (+) when using the ground on J2 or J20 (or J4/J6/J7, etc) so the bridge rectifier "+" output is connected to the 7809 input. Also the resistance between those points is 0,5 Ohms. The same resistance between the 12V pins and other ground pins. The thermal paste that i use is bought from an electronic parts shop and it's silicon based. I believe it's either this one or this one so i don't think that's the problem although i have to admit, the paste was touching all 3 legs of the 7809 voltage regulator (cleaned most of it now with some toothpicks and some cotton wool). As i said before..the funny thing is that the voltages were great two weeks before. Thanks a lot for all the help and making me feel there's still a chance to hear it someday :D, Dan. Quote Link to comment Share on other sites More sharing options...
nILS Posted February 11, 2010 Report Share Posted February 11, 2010 Was the thermal paste incident between it working and it not working? Quote Link to comment Share on other sites More sharing options...
ieatmumble Posted February 11, 2010 Author Report Share Posted February 11, 2010 Was the thermal paste incident between it working and it not working? It was like that during the period in which it worked and after, until i cleaned it up a bit two days ago. I noticed it there but i didn't think it was a problem since it was silicon-based. Quote Link to comment Share on other sites More sharing options...
nILS Posted February 11, 2010 Report Share Posted February 11, 2010 0.5Ohms between +12V and ground is bad. There's a short somewhere. I guess this is where you quintuple check every solder joint and then start to remove parts until the short is gone. I'd start removing the 7809 as it's a central point in the PSU part. Quote Link to comment Share on other sites More sharing options...
ieatmumble Posted February 13, 2010 Author Report Share Posted February 13, 2010 Hello, i have to leave town for a while but when i will be back i will start rechecking everything, eventually i'll start removing parts. The period is about two weeks..just like the first time..maybe everything will repair itself :D Thanks a lot, Dan. Quote Link to comment Share on other sites More sharing options...
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