l0calh05t Posted July 2, 2006 Report Share Posted July 2, 2006 Ok, i just soldered everything onto the board and went on to the step where i check the voltages. 0V practically everywhere except directly at J1, where i get the 9V dc from my psu. trying to find out whats wrong myself i also found a voltage of 0.5V between pins 1 and 2 of the 7805, and a resistance of 1.5MegaOhm or just a few depending on polarity between two of the pins of the rectifier and infinite resistance between all other pins of the rectifier, regardless of polarity. what's wrong? did i fry the rectifier during soldering, or the 7805, or is it something completely different?edit: just in case it matters, it's one of the old core boards, with the quartz on the bottom Quote Link to comment Share on other sites More sharing options...
Shum Posted July 2, 2006 Report Share Posted July 2, 2006 Hi,The voltage at J1 is where the power supply is connected. In your case you measured 9V. This is ok. You mentioned you got only 0.5v a between pin 1 and pin 2 of the 7805. This seems to me that you may have wired the rectifier X1 incorrectly. Are you using 4 diodes or just unit with 4 leads. Make sure you follow the schematic and wire the diodes correctly. Disconnect pin 1 of the 7805 and with no power applied to J1, use an ohm meter to measure the positive (+) and the negative (-) line, (positive lead of meter red colour) to the (+) side, you should get some reading in k ohms and almost infinity if the leads were reversed.RegardsShum Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 2, 2006 Author Report Share Posted July 2, 2006 i used a unit with four leads, and it is on the board just as it is supposed to according to the schematic. how am i supposed to disconnect pin 1 without removing the 7805 completely? ??? Quote Link to comment Share on other sites More sharing options...
Shum Posted July 3, 2006 Report Share Posted July 3, 2006 Hi,On the rectifier unit (with 4 leads) two of them are marked (+) and (-) and the other two are not mark or marked as AC. Before you remove the 7805, use your ohm meter to measure the terminals on J2, there should not be a short circuit (zero ohm). I also attached a a drawing to help you troubleshoot. If all things failed, then remove the 7805 and do the measurement again. Hope this will help.Best of luckShumpsu.JPG Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 3, 2006 Author Report Share Posted July 3, 2006 well, as i mentioned it is mounted exactly as it is supposed to with the + the - and the two ~ leads at the same place as shown in the schematic. between the + and the - (with 7805 mounted) there is a resistance of infinity, regardless of polarity, as mentioned in the first post, and where the voltage is marked 9v behind on your drawing is where i measured 0.5V (between 1 and 2 of the 7805) and where there should be 5v i measured 0. between the pins of J1 i measured an infinite resistance (or at least larger than 2MegaOhms, which is the highest my multimeter can measure) and between the two pins of J2 a resistance of 10.5kOhm.EDIT: I re-measured the + and - of the rectifier and although it displays infinity, when i switch polarities it displays a non-infinite resistance for a short moment, but i'm pretty sure i just charged the caps with my multimeter :P Quote Link to comment Share on other sites More sharing options...
docbrown Posted July 3, 2006 Report Share Posted July 3, 2006 Try removing the 7805 and apply power to it and check if you get any voltage from the pins that you've mention. It should read 9VDC. Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 3, 2006 Author Report Share Posted July 3, 2006 yeah, i was pretty sure 9vdc is what i was supposed to get. well, gotta get some unsoldering wick to get that damn thing out... Quote Link to comment Share on other sites More sharing options...
docbrown Posted July 3, 2006 Report Share Posted July 3, 2006 yeah, i was pretty sure 9vdc is what i was supposed to get. well, gotta get some unsoldering wick to get that damn thing out...By removing that regulator will prove two things. If you get 9vdc, your rectifier is good and your 7805 could be bad (internal short). If no voltage at those points, your 7805 is good and your rectifier is then could be bad.hope this helps... Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 3, 2006 Author Report Share Posted July 3, 2006 [...]If no voltage at those points, your 7805 is good and your rectifier is then could be bad.hope this helps...or both are bad... considering my usual luck with these things this is probably what will have happened...i hope so too, now i just have to see how i manage to unsolder the 7805... Quote Link to comment Share on other sites More sharing options...
docbrown Posted July 3, 2006 Report Share Posted July 3, 2006 Don't you wish you have one of these: http://www.howardelectronics.com/goot/tp100as.html Instead of the wick... Coz, I drooling all over this tool... its too pricey for my taste..I can only afford this tool: http://www.radioshack.com/sm-45-watt-desoldering-iron--pi-2062731.html At least this works... Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 3, 2006 Author Report Share Posted July 3, 2006 sure i'd like to have one of those, but i currently have just about enough cash to buy a roll of unsoldering wick... Quote Link to comment Share on other sites More sharing options...
Shum Posted July 3, 2006 Report Share Posted July 3, 2006 Hi,I hope you have some luck with the power supply. I attached there snapshot of the core layout and a cheap device that I use to desolder by sucking out the molten solder.RegardsShum Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 5, 2006 Author Report Share Posted July 5, 2006 ok i managed to desolder the 7805, or rather to desolder it a bit as the wick practically didn't seem to remove anything and tear it out. if it wasn't broken before i'm pretty sure it is now, considering how hot it became during the process and how hard i had to pull on that thing... >:(now, i conntected the psu, and checked the voltage between the + and the - pins of the rectifier. it seemed to fluctuate between 1 and 2 volts (the fluctuating may be the multimeter though as it's on of those sucky cheap ones) so yeah, i guess the retifier is fubar. (and probably the 7805 as well, and if not i don't know how i would manage to get it back in...)and with my luck i probably fried the single diode and the transistor as well Quote Link to comment Share on other sites More sharing options...
Shum Posted July 5, 2006 Report Share Posted July 5, 2006 Hi,You conntected the psu, and checked the voltage between the + and the - pins of the rectifier and the voltage fluctuates between 1 and 2 volts, it would seem that the rectifier is either connected incorrectly or the rectifier is no good. Try us the AC scale of the multi-meter to measure the + and the - pins of the rectifier again. If you got a higher voltage, then it is connected the wrong way round. Try buy one of the sucking devices shown in the picture in my pervious posting, it will help very much to desolder component from circuit board. Radio shack sells them.Shum Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 5, 2006 Author Report Share Posted July 5, 2006 the only way the rectifier could be connected wrong is if the writing on the rectifier is wrong, and as i mentioned, i think the fluctuating is the multimeter (it also fluctuates between 8.5 and 9.5 volts when directly at J1, and also fluctuates when i check a resistor by itself, as i said: its a piece of junk)well i have another one of those rectifiers lying around (for the SID board, but there's no point in starting to build that before i get the core in working order) so i might just try to replace the current one this evening and hope not to break that one as well... Quote Link to comment Share on other sites More sharing options...
docbrown Posted July 5, 2006 Report Share Posted July 5, 2006 Good luck.. I still think a desoldering tool is a good investment. It is easy to pull out components with it without over heating the traces that can damage the PCB.Not sure if you have an Oscilliscope because here is SmashTV's power supply check point guide. http://www.avishowtech.com/mbhp/ps/Hope it helps.. Quote Link to comment Share on other sites More sharing options...
Shum Posted July 5, 2006 Report Share Posted July 5, 2006 Hi,Perhps a little tip to clear the hole of solder on the soldering pad. Melt the solder on the pad quickly at the same time use a fine tooth pick to poke through the melted solder leaving a clear through hole.Shum Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 5, 2006 Author Report Share Posted July 5, 2006 Good luck.. I still think a desoldering tool is a good investment. It is easy to pull out components with it without over heating the traces that can damage the PCB.Not sure if you have an Oscilliscope because here is SmashTV's power supply check point guide. http://www.avishowtech.com/mbhp/ps/Hope it helps..i have 25€ on my bank account, 15 of which will be gone in a few days and 5€ in my pocket... so any investments are currently not an option...nope, don't have one, although i wish i did, so if anyone wants to donate one to me i'd gladly accept :P Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 5, 2006 Author Report Share Posted July 5, 2006 one word... it starts with an f and ends with a k...i just removed the rectifier put in the one i had lying around and it conducts just fine between + and -... regardless of polarity. and i double, and triple checked for any solder going across two lanes... nothing.i think this is my first and last real diy electronics project. i guess i should stick with soldering my own audio cables. Quote Link to comment Share on other sites More sharing options...
smashtv Posted July 5, 2006 Report Share Posted July 5, 2006 i just removed the rectifier put in the one i had lying around and it conducts just fine between + and -... regardless of polarity. and i double, and triple checked for any solder going across two lanes... nothing.Keep in mind you are testing it in circuit, meaning your meter is showing you the continuity of everything connected to the bridge rec, not just that one part......ceramic caps usually show as shorted or very low resistance, etc. so the path you are seeing on the meter is probably not the bridge rec.i think this is my first and last real diy electronics project. i guess i should stick with soldering my own audio cables.You give up too easily.....this statement says you are not willing to learn, and I doubt that is true else you would not be here. :)I am still learning (and forgetting!) all the time after all the years.Back to the kit mill......BestSmash Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 5, 2006 Author Report Share Posted July 5, 2006 Keep in mind you are testing it in circuit, meaning your meter is showing you the continuity of everything connected to the bridge rec, not just that one part......ceramic caps usually show as shorted or very low resistance, etc. so the path you are seeing on the meter is probably not the bridge rec.hm, well there *is* that huge electrolytic cap right there where i was measuring... and charging that thing via my multimeter might actually take a looong time...You give up too easily.....this statement says you are not willing to learn, and I doubt that is true else you would not be here. :)I am still learning (and forgetting!) all the time after all the years.Back to the kit mill......BestSmashnah, that statement just says i'm currently pretty fed up with circuits that don't work (and i never had that problem with my cables, those all lasted longer than any commercial one i bought, and the one that did break after two years of stage and practice (ab)use was really easy to repair)... ah, doesn't matter, in a few hours i'll be dreaming of building my own preamps, equalizers, compressors, microphones and synths again ;D EDIT: hohoho, i just measured the voltage across that cap .5V which is a pretty good sign that its probably charged (at least partially). hey, i'm beginning to feel better already! now i have some hope again that this thing might actually even work in a few weeks time. Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 5, 2006 Author Report Share Posted July 5, 2006 hrmm, i just connected it to the psu once more, and the voltage i measured behind the rectifier is now 0.9V, this can't be right... or is it? Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 6, 2006 Author Report Share Posted July 6, 2006 so, what to do now? are the 0.9V correct? should i get a new 7805 or is it a waste of my time? anyone? ??? Quote Link to comment Share on other sites More sharing options...
docbrown Posted July 6, 2006 Report Share Posted July 6, 2006 so, what to do now? are the 0.9V correct? should i get a new 7805 or is it a waste of my time? anyone? ???If you have a breadboard (http://en.wikipedia.org/wiki/Breadboard), you could build or test your components in stages.1. Install the bridge rectifier first and apply power = if 9v is present goto next step.2. Add capacitors = if 9v is present goto next step.3. Add the regulator (7805) and so on... I'm sure you got the picture.I know you might say, here he goes again suggesting another tool/equipment. Unfortunately, having the right tools make it more fun ;D as suppose to be a chore. This rule apply's to just about any hobby out there. Quote Link to comment Share on other sites More sharing options...
l0calh05t Posted July 6, 2006 Author Report Share Posted July 6, 2006 it's not as if i didn't want all that equipment... there are many things i want... an oscilloscope (+ signal generator), a nice lab psu, a GOOD multimeter, a CNC machine, heaps of components for experiments... and i could go on and on... Quote Link to comment Share on other sites More sharing options...
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