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Problem with Mini3 :(
Jun 4, 2010 at 6:40 PM Post #31 of 54
Yeah... I guess it does help if I actually read a post before replying to it.
tongue_smile.gif

 
Jul 3, 2010 at 7:45 PM Post #32 of 54
So I finally (been busy/out of town) replaced the D4 diode and now all of the points to measure resistance between check out fine now. When I try to measure quiescent current draw the power LED lights up but I only get .2mA? (range is 200mA on my meter)
 
Jul 4, 2010 at 4:53 AM Post #33 of 54
Quote:
nate911 said:
So I finally (been busy/out of town) replaced the D4 diode and now all of the points to measure resistance between check out fine now. When I try to measure quiescent current draw the power LED lights up but I only get .2mA? (range is 200mA on my meter)
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I think your DMM is lying to you, because the LED alone would draw more current than that.
 
Jul 4, 2010 at 4:22 PM Post #35 of 54
Yep, multimeter was screwed up. Everything is fine now, all of the tests checked out fine. The only problem left is how to file down the slot in the Hammond case for the PCB to ground to. All of the nail files/metal files I've used are too thick to fit in the slot...
 
Jul 7, 2010 at 1:57 AM Post #39 of 54
So I got it all cased up but when I tested it...it clicked when I turned it on, pretty loud. Turns out somehow now my DC offset in my left channel is over 4V now... I guess U5 is fried. :/
 
Sep 22, 2010 at 8:32 PM Post #40 of 54
I have a problem with my mini3 as well. After the C2 capacitor exploded due to wrong walwart polarity I replaced it by another cap but now quiescent current is 0 mA.  When I turn the amp on led2 illuminates for a brief period and then fades out. I made sure battery is fully charged. Also I  have replaced U1, U2 and D4 but the problem still persists, I get 0 mA and  led2 illuminates very briefly only.
 
Sep 24, 2010 at 2:17 AM Post #41 of 54


Quote:
pterodactilo said:
I have a problem with my mini3 as well. After the C2 capacitor exploded due to wrong walwart polarity I replaced it by another cap but now quiescent current is 0 mA.  When I turn the amp on led2 illuminates for a brief period and then fades out. I made sure battery is fully charged. Also I  have replaced U1, U2 and D4 but the problem still persists, I get 0 mA and  led2 illuminates very briefly only.
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You pretty much replaced everything that could probably go bad in the Mini³ power section.  Does the amp still work on battery power?
Is there a possibility that your wallwart is bad?  Measure its output voltage.
 
Sep 24, 2010 at 4:59 PM Post #42 of 54


Quote:
amb said:
You pretty much replaced everything that could probably go bad in the Mini³ power section.  Does the amp still work on battery power?
Is there a possibility that your wallwart is bad?  Measure its output voltage.
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    Sadly no, it does not work on battery anymore since C2 failure. Reason was bad wallwart's polarity (center-negative it seems) but somehow it has affected other parts than those which were obviously damaged . So far I have replaced: C2 and U2 (these where necessary since both were physically destroyed ) and also: D4, U1, U3, U5 and U4. None of these changes made the amp to work on battery power. Symptoms are: led2 does not turn on, or it does for a few seconds at most and quiescent current is 0 mA. Voltage of battery is 7.8V.  I 've tested D4 and rectifiers with the DMM, they seem ok: D4 reads 0.842 k forward and 1. reverse (out of range in my DMM). Rectifiers : D3 0.603 k forward and 1. reverse; D2 0.582 k and 1.; D3  0.588k  and 1 . I'm afraid of  desoldering and soldering more  parts since some pads are starting to deteriorate like D4's ones on the bottom of the pcb (half of one  is gone but still makes contact witht he lane) and U4's 1, 5 and 8 . I've inspected bridges and cold joints but didn't find any obvious one.
 
 
Sep 25, 2010 at 12:12 AM Post #43 of 54
The voltage polarity problem should not have damaged the opamps or anything else because there are reverse protection diodes D1, D2 and D3.  The most likely casualties from a reversed wallwart are C2 and U2, that's it.
There must have been another problem to begin with...  Go through the initial check procedures again to see where it fails.
 
Sep 26, 2010 at 5:55 AM Post #44 of 54


Quote:
amb said:
The voltage polarity problem should not have damaged the opamps or anything else because there are reverse protection diodes D1, D2 and D3.  The most likely casualties from a reversed wallwart are C2 and U2, that's it.
There must have been another problem to begin with...  Go through the initial check procedures again to see where it fails.
Click to expand...


   I've discovered that the fuse of my DMM is broken. I guess that this is the reason why I can't read any quiescent current.
  Sanity check is ok. No shorts so far then.
  Rail spiltter check: voltage between V- and V+ is 8.6V but between V- and IG 5V, more than half. Not only that but oddly enough voltage between V- and IG does not stabilise and drops fast while I measure it: 5V, 4.9V, 4.8V ..  and goes as low as 1.14V in a a few minutes. It stabilise there more or less but keeps dropping, albeit much slower.
 DC offset voltage:  IG-OG reads 1.7mV, IG-OL 1 mV and IG-OR 0.2 mV.
I don't have the right wallwart to use with mini^3 by now so I can't do the rest of tests.
 
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