Re: Apple M8536, Inverter cap replacement question.
Yes, I'm hoping it's one or the other or both of the caps are causing the issue. Knowing my luck it probably isn't though. Anyway thanks!
Xandros
Senior Member
Last Activity: 08-12-2017, 06:25 AM
Joined: 12-25-2014
Location: London
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Apple M8536, Inverter cap replacement question.
Hey. I've revisited a 23" Cinema HD Display I had issues with and have narrowed down the problem to the inverter board. It's essentially a 2 seconds to black issue as detailed in the sticky thread, though I've followed several of the tests in that and not come up with any obvious issues.
The only thing I haven't been able to test are the two caps on the board, as I don't have any of the equipment to do so. The two caps however, are Teapo:
[ATTACH]159499[/ATTACH]
[ATTACH]159500[/ATTACH]
I've been lead to believe from what I've read on here... -
Re: M-Audio GSR18 speaker, powers on but no sound.
OK so, after another lengthy absence I've finally done the tests you suggested.
Resistance between pin 1 and gnd is 3.270kΩ and pin 2 and gnd is 2.950kΩ
I tested the voltage of those caps, one reads aprox 20v the other is approx 19v.
Cheers.Leave a comment:
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Re: M-Audio GSR18 speaker, powers on but no sound.
Hello, sorry for the extremely late reply. I went on holiday around Easter and have been really busy since I got back and sorting this thing out has been an afterthought. But anyway I got around to testing the resistance today and it just keeps reading OL on those pins and gnd. Didn't bother with the caps yet.
Unless OL was an expected result, then I think you may be right and my meter's kaput. Yet another thing goes wrong when I'm trying to fix something else. Story of my life that is.Leave a comment:
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Re: M-Audio GSR18 speaker, powers on but no sound.
Yea I must have done something wrong. I just did it again, now both pins are reading 2.6v or there abouts.
Sorry about that! Not sure if that makes any difference though, but anyway I guess before with the other readings I must have knocked the meter onto a different range or something. This time I made sure it was on dcv autorange and just let it do its thing. As for the ground, I'm using the earth wire as cold ground, presumed that was right since it's attached to one of the screwholes/chassis.Leave a comment:
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Re: M-Audio GSR18 speaker, powers on but no sound.
pin 4 seemed to hover around 1.03v, pin 8 hovered around 0.61vLeave a comment:
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Re: M-Audio GSR18 speaker, powers on but no sound.
I think so but just to be sure; I looked at the IC next to it which has a stripe on one side as do the other chips in the vicinity and based the pin layout on them.
[ATTACH]155206[/ATTACH]
That right?Re: M-Audio GSR18 speaker, powers on but no sound.
I think so but just to be sure; I looked at the IC next to it which has a stripe on one side as do the other chips in the vicinity and based the pin layout on them.
[ATTACH]155206[/ATTACH]...Leave a comment:
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Re: M-Audio GSR18 speaker, powers on but no sound.
Not a thing, even with audio being piped into one of it's two inputs it just sits there quiet as a mouse....Leave a comment:
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Re: M-Audio GSR18 speaker, powers on but no sound.
Good spot, they do seem soldered properly on the underside though;
[ATTACH]155041[/ATTACH]
Here's as best shot I can get with my phone camera top and bottom of both boards with a couple of closeups:
[ATTACH]155033[/ATTACH][ATTACH]155035[/ATTACH][ATTACH]155036[/ATTACH][ATTACH]155037[/ATTACH][ATTACH]155038[/ATTACH]
Not sure. There are a few splodges similar to it dotted across the board, it seemed to wipe off and didn't appear to be damage...Leave a comment:
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Re: M-Audio GSR18 speaker, powers on but no sound.
I don't hear anything when I power it on, no clicks or buzzing or... Well anything. Also I can't use the other amp though, it was just a small thing from a stereo we used to test the speaker that wasn't mine and I no longer have access to it (not for a good few weeks anyway).Last edited by Xandros; 04-07-2017, 09:52 AM.Leave a comment:
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Re: M-Audio GSR18 speaker, powers on but no sound.
Only a multimeter. It has a few useful capabilities but it's nothing special.
To be honest I was hoping for an easy fix, like I'd pull the board out and see something obviously wrong with it such as an exploded/leaking/buldged cap or two or perhaps broken solder joints that I could easily touch up but beyond the corrosion there doesn't seem to be anything visibly wrong with it. I knew right from the start if it was anything more complex wrong with it I was going to be out of my depth. Total hobbyist here you see.Last edited by Xandros; 04-07-2017, 06:07 AM.Leave a comment:
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M-Audio GSR18 speaker, powers on but no sound.
This is a big powered sub, it appears to power on ok (lights come on) but there's no sound from the speaker, not even crackling/pops/hissing. I took the actual speaker out and tested it passively using another amp and it did output music I played (all be it very quietly but as I say I only tested it passively) so that seems to work.
The sub has been used outside a lot and it seems to have been stored in somewhat cold/damn conditions. When I took the circuitry out to have a look I could see straight away there's lots of corrosion on many of the metallic parts and around some solder...Last edited by Xandros; 04-07-2017, 04:49 AM. -
Re: Way of testing LG main board to find odd issue with it not turning on.
OK so I was mostly wrong in my assumptions about that plug, turns out it does carry the USB wires, but only three of them (ground, d+, d-), the rest are other things to do with the monitor. I took the cable off and looked at a pin out for the ADC connector and then used a continuity test to find out which pin on the ADC plug corresponded to the wire in the plug that went in the mainboard, and here they are. I also tested the voltages of each wire while the computer was plugged in (but not turned on, as it...Leave a comment:
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Re: Way of testing LG main board to find odd issue with it not turning on.
Whatever is wrong with it, it's the USB circuitry on this mainboard. I need to test the pins later of the plug that wasn't connected. It goes from left to right if I'm to understand USB wiring correctly, Ground (black) Data + (green) Data - (white) +5V (red) +5V (orange) Data - (blue) Data + (yellow) Ground (brown).
I can only assume that in order to actually prevent the Mac turning on, it must be shorting out the 5v.Leave a comment:
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Re: Way of testing LG main board to find odd issue with it not turning on.
Thanks for the response. Sorry I forgot to upload the full shot of the board.
Between those points I'm getting 25.1v on both sets, which I believe is OK since although the pinout for the ADC states it's 28V the service manual for the monitor states anywhere between 24 and 28 is OK when testing.
Though while I was putting it back together to test those points I seem to have inadvertently found (or rather narrowed it down to) why the Mac won't switch on. The monitor has built in...Leave a comment:
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Way of testing LG main board to find odd issue with it not turning on.
I have this Apple display, it's an ADC display, connects to a Mac using a special ADC connector gets it's power from the computer via the same connector. I'm trying to troubleshoot it's mainboard which is made by LG model LA291Z.
The odd problem is, that when the monitor is plugged into the Mac, the Mac won't turn on (nor will the monitor of course). I've ascertained this is because of the mainboard in the monitor as I swapped the mainboard with another and that one works fine, I just don't know what on the board is causing it to happen. If I unplug the monitor and then plug it back...Last edited by Xandros; 07-12-2016, 05:22 AM. -
Re: Apple G4 AcBel API1PC36 PSU has a bad cap?
Here's an mp3 file (in a zip) of the squealing sound, let me know what you think....Leave a comment:
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Re: Apple G4 AcBel API1PC36 PSU has a bad cap?
Possibly. Unless I'm just going deaf in my old age and it actually was doing it before but being enclosed in the case and in the Mac I just couldn't hear it.
If I record it making the noise perhaps some of you can have a listen and verify it is indeed coil whine and not something else though, just to be sure I've not buggered something serious up.Leave a comment:
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Re: Apple G4 AcBel API1PC36 PSU has a bad cap?
OK, so with the old cap back in, testing it jumpered I couldn't hear anything from it except for the fans, so I figured I should test it with a load since that's when I heard the noise last time, so I hooked it all up to the Mac and sure enough under load it is still squealing.
Yes I think you're right, it is coil whine. It sounds not too dissimilar from [url=https://www.youtube.com/watch?v=SsMXotF33mU]this video of someone showing coil whine on a graphics card[/url], only it varies quite a...Last edited by Xandros; 07-11-2016, 09:41 AM.Leave a comment:
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Re: Apple G4 AcBel API1PC36 PSU has a bad cap?
SC I guess. Other side says "SC105°C" then "10/03" under that and "A3" under that.
[ATTACH]137172[/ATTACH]...Leave a comment:
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