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Alien DAC v1.1 Construction Thread - Page 76

post #1126 of 1560
3/28/08 at 12:23am
Quote:
Originally Posted by FallenAngel View Post
Whoops, sorry, keep S1 jumpered

This still doesn't explain why you get nothing out of those voltage regs though. Do they get warm at all?
hooked to 9v alkaline with s1 jumpered i measure 0v and the only thing that gets warm is the battery.

By the way, thanks for the help.
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post #1127 of 1560
3/28/08 at 12:36am
Ok, that makes pretty much no sense, are you SURE the DMM is working properly? Measure the battery voltage

The chances that both regulators are dead are VERY slim, but even then, I'd expect them to just not regulate, not short out. Both the regulators run independent of each other, so they must both be not working properly.

Now that I think about it, shorting a battery will make it heat up, but I don't see a short anywhere. Could one be under a part?
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post #1128 of 1560
3/28/08 at 1:07am
I might start by ohming out the 3.3V and 5V pads to ground... really any voltage pad to ground and see if any of them show shorts.

I take it you have used a meter on both the 3.3V and 5V pads to ground for voltage readings with the thing plugged into a USB cable? I had asked you earlier about that and didn't see you post what you were getting?
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post #1129 of 1560
3/28/08 at 2:33am
I agree with Pars and FallenAngel. It sounds like you've got a dead short somewhere. You might also try to see if you read zero resistance between the pads on any part. If you do, that would indicate you have a solder bridge underneath. Start with L12, for instance - if the short is there, that's where it would get hot. If you can measure zero ohms between the two pads of L12, that would be it. Remove L12 and clean up any solder bridge with heat, flux, and some braid.
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post #1130 of 1560
3/28/08 at 12:39pm
Ok, I removed the voltage regulators, l12, and c22 to check for bridges. I found none. FallenAngel, yes I have checked for voltage on the 3v and 5v pad with both 9v battery and usb connections and both read 0 volts. Anything I can check while the voltage regulators are off to eliminate them as the issue? Resistance between 3.3v and g1 starts at 400k ohms and drops, the resistance between 5v and g1 starts at 49k ohms and drops. These are without the regulators, l12, and c22 attached.




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post #1131 of 1560
3/28/08 at 12:56pm
Check the resistances between pins 3 and 4 of IC2 and IC3
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post #1132 of 1560
3/28/08 at 1:01pm
Quote:
Originally Posted by Pars View Post
Check the resistances between pins 3 and 4 of IC2 and IC3


ic2 pin3 to pin4 measures 0L ohms without c22 installed (meter does not react)

ic3 pin3 to pin4 measures 9.664k ohms with r32 installed

between g1 and one pad for l12 i measure .15 ohms
between g1 and the other pad for l12 i measure 8M ohms and rising


ok, did some more probing without ic2 and ic3 installed. I measure continuity between av+ and pins 5-8 on ic2 and ic3, which is normal. However, I also read continuity between g1 and pins 5-8 on ic2 and ic3. Which means there is a short between ground and voltage somewhere on the board. Any ideas?
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post #1133 of 1560
3/28/08 at 1:55pm
Quote:
Originally Posted by cronic View Post
ic2 pin3 to pin4 measures 0 ohms without c22 installed
That doesn't sound right... I don't have a schematic in front of me right now though. You shouldn't have a short there though, as a cap in parallel with a short is... a short. You might try running an xacto knife or whatever between those pads, and also check the schematic to see what feeds those two pins. That should be open unless there is something else connected to it.

Quote:
Originally Posted by cronic View Post
ic3 pin3 to pin4 measures 9.664k ohms with r32 installed

between g1 and one pad for l12 i measure .15 ohms
between g1 and the other pad for l12 i measure 8M ohms and rising


ok, did some more probing without ic2 and ic3 installed. I measure continuity between av+ and pins 5-8 on ic2 and ic3, which is normal. However, I also read continuity between g1 and pins 5-8 on ic2 and ic3. Which means there is a short between ground and voltage somewhere on the board. Any ideas?
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post #1134 of 1560
3/28/08 at 2:24pm
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post #1135 of 1560
3/28/08 at 2:26pm
Quote:
Originally Posted by Pars View Post
That doesn't sound right... I don't have a schematic in front of me right now though. You shouldn't have a short there though, as a cap in parallel with a short is... a short. You might try running an xacto knife or whatever between those pads, and also check the schematic to see what feeds those two pins. That should be open unless there is something else connected to it.
I misspoke. My meter reads 0L meaning it does not react at all when connected to pin3 and pin4 of ic2.
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post #1136 of 1560
3/28/08 at 3:17pm
Quote:
Originally Posted by cronic View Post
ok, did some more probing without ic2 and ic3 installed. I measure continuity between av+ and pins 5-8 on ic2 and ic3, which is normal. However, I also read continuity between g1 and pins 5-8 on ic2 and ic3. Which means there is a short between ground and voltage somewhere on the board. Any ideas?
Unfortunately, this could be about anywhere... since this appears to be a short between V+ and gnd, caps like C31, C21 etc. You don't have IC4 in so that is unlikely. It is also possible that the short is in the board itself, so try to look under the soldermask if you can't find anything else wrong.
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post #1137 of 1560
3/28/08 at 3:29pm
You guys ROCK! I removed c31, cleaned it up, reattached it and the regulator and bam, I got 3.3v on the 3.3v pad. I'm out of desolder braid, so I gotta run to the store and get some to re attached everything else. Cross your fingers but I think we are headed in the right direction. Thanks again guys, and I will update soon.
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post #1138 of 1560
3/28/08 at 6:00pm
Its ALIVE! Thanks everyone for your fantastic help. It is working but I am noticing some static in the sound, when using the touch pad or a usb mouse.


I got about 15 hours on the alien so far and I am impressed. I found that the static issue was only in win xp pro sp2, so I installed vista and have no issues so far..........
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post #1139 of 1560
4/5/08 at 10:45am
I can only obtain REG101-3 3 Volt versions not the 3.3 V ones. Can they still be used?
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post #1140 of 1560
4/5/08 at 2:55pm
Quote:
Originally Posted by Kenneth S View Post
I can only obtain REG101-3 3 Volt versions not the 3.3 V ones. Can they still be used?
The 2702 datasheet says the minimum digital voltage is 3v, max is 3.6v.

So I'd say theoritically* it could possibly work, however I'd be more inclined to track down the 3.3v version... can you get a reg102-3.3 instead ?

I'll check my parts stash... I don't think I have any laying around but you never know.


* I'd just be concerned that the regulator might put out slightly under 3v which doesn't meet the spec or even if it does put out 3v or a little more that the 2702 might not perform as well or even be erratic at that sort of voltage.
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