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Old 5th February 2012, 12:47 AM   #2041
tamu is offline tamu  Australia
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I pulled the d6, d2, r1, r2 and also the q2. trying to find if any of them were the problem. well that didnt help much..

Ill do what you suggested now.
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Old 5th February 2012, 12:56 AM   #2042
agdr is offline agdr  United States
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Quote:
Originally Posted by tamu View Post
I pulled the d6, d2, r1, r2 and also the q2. trying to find if any of them were the problem. well that didnt help much..

Ill do what you suggested now.
Yep, just follow those traces you can see on the bottom of the board going to pin 7. Either one of those 4 things hooking to it has to be shorted, or a short (solder bridge) directly to that trace.
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Old 5th February 2012, 01:01 AM   #2043
tamu is offline tamu  Australia
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Originally Posted by agdr View Post
Yep, just follow those traces you can see on the bottom of the board going to pin 7. Either one of those 4 things hooking to it has to be shorted, or a short (solder bridge) directly to that trace.
I made a very noob mistake. r25 was 133ohms.

put the correct value in and now there is no more short. Ill solder everythg and see what happens.

thanks for the help agdr
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Old 5th February 2012, 01:13 AM   #2044
agdr is offline agdr  United States
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Quote:
Originally Posted by tamu View Post
I made a very noob mistake. r25 was 133ohms
Yes but you've successfully troubleshooted it! Mistakes like that are easy to do and can be hard to find. You should have music shooting out of that O2 real soon.

Last edited by agdr; 5th February 2012 at 01:35 AM.
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Old 5th February 2012, 03:46 AM   #2045
MrSlim is offline MrSlim  Canada
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Originally Posted by apassgear View Post
Hi guys,
been reading part of this big thread, but was wondering where to get the PCB and shematic.
Thanks
Tony
O2 Details is the best place to start. He has the Schematic, board layout, etc.. Check the Vendor bazaar here for any Boards for sale (a few people are offering completed boards, but they may sell you one unpopulated).
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Old 5th February 2012, 06:01 PM   #2046
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Quote:
Originally Posted by MrSlim View Post
O2 Details is the best place to start. He has the Schematic, board layout, etc.. Check the Vendor bazaar here for any Boards for sale (a few people are offering completed boards, but they may sell you one unpopulated).
Thanks Slim
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Old 5th February 2012, 10:38 PM   #2047
jfrana is offline jfrana  United States
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Alright. I think I may be getting close.

Volume control is working properly (I ran a wire to the 20mm pot holes after damaging the board cups when trying to remove the pot -- it seems to work.)

After resoldering the leads near the U2 chip, I now have these measurements.

AC, on, no batteries for U2
1=-11.7
2=-8.8
3=-10
4=-11.7
5=-10
6=-11.7
7=8.5

Are these within proper ranges?

Measuring the resisters on top of the board (still connected), I have the measurements
R25= .39 on 20M
R5= .23 on 20M
R9= .02 on 20M
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Old 6th February 2012, 12:08 AM   #2048
agdr is offline agdr  United States
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Originally Posted by jfrana View Post
Alright. I think I may be getting close.
Good job! Those voltage readings look a lot better. P2 of U2 is spot on now. You didn't list the positive rail voltage at P8, but that has to be OK (around +11.8Vdc) to produce that correct P2 reading. You must have your U2 back in the socket too since those output readings on P1 and P7 are doing their thing (almost) properly. The voltage on P7 is a little lower than what I would expect, but that could just be due to part tolerances.

What is the color code on your R25? The fellow I helped a few posts up had a wrong value in there. Maybe there are a couple of color codes that look pretty similar. If R25 is too low it could drag P7 down. Your R25 measurement is probably correct though. You are essentially getting R9 plus some power supply internal resistance, which is essentially in parallel across R25.

OK, so you've fixed up the U2 circuit and it is should be sending the proper control signals to the mosfets. So back to the original test you did in your first post in #1834 of running it on batteries with the chips in (headphones still unplugged though!), rather than AC, and then pulling out one battery and seeing if P4 and P8 of U4 go below one volt. P4 and P8 on U4 should be around the rail voltages (-11.8Vdc and +11.8Vdc) before pulling the battery out. If they do drop the mosfets have toggled properly and your power management circuit is working.

If that test works your O2 may be working. Run through RocketScientist's list of setup instructions again - especially the one about measuring the DC output voltage offset of each output channel and confirming it is around 3mV and not higher - and you may have a working O2. Give it a try after confirming those tests.

If one channel still won't work with the pot, try reheating both ends of R16 and R22, even if they look OK. Also make sure you have done that gain switch mod of bending the tab on the front left corner of the gain switch under, so as not to hit that via hole under it.

Last edited by agdr; 6th February 2012 at 12:32 AM.
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Old 6th February 2012, 10:59 AM   #2049
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Location: Smoky Mountains, NC
Default O2/DAC combo

Thought I would share this.
An O2 and AK4393(with a couple of mods) crammed into a rather nice chinese aluminum enclosure. Need to straighten up the wiring.
Many thanks to RS for a very nice amp.
The input to the DAC is via an HA info spdif device.
This is my first effort at going PC based music system.
I'm very happy with the sound but would consider replacing the DAC with a decent USB input board. Anyone suggest one that would fit and sound as good?

Cheers

Peter
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Old 6th February 2012, 11:04 AM   #2050
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Join Date: Mar 2009
Location: Smoky Mountains, NC
Default O2/DAC combo

Thought I would share this.
An O2 and AK4393(with a couple of mods) crammed into a rather nice chinese aluminum enclosure. Need to straighten up the wiring.
Many thanks to RS for a very nice amp.
The input to the DAC is via an HA info spdif device.
This is my first effort at going PC based music system.
I'm very happy with the sound but would consider replacing the DAC with a decent USB input board. Anyone suggest one that would fit and sound as good?

Cheers

Peter
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