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γ3 Build

gamma3, gamma24 (plug-in for the γ3)

γ3 Build

Postby Salmonkid » October 5th, 2019, 7:38 pm

Finished product, ft beta 22
https://i.imgur.com/DoOscag.jpg

https://i.imgur.com/MLWtyfX.jpg

Original Post with troubleshooting
--------------------------------------------------------------------------------------------------------------------
Hi all,
I'm getting towards the tail end of my gamma 3 build, but have hit some discrepancies with the basic sanity checks.
I'm getting non-0 values for the following measurements

LVDD (backplane) and G (backplane) ~6.5K
GVDD (backplane) and IG (backplane) ~15K
AVDD (backplane) and IG (backplane) ~10K
AVSS (backplane) and IG (backplane) ~10K
Additionally, when measuring the resistance takes a while to actually hit those numbers, ~30 seconds or so

Other points are also getting non-0 readings, but im assuming the above is the main problem I need to sort out first given the same results for each α24 channel.
IN+ (α24 L) and G (α24 L) ~250K
IN- (α24 L) and G (α24 L) ~250K
OUT+ (α24 L) and G (α24 L) ~18K
OUT- (α24 L) and G (α24 L) ~8K
OUT (α24 L) and G (α24 L) ~25k

IN+ (α24 R) and G (α24 R) ~250K
IN- (α24 R) and G (α24 R) ~250K
OUT+ (α24 R) and G (α24 R) ~18K
OUT- (α24 R) and G (α24 R) ~8K
OUT (α24 R) and G (α24 R) ~25K

What i've tried so far:
  1. Unplugging all wiring harnesses - same results
  2. removing all modules - same results
  3. Reflowing all of the galvanic isolation chips on top - same results
  4. Reflowing all solder joints underneath the board - same results
  5. Visually inspecting for shorts - couldnt see any

https://i.imgur.com/awi7Xpf.jpg
https://i.imgur.com/HKcYdR4.jpg

I'm not sure how to start running this down - any help would be much appreciated
Last edited by Salmonkid on October 7th, 2019, 4:08 am, edited 2 times in total.
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Re: γ3 Build

Postby amb » October 5th, 2019, 9:26 pm

None of those checks should give you zero readings. 0Ω means a dead short! Your readings are high-ish resistance which are normal. In a non-auto-ranging DMM in the lowest range, you would have gotten “open circuit” (usually “OL”). In an auto-ranging meter you would get the kind of results you saw, because you’re either reading rail capacitors charging from the meter probe current, or circuit internal resistances.
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Re: γ3 Build

Postby Salmonkid » October 5th, 2019, 9:38 pm

Hey Ti,
Thanks for the reply - I think thats just my bad on wording - I meant that I got a reading, instead of the usual no connectivity behaviour that the multimeter does - I noticed that it was briefly flickering from no connection, going up quickly, and then going back to no connection when I was on the lowest setting - so i tried in higher settings until I could get a lock.

I'll finish testing everything everything else now then and should have some more pictures soon if everything goes well!
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Re: γ3 Build

Postby Salmonkid » October 6th, 2019, 12:21 am

So, all of the other initial checks were fine - I've cabled it all up and put it back in the case.
I've ran through the initial setup of the lcduino successfully, however I've got no sound from any of the inputs (3x optical + USB). I think the output stage is working, as theres a soft "thump" audible from my speakers when powering the gamma 3 on/off.
The ζ1 is picked up by both my laptop and desktop, and the optical out has been working on the desktop for ages via a gamma 2 - Any suggestions on running this down?
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Re: γ3 Build

Postby Salmonkid » October 6th, 2019, 12:43 am

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Re: γ3 Build

Postby amb » October 6th, 2019, 12:07 pm

Let's start with the basics.

1. All voltage test points measure correctly?
2. LCDuino-1 screen shows the correct information? I.e., the volume control bargraph and dB readout work while you turn the volume knob or use the remote control, and it shows the correct sampling frequency? You are able to select the input? Is the volume control turned up high enough?
3. You're able to go into the menu setup and make changes to settings? I.e., upsampling rate, USB audio class, etc. For USB audio class, you can see the indicator LED change color?
4. Try connecting the γ3 digital outputs (coax and optical) to another DAC and see if you can hear music through that DAC. Use a S/PDIF input source first, then try USB.

Btw, very clean and neat looking build!
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Re: γ3 Build

Postby Salmonkid » October 6th, 2019, 3:34 pm

Hey Ti,
Answers inline below:

amb wrote:Let's start with the basics.

1. All voltage test points measure correctly?

Yeah - all voltage points measured correctly per the instructions, +/1 0.1v which should be fine?

amb wrote:2. LCDuino-1 screen shows the correct information? I.e., the volume control bargraph and dB readout work while you turn the volume knob or use the remote control, and it shows the correct sampling frequency? You are able to select the input? Is the volume control turned up high enough?

Volume control works, I can change inputs etc. I've got it almost at max (-10db) - I dont see a sample rate though.

amb wrote:3. You're able to go into the menu setup and make changes to settings? I.e., upsampling rate, USB audio class, etc. For USB audio class, you can see the indicator LED change color?

Yeah I can change USB classes, and I can see the LED switch between red and green (both on the zeta 1, and on the gamma 3 mainboard)

amb wrote:4. Try connecting the γ3 digital outputs (coax and optical) to another DAC and see if you can hear music through that DAC. Use a S/PDIF input source first, then try USB.

Using optical in / optical out - I can get some audio when in loopout mode, but not when upsampling (either 96 or 192khz). I dont see a sampling frequency on the display here either. I've tried going straight in to my gamma 2, as well as the DAC built in to my pc speakers - same behavior for each
Using USB - I don't get any sound at all, even for loopout. I'm only trying in UAC1 mode - the red light does go off on the zeta 1 when music starts playing.

amb wrote:Btw, very clean and neat looking build!

Thanks! I've almost finished rehoming a Beta 22 in a similar fashion - but thats a story for another thread once this is done!
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Re: γ3 Build

Postby amb » October 6th, 2019, 4:18 pm

The LCD not showing a sample rate is a clue that something isn’t working in or around the SRC4392. Check your work very carefully, reflow solder joints if any looks less than perfect.

Do you have an oscilloscope? Is so, it might be helpful to check that the master clock is propagating to the various ICs, and to verify the data and clock lines on the I2S and I2C buses.
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Re: γ3 Build

Postby Salmonkid » October 7th, 2019, 2:55 am

It lives!
I had missed/poorly soldered the middle pin on both U5 and U11, and also re-soldered X1 because it didn't look 100% clean. In hindsight I should have done 1 at a time to work out what was the actual issue.
All 3 optical inputs + USB are working, I don't have any coax sources to test but i'm going to assume its all behaving.
Thanks so much for all of your help with where to look Ti - I really appreciate the service you do here for the DIY community!

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Re: γ3 Build

Postby amb » October 7th, 2019, 3:04 am

Excellent! Enjoy the γ3. I think you’ll love the sound and features.
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