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LCDuino on γ3 - strange volume behaviour

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Re: LCDuino on γ3 - strange volume behaviour

Postby Balcmeg » August 18th, 2019, 7:43 pm

amb wrote:
Balcmeg wrote:Im getting LEFT channel 60Vpp 50hz on both a24 INPUTS, moving it reduce the voltage to 16V...

Those are impossibly high voltages. You're probably not measuring or reading the results properly...

Just use a good 'ol DMM in AC V mode for this.

GVDD is a bit low at 4.65V. Check the molex connector J14 on the γ3 backplane.
Check all other voltage test points on the γ24 board, as well as the supply voltages to the α24 boards.


Justas yesterday
DVDD J14 - 4.65V, but on the PSU S11 5.02V it was, then back to J14 went back to 4.98V. Oxidization on the molex pins here too?

All test points on a24 within 0,02 V of what they are supposed to be.

a24 DC inputs pins:
Pin 70/71 4.95V
Pin 67/68 9,96/-10.06V

Still cant detect any AC on the in- or outputs of the a24, or on g24 outputs.
/Stefan
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Re: LCDuino on γ3 - strange volume behaviour

Postby amb » August 18th, 2019, 8:16 pm

Balcmeg wrote:DVDD J14 - 4.65V, but on the PSU S11 5.02V it was, then back to J14 went back to 4.98V. Oxidization on the molex pins here too?

Quite likely. Is there high humidity or air quality issues where you are?

Still cant detect any AC on the in- or outputs of the a24, or on g24 outputs.

Try connecting a computer as the player to the γ3, make sure all software volume controls are set to maximum, as well as the volume knob on the γ3. Play the 1KHz test tone file I linked previously and check the AC output voltage at your analog output jacks. 0dBFS with no attenuation should give you 2Vrms at the unbalanced outputs, or 4Vrms differentially at the balanced outputs.
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Re: LCDuino on γ3 - strange volume behaviour

Postby Balcmeg » August 18th, 2019, 8:44 pm

Still can't detect any AC on the in- or outputs of the a24, or on g24 outputs.

Try connecting a computer as the player to the γ3, make sure all software volume controls are set to maximum, as well as the volume knob on the γ3. Play the 1KHz test tone file I linked previously and check the AC output voltage at your analog output jacks. 0dBFS with no attenuation should give you 2Vrms at the unbalanced outputs, or 4Vrms differentially at the balanced outputs.[/quote]
I tried and didn't get any, from my previous reply. then realised that I had set the input to optical switch just before going to bed last night to make sure it wasn't the USB input that had failed. Probem is my work space is so small so I cant see the display easily.
I connected again and measured 1.936VAC on left and 1.940VAC on right

amb wrote:
Balcmeg wrote:DVDD J14 - 4.65V, but on the PSU S11 5.02V it was, then back to J14 went back to 4.98V. Oxidization on the Molex pins here too?

Quite likely. Is there high humidity or air quality issues where you are?

Hong Kong, we got about 40%RH with AC running full, outdoors is 80%RH, probably higher here than what Observatory tells, pretty close to the sea (with salt water), When i moved there i brought a designer lap in chromed steel with me, the surface of that one was destroyed by oxidation after 2 years.
Should I change the pins to gold?
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Re: LCDuino on γ3 - strange volume behaviour

Postby amb » August 19th, 2019, 12:46 am

Balcmeg wrote:Should I change the pins to gold?

Probably a good idea. Change both the male headers and the female receptacle pins.
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Re: LCDuino on γ3 - strange volume behaviour

Postby Balcmeg » August 19th, 2019, 12:56 am

amb wrote:
Balcmeg wrote:Should I change the pins to gold?

Probably a good idea. Change both the male headers and the female receptacle pins.


I put in my todo list that I should open the amp and check wich headers receptacles and headers that are not gold - I know I used gold on some places and some places I didn't.
I should change all that is not gold at the same time, or I bet that one of the ones I don't change will be the next to make trouble.
That means I need to redo most of the wiring too, a task I dislike almost as much as making enclosures.
I REALLY dislike crimping the MOLEC receptacles. :D

Wish I had used the same par-metal case as you so I could have used the ε31 bridge board - a drawback of being in the development team.
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Re: LCDuino on γ3 - strange volume behaviour

Postby amb » August 19th, 2019, 10:18 pm

Meanwhile you can unplug and plug all the connectors a few times, doing so "wipes" the contact mating surfaces and helps to clean them. You can also apply a small amount of DeoxIT D series contact cleaner/preservative. This stuff is good.
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Re: LCDuino on γ3 - strange volume behaviour

Postby Balcmeg » September 28th, 2019, 12:38 am

Tried both but it came back pretty soon again.
I ordered a full set of replacement connectors in gold, but had to go for an extended time to work in Sweden before I had time to switch them all.

Will not be back until late November.


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Re: LCDuino on γ3 - strange volume behaviour

Postby cobretti » September 28th, 2019, 5:36 am

I wrote here many times before those plug in Molex connectors are bad idea from the beginning. I had a lot of troubles with them as well.
Replaced them with screw down type like this:
https://www.mouser.com/ProductDetail/Phoenix-Contact/1725685?qs=A%2FKWGUWTCZiuYWt6zAMYZA%3D%3D
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Re: LCDuino on γ3 - strange volume behaviour

Postby Balcmeg » September 28th, 2019, 5:50 am

Tempting, but it’s a lot of screws to tighten if youu use the Phoenix terminals all over the gamma3 ;)


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