AMB Laboratories DIY Audio Forums

[yeahyeah]

Hi, i finally solder my sigma 24+25 for gamma2. It output 5.01V on my test and work fine for gamma
yet after a few minutes of listening, gamma 2 generate some strange noise, i would say hum, and LED of input selector goes off.
Checking the voltage of sigma 25 again gives 1.8V,

Turn off sigma 24/25 for a few minutes and turn it on again, it output 5V again.
But it dropped to 1.8V again after few minutes on Gamma.

Using Gamma only or Gamma + Mcube produce the same result.

I've no idea why this happen, can anyone help?

[Anonanimal]

Seems a good possibility that you've got a cold/marginal solder joint that becomes an issue only as the power supply heats up during use.

Have you tried reflowing all of your solder joints?

[MisterX]

What's the current draw of the DAC?

[Nebby]

Oh boy, those symptoms are giving me deja vu...

When checking the voltage of the s25 and getting 1.8v, are you doing it with the power supply disconnected from the gamma?

[yeahyeah]

Oh boy, those symptoms are giving me deja vu...

When checking the voltage of the s25 and getting 1.8v, are you doing it with the power supply disconnected from the gamma?

yes, after gamma "turn off", i disconnect to measure the voltage

[yeahyeah]

Oh boy, those symptoms are giving me deja vu...

When checking the voltage of the s25 and getting 1.8v, are you doing it with the power supply disconnected from the gamma?

yes, after gamma "turn off", i disconnect to measure the voltage

even i don't disconnect it, the voltage is still 1.8V
and seems like the voltage keep dropping, slowly

[yeahyeah]

What's the current draw of the DAC?

i tried to measure it but the LED goes dim and i get either zero or infinite....
i've no idea on this one either...

what i can see now is the voltage drop to 1.67V and stay here.

[yeahyeah]

the EL-30 transformer output drops to 4.6V (originally 9.9V), and it's hot,

[amb]

On your σ25, did you install the 10uF tantalum cap backwards? That's a classic symptom of a shorted tantalum cap as a result of reverse-polarity.

[MisterX]

Read my mind...