Eros2 PSU

[feras]

I am testing almost finished Eros 2. It plays nice, but I hear some oscillation noise with no music.
I checked voltages on PSU and key points. It looks fine in VDC:

IA (initial PSU, non regulated supply) - 298 VDC
Reg (regulated supply comes out of the board above 12AU) - 218 VDC
AO/OB (post C4S)- 159.5 VDC
OC/OD (post C4S) - 96.3 VDC

Surprisingly the DC supply is not clear of AC and it decreases with drop of VDC proportionally:
IA - 6.45 VAC
Reg - 4.5 VAC
AO/OB - 3.2 VAC
OC/OD - 1.7 VAC

Obviously that is the noise I hear and comes straight from the initial PSU.
Do others have it too? Is that because the initial PSU set as half wave bridge?
FG

 

[Paul Birkeland]

Are you measuring these AC voltages with a scope?  A DVM will usually not resolve AC in the presence of DC.  AC ripple from the raw PSU will be nearly eliminated by the regulator.

What is the frequency of the noise you're hearing?  (Listen to 60Hz and 120Hz tones to compare)

Do you hear the noise with the inputs of the Eros shorted?

You say the Eros is almost finished, what's left to do?

 

[feras]

Thanks for the tips. I will measure it with a scope tomorrow and will post results.

 

[feras]

I tried to measure with a scope. The frequency is 60 Hz on RCA outputs with approx. +/-50mV.
I tried to measure power supply points via MKP cap - 120Hz before regulated PSU and 60Hz on REG. My scope doesn't show such high VAC as seen on voltmeter (Vichy VC99), but still it detects hundreds mV. It seems to be fluctuating and values are not stable.

On speakers I do hear 60Hz. On top of that there is a slow sound like ticking, approx. x1s.
After shorting inputs the noise decreases and almost dissapears.

Eros2 is finished, but until is not works fine is not finished for me.

 

[Paul Birkeland]

After shorting inputs the noise decreases and almost dissapears.

Well measuring the ambient noise that the Eros picks up isn't all that useful.  For testing purposes, you'd want to have the inputs shorted.