High Distortion On New Built Unit [resolved]

[hyperkin]

Good morning / Good afternoon,

Just finished building my Eros2. Unit worked fine for 2 sessions and total 5-6 hours, then suddenly, when I came back to the audio room, it start to play with very high distortion. Both channels sounds lack of mid and high, and the bass sounds like a bad sub woofer. there is this sound reassemble to a fan or air compressor while no music playing, very strange.

I took it off the chain and checked voltage and input&output resistance a few times, everything seems normal according to manual, all three modules were tested.

Only exception is i get a tiny bit of resistance on ground terminals, lets say between .7-.9, but a few test it went to around 1.5-2 ohm. it is consistent across all input and output terminals. Could be the meter i use, as it get similar reading just by measuring the chassis itself. This reading was there when first finished, did not change after its "broken".

Also tried to change the 6922, did not help.

Also tried another wall outlet, did not help.

Also played around with grounding from MC step up and TT, did not help.

Once Eros2 replaced with my old phono amp, system working fine.

I ran out of idea what could went wrong at this point...

Appreciate your help.

Stay safe,

[Paul Birkeland]

Can you post the voltages you have and some build photos? 

Loose connections will cause this kind of issue, where you get fine DC voltages and sound passes through, but it sounds terrible. 

[hyperkin]

Can you post the voltages you have and some build photos? 

Loose connections will cause this kind of issue, where you get fine DC voltages and sound passes through, but it sounds terrible.

Paul, Is there a way to check the DC easily? This is happening to both channels.

I will measure again and post additional info later.

Thanks

[Paul Birkeland]

Both channels would suggest a loose ground usually.

[hyperkin]

Both channels would suggest a loose ground usually.

Thank you Paul,

PSU measured 271.6 and 6.275.

The other board measured 216.35 and 214.44

C4S measurements are below.
IA - 216.92
IB - 215.83
OA - 164.4
OB - 163.1
OC - 94.82 ( i kept the unit on for 15 mins, it dropped to 93.65)
OD - 94.48 (15mins, 92.93)
OKA - 96.21 (15mins, 94.98)
OKB - 95.67 (15mins 94.46)
OKC - 1.515
OKD - 1.524

Now A2&A7, B2&B7 shown around .3-1.2 ohm reading, right after power cut off.

There is a DC reading on out output terminals. jump around .02 to .08. Measured while no input signal given. It is constantly changing its value, happening to both channels.

I checked the soldering joints and applied a bit of shake to each of them, they seems sturdy.

I attached two pictures to help. Will take more close up ones if needed.

Now i am thinking maybe its the thicker wires i used, could it be?

[Paul Birkeland]

I would reflow all of the joints on your terminal strips, and I think you could add a little more solder to many of them.

[hyperkin]

I would reflow all of the joints on your terminal strips, and I think you could add a little more solder to many of them.

Thank you Paul, added some solder and re flowed all major joints, it seems stable now.

OC,OD, OKA, OKB now shown 98-99.

Stay safe.