Eros is humming

[Why1504]

I have a new build.  probably has 100 hours of burn in.  I noticed a yesterday that I had a hum.  It is coming from the Eros.  There is a minor hum when it is powered off and is more pronounced when powered up.

I have no idea how to proceed here.  Please help.

[Paul Birkeland]

I would start with a check of the voltages.

-PB

[Why1504]

got to the bench this morning.  on the A side the of the chassis,  A side of the C4S card, when powered up, the A side LEDs light, B side  LEDs do not light.  After about 4 seconds the A side LEDs go out.

[Why1504]

I would add, that all of this was operating normally when I did the testing at the conclusion of the build.  Eros has about 100 hours on it.

[Doc B.]

Why don't you post your voltages, noting the ones that are not to spec. That is always the place to start. It could be that you have a bad connection that has shown itself after a few heat cycles, and voltages might help us isolate where the problem lies.

[Why1504]

Finally got a chance to catch my breath this morning ( I run a company and the last two weeks have been insane.  Today I leave on travel for a week, back Friday and Sat of next week then gone for two more weeks)  Here are my voltages:

                  A                       B
KREG         .6                      1.77
BREG        7.42                   96.8
OB            221.4                 95.1
OA            220.8                169.7
bA                  0                     0
IA             223.0                 223.9


Thanks for any assistance!!

[Paul Birkeland]

KREG         .6                      1.77
BREG        7.42                   96.8
OB            221.4                 95.1
OA            220.8                169.7
bA                  0                     0
IA             223.0                 223.9

I would suspect you have a broken wire or very loose solder joint in your build somewhere.  It could be the ground connection for the board with all the out of whack voltages. 

[Sugar Man]

I added the MourQuiet to my Stereomour and wasn't totally happy with the sound.  When I turned it back over to investigate, I had totally forgotten to solder a terminal tab with a bunch of resistor leads.  I could have sworn I double- and triple-checked everything.  Sounded much better after I applied a bit of solder to the oversight.  Good luck finding your problem.

[Why1504]

Thanks. I plan to work on her this Saturday.

[Why1504]

After 4 weeks of travel followed by 3 weeks of sickness I finally got in this morning and began doing some serious investigation.  Almost immediately I found a wire that wasn't connected.  Fixed that.

All of the voltages are now in spec.

But, the preamp has now developed a white noise with some thumps that sound much like a dirty album.  the noise is coming out of both channels.  I get it with the turntable disconnected.

HELP!!

[Why1504]

I cleaned up a couple of solder bridges. I know I have a bad joint somewhere.  When I tap on the chassis the noise will come and go.

All of the LEDs are glowing.  I have requested one of my engineers to help me with this next week.

[Paul Birkeland]

I cleaned up a couple of solder bridges. I know I have a bad joint somewhere.  When I tap on the chassis the noise will come and go.

You can get in there and poke around with a wooden chopstick to find the joint that is aggravated by tapping on the chassis.

-PB

[Why1504]

I found the bad Joint!! Fixed it!!

The rattle is gone.  However, I still have a hum but it only becomes audible at about 1/2 volume which is a significant improvement.

Any suggestions on the hum??

[Why1504]

The hum is still there but with music the sound is fantastic.

I ma guessing the signal is way overpowering the hum.

[Doc B.]

Is the music too loud to listen to at 1/2 volume? If the cartridge has a relatively low nominal output level, the hum can just start to be audible with no signal playing at very high volume settings. That hum would be a soft, sine wave type of hum. If the hum is buzzy that would be a grounding issue, most likely between the turntable and the Eros.