Eros is humming

[Why1504]

Is the music too loud to listen to at 1/2 volume?

YES!!

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.

It is a soft sine wave hum.


I am guessing I finally have my issues solved.

[Why1504]

Well, I was premature in my assessment that I had it fixed.  After about 3 hours of playing, I began to have some very nasty pops and static.  I shut it off, let it cool for a couple of hours fired it back up and within about 5 min the same noise returns. 

This noise is coming thru regardless of whether music is playing or not. 

[Why1504]

I touched up several solder joints.  none were particularly bad.  Retook all of the voltage measurements,  the only one that was out of spec was Kreg.  Specification is 1VDC it came in at 1.5VDC and 1.8VDC.

Is this an issue??

[Why1504]

Problem only exists on the "B" side.

Using the chopstick tap the to LED's on the A end of the B board flash on on off. I touched up several joints that made the flashing significantly less frequent.  However the pops, snaps and rumble continues on the B channel. 

My next step is to remove the board, and touch up every other joint, then re-install and move forward.

[Why1504]

It may be fixed.  I touched up every solder joint.  1/2 of a album in, no noise.  I guess I will know in a few days.

On the upside, I have learned a ton about troubleshooting this kind of equipment.  Should the noises return, I now have a good idea on how to proceed.

[Doc B.]

Yes, this is why we always recommend reflowing every solder joint. Might as well take care of all the cold ones at the same time.

[Why1504]

I spoke to soon.  For the first 1-2 hours this thing sounds fantastic.  And then periodically I get a horrible scratchy popping noise (its like you drug your finger over the stylus on your cartridge at a medium high volume).  It will last less than 15 seconds then it will stop.  Sounds beautiful for 4-15 min then it happens again.  It is so violent I was worried it was going to damage the speaker.  It is only occurring on the B side.  Right now I am in the 4th iteration of good sound. 

If I tap on the chassis nothing.  If I wiggle the Phono input into the Eros when it occurs it makes it much worse.  If I wiggle the input when it isn't occurring no noise.

I am stumped.

Edit:
Re-wet everything again this morning....  Man it sounds good.  I hope the gremlin is gone.

Edit 2:
This is promising,  I swear it is sounding better and better!!

[Why1504]

After multiple de-soldering/re-soldering of all of the  connections on the "B" side the problem persist.  I no longer believe the problem is my poor soldering skills.

I find that 2 of the socket pins from below are loose even with the tube plugged into it.  When I push on the offending tube the noise occurs. Could this be a dirty / bad socket or tube? please advise.

[Why1504]

The Static on the B channel is constant now.  Channel A is clean.  Voltages are within spec.


I checked the tube pins,  They were black.  I got some DeoxIT contact cleaner.  I polished the pins and cleaned them and the sockets with the cleaner and some 800 grit sandpaper.  Zero Effect.  Swapped tubes, no change.


HELP!!

[Why1504]

I re-checked the voltages this morning.  on the "B" side card OA is oscillating between 180VDC and 130VDC.

I am not an engineer or a good technician but I suspect the capacitor has failed.

[Doc B.]

When the voltage moves up and down do you see a change in the brightness of any LEDs?

[Why1504]

When the voltage moves up and down do you see a change in the brightness of any LEDs?

Turned it on, no real change. Waited maybe 20 seconds, then the two towards the "A" end flash on and off.  a few seconds past and the two LED's toward the "B" end got bright then went dim, then back to "normal"

The voltages are changing very rapidly and violently.

[Doc B.]

One possibility is that there has been some damage to one of the carbon comp resistors that connect to the grid terminals of the EF86 and the 6922, and maybe also the one that connects to the plate of the 6922. Try gently prodding at those with a chopstick with the preamp on, and see if you can make the fluctuation happen as you prod them. The leads on the carbon comps can develop a bad contact where they are inserted in the end of the resistor body if they get a little too hot when being installed and soldered.

[Why1504]

One possibility is that there has been some damage to one of the carbon comp resistors that connect to the grid terminals of the EF86 and the 6922, and maybe also the one that connects to the plate of the 6922. Try gently prodding at those with a chopstick with the preamp on, and see if you can make the fluctuation happen as you prod them. The leads on the carbon comps can develop a bad contact where they are inserted in the end of the resistor body if they get a little too hot when being installed and soldered.

I did as requested.  I was unsuccessful in getting the LED's to blink or dim.  The voltage spikes now seem to only be bouncing between 140 and 160.

So,  I re-installed the Eros back into the 2 channel system.  The "B" channel is producing music but it is way over shadowed by the noise.  Again I was not able to get the LED's to blink or dim, nor was I able to cause the noise to increase, or decrease when pushing on everything (focused on the Resistors at first).  Tapping on the plate also had zero effect.

I expect when I started I had several bad joints which I believe I have now repaired.  The noise is popping, scratching, loud even at low volume and very violent.

[Doc B.]

Another possibility is the 6922 is making the noise. You mentioned wiggling the tubes generated the problem at one point. Not sure if that is the case now. Does wiggling the 6922 create the noise? Even if it doesn't make noise when moved it could be that the tube is misbehaving. Of course the best way to test is to try a different 6922.