droning sound in R channel- possible damage from moving

[kip.duff]

Eros Phono 2.

Happily moving HiFi system to home in desert! But I believe I screwed something up while moving:

1) pressure on bottom- C4S board components bend down. I straightened them and did the voltage and resistance tests in the manual: all good. All red LEDs are lit- but dim (can't remember if that's normal). Voltages almost identical for channels. On quick viewing, no other damage seen on bottom of unit.

2) installed tubes C and D backwards: 6922 in position C (regulator board) and 12AU7 in position D (output stage). No sound in L channel with droning sound present- and tube temperatures too cool. After installing tubes in correct positions, L channel seems fine- but R channel has a little less gain, deteriorated sound quality, and significant droning noise in background (MP3 sound file attached). Something is clearly wrong.

I have replaced the two tubes and reversed the input tubes: no help. Tubes are now normal temperature. Power to the unit is good at 124 VAC. Although I suspect the two possible causes mentioned above, the problem could be unrelated.

Thanks in advance, Kip......

 

[Paul Birkeland]

The voltages are all OK after the incorrect tubes were installed?

Putting a 12AU7 into the 6922 socket may damage the 75K/2W resistor on the power supply PC board, how does that look? (it's probably OK).

I would still go ahead and post the DC voltages on the front C4S board so we can look over them.

-PB

 

[kip.duff]

The voltages are all OK after the incorrect tubes were installed?

Putting a 12AU7 into the 6922 socket may damage the 75K/2W resistor on the power supply PC board, how does that look? (it's probably OK).

I would still go ahead and post the DC voltages on the front C4S board so we can look over them.

-PB

I am not at the location right now. Took pic of voltages when testing (attached). These voltages are from the board closest to the inputs. I believe the measurements were made after installing good tubes correctly.

Did the audio of the dronning sound ring a bell?

Thanks.....

 

[Paul Birkeland]

I'm not sure what is meant by "droning". Is it a hum, buzz, or something else? (hum=60Hz tone, buzz=120Hz tone)

 

[Jameson]

He posted an audio file in the initial message. It sounds almost like a helicopter.

 

[kip.duff]

I'm not sure what is meant by "droning". Is it a hum, buzz, or something else? (hum=60Hz tone, buzz=120Hz tone)

There's an MP3 audio file attached to the original post.

 

[Paul Birkeland]

That is most likely wireless interference from a nearby device.

 

[kip.duff]

That is most likely wireless interference from a nearby device.

It's only in one channel and pretty high gain and obnoxious.

 

[Paul Birkeland]

It has the periodicity that I would expect from wireless interference. Often whatever is producing this noise will only need to be moved a foot or two away from the Eros to get rid of it.

 

[kip.duff]

It has the periodicity that I would expect from wireless interference. Often whatever is producing this noise will only need to be moved a foot or two away from the Eros to get rid of it.

That's hard to believe- but would be an easy fix. I'll try moving things around when I'm up there soon. I don't believe placement is not much different that before I moved but I'll certainly give it a try.

 

[kip.duff]

That's hard to believe- but would be an easy fix. I'll try moving things around when I'm up there soon. I don't believe placement is not much different that before I moved but I'll certainly give it a try.

Come to think of it, one of the low level (0.5 mV) signal wires from the MC cartridge to the Eros input may be laying on my Bluesound Node 130 streaming device for the DAC which is controlled by WiFi. Keeping my fingers crossed that will be the solution .

 

[kip.duff]

Paul:

I have powered down everything from the area where the hifi is that could have anything to do with wifi. I disabled the wifi in the house. I relocated the RCA input and output cables. No improvement.

To review, the symptoms are: 1) the helicopter noise in R channel only- L channel seems fine 2) I believe some reduced gain and sound quality in effected channel. I have attached the sound file again.

The 75K 2W resistor on the PSU board looks normal- I measured resistance in place: "OL". I don't see how a problem here could cause a problem in one channel only.

I am thinking of comparing voltages between R and L channels at multiple points to hopefully find a pair of values that are significantly different between R and L channels. That might provide a clue for you guys. Also was thinking of checking voltage across the coupling caps. I plan to do this later today.

 

[kip.duff]

Also, as a reminder, possible causes could be 1) reversing tubes C and D and/or 2) bending over most components on C4S board.

 

[Paul Birkeland]

Maybe you could post some build photos?

 

[kip.duff]

OK.

 

[kip.duff]

Here are some pics- mostly right side.

Let me know if you need more.

 

[Paul Birkeland]

It might be worth poking around with a wooden chopstick to see if you can make the noise come and go by touching a specific part of the circuit.

 

[kip.duff]

I was thinking same. With unit hooked up and running- with droning audible. I'll try that ASAP- may have to do a few other things first around the house. Need to find skinny, pointed, hardwood stick.

 

[Jameson]

Order some Chinese takeout. Now you're fed and supplied with chopsticks.