Interrmiten loss of high frequencies in one channel...

mediumgrade · 1362

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Offline mediumgrade

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on: November 29, 2022, 02:23:51 PM
So, I installed a couple of Sowter 1090 transformers, as was recommended, to pair with my Hana EH cart. The results were very positive (more on that in another post). That being said, maybe I'm dummy, but I had a rough time stripping the wire without damaging the strands and then wrapping those reamining strands around the posts before soldering. My work was, hopefully, good enough. Everything seemed fine for the first few days of play.

Then, the weekend came around and I, apparently, left the Eros on from Friday or Saturday (I forget which) until Monday when I came back into the office. Yikes! So, starting yesterday, I noticed that the high frequencies in the left channel sometimes flicker in and out. It took me a few tracks to notice and I don't think it was doing it until the unit was on for at least an hour or two, but the highs definitely seems to flick in and out in that channel occasionally. I am not sure if this is due to some mangled soldering when I wired the transformer (I didn't notice it those first couple of days, but it might have been present) or something that was potentially damaged from leaving the unit on for days at a time. Either way, I could use some guidance. Does this symptom sound familiar to anyone?



Offline Paul Birkeland

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Reply #1 on: November 29, 2022, 02:56:19 PM
That could easily be a loose cap in the EQ circuit.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline mediumgrade

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Reply #2 on: November 29, 2022, 06:31:50 PM
So, one of these (see attached image)?



Offline mediumgrade

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Reply #3 on: November 29, 2022, 06:38:00 PM
If I messed with the output cap, could that have caused this?



Offline Paul Birkeland

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Reply #4 on: November 30, 2022, 04:13:53 AM
That's unlikely to cause the issue you're having.

Paul "PB" Birkeland

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Offline mediumgrade

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Reply #5 on: November 30, 2022, 06:19:21 AM
Thank you.

To be clear the EQ circuit caps are just those red/orange ones I circled which are soldered to the posts between the EF86 tubes?



Offline Paul Birkeland

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Reply #6 on: November 30, 2022, 06:29:33 AM
The 0.01uF and 0.030uF caps and the 10.5K resistor close by.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline mediumgrade

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Reply #7 on: November 30, 2022, 12:53:55 PM
Damn. Now's the channel's out entirelly. I'm going to bring it back to my home and check it out sometime this week.



Offline Paul Birkeland

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Reply #8 on: November 30, 2022, 01:32:48 PM
That will be an easier problem to track down and may be related to what you were hearing.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline mediumgrade

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Reply #9 on: December 01, 2022, 06:13:17 AM
Quick update to what is now a somewhat weird issue.

I noticed that when the phono stage is plugged into my amp, if I turn the volume nob up or down, I can hear a loud scratching noise in the channel with no output. This symptom does not manifest itself with my DAC or my other phono stage. Only the Eros.

Secondly, as I was playing with the RCA connections, I noticed that if I unplug the RCA connection from the output of the bad channel and then back in again, the music comes in very briefly and then quickly fades out. This symptom was repeatable.

Anyway, I'll probably take another look at it later this week. Thanks!



Offline Paul Birkeland

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Reply #10 on: December 01, 2022, 06:17:29 AM
That sounds a lot like a loose solder joint.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man