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PostPosted: August 16th, 2019, 9:42 am 
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Joined: March 12th, 2013, 11:12 am
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Hi folks,
Starting yesterday, I am getting a brief LOUD static, popping noise out of my left channel only at initial, cold startup. If amp is powered down and then powered up, no noise or issues. These are 2-stage, cap coupled SET monoblocks. All PS caps are polyprops and were installed about 15 years ago.

1) first swapped tubes, and got no noise
2) swapped back tubes and this morning the pop returned, again in the left channel at startup
3) B+ appears correct for output (467v left channel, 470v right channel) and driver (~287v).
4) once amp is warmed up, no issues and they sound fine (no noise, hum, pops etc)

Any suggestions for an order of things to start checking? Thanks.


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PostPosted: August 16th, 2019, 9:45 am 
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TubeDriver wrote:
Hi folks,
Starting yesterday, I am getting a brief LOUD static, popping noise out of my left channel only at initial, cold startup. If amp is powered down and then powered up, no noise or issues. These are 2-stage, cap coupled SET monoblocks. All PS caps are polyprops and were installed about 15 years ago.

1) first swapped tubes, and got no noise

Did you swap different tubes into the left channel, or swap the left and right channel tubes? :confusion-confused:

Roscoe


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PostPosted: August 16th, 2019, 10:09 am 
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Joined: July 24th, 2015, 4:17 pm
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Location: Parkville, Maryland
Any suggestions for an order of things to start checking? Thanks.[/quote]

It sounds like the behavior of a cold solder joint. It is not an easily observable problem, but you may fire up your soldering gun and touch up each connection with fresh solder.

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PostPosted: August 16th, 2019, 10:17 am 
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Joined: January 15th, 2015, 7:19 am
Posts: 887
Location: Baltimore MD
I agree with Walt, sometimes its the simplest things at drive one crazy.
Resolder everything.
Clean tube socket pins by exercising them by pulling tubes and reinserting,
check to see if any pins are not tight. with a sharp tool you can close down loose socket pins


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PostPosted: August 16th, 2019, 10:21 am 
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Pelliott321 wrote:
I agree with Walt, sometimes its the simplest things at drive one crazy.
Resolder everything.
Clean tube socket pins by exercising them by pulling tubes and reinserting,
check to see if any pins are not tight. with a sharp tool you can close down loose socket pins


Paul is correct. Tube socket pins can corrode over time and loosen. Cleaning them and carefully tighten them for a snug fit can be beneficial.

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PostPosted: August 16th, 2019, 10:35 am 
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Joined: March 12th, 2013, 11:12 am
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Just swapped tubes from left amp to right and vice versa.


Roscoe Primrose wrote:
TubeDriver wrote:
Hi folks,
Starting yesterday, I am getting a brief LOUD static, popping noise out of my left channel only at initial, cold startup. If amp is powered down and then powered up, no noise or issues. These are 2-stage, cap coupled SET monoblocks. All PS caps are polyprops and were installed about 15 years ago.

1) first swapped tubes, and got no noise

Did you swap different tubes into the left channel, or swap the left and right channel tubes? :confusion-confused:

Roscoe


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PostPosted: August 16th, 2019, 10:39 am 
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Thanks Walt and Paul. Will start by cleaning and tightening socket connectors. If that does not do it, may start hitting solder joints although I did them correctly and they have worked fine for more than a decade.



SoundMods wrote:
Any suggestions for an order of things to start checking? Thanks.


It sounds like the behavior of a cold solder joint. It is not an easily observable problem, but you may fire up your soldering gun and touch up each connection with fresh solder.
[/quote]


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PostPosted: August 16th, 2019, 10:40 am 
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TubeDriver wrote:
Just swapped tubes from left amp to right and vice versa.


Then I'd say Walt's suggestion is a good place to start...

Roscoe


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PostPosted: August 16th, 2019, 10:54 am 
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Location: Parkville, Maryland
[quote="TubeDriver"]Thanks Walt and Paul. Will start by cleaning and tightening socket connectors. If that does not do it, may start hitting solder joints although I did them correctly and they have worked fine for more than a decade.


About that -- soldering is not as simple as some would believe. I worked with a guy that was an electronics technician at General Electric. He had to have six weeks soldering training before G.E. management let him near any work.

Keep in mind that cold solder joints can be sneaky. That very-thin rosin barrier with an electrical connection that was just barely there can be become unstable from aging.

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Walt


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PostPosted: August 16th, 2019, 11:02 am 
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Leftover flux over time can get things really fluxed up. :lol:


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