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PostPosted: Fri Mar 27, 2020 3:02 am 
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Thanks for the update. Glad you got to try the amp with so many different speakers and it sounds great with all of them.

With the treble pot, it has two fairly long wires heading back to the board. You could try re-routing them so they aren't so close to other wires.

And maybe it's just hard to see exactly where the wires go in the photo, but it looks like the wires heading back to the board from the treble pot and the bass pot are reversed!

Make sure the wire from the 220k resistor goes to lug 3 on the treble pot and the wire from the 47n capacitor goes to lug 2 on the bass pot.


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PostPosted: Fri Mar 27, 2020 12:29 pm 
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mitch m wrote:
With the treble pot, it has two fairly long wires heading back to the board. You could try re-routing them so they aren't so close to other wires.
And maybe it's just hard to see exactly where the wires go in the photo, but it looks like the wires heading back to the board from the treble pot and the bass pot are reversed!
Make sure the wire from the 220k resistor goes to lug 3 on the treble pot and the wire from the 47n capacitor goes to lug 2 on the bass pot.


Mitch, thanks for your continued dedication and extremely prompt replies! I looked at all of my photos after reading your suggestion that the wires were reversed and was convinced you were right, in spite of having traced all of the leads on final inspection. BUT alas, after cracking it open one more time and in spite of what the pics look like, things were actually connected correctly. I did my best to send the wires to less populated areas but didn't see any change. The mystery continues...


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PostPosted: Mon Mar 30, 2020 1:27 am 
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Not really surprised that the wiring is OK. If the wires were reversed, I think you would have known long ago because the tone stack wouldn't work as expected. They do look reversed in your photo, though!

Not really sure what to suggest next. Maybe change C6. It's interesting that the treble issue doesn't happen with the overdrive engaged. Does it matter where the master volume control is set when you hear the treble control act up?


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PostPosted: Wed Apr 01, 2020 2:28 pm 
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mitch m wrote:
Maybe change C6. It's interesting that the treble issue doesn't happen with the overdrive engaged. Does it matter where the master volume control is set when you hear the treble control act up?


Just checked for your Master Vol question--if the master is above about 5 o'clock (aka dimed), the treble knob issue as shown in the YouTube video doesn't happen when turning the Treble knob. Alternately, if Treble is maxed and has already gone past the "pop" into the attenuated territory and you rotate the Master from below 5 o'clock to above it, there's a less drastic static burst noise that occurs when the knob passes 5 o'clock. These are all pretty extreme settings!

I went ahead and ordered a .001 replacement for C6 in an Amplified Parts order I just happened to be placing, so we'll see if that has any effect!


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PostPosted: Thu Jul 16, 2020 12:26 pm 
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mitch m wrote:
Maybe change C6.


So, I changed the C6 capacitor a while back with no effect. I've just been living with this slight issue and going on with my life, but I've also been learning a lot about amp design and construction and completing more projects: a 5F1, a Princeton Reverb, and a 6G3. Yesterday I came across an older D-Lab video where he diagnoses a Princeton experiencing an extremely similar issue using an oscilloscope. He describes the issue as parasitic oscillation/distortion--the fix? Grid stopper resistors. But the Triwatt already has one on each power tube. I'm wondering if there's more than one way to combat this issue, especially since he claims that the issue shortens power tube life.


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PostPosted: Mon Jul 27, 2020 3:27 pm 
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ElliotKnapp wrote:
There's only one strange issue that I wonder if anyone here has any thoughts about: the treble control does something weird in the final 1/12 or so of its travel (between ~5 o'clock and dimed). Up to this point, it performs as expected, but once it crosses this point there's a slight audible (through the speaker) pop, and the sound stays bright, but gets suddenly sort of choked or pinched sounding (though still bright). Seems strange, and I have no idea what kind of issue would cause this to only occur at the upper extreme of the knob's travel. I could live with it, but I'm OCD enough to want to chase down a cause.


I just read through this thread and I have the exact same thing happening with my build. I noticed it when I first took the amp through its paces, and figured that since I likely would never run treble all the way up like that, it wasn't something I wanted to chase down. The overall performance of the amp seems fine other than that.


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PostPosted: Tue Jul 28, 2020 11:07 am 
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At this point, my suggestion is to review your lead dress. Shortening, Separating wires and crossing wires at 90 degrees. I've not had this issue in my builds.
Check out the picture for clues.

Attachment:
triwatt inside.JPG
triwatt inside.JPG [ 1.48 MiB | Viewed 83 times ]


and here's a large hi res picture

http://www.trinityamps.com/ForumGallery/trinity/triwatt/circuit_board.jpg

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