trinityamps.com

Hello- I built my Tramp over a year ago and it has worked perfectly up until this point. Now, I'm getting a crackling/static-type sound only when I hit certain notes on the guitar. It doesn't seem to be connected to volume at all.... what could it be?
I've changed out both tubes and I still get it. Different guitars all produce the same result. Could it be a speaker issue?

Thanks,
Mike

Mike, you could try plugging the Tramp into another speaker/cab, just to see if the result is the same.

Snowy

Check for loose connections and solder joints.

Rule out external factors first though, cables, cab, speaker, guitar, pedals, tube, etc.

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Any other amp inserted with identical peripherals is an easy experiment to test the peripherals [required gear the amp requires to be working].
Then the one handed dry woodstick technique, also pretty easy.
The 'danger' readings should come pretty soon after the chains have been examined for continuity/goodness. THE best way to test a chain is to start at one end and work your way link by link, [if the plug doesn't actually connect the speaker, then any amp testing would be moot], a 9v across tip/sleeve of speaker cable tells of some speaker continuity, a monitored amplified source is even better. Speaker cables, plugs and jacks can also be 'partial' or partially shorted...even worse...intermittency dependent upon position.
Take it to an amp tech, or know how to work with great focus and understanding for safety, how to not get zapped by HV.
An Audio probe allows starting from the source end of the chain, pickup for test source goodness/continuity, next, through the cable at the input jack tip, then first tube stage grid, then first tube stage output...working from front to back of amp circuit, listening for what you'd expect...if a gain stage [gain] or...if a passive loss stage [like tone control], a % of loss.
A guitar/cable that works with another amp passes would pass the first half of the above chain test. Make sure a good source gets through the cable to the amp.
Continuing to probe...but stopping at the output tube grid/input.
After that it involves the magnetic coupler [transformers are a bit tricky to test but most commonly seem to work or not work at all], without a swap test or a scope, intuition or a swapped OT may offer conclusions. I sorta doubt there's trouble as described in the output transformer. The basic probe amp will not like having another amps output feeding it, this is where an oscope would come in handy.
Hope This Helps, Good Luck !