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Hi All, I've been battling some noise issues and could really use some outside opinions and expertise. I have a Traynor YBA-1 Bassmaster on the bench and it's seems there's a measured 60hz hum that creeps in (up to about half volt). This usually takes between 10-30 seconds to become audible. The longer the amp sits the longer it takes to creep in.
Currently - I can ground V1 coupling caps (or pots) and it's pretty much gone. When I ground the V1 grids it's still there (or worse). I feel like that's where it's creeping in.
Background - the amp's of course been worked on prior, maybe multiple times. Some of the plate load resistors were updated. The power cable updated. I updated all electrolytic caps, node dropping resistors, screen resistor (1 470/10w per schem), filter resistor 470/10w, originally I had what I thought was a better grounding scheme but in chasing my tail I've moved grounds back where they were stock (moved caps closer to where they were stock too). Changed AC cable, the power switch broke so I put the power on the polarity switch and swapped chassis holes.
In general - I've tested most resistors, diodes measure about right in circuit, voltages by and large look good, AC on B+ about 2.9v, very low ripple on bias. I wasn't seeing much for voltage on the other side of coupling caps.
Per request I installed a LarMar style MV, nfb control, upped some mixer and PI resistors, changed grid input wires to shielded. 1 ohm cathode resistors so I could easier juggle tubes, bias trimmer/network. In back tracing and second guessing I've reverted most "mods" back to stock (in case my layout was bad/it's easy enough to redo later). I feel like I've juggled or swapped all tubes. I've tried to put the lead dress back as close to pictures as I could. At one point there were multiple sources of noise, lead dress cleanup helped a lot. One time when I wiggled V1 it seemed like some buzz occurred so I dremel cleaned the plug-in side of the socket, in the event of some carbon or something I couldn't see. All tube pins re-tension'd. Tightened jacks to chassis.
The amp actually sounds great otherwise, the new filters sound tight. I don't have a good point of reference to the noise floor pre-updates, I now wish I'd spent more time with it loud. Sometimes it gets to the point where you start second guessing everything, I trust we've all been there. Any thoughts much appreciated.
Currently - I can ground V1 coupling caps (or pots) and it's pretty much gone. When I ground the V1 grids it's still there (or worse). I feel like that's where it's creeping in.
Background - the amp's of course been worked on prior, maybe multiple times. Some of the plate load resistors were updated. The power cable updated. I updated all electrolytic caps, node dropping resistors, screen resistor (1 470/10w per schem), filter resistor 470/10w, originally I had what I thought was a better grounding scheme but in chasing my tail I've moved grounds back where they were stock (moved caps closer to where they were stock too). Changed AC cable, the power switch broke so I put the power on the polarity switch and swapped chassis holes.
In general - I've tested most resistors, diodes measure about right in circuit, voltages by and large look good, AC on B+ about 2.9v, very low ripple on bias. I wasn't seeing much for voltage on the other side of coupling caps.
Per request I installed a LarMar style MV, nfb control, upped some mixer and PI resistors, changed grid input wires to shielded. 1 ohm cathode resistors so I could easier juggle tubes, bias trimmer/network. In back tracing and second guessing I've reverted most "mods" back to stock (in case my layout was bad/it's easy enough to redo later). I feel like I've juggled or swapped all tubes. I've tried to put the lead dress back as close to pictures as I could. At one point there were multiple sources of noise, lead dress cleanup helped a lot. One time when I wiggled V1 it seemed like some buzz occurred so I dremel cleaned the plug-in side of the socket, in the event of some carbon or something I couldn't see. All tube pins re-tension'd. Tightened jacks to chassis.
The amp actually sounds great otherwise, the new filters sound tight. I don't have a good point of reference to the noise floor pre-updates, I now wish I'd spent more time with it loud. Sometimes it gets to the point where you start second guessing everything, I trust we've all been there. Any thoughts much appreciated.
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