Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: hesamadman on November 10, 2014, 01:56:55 pm
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I laid out another 5 watt. This time there were 2 differences.
1. I used a 290ax PT rather than a 269JX. This is about 100 more volts on the secondary.
2. I didn't have much board material so I compacted the layout pretty close.
The amp worked and sounded great, but it had a hum that was pretty annoying. It was loud. Not normal loud. I tried everything. Moving wired, grounding, had to make a heater filament center tap. I could not get that hum to budge. Im wondering if its possible to have laid out components too close. There wasnt any AC wires close to the preamp circuitry. Power amp and preamp had a sufficient amount of gap between. Could I have something mounted too close on the board?
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The last board I made had the turrets on a .25" spacing. Show us a schematic and some hi-rez pics.
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The last board I made had the turrets on a .25" spacing. Show us a schematic and some hi-rez pics.
I didnt think this was the case. I mean PCB has components neck and neck. I pulled the board. Gonna work on wire routing later and will get better pics.
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And this
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Would filtering be an issue if volume control will control hum? Since this transformer is of a higher voltage, wondered if filtering should be adjusted.
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If you mean turning the volume down reduces the hum (or turning it up increases hum), then no. The hum is between the input jack and volume control.