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I recently got around to building the Boogie 57 pcb. Im trying to set the bias on Q1-Q4 and i am in the 4.5v-6v range for Q1,Q2, and Q4, but Q3 will not go below 8.23v. Any ideas where i might start looking to fix this? I tried switching out all the transistors but it only changes Q3 a small amount and 8.23v is the lowest I’ve been able to get Q3. Any help is appreciated Thanks!
Hi.
Do me a favor and try changing the resistor R11 to anything between 3k and 4k7 and let me know how that reacts.
Woohoo! I replaced r11 with a 3k3 resistor and I am now able to get Q3 to bias properly. So my vague understanding is, because we used a lower resistor value it allowed more current from the transistor to ground which lowered the voltage of the drain leg of the transistor. Is that correct? Also do you think this happened because of deviations in my components and if so any broad idea who the culprit might be?
Ok so I have a new problem. After I switched the resistor I played around with it for an hour or so and it worked great. Found some awesome tones however my enclosure was unfinished so I pulled everything painted the enclosure put everything back, the only connections I had to resolder we’re the three 9v jack connections, and now the gain pot when turned up makes a loud high pitched helicopter noise and when I turn bass pot up it turns into an angry satanic feedback. I have resoldered the gain pot the bass pot the 9v jack, input and output jacks, and the ground connections to the board and 3pdt with no effect. Bias is still within perameters and I found out when I stick my finger on the board(or the resistors) @ the r2,r1,r3,r4 area the squelching/feedback goes away completely. It does this under both battery and 9v wall power. I feel like I’m loosing my mind! Haha. I’m hoping someone with a bit more mojo than me has an idea what is going on here. Thanks.
You need to re-flow the entire board. While moving it around you likely uncovered a bad solder joint that gave on you. Consider that a troubleshoot 101 must do item anytime you have an unexpected issue like that. Especially when it goes from working to not working.
Recheck or redo all off-board wiring as well. Especially grounds.
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