Author Topic: Problems with circuit  (Read 4001 times)


Problems with circuit
« on: November 09, 2009, 05:04:49 PM »
Hi guys, having a bit of a problem with this boost circuit. I'm getting attenuation instead of a boost, but hey at least the pot does something, thats better than my fuzz face attempt!! I've hunted through the circuit many a time now and found a couple of problems (the 10k and 100k going up to 9v were the wrong way round). Im now 99% sure its built as shown in the schem, and i've used the wiring picture provided but omitted the led part. I've gone through and checked all the voltages and all are correct apart from the collector voltage which is only 4.5v this goes up to 8.8v when the transistor is removed. I've double checked the resistor value between the C and 9v and its 10k (measureing 7.9k in situ).

Now this thing might be an associated problem or maybe not even a problem at all... I originally built it using a blue 0.1 uf resin dipped ceramic monores ??? cap as the input cap, but after finding about 3v on the input (before cap) and 1.5v on the output (after cap) I swapped it for a green film one as suggested, this brought he voltage down to 1.2v and 0.8v but just now as ive tested it it seems they discharge as i hold my meterleads on so guessing this is nothing?

Could it be anything to do with my pickups being 2 big humbuckers on a balance pot set up?? turning the tone on my guitar down also makes a heart beat type sound when the circuits running. This reduces slightly if i use a 2n2222 instead of the 2n3904.

Sorry I know I've waffled on a bit but tried to include everything I've found. any help would be greatly appreciated.

Thanks Tom


Re: Problems with circuit
« Reply #1 on: November 09, 2009, 05:36:50 PM »
What kind of transistor and are you sure you are getting 1.2V before the input capacitor???? Also .8 after the output capacitor too?


Re: Problems with circuit
« Reply #2 on: November 09, 2009, 05:56:21 PM »
yep, 1.9v before the input cap (green film with 104k on it) and after the output cap (10uf 63v) im getting 0.44v but it doesnt seem to be discharging now, might not have had the tranny in earlier. what should the voltage be here? 0v?

still confused by the 4.5v on the collector....

I've got a 2n3904 in it at the mo (flat side pointing toward output) and Ive tried a black semicircle plastic 2n2222 and a little metal tin version.


Re: Problems with circuit
« Reply #3 on: November 10, 2009, 02:47:25 PM »
FIXED IT!!!!! such a simple stupid problem as well, the mono socket i used has 4 tabs, 2 sleeve, 2 signal, when building the circuit I had grounded the jacks to each other but not to the circuit, so whilst i was still doing the initial wiring up, instead of cutting off the heat shrink and using the sleeve tab I had already used, I simply/stupidly used the second sleeve tab on the opposite side, little did I know this worked like a switch when the jack is inserted. Swapped it back over and puuuurfect!!! Sounds even better to me now though because of all the anger and frustration of debugging .Hopefully this will have also solved the problems I had with my fuzz face attempt.

Many thanks for taking the time to set up a project like this and then helping me and my fellow retards accomplish something new and otherwise unreachable.

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