SOLVED Deofol Overdrive : low volume boost

Bruce Feuillette

New member
Hello!
I can't have the Boost mode functionnal. When it's on, the volume is getting really low.
I've checked the voltage on all J201. It seems fine, to me. If somebody can confirm.
ComponentDrain (V)Source (V)Gate (V)
Q84.360.230
Q94.598.93.02
Q103.890.060
Q114.58.93.02
Q121.688.91.51
Q134.620.350
Q143.028.94.84
I'm trying to follow the boost stream but it's a bit tricky. From the schematic, can someone confirm that enabling SW2 leads to use the IN2 section ?
So I had to check R17, C14 and so on.
 
I think you have source & drain swapped on several of your measurements. Recheck and update your test data. Also looks like your DMM is loading down some of the readings, Q9-G for instance. Show us some pix and make sure all of the trimmers are centered.
 
Thanks for your reply. Here's the photo.
20210329_112948.jpg

And you're right. I've spent too much time on this... :oops: Here's the correct table
ComponentDrain (V)Source (V)Gate (V)
Q84.360.230
Q98.894.593.01
Q103.880.060
Q118.894.493.02
Q128.891.541.34
Q134.680.340
Q148.894.833.02

I used an oscilloscope too, that confirmed more or less the measures. When it's written 0 for the gate, the oscilloscope was around 0.2-0.4V, like when it's not plugged anywhere.
For Q9-G it should be 3.22V, according to the oscilloscope. It's a cheap one, not a real "big" one.

EDIT : I have the whistle problem too. 😓
 
Last edited:
Your measurements are all good. Your scope and meter must have a 1M input resistance, because they are loading the measurements of the gate of Q9, Q11 & G14. Those will all read 4.45V if your meter & scope have 10M input resistance.


FOUND IT! You have C1 & C17 swapped. That 0.1u cap is partly melted, toss it in the trash and use a new one.

Visual Inspection saves the day!
 
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