# Son Of Ben Q2 Biasing Issue



## Stephenthegun (Oct 31, 2021)

I built the Son of Ben and used what are probably not genuine J201's. I got the biasing close but not quite on Q1, however, Q2 and Q3 were in the low 3v range. The pedal sounded good, but I was hoping I could make it better, so I ordered the surface mount J201's. I installed them today and got Q1 and Q3 bang on at 5.1v and 4v but now I cannot get Q2 to drop below 9v. With the trim pot all the way down Q2 reads 9.10v and with it all the way up it reads 9.15v. What have I done? Help!


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## Cybercow (Oct 31, 2021)

Can you provide some good clear photos of both sides of the PCB?


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## Stephenthegun (Nov 1, 2021)

Cybercow said:


> Can you provide some good clear photos of both sides of the PCB?


Sorry it took me so long to get the photos up. Here they are...


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## Cybercow (Nov 1, 2021)

Well, the photos don't show anything obvious to my eyes. What about swapping the J201s around and see if the bias problem follows that one J201.


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## Stephenthegun (Nov 5, 2021)

So, I solved the mystery. I messed up my board desoldering the through-hole J201 in order to instal the surface mount ones. Thanks for your help. I guess I need to order a new board and start desoldering all my parts.


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## fig (Nov 5, 2021)

Was it just a pad that was damaged? It may be possible to bypass it.


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## benny_profane (Nov 5, 2021)

Yeah, you shouldn't need to toss the project if it's just a compromised trace. Simply run a jumper to connect the correct parts.


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## Username123 (Nov 5, 2021)

Stephenthegun said:


> So, I solved the mystery. I messed up my board desoldering the through-hole J201 in order to instal the surface mount ones. Thanks for your help. I guess I need to order a new board and start desoldering all my parts.


Benny profane is right. Plus you might damage your components if you are new to soldering and you desolder them.


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## Stephenthegun (Nov 6, 2021)

Thanks so much guys. I am new to soldering and to electronics in general. I messed up the first pad trying to desolder the original j201 and then messed up the other two trying to get the new j201 out. How would I go about making a jumper? Sorry if this is a stupid question. This is all new to me.


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## Stephenthegun (Nov 6, 2021)

If I am reading the schematic right, it looks like I need to connect the J201 to R7, R8, and R9 as well as C6. Is that right?


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## Mcknib (Nov 6, 2021)

If it's Q2 that's correct you'd only need to solder a jumper on the damaged pads not all

I usually do it on the solder side of the board simply tin the ends of your jumper and solder/ melt them onto the solder that's already there and direct to the component leg where the pads a goner

Obviously you'd need to continuity check to make sure you solder to the correct side e.g. R9 you'd want to solder to the side not connected to trim 2 along to Q2 drain pin or C6

Which pads have you damaged left, middle or right or a wee combo

If you use this image you can see some traces so you know from the J201 pinout left to right is D, S, G you can also see how the SMD J201 connects and where they connect to resistors etc


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## Stephenthegun (Nov 6, 2021)

Mcknib said:


> If it's Q2 that's correct you'd only need to solder a jumper on the damaged pads not all
> 
> I usually do it on the solder side of the board simply tin the ends of your jumper and solder/ melt them onto the solder that's already there and direct to the component leg where the pads a goner
> 
> ...



I did the full trifecta and screwed all three of them up. I want to make sure I do this right so I am going to ask what is probably an obvious question, just not obvious to me. Looking at the PCB picture posted would it be the top side of R7, R8, and R9? And would it be the positive side of C6? I think I am reading the schematic and the picture correctly, but I am not in any way self-confident. Thanks for your help!


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## music6000 (Nov 6, 2021)




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## benny_profane (Nov 6, 2021)

Can you provide a picture of your board? Which pads exactly are damaged? If you were able to successfully install the SMD parts, the only connection that might be damaged by destroying the through-hole footprint would be between R8 and the anode of C5.

The previous posts have good information about the connections you'll need to confirm / jump. Before running jumpers, test for continuity.


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## Stephenthegun (Nov 6, 2021)

benny_profane said:


> Can you provide a picture of your board? Which pads exactly are damaged? If you were able to successfully install the SMD parts, the only connection that might be damaged by destroying the through-hole footprint would be between R8 and the anode of C5.
> 
> The previous posts have good information about the connections you'll need to confirm / jump. Before running jumpers, test for continuity.


Thank @music6000 for the help; the picture makes things really clear to me. I only screwed up Q2 so I should just need to run the jumpers for this section. As you can see in the photo my desoldering attempts really jacked up the board.


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## benny_profane (Nov 6, 2021)

Oh wow. Are the pads absent on the other side of the board too? Check continuity between the all of the Q2 circles as noted in @music6000's post above.


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## music6000 (Nov 6, 2021)

If only Q2 Through Holes are damaged, this should work , Run Blue Jumper with Insulated wire from Solder side (Back) of PCB Board :


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## Stephenthegun (Nov 6, 2021)

benny_profane said:


> Oh wow. Are the pads absent on the other side of the board too? Check continuity between the all of the Q2 circles as noted in @music6000's post above.


Yeah, pretty much just gone. I took out the through-hole J201 and messed up the drain. Then, trying to get out the surface mount adapter J201 I screwed up the other 2. To be honest, I have a cheap soldering Iron from Amazon and I was getting really frustrated. Plus, I'm not yet good at soldering or desoldering. It's was the perfect storm for screwing up the board 😂


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## Stephenthegun (Nov 6, 2021)

music6000 said:


> If only Q2 Through Holes are damaged, this should work , Run Blue Jumper with Insulated wire from Solder side (Back) of PCB Board :


I feel like a child that keeps asking the same question over and over, but I want to clarify. I should link up the yellow and pink, and then wire the blue as you have shown (R8 connected to the J201 and C6). Is that right?


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## benny_profane (Nov 6, 2021)

Stephenthegun said:


> I feel like a child that keeps asking the same question over and over, but I want to clarify. I should link up the yellow and pink, and then wire the blue as you have shown (R8 connected to the J201 and C6). Is that right?


Check for continuity between the circles and verify that the SMD part is installed and making connections. The only jumper you’ll probably need is the light blue line between R8 (1k) and C5 (10u).


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## Stephenthegun (Oct 31, 2021)

I built the Son of Ben and used what are probably not genuine J201's. I got the biasing close but not quite on Q1, however, Q2 and Q3 were in the low 3v range. The pedal sounded good, but I was hoping I could make it better, so I ordered the surface mount J201's. I installed them today and got Q1 and Q3 bang on at 5.1v and 4v but now I cannot get Q2 to drop below 9v. With the trim pot all the way down Q2 reads 9.10v and with it all the way up it reads 9.15v. What have I done? Help!


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## Stephenthegun (Nov 6, 2021)

benny_profane said:


> Check for continuity between the circles and verify that the SMD part is installed and making connections. The only jumper you’ll probably need is the light blue line between R8 (1k) and C5 (10u).


I actually ruined the SMD part while trying to desolder, so I am going to reuse one of the fake J201's I bought that should go high enough to reach 4v. Sorry, for the confusion.


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## Mcknib (Nov 6, 2021)

I was waiting for you to come in @music6000 with one 'a those magnificent pix 

Yes you would just run jumpers colour to colour, connect the colours so to speak


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## Stephenthegun (Nov 6, 2021)

Yes, @music6000 the picture was really helpful. The colour-coded picture was probably necessary for my thick skull to understand. With this stuff I really need it spelt out like I am a small child.


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## music6000 (Nov 6, 2021)

Stephenthegun said:


> Yes, @music6000 the picture was really helpful. The colour-coded picture was probably necessary for my thick skull to understand. With this stuff I really need it spelt out like I am a small child.


You could use the Blue jumper as drawn & put the J201 to the 3 Resistors all from the back side of PCB.
Just make sure the J201 is oriented the right way !!!!


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## Stephenthegun (Nov 10, 2021)

music6000 said:


> You could use the Blue jumper as drawn & put the J201 to the 3 Resistors all from the back side of PCB.
> Just make sure the J201 is oriented the right way !!!!
> 
> View attachment 18266


I am about to try this method now. I tried the other way, using jumpers, and it is really ugly but I thought it should work. It doesn't. Does anyone see a glaring problem other than my board looks like an absolute dumpster fire at this point?


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## music6000 (Nov 10, 2021)

Stephenthegun said:


> I am about to try this method now. I tried the other way, using jumpers, and it is really ugly but I thought it should work. It doesn't. Does anyone see a glaring problem other than my board looks like an absolute dumpster fire at this point?


Your J201's may be fake???
Try This, It's more user friendly :
Test voltage at *D *?


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## Stephenthegun (Nov 11, 2021)

music6000 said:


> Your J201's may be fake???
> Try This, It's more user friendly :
> Test voltage at *D *?


I think the J201s are fake. They worked previously though (albeit not quite to the voltages I needed). I have tried soldering everything the way you suggested and it still isn't working right. I am really confused as to why this isn't working. I am still unable to get less than 9.1v from the drain of Q2. I plugged in the pedal to my amp just to see what would happen and it was really really sputtery. Perhaps I have wired something wrong? Any ideas?


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## music6000 (Nov 11, 2021)

Stephenthegun said:


> I think the J201s are fake. They worked previously though (albeit not quite to the voltages I needed). I have tried soldering everything the way you suggested and it still isn't working right. I am really confused as to why this isn't working. I am still unable to get less than 9.1v from the drain of Q2. I plugged in the pedal to my amp just to see what would happen and it was really really sputtery. Perhaps I have wired something wrong? Any ideas?


If you got them off Ebay, they are probably fake, Do the other 2 bias to 4.5v?
Where are you on planet Earth?


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## music6000 (Nov 11, 2021)

Check this for for Voltage & Continuity.


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## Stephenthegun (Nov 12, 2021)

music6000 said:


> If you got them off Ebay, they are probably fake, Do the other 2 bias to 4.5v?
> Where are you on planet Earth?


I got the through-hole ones from Banzai. I purchased the SMD from Musikding. The through-hole parts never made it all the way to full bias. two of them were around 3.1V. on Q2 and Q3 and the other was around 4.6V. at Q1. I got the SMD parts installed and soldered correctly in Q1 and Q3 and they are set at 5.1V for Q1 and 4V. for Q3. 

I am in Ireland.


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## music6000 (Nov 12, 2021)

Stephenthegun said:


> I got the through-hole ones from Banzai. I purchased the SMD from Musikding. The through-hole parts never made it all the way to full bias. two of them were around 3.1V. on Q2 and Q3 and the other was around 4.6V. at Q1. I got the SMD parts installed and soldered correctly in Q1 and Q3 and they are set at 5.1V for Q1 and 4V. for Q3.
> 
> I am in Ireland.


Have you tried here:




__





						Semiconductor: J201 (J 201) - N-CHANNEL GENERAL PURPOSE AMPLIFIER...
					

j 201, n-channel general purpose amplifier case: to-92 transistor




					www.donberg.ie


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## music6000 (Nov 12, 2021)

music6000 said:


> Check this for for Voltage & Continuity.
> View attachment 18474


Do you get aprox. 9.1v on the 2 Red Circles?
If you adjust the trimmer can it get less voltage on the 2 Yellow Circles?


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## Stephenthegun (Nov 14, 2021)

Sorry it took me so long to get my measurements taken. I wasn't able to get to the pedal the last couple of days. 

Yellow is measuring between 9.12-9.17 as the trim pot is turned in either direction
Red is only measuring a few mV and bouncing around inconsistently.


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## Stephenthegun (Nov 14, 2021)

Stephenthegun said:


> Red is only measuring a few mV and bouncing around inconsistently.


I am an idiot. I was not running a probe to ground. Once I did this, they all measured 9.16V


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## music6000 (Nov 14, 2021)

Stephenthegun said:


> I am an idiot. I was not running a probe to ground. Once I did this, they all measured 9.16V


With Black probe to Ground & Red probe to yellow circles, what 2 voltages are you getting with the trimmer adjusted at minimum & maximum rotation?


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## Stephenthegun (Nov 14, 2021)

music6000 said:


> With Black probe to Ground & Red probe to yellow circles, what 2 voltages are you getting with the trimmer adjusted at minimum & maximum rotation?


At minimum, I am getting 9.11 and at maximum, I am getting 9.16


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## music6000 (Nov 14, 2021)

Stephenthegun said:


> At minimum, I am getting 9.11 and at maximum, I am getting 9.16


what happens to the Voltage on the Yellow circle if you desolder the J201 from the yellow pad?


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## Stephenthegun (Nov 15, 2021)

music6000 said:


> what happens to the Voltage on the Yellow circle if you desolder the J201 from the yellow pad?


It is the same either way. Nothing changed.


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## music6000 (Nov 15, 2021)

Stephenthegun said:


> It is the same either way. Nothing changed.


Does the trimmer have the number *503* printed on the side?


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## Stephenthegun (Nov 15, 2021)

music6000 said:


> Does the trimmer have the number *503* printed on the side?


Yes, P503.


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## Stephenthegun (Oct 31, 2021)

I built the Son of Ben and used what are probably not genuine J201's. I got the biasing close but not quite on Q1, however, Q2 and Q3 were in the low 3v range. The pedal sounded good, but I was hoping I could make it better, so I ordered the surface mount J201's. I installed them today and got Q1 and Q3 bang on at 5.1v and 4v but now I cannot get Q2 to drop below 9v. With the trim pot all the way down Q2 reads 9.10v and with it all the way up it reads 9.15v. What have I done? Help!


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## music6000 (Nov 15, 2021)

Stephenthegun said:


> Yes, P503.


With DMM on Volts,  Black probe on Yellow circle & Red probe on Red circle, adjust Trimmer, it should go from aprox.1.5v to 9v!


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## Stephenthegun (Nov 16, 2021)

music6000 said:


> With DMM on Volts,  Black probe on Yellow circle & Red probe on Red circle, adjust Trimmer, it should go from aprox.1.5v to 9v!


I am not getting much of anything at all when I do this, only a few mV. Do you think my trim pot is bad?


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## music6000 (Nov 16, 2021)

Stephenthegun said:


> I am not getting much of anything at all when I do this, only a few mV. Do you think my trim pot is bad?


Try putting a temporary 27K resistor or something close from Red circle to Yellow circle.
With Black probe to Ground, Test voltage on yellow circle.


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## Stephenthegun (Nov 22, 2021)

music6000 said:


> Try putting a temporary 27K resistor or something close from Red circle to Yellow circle.
> With Black probe to Ground, Test voltage on yellow circle.


I soldered on the temporary resistor and once again got no change in voltage.


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## music6000 (Nov 22, 2021)

Stephenthegun said:


> I soldered on the temporary resistor and once again got no change in voltage.


Was this with the transistor Drain leg disconnected from the yellow circle?


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## Stephenthegun (Nov 22, 2021)

music6000 said:


> Was this with the transistor Drain leg disconnected from the yellow circle?


no the drain leg was not disconnected. I will do that and try again.


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## Stephenthegun (Nov 26, 2021)

music6000 said:


> Was this with the transistor Drain leg disconnected from the yellow circle?


I disconnected the drain leg and got the same result.


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## music6000 (Nov 26, 2021)

Stephenthegun said:


> I disconnected the drain leg and got the same result.


Are you using a good quality Digital Multi Meter, It has to change or your defying the physics of electronics!


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## Stephenthegun (Nov 26, 2021)

music6000 said:


> Are you using a good quality Digital Multi Meter, It has to change or your defying the physics of electronics!


The multi-meter has never given me trouble before, I am most likely just a moron. I will go back and do things again.


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## Stephenthegun (Dec 1, 2021)

I tried the multi-meter again and got the same result. Have I done something wrong?


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