JHS Double Barrel clone sounds like dying fuzz at times

giovanni

Well-known member
Just to be clear, the voltage you are measuring is DC not AC? Do you have a probe to test the audio path? Next thing I would do is test the audio before the transistor, i.e., before or after C9. If the pedal sounds normal there, it’s definitely that Q1 stage.
 

Sasan

Member
First of all: Thanks for the time you're taking to help me! I really appreciate it! Thanks!
That’s really weird. Do you have cold joins at R32 and R33?
I don't think so; I even changed them both...
Just to be clear, the voltage you are measuring is DC not AC? Do you have a probe to test the audio path? Next thing I would do is test the audio before the transistor, i.e., before or after C9. If the pedal sounds normal there, it’s definitely that Q1 stage.
You had me for a second....but I checked thrice, I'm 100% sure I measured DC. Unfortunately, I don't have a probe...
Also what happens if you blend the clean tone 100%?
Nothing changes....
One more measurement: what voltage do you see across C9?
8.34 & 5.99

Don't know what I've changed but it seems most of the values that have been 4.04V before are now around the 8.6V mark...
And there's basically no sound coming from the TS side at all....just fizzly noise....BB side works perfectly though!
 

zgrav

Well-known member
Where are you touching the probe and measuring the voltage drops? Which side of a specific part?

I don't suggest changing any parts until you isolate the cause for your voltage drops. Seems unlikely to be a short or a resistor.
 

Sasan

Member
Where are you touching the probe and measuring the voltage drops? Which side of a specific part?

I don't suggest changing any parts until you isolate the cause for your voltage drops. Seems unlikely to be a short or a resistor.
Hmm, one of the probes is touching ground (from the DC jack) and the other one leg of the particular component...
 

giovanni

Well-known member
Ok so 8.6V means some of the components you replaced are now shorted :(
If you have 100% clean but still experiencing the same issue that tells me that Q1 may not be the problem. But to verify it you really need a probe. You should be able to make one with two alligator clips. Connect one to the path you want to test and to your guitar cable tip, the other to ground (on the board and the cable).
 

Sasan

Member
Ok so 8.6V means some of the components you replaced are now shorted :(
If you have 100% clean but still experiencing the same issue that tells me that Q1 may not be the problem. But to verify it you really need a probe. You should be able to make one with two alligator clips. Connect one to the path you want to test and to your guitar cable tip, the other to ground (on the board and the cable).
I just built myself a simple probe and checked some of the flow...
The sound is clear until I reach the TL074...not sure if it's supposed to be like this, but on pins 5 & 10 I hear the clean/clear sound, on the pins 6/7/8/9 it's already fuzzy...obviously, everything after these parts in the schematics sound like shit...
 

giovanni

Well-known member
Test pins 7, 8, 1, 14 of the TL074. 7, 8 should always have the clean sound; 1 should be the TS sound with full tone up; 8 is after the tone control. If it’s fuzzy at 7,8 it means we have a problem with the IC. Check the solder joints (can’t tell from the picture) and if you can, try replacing the IC. The IC is powered directly by the 9V so it shouldn’t be a power issue since the other side works fine.
 
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Sasan

Member
Could it be that IC2 got too much voltage due to the lately measured 8.6V? On the other hand, the sound was the same before the change...
 

giovanni

Well-known member
Updated my post above. The 8.6V reading wouldn’t affect the IC because that voltage divider is not part of the IC circuit. My guess is cold solder joints or a busted IC.
 

giovanni

Well-known member
And by the way, you should also address the R32/R33 divider where you measured 8.6V. It really should be ~4V at the node connecting them. That’s why you no longer hear any output.
 
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Sasan

Member
And by the way, you should also address the R32/R33 divider where you measured 8.6V. It really should be ~4V at the node connecting them. That’s why you no longer hear any output.
I replaced the diode and the two resistors, it now shows 4.2V again.

Updated my post above. The 8.6V reading wouldn’t affect the IC because that voltage divider is not part of the IC circuit. My guess is cold solder joints or a busted IC.
I replaced the IC and re-soldered EVERYTHING...don't know what helped, but it is working now!!!! At least the TS side! Thanks a lot, man.

Somehow I get a real loud beeping sound when I turn on the BB side now :D
 

giovanni

Well-known member
Awesome that the TS side works! Bummer about the BB side. In the debugging process, I believe you might have replaced some resistors used in the BB circuit? Like R34/R35? Maybe something got messed up there?
 

Sasan

Member
Awesome that the TS side works! Bummer about the BB side. In the debugging process, I believe you might have replaced some resistors used in the BB circuit? Like R34/R35? Maybe something got messed up there?
Yeah, this thing is driving me nuts :D Will try to check the BB section over the weekend, but I am pretty sure I haven't touched or replaced anything on the BB side...
 

Sasan

Member
Ok, I really really thought it’s only my fault and disability to properly solder that this sounds as it sounds...but I have a second one built that behaves almost the same (It sounds great until you really start shredding, then the TS side starts to get fuzzy) and therefore i think that (besides my soldering capabilities) something in the schematics of this pcb is not thought out well...
 

Sasan

Member
I've changed all the 100k resistors in the power section to 10k and R3 (10M) in the TS-side to 1M....not facing any problems atm
 
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