SOLVED AionFX Heliodor- low volume and gain

Synchrony Pedalworks

Synchrony Pedalworks

Well-known member
I could use some guru help with troubleshooting this issue. I have a great run of pedals working on the first try, but my luck has run out.....

Just last week, I made a Heliodor and it worked. Yesterday, not so much. When first tested, the output had low output and gain. The Drive knob did not do much. The testing was ended quickly, because Q3 got really hot. I have tried to get voltages, but the smell of "magic smoke" is lurking. Attached is the schematic and pictures.

Right now, I have exchanged Q5. When Q5 is removed, the heat is gone, but it returns with a new 2N3906. I have not gotten voltages, because Q3 gets hot quickly and I am fearful of frying it (if not already done). I have reflowed all the parts surrounding Q3 without luck. The parts, for the most part, are verified as correct in specs. The only deviation is that I placed a parallel caps for C13, which is now 12.2 uF.

I could use a good plan for attacking this trouble shooting. With my pictures, I question a cold solder joint with the ground for the two PCBs. I was going to address that first. If the problem persists, does it sound like the issue is with the powering of VA to the Fets? Would you all evaluate that line of parts first or do I need to look elsewhere? Would you remove Q3 and get voltages for the other Fets?
Thanks,
AE

Helidor amp overdrive.JPG CA097685-67D3-487B-A0B0-A5FFB291925E.jpeg CAF340C2-58C9-4695-9AE4-271A49E98213.jpeg AE4F58E4-F68A-4BCC-9149-5705A566BA03.jpeg
 
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Synchrony Pedalworks said:
I could use some guru help with troubleshooting this issue. I have a great run of pedals working on the first try, but my luck has run out.....

Just last week, I made a Heliodor and it worked. Yesterday, not so much. When first tested, the output had low output and gain. The Drive knob did not do much. The testing was ended quickly, because Q3 got really hot. I have tried to get voltages, but the smell of "magic smoke" is lurking. Attached is the schematic and pictures.

Right now, I have exchanged Q5. When Q5 is removed, the heat is gone, but it returns with a new 2N3906. I have not gotten voltages, because Q3 gets hot quickly and I am fearful of frying it (if not already done). I have reflowed all the parts surrounding Q3 without luck. The parts, for the most part, are verified as correct in specs. The only deviation is that I placed a parallel caps for C13, which is now 12.2 uF.

I could use a good plan for attacking this trouble shooting. With my pictures, I question a cold solder joint with the ground for the two PCBs. I was going to address that first. If the problem persists, does it sound like the issue is with the powering of VA to the Fets? Would you all evaluate that line of parts first or do I need to look elsewhere? Would you remove Q3 and get voltages for the other Fets?
Thanks,
AE

View attachment 46061View attachment 46062View attachment 46063View attachment 46064
Click to expand...
Did you use the same Power supply through the Build when it was working as you used when the pedal went bad?
Is R11 - 2K7 Red, Purple, Black, Brown, Brown ?
Is Q5 2N3906, not 2N3904 ?
 
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Guardians of the analog said:
are you getting the right voltages at all VA and VB points? Make sure you have 9v and 4.5v at all appropriate places. if you don't then check those areas
Click to expand...
Q3 was getting so hot and I could smell the magic smoke, so I was fearful of measuring voltages. I thought the time needed would fry Q3.
Would you all remove Q3 to check the voltages or take the plunge and work fast? I fear that removing Q3 would alter the measurement of Q4.
 
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Synchrony Pedalworks said:
Q3 was getting so hot and I could smell the magic smoke, so I was fearful of measuring voltages. I thought the time needed would fry Q3.
Would you all remove Q3 to check the voltages or take the plunge and work fast? I fear that removing Q3 would alter the measurement of Q4.
Click to expand...
Take them out and measure the voltages. Something is clearly not right in that spot if it's hot.
 
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I'll play devil's advocate and ask the correct questions. Does your tone pot have the right taper? Did you source your jfets from a reliable source? Are all your components name brand and from mouser, we all know tayda parts don't work right 😂 imagine if we always approached it from a rational pov🤦
 
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Guardians of the analog said:
I'll play devil's advocate and ask the correct questions. Does your tone pot have the right taper? Did you source your jfets from a reliable source? Are all your components name brand and from mouser, we all know tayda parts don't work right 😂 imagine if we always approached it from a rational pov🤦
Click to expand...
Ha! Always important to remember the basics. So, yes. Pots are from Stompbox, jFets from Aion, but caps and resistors from Tayda. Electrolytics are from an Amazon bundled, so that is the biggest risk point from quality. Historically, those caps have not been problematic, but today may be the first. There are several electrolytics in the pathway of this issue.... If needed, those electrolytics (specifically C23 and C24 could be replaced). All the pots have the right taper and resistance.
 
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Guardians of the analog said:
I'll play devil's advocate and ask the correct questions. Does your tone pot have the right taper? Did you source your jfets from a reliable source? Are all your components name brand and from mouser, we all know tayda parts don't work right 😂 imagine if we always approached it from a rational pov🤦
Click to expand...
As he is a well known member with 300 plus messages, I presumed he knows that Tayda has issues with transistors & such but???
 
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@Guardians of the analog and @music6000, here is the update. I believe that Q3 and Q4 have problems, but do not know the direction that I should advance. I removed Q3 and the voltages appear to approximate what I think is correct. I switched Q4 for Q3, but the problem reappeared. What are your thoughts? Could both FETs be bad or are there downstream issues causing the voltage issues? Thanks again! Below is the table for the voltages:

1681438557693.png
 
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Why is Q3 D only reading 4.18v with the Transistor removed.
Q3 Drain is connected to Q5, can you test with power unplugged to see if Q3 D To Q5 B or E has Continuity?
 
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Confession- I found the issue. My 6.8k stash had some 6.8 ohm resistors. When double checking my values, I just compared the resistors in the stash to that in the pedal. I did not calculate the stripes to ensure the needed value. Replaced R12 and it worked. R25 also needed to be changed, but it did work with that lower value. Many thanks to those that helped and encouraged.
 
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