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PostPosted: Tue Sep 01, 2020 11:04 pm 
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I built one last week with no problems. Anyways, here's the scoop on this one:

1) Bypass works fine
2) LED lights up and changes speed as expected with changes to rate knob.
3) Signal passes in effect mode and the volume works (will make a nice booster if I can't get it working otherwise.
4) I can hear the buzz modulating, but the signal does not..something is not letting the clean signal modulate.

I have checked for resistor errors (please double check me good sirs). I have also checked to make sure the transistors are properly oriented and in the right spot. I have reflowed and looked for shorts...while my soldering is not perfect, i have built 25 or so bad ass pedals with no (ok, a few) problems.
https://imgur.com/SGfEtga
https://imgur.com/oPeIp9T


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PostPosted: Wed Sep 02, 2020 5:10 am 
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Got a multimeter and know how to measure DC voltage with it? I'd suggest getting lead voltages on all four transistors and reporting them here.

BTW, if you haven't closely inspected the solder side of your PCB using magnification, I would recommend doing that. It's easy to bridge two adjacent eyelets on the trannies or the electrolytic caps and cause a short that renders the circuit non-functional.

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PostPosted: Wed Sep 02, 2020 10:36 am 
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If the LFO is working, and Q2 is working as a boost, then that means you have either a cold solder joint, short, or a component failure somewhere between (and including) C3 and C5. Something is stopping the LFO from modulating the resistance between the emitter of Q2 and ground.

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PostPosted: Wed Sep 02, 2020 4:32 pm 
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byoc wrote:
If the LFO is working, and Q2 is working as a boost, then that means you have either a cold solder joint, short, or a component failure somewhere between (and including) C3 and C5. Something is stopping the LFO from modulating the resistance between the emitter of Q2 and ground.


I looked at the schematic and checked all those components for shorts with a meter, all good. Thanks for taking the time to look. I love me some BYOC!!

Measuring the transistors from the left lead left (1) to right lead (3) as looking at the flat side from component side of board

Q1
1) 9.43
2) 6.89
3) 4.5

Q2)
1) 1.04
2) 1.68
3) 5.3

Q3
1) 0
2) 0
3) fluctuates with around 180-220 MV
Certainly, these seem off.

Q4)
1) .2 MV
2) 570 MV
3) Fluctuates 3.6-4 VDC

I don't know what they should be, but this looks wrong.


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PostPosted: Thu Sep 03, 2020 4:35 pm 
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Hey all, I am fairly certain I don't have any shorts, so I am thinking I might have some bad transistors or I damaged them during install. I have some extras. Would a 2N3904 work in place of the 5088's? I am assuming they will, but don't want to go through all the trouble if they won't work. I have plenty of 5457's on hand. thanks.


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PostPosted: Thu Sep 03, 2020 4:45 pm 
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Before you go to that trouble, let me get a set of transistor voltages from a working BYOC Trem to compare to yours. Unfortunately, mine is on my pedalboard at church, but I'm looking around for another forumite who has one and can check the voltages.

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PostPosted: Thu Sep 03, 2020 4:49 pm 
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Ah, the Tremolito is the same circuit and I have one of those here, so let me check that and post my results here....

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PostPosted: Thu Sep 03, 2020 4:50 pm 
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duhvoodooman wrote:
Ah, the Tremolito is the same circuit and I have one of those here, so let me check that and post my results here....


Thanks, so nice of you!!


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PostPosted: Thu Sep 03, 2020 5:23 pm 
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Only Q3 can possibly be damaged or defective. Everything else is working. Here's a list of components that you need to check:

C3
Q3
VR1 (depth pot)
R10
C5

Can you see how they connect between the emitter of Q2 and the output of the LFO? I would be more concerned with making sure you have good continuity between these components before you go replacing them.

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PostPosted: Thu Sep 03, 2020 7:00 pm 
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duhvoodooman wrote:
Ah, the Tremolito is the same circuit and I have one of those here, so let me check that and post my results here....


OK, here's what I see on my Tremolito:

Q1 (2N5457):

D = 9.96V (= my DC voltage source)
S = 5.90V
G = 4.74V

Q2 (2N3904):

E = 1.21V
B = 1.84V
C = 7.58V

Q3 (2N5457):

D = 0V
S = 0V
G = variable @ mV level

Q4 (2N5089):

E = 0V
B = varies between 0.51 - 0.60V
C = widely variable voltage; range changes with Rate pot setting

These values would appear to compare quite closely with yours, given that there are some differences in resistor and cap values between the Tremolito and Tremolo circuits. I would suggest that you just follow Keith's guidance per preceding post.

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PostPosted: Thu Sep 03, 2020 11:07 pm 
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I’m thinking the collector voltage on Q2 is pretty low. Wondering if that might cause the transistor to not modulate correctly.

How old is this kit? There were some cases of weird 2N3904s...

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PostPosted: Sun Sep 06, 2020 3:04 pm 
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Thanks for all the help. Replaced Q3 and all is well.


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PostPosted: Sun Sep 06, 2020 3:09 pm 
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Great to hear! ENJOY!! :mrgreen:

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My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2


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