Muffler Noise Gate

Mourguitars

Mourguitars

Well-known member
I socketed my Q1-Q3 and picked the pedal up and heard a rattle and one fell out , so i wanted to test to see if they were reading right since they were loose in the sockets, got weird readings , sent this to CDB had me try a few things and wanted me to move it here...
here's what i sent CDB

https://imgur.com/84Wdtz6

his reply to check......

Going left to right...
Q1-E This reading makes no sense. Should be 0.6V lower than Q1-B
Q1-B Correct
Q1-C Correct
Q2-E Correct
Q2-B Correct, your meter is loading it down a little.
Q2-C Correct
Q3-D Wrong, should be near 5V, maybe a little lower from meter loading.
Q3-S Wrong, should be 5V (Vref_B)
Q3-G Correct, same voltage as Q2-C

I can't tell you why they are wrong. Dirty board? ( no triple checked ) Short somewhere? (looked every where , none that i see) Verify R3 is 22K. (did ) You can measure it in-circuit, just power off and pull Q1 out of the socket. reading below

R3 is reading 21.7

triple checked board for any flux or shorts....

Mike
 
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We still have to solve the incorrect voltage on Q1's emitter. Any chance that transistor is the wrong part no. also? Try measuring the voltage at Q1-E socket with Q1 not installed. Should be zero volts, unless there is a sneak path somewhere.
 
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Chuck D. Bones said:
We still have to solve the incorrect voltage on Q1's emitter. Any chance that transistor is the wrong part no. also? Try measuring the voltage at Q1-E socket with Q1 not installed. Should be zero volts, unless there is a sneak path somewhere.
Click to expand...

Ok, got a half day of work today but will do that this afternoon, those are the right ones in Q1-Q2 . I trimmed them low profile after testing them on the meter and retested , one fell out and was rattling around that’s what caused me to inspect things. I’ll post the reading’s as well....I put the correct Q3 2n5485 I my cart at Tayda....I googled a sub but all the ones I have won’t work...

Very good catch CDB ...when you said the readings were wrong on Q3 , rechecked , pulled it out and it was the wrong part #

Mike
 
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Q1 and 2 are 2n3904 both read around
hFE 288
vF 686mV on tester , Q2 is 288 and 688

Q1 reads with 2n3904 out these readings below tested 4 times and pedal on CDB

0.05
5.59
9.08


Mike
 
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I received the 2n5485 yesterday , tested them... there all in the same ball park.. installed ...checked the readings that you said Q3 should read ill post them later...but still the pedal isn't clamping down on the noise like say a Hush or the EHX silencer..
 
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You reported two different readings for Q1.
Tues 10/8:
E 0.05V
B 5.59V
C 9.08V

and on the notpad above:
E 7.20V
B 4.98V
C 9.09V
Is is possible that the 7.20 is 7.20mV?

Q1 should read (approx)
E 4.4V
B 5V
C 9V

The only way to get the reading you got on Tues is for Q1 to be blown (your meter says it's good) or for Q1's connection at the socket to be bad. Where exactly do you put the meter when measuring Q1's voltages? Try measuring right on the leads.

Matching the 2N3904s is completely unnecessary in this circuit. Any transistor that is in-spec should work.
 
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Chuck D. Bones said:
You reported two different readings for Q1.
Tues 10/8:
E 0.05V
B 5.59V
C 9.08V

and on the notpad above:
E 7.20V
B 4.98V
C 9.09V
Is is possible that the 7.20 is 7.20mV?

Q1 should read (approx)
E 4.4V
B 5V
C 9V

The only way to get the reading you got on Tues is for Q1 to be blown (your meter says it's good) or for Q1's connection at the socket to be bad. Where exactly do you put the meter when measuring Q1's voltages? Try measuring right on the leads.

Matching the 2N3904s is completely unnecessary in this circuit. Any transistor that is in-spec should work.
Click to expand...


I took it out of the enclosure this morning , before i was putting the ground inside the screw hole in the enclosure and making sure it made contact with my hand by pressing...this morning i tested the ground by putting it on the ground pad at the top of the board

Do you want me to remove the socket's for Q1 then retest with Q1 2n3904 on the PCB ?
 
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Found some 2n3904 i bought from Mouser vs Tayda

6.65
5.58
9.08

tested all 10 i bought #'s were pretty much the same out of this pack..plus or minus 1 either way
 
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This build called for a LM4558 but I subbed with a TL072...could that be the problem?

Ill recheck all the resistors , and make sure I didn’t put a different value one in the wrong spot , 6 hrs today staring at this thing, removed Q1 socket and like I said tacked it to the PCB....it’s has to be something simple I’ve overlooked

Ill stay on it !
 
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