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 Post subject: Classic fuzz
PostPosted: Sat Apr 25, 2020 1:31 pm 
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So they pedal turns on and the volume pot works. I can't turn my fuzz all the way up without it farting out. Also having problems with the bias pot. When I turn it all the way up it works but as soon as I turn it down it cuts my fuzz out.


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 Post subject: Re: Classic fuzz
PostPosted: Sun Apr 26, 2020 11:41 am 
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The only thing I see that doesn't look correct is that you have the ring and sleeve wire ground connections on the input jack reversed, but I don't think that would have much if any effect on the problem you're describing. Still, I would correct that so that the "battery saver" feature of the input jack wiring works.

Do you have access to a multimeter and know how to use one to measure DC voltage?

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 Post subject: Re: Classic fuzz
PostPosted: Sun Jun 07, 2020 9:53 am 
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yes what are some voltages I should be getting?


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 Post subject: Re: Classic fuzz
PostPosted: Sun Jun 07, 2020 10:12 am 
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On the 2n5088
E=0.0
B=01.5
C=.663

On the other 2n5088

E=01.5
B=.663
C=17.1


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 Post subject: Re: Classic fuzz
PostPosted: Sun Jun 07, 2020 10:30 am 
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OK, something amiss here, since the voltage on ANY of the transistor legs can't be higher than your power source. So unless you're using an 18V PS, that 17V value can't be correct. Are you sure you're taking the DC measurements correctly?

The voltage on the Q2 collector should nominally run right around 4 - 5VDC, depending upon where you have the Bias control set. I'd like to see three voltage measurements on the Q2 collector:

  1. Bias pot at full CCW
  2. Bias pot at midpoint
  3. Bias pot at full CW

Reference PCB map and schematic below.

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Classic_Fuzz_PCB_map.jpg
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Attachment:
Classic_Fuzz_schemo.gif
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 Post subject: Re: Classic fuzz
PostPosted: Sun Jun 07, 2020 10:39 am 
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okay so something weird here

Bias all the way
E=3.7
B=.678
C=33.6

Bias in the middle
E=02.0
B=.667
C=21.3

Bias all the way down
E=01.5
B=.663
C=17.1


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 Post subject: Re: Classic fuzz
PostPosted: Sun Jun 07, 2020 10:51 am 
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What kind of power source are you using?

What type of multimeter are you using and on what setting?

Are you taking the readings per this procedure:

Set your multimeter to the DC voltage mode, indicated by a solid line above a dotted one. Use the 20VDC range setting if it's not an auto-ranging meter. Your power source needs to be connected and there needs to be a cable in the input jack. If the pedal is assembled into the metal enclosure, put the black probe into one of the corner screw bosses of the enclosure--this is your ground connection. If the "guts" are out of the enclosure, use the sleeve tab of the input jack for the ground connection. Then touch the red probe to each point that you want to measure.

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 Post subject: Re: Classic fuzz
PostPosted: Sun Jun 07, 2020 11:03 am 
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im using a 9v one spot power supply

I have a auto ranging DMM

I have it set to DV

I did all of that when I got those readings.


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 Post subject: Re: Classic fuzz
PostPosted: Sun Jun 07, 2020 11:10 am 
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Very strange. You obviously can't have DC voltages higher than your power source unless the circuit contains a charge pump, which it doesn't.

What voltage do you see right at the top of the PCB on the rightmost + solder joint?

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 Post subject: Re: Classic fuzz
PostPosted: Sun Jun 07, 2020 11:42 am 
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im sorry but could you explain better


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 Post subject: Re: Classic fuzz
PostPosted: Sun Jun 07, 2020 11:45 am 
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I figured out what you meant and I got 9.37


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 Post subject: Re: Classic fuzz
PostPosted: Sun Jun 07, 2020 12:07 pm 
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OK, that seems spot-on. But something is amiss with your transistor voltage readings, as a value above that 9.37V value simply isn't possible. Are you sure that the units on the measurements are volts and not millivolts or some other smaller unit??

FYI, here are the voltages on both transistors in my own Classic Fuzz. The Q2 collector voltage is shown at both extremes of the Bias pot. Note that the Q1 collector and the Q2 base have to read the same, as they are directly connected:

Image

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 Post subject: Re: Classic fuzz
PostPosted: Sun Jun 07, 2020 12:12 pm 
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im sorry lol its 17.1 mv not volts I didn't specify that. also on my readings for Q1 are E=0.0 B=01.5 C=.663


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 Post subject: Re: Classic fuzz
PostPosted: Sun Jun 07, 2020 12:31 pm 
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OK, then you aren't getting the expected voltage levels to either transistor collector. I would suspect one or more poor solder connections in the circuit as the most probable cause. Please carefully work through this process and then retake voltage readings when completed: viewtopic.php?f=9&t=52188 Pay particular attention to the two transistors, R4, R5, R6, R8 and the Bias pot connections.

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 Post subject: Re: Classic fuzz
PostPosted: Mon Jun 08, 2020 2:27 pm 
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so I flowed those solder joints and now im getting crazy negative voltages I cant get a steady reading


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 Post subject: Re: Classic fuzz
PostPosted: Mon Jun 08, 2020 2:38 pm 
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Make sure that your two meter probes are firmly seated in the multimeter. Has the meter's battery been changed recently?

Have you tested the sound of the pedal since reflowing the solder joints?

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 Post subject: Re: Classic fuzz
PostPosted: Mon Jun 08, 2020 3:03 pm 
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I plugged it in and its still doing the same thing. I also used a different multimeter and I couldn't get a reading with that ether


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 Post subject: Re: Classic fuzz
PostPosted: Mon Jun 08, 2020 3:10 pm 
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here are some photos of the joints


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