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Projects => Tech Help - Projects Page => Topic started by: Sibob on February 27, 2014, 01:06:47 AM

Title: Big Muff issues - no sound - strange Q readings?! Pictures added
Post by: Sibob on February 27, 2014, 01:06:47 AM
Hi guys, late here in the UK so I'm not thinking straight, standard :)

I'm building a Green Muff from the pedalparts.co.uk PCB/PDF:
http://pedalparts.co.uk/wp-content/uploads/2013/08/BigMuff.pdf

Component Changes:
R19 - 10k
C1 - 330n
C3 - 330n
C4 - 330n
C7 - 330n
C10 - 22n

I think I have some serious issues as here are my transistor readings:

Power in    8.71v

Q1   
C   4.44
B   0.72
E   0.13

Q2   
C   0
B   0
E   0

Q3   
C   7.67
B   0
E   0

Q4   
C   4.37
B   1.36
E   0.86

(http://i57.tinypic.com/v6nqpx.jpg)

(http://i57.tinypic.com/2vb4xgw.jpg)

(http://i58.tinypic.com/2wf1p4o.jpg)

Socketed components are currently long-legged...an issue perhaps?

:'(
Where to start? I tried putting a different 2n5088 in place of Q2, still no readings.
I very new to debugging/troubleshooting, so any pointers, starting points etc are very welcome

Thanks
Si
Title: Re: Big Muff issues - no sound - strange Q readings?!
Post by: jimilee on February 27, 2014, 03:14:52 AM
Pictures of both sides of the board would be a good start.
Title: Re: Big Muff issues - no sound - strange Q readings?!
Post by: murdog47 on February 27, 2014, 04:24:37 AM
If you are getting no sound an audio probe would be a good start. Follow the audio path with the schematic, starting at the pcb input. Finding where you lose signal can point you to a bad component, solder bridge, etc.

Title: Re: Big Muff issues - no sound - strange Q readings?!
Post by: Sibob on February 27, 2014, 07:53:23 AM
Thanks guys. Pictures added
I don't have an audio probe, will look into making one :)

Thanks
Si
Title: Re: Big Muff issues - no sound - strange Q readings?! Pictures added
Post by: murdog47 on February 27, 2014, 11:42:08 AM
He's currently restocking but this is a great way to get an all inane testing rig  ;)

http://www.jmkpcbs.com/JMK_PCBs/Store_files/The%20Testing%20Rig.pdf
Title: Re: Big Muff issues - no sound - strange Q readings?! Pictures added
Post by: murdog47 on February 27, 2014, 11:45:58 AM
Long legs are not an issue. Just make sure they are all set in the sockets and making connection. Are you getting a bypass signal and no effect or neither?
Title: Re: Big Muff issues - no sound - strange Q readings?! Pictures added
Post by: Sibob on February 27, 2014, 04:09:15 PM
Yes, I've made sure all socketed components are pushed into the sockets and connected. Although I'll go through again and triple-check.
I haven't got a switch setup on my (very) rudimentary test rig, so it's just Ins/Outs to jack sockets.
I'll put another circuit on it to test it's not the 'rig', however it was working on the previous circuit (I know that means nothing ;) )

That test rig PCB looks awesome! Thanks for the headsup!

Si