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Keskin
Copper Member
5 Posts |
 Posted - 05/24/2009 : 11:31:32
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Hi all,
hope someone can help me with this so here is the problem:
When connecting the battery or power supply to the pedal, everything seems fine but after a few seconds, the signal just fades away (even in bypass mode) and gets a bit distorted (kinda sounds like a dying battery) .
This happens every time i dis-reconnect the power.
Summary:
- Problem occurs with both, battery and PS.
- Signal fades away with both, pedal on or off.
- (With pedal off) the bypass signal almost completely fades away, (With pedal on) i can still hear some distortion and with the level pot past 3 it gets very loud all of a sudden.
- LED, switch and pots are working.
I already measured all the resistors with my multimeter but they are ok.
Thanks
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 05/24/2009 : 11:44:07
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Hi keskin and welcome!
It almost seems like the FETs aren't switching properly. One quick check - what's the DC voltage across C40 when the sound has died?
The other thing that's worth checking is Q1. Are you able to make a signal probe? - a guitar lead with a 0.1�F capacitor on the end works well. Plug it into an amp with the volume turned way down. Probe both sides of C2 and see if you have full volume there. Then probe both sides fo C1 and see if it's the same as C2.
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Edited by - Laurie on 05/24/2009 11:51:51 |
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Keskin
Copper Member
5 Posts |
Posted - 05/24/2009 : 12:27:24
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Hi Laurie,
The voltage across C40 is 4,5 V.
I couldn`t figure out the signal probe thing but i replaced Q1 with a BC168 (it`s supposed to be the equivalent to the original 2SC3378) but nothing changed.
I also replaced C1 and C2, also no improvement.
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Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 05/24/2009 : 12:34:30
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This is the type of probe I was thinking of:
http://www.bossarea.com/forum/topic.asp?TOPIC_ID=6284
Did anything happen to the pedal to make it stop working? Did it just fail one day? Did you buy it dead?
If you can do some probing....
1) Check the incoming signal is strong and clear on connection point #20 on the circuit board.
2) What is the signal like on both sides of R55? How about both sides of C3?
3) What signal are you getting on pin 5 of IC3 when the LED is lit?
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Edited by - Laurie on 05/24/2009 12:35:55 |
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Keskin
Copper Member
5 Posts |
Posted - 05/24/2009 : 13:46:31
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Found it!
On one side, R2 and R3 are connected together but somehow the copper on the PCB broke and separated them. Had to use a magnifying glass to see it though :)
Somehow you were right with Q1, R2 is right under it and connected to Q1. Thanks again. |
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MT-2 problem, help needed
