| Author |
 Topic  |
|
Laurie
Double Platinum Member
Canada
4854 Posts |
 Posted - 01/12/2009 : 17:33:53
|
OK... that made me smile! 
What i'm going to do tonight is take a full set of readings on my known good one and get you to replicate those readings on yours. Instead of "poking around" one piece at a time and getting confused, this will give us a complete snapshot of the status of the entire flip/flop switching circuit.
We'll do it with the status LED on and with it off. The differences between mine and yours will hopefully tell us where the fault lies.
|
 |
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/13/2009 : 04:05:43
|
Here are the readings from my good pedal. Please take the same readings and post them back here - just maybe make a table with the reference letter ("A" through "W" - note that there is no "I") with the "ON" reading and the "OFF" reading.
Note that where my meter read something small like 0.02V I just recorded that as "0V".
Please check whether the LED is on or off when making each reading - touching your meter to some of the components can cause the pedal to flip from ON to OFF (or OFF to ON). Sometimes I had to put the probe on the component then press the switch to put the LED back to where I wanted it.
Please don't forget to record the voltage on the stripe side of D4 as well.
|
|
|
|
Mesjoggah
Gold Member
Netherlands
595 Posts |
Posted - 01/13/2009 : 16:45:56
|
Great Laurie!
Unfortunately i don't think i can find time for it until friday |
|
|
|
Mesjoggah
Gold Member
Netherlands
595 Posts |
Posted - 01/14/2009 : 07:05:16
|
Quicker than expected i found time to measure!
here we go:
LED 'ON'
A-5,8
B-9,1
C-5,8
D-3,0
E-0,6
F-5,8
G-0
H-5,8
J-0
K-0
L-0
M-0,6
N-0
P-0
Q-0,6
R-0
S-9,1
T-0
U-4,6
V-4,6
w-3
With the LED 'OFF'
A-0
B-9,1
C-0
D-0
E-0
F-0
G-0,6
H-0
J-0
K-0
L-5,8
M-0
N-0,6
P-5,8
Q-0
R-0
S-9,l
T-5,8
U-4,6
V-4,6
W-0
Next set of measurements please!, no just kidding, hopefully these lead to a clue! |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/14/2009 : 14:51:13
|
Cool! Thanks!
This tells us definitively that the flip/flop itself is working fine. What's happening is that the gate drive for the switch FETs is not high enough. Point "D" should be 5V or higher when the effect is ON.
The drive into R45 is good (point "C", 5.8V) but something on the other side of R45 is pulling it down to 3V which isn't enough to switch the FET - it should be over 5V like in my pedal. I suspect one of the switch FETs has failed.
Pull D1, turn the pedal ON and see what the voltage is at point "D". If it is still 3V, pull D5 and measure again.
|
|
|
|
Mesjoggah
Gold Member
Netherlands
595 Posts |
Posted - 01/14/2009 : 17:12:09
|
quote:
Originally posted by Laurie
Cool! Thanks!
This tells us definitively that the flip/flop itself is working fine. What's happening is that the gate drive for the switch FETs is not high enough. Point "D" should be 5V or higher when the effect is ON.
The drive into R45 is good (point "C", 5.8V) but something on the other side of R45 is pulling it down to 3V which isn't enough to switch the FET - it should be over 5V like in my pedal. I suspect one of the switch FETs has failed.
Pull D1, turn the pedal ON and see what the voltage is at point "D". If it is still 3V, pull D5 and measure again.
I pulled D1 and still measured 3 volts, then i pulled D5 (D1 and D5 are both pulled then, ok?) and still measured 3 volts.
|
Edited by - Mesjoggah on 01/14/2009 17:25:13 |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/14/2009 : 18:13:21
|
OK. Replace D1 and D5 and pull C30.
It should work now(!), but will have a "plop" when switching. |
Edited by - Laurie on 01/14/2009 22:57:34 |
|
|
|
DeFrag
Moderator
USA
3409 Posts |
Posted - 01/14/2009 : 21:06:21
|
Quite the evolution guys!  |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/14/2009 : 22:57:06
|
quote:
Originally posted by DeFrag
Quite the evolution guys!
It's coming along... if it's not C30 it can only be a fault in the PCB fabric. |
|
|
|
Mesjoggah
Gold Member
Netherlands
595 Posts |
Posted - 01/14/2009 : 23:34:02
|
quote:
Originally posted by Laurie
OK. Replace D1 and D5 and pull C30.
It should work now(!), but will have a "plop" when switching.
Laurie, with 'replace D1 and D5' do you mean to put new ones in or the old ones?
I placed the old ones back in (in the right direction) and pulled C30, there's no 'plop' when turning on and the pedal acts like before.
Edit: the LED got less bright and died a second later.. R.I.P. odb-3? |
Edited by - Mesjoggah on 01/14/2009 23:44:34 |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/15/2009 : 00:11:43
|
quote:
Originally posted by Mesjoggah
quote:
Originally posted by Laurie
OK. Replace D1 and D5 and pull C30.
It should work now(!), but will have a "plop" when switching.
Laurie, with 'replace D1 and D5' do you mean to put new ones in or the old ones?
I placed the old ones back in (in the right direction) and pulled C30, there's no 'plop' when turning on and the pedal acts like before.
Edit: the LED got less bright and died a second later.. R.I.P. odb-3?
OK.... no, it won't be RIP. We may have a "hard failure" now though (a good thing). With D1 and D5 removed, there was nothing else but C30 in the signal path. Does it go back to the "normal" failure with C30 replaced?
"replace D1 and D5" meant to put the old ones back in, just like you did.
Time for some high-res pics of the area........
|
Edited by - Laurie on 01/15/2009 00:19:10 |
|
|
|
Mesjoggah
Gold Member
Netherlands
595 Posts |
Posted - 01/15/2009 : 07:21:04
|
| Pfff, i thought i killed it, but after i put back C30 it came back alive just like you said Laurie, i will try to make some pictures today and post them here. |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/15/2009 : 14:44:26
|
Let me think on this... We are definitely looking in the right place. Removing C30 should NOT kill the pedal.
C30 is the "soft switching" capacitor - R45 and C30 form an RC network with a "time constant" of 47ms... in other words it takes 0.047 seconds for the pedal to switch states. Slow enough that you don't hear a "thump" or a "plop".
Removing C30 should just make it switch faster producing a plop.
EDIT: To confirm my statement above, I removed C30 in my known good pedal, and it continued to work with no issues.
We are definitely in the right place with the fault-finding. Now just WTF it could be is another question entirely....
|
Edited by - Laurie on 01/15/2009 16:24:58 |
|
|
|
Laurie
Double Platinum Member
Canada
4854 Posts |
Posted - 01/15/2009 : 17:30:39
|
quote:
Originally posted by Mesjoggah
i will try to make some pictures today and post them here.[/red]
The areas of interest are around C30 and R45, and around D1 and D5. "macro" closeups of those areas would be cool |
|
|
|
Mesjoggah
Gold Member
Netherlands
595 Posts |
Posted - 01/15/2009 : 21:33:08
|
One thing i am never without is a set of full charged batteries for my cam.. until today...
Laurie, as this should be a learning proces for me i have a question:
It is clear that my pedal lacks voltage on some point, so what component normally provides the necessery 5V where i measured 3V ?
Is this short of voltage most likely the problem or what is your opinion on this?
The current flows through C30 but when pulled it should also flow somewhere else (otherwise your pedal should be killed too)
I pulled C30 again tonight just to see if i was not mistaken by telling the pedal died, i saw the LED die but noticed the signal comes true like it always does.
Aaaargh i putted C30 back again and now the LED won't go anymore, signal is still bypassed. |
|
|
|
Topic |
|
ODB-3 troubles
