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Made it through the build process, everything was looking good. Tap tempo seems to function, all the voltage test points from the troubleshooting guide seemed alright, etc. But I don’t seem to be getting any audio through, regardless of whether it’s bypassed or not. In terms of troubleshooting thus far…
– Bypassed, I don’t get any connectivity registering from input jack to output jack. My thought would be bad solder points on the jacks, except…
– Engaged, the continuity between input jack/R1 and output jack/center VOLUME lug works fine. So that would suggest the jacks are connected to the board fine. It would also suggest that the relay is switching fine, as continuity disappears when bypassed.
– Orientation of D1, D2, Q4, and Q5 are fine.
– In terms of the relay silencing circuit, measuring 5V at R28 as per the guide. Components seem secure, C18 and Q3 are oriented correctly, and no sign of bridging on C17 and C18.The only weird thing I can spot is checking the U2 voltages, op amps C and D are off; pins 8 and 9 are ~1.5 V and ~6.5 V respectively, and 13 and 14 are ~1.5 V and 8.5 V. Pins on A and B are fine. Don’t know if it could be at all related, or whether that’s just a separate issue I’ll have to track down.
Just looking for any suggested test points or next steps given the above info before I go ripping stuff apart. Any help would be greatly appreciated.
Sorry, meant to include: yes, I did check the input/output cables; both were fine into the amp directly.
Ugh… okay, passes audio when bypassed… which it doesn’t seem to actually, do as the relay seems to latch on (despite what the LED would indicate). And since the U2 voltages are an issue on op amps C and D, that’s likely the lack of signal. So… relay not bypassing, effect circuit problem. Time to go hunting…
Trilby,
It seems like you are, but i just wanted to make sure that you are working through the troubleshooting guide…correct?
The red LED beside the bypass foot switch should be dark when the pedal is in bypass, and bright when the effect is engaged…is this correct or is it backwards?
Just follow the steps in the troubleshooting guide and let me know where you get stopped.
Good luck.
-Brach…about the voltages on pins 8 and 9…make sure you are able to get a resistance reading across the gain trim pot (TP5 and TP6), because that’s the only thing the separates those pins. Just make sure the gain trim pot isn’t open (not connected).
Pins 13 and 14 are connected so they should be the same voltage. Please re-check this.
Yep, using the troubleshooting guide, as well as the schematic in the assembly guide (both of which are incredibly helpful, you guys are amazing).
I’m not usually one to buy in to superstition around unlucky numbers… but…
I traced the ‘always-on’ regardless of bypass switch/LED back to pin ***13*** (i.e. RLY2) on the microcontroller. It looks like the connection must be shorted in some way to pin 14; a continuity test shows both pins are connected to R31, instead of R32 and R31 respectively.
As to the lack of audio and bad opamp voltages… it looks like the solder joint on pin ***13*** (i.e. opamp D, V-) on the opamp IC isn’t connected; the pad is reading 4.5V (well, 4.7V) but the pin itself is reading 1.5V… which is likely then screwing up the values of opamp C downstream.
Pin 13 on the microcontroller… pin 13 on the quad opamp… jeez. I’ll break out the soldering iron later and see if that does it.
Yes, that is very odd…unlucky pins and all.
You are doing those continuity tests with the power off, correct? Are you sure your meter’s battery is good and it’s working correctly?
Are you referring to the “power led” or the “bypass led”… when you said it is connected to pin 13 of the microcontroller?
With the opamp…that is very unusual that pin 13 isn’t connected to the board somehow. With the power off, do you get continuity between pin 13’s pad and pin 13 on the IC? If not, try soldering the pin to the top of the baord. Do you get continuity between the pad of pin 13 and the pad of pin 14?
Lets try some higher order logic…When you test the relay connections as per the troubleshooting guide (5-C), does it appear that the relay is working as it should? (do this test with the power on so you can switch the relay).
Let me know what you find.
-Brach
Confirmed the bad connection on pin #13 of the opamp IC. Didn’t have my soldering station handy, but I VERRRRY carefully bridged the pin and pad with a metal twist-tie I had lying around. Instant audio output. So that’s an easy fix 🙂
Also confirmed pin #13 “RLY 2” on the Atmega. The moment I connected pin #13 to R32, I heard the tell-tale “click” described in the troubleshooting guide that I hadn’t been hearing. Hopefully it’s the solder joint at R32 which should be easy to fix from the top of the board; if it’s the pin on the socket, I’ll likely have to go pulling it apart (unless I want to throw caution to the wind and solder a jumper wire directly from the pin of the chip to R32… which I don’t).
Ok, good work. Look at the solder side of the board to make sure all the solder joints are solid and there aren’t any bridges on that side (i’m still thinking uC pin 13 could be bridged).
Let me know what happens when you fix those connections.
Good luck.
-Brach
Success! Touched up pin #13 on the opamp from the component side, output problem solved. Tried touching up R32 from the component side, but no change in the relay, so I took the board back out and re-soldered pin #13 on the socket (which admittedly looked like I had either missed it or barely got much soldered flowed on it); relay switching fixed. I now have a functional, kick-ass pedal! Thanks for the help!
