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I’m just now seeing your post from the 12th. I’m sorry that I haven’t been more available to help you. I’ve been so busy with trying to get a new product released, taking care of a very sick 6 year old, and staying up with my baby who’s not sleeping well that i haven’t had time to help you (or anyone else that i’m currently in the process of helping) troubleshoot anything for the past few days. I’m sorry that you took my busyness as “blowing you off”. We are not obligated to help our customers build their kits, but we do it because i have a passion for helping people understand their gear. When someone gets a kit (instead of a ready to play product) part of the process of building it is troubleshooting, which takes a lot of patience. I will do my best to help you, but i can’t guarantee anything because a lot has to do with your skills and knowledge. In our previous posts i think maybe i was assuming too much…I’ll try not to assume anything.
Now, let’s get on to troubleshooting…
I don’t want to assume anything or be condescending, but it would be helpful for me to know if you can read and understand the schematic in the back of the assembly manual. And (also not to be condescending, but) if you don’t understand anything i’m asking of you please just let me know and i’ll explain…we’ll save a lot of time and frustration that way.
The high frequency signal path works, but the low frequency path doesn’t. We’ve narrowed down that the digital side of things is working…the low opto led is lighting up. So we know the issue is in the analog path. You said you corrected the jumpers and now they are soldered correctly. To be sure of that, (with the power off) please test the continuity between pin 1 on U2 (the TL074) and TP3 (they should be connected, test them with your meter’s beep test). Also test the continuity between TP4 and R5 (the pad closest to R19 and R20). These tests will tell us if the jumpers are soldered correctly. Sometimes when the jumpers are heated up too much one of the little rectangular pads can come off the board.
Please make those tests and let me know what you find.Thanks for your interest in the VPM-1.
We don’t do anything to the actual pedal hardware. On the 20 or so units that I’ve modded on used Ernie Ball VP Jr pedals, all of them seem to behave properly…the treadle stays in place when it’s set in one position. It sound’s like your VP Jr may be too worn out to use this way. When I get some time I’ll take the treadle off of one of them and see if there is any adjustments that can be made to tighten the axel up.
-BrachEven in calibration mode there is still no low frequency sound?…after turning up the trim pot? Keep the depth knob fully counter clockwise all the way off when you test the calibration mode.
Make a tiny incision on the heat shrink in the back of low side optocoupler (with your xacto knife), near the the leads of the opto’s led. No longer than 1mm long. In calibration mode, with the harmonic mix knob on the low side, look to see of the opto’s green led is lighting up. If not, turn the low side trim pot all the way up (clockwise 20 times) to see if you can see it light up. If it does light up then you have a problem with the analog signal path, if it does’t light up there is a problem with the led or it’s driving circuit.
Let me know what you find.
-BrachThanks for checking that stuff. That is good information to have.
Are you sure the jumpers are jumped correctly? JP1 and JP2 aren’t connected, are they?Yes, I agree…the loudness is probably just the gain pot over adjusted.
When the pedal is engaged, does it sound different than in bypass (other than it being louder)?
On the middle pin of depth knob…Are you getting a variable DC voltage between 0 and 5V as you turn the knob?…or is it always at some low voltage, close to 0V?
Are Q1 and Q2 installed properly?
Are you hearing both channels (high and low) fine in calibration mode?
-BrachMake sure all the tube pins are making good connection in their sockets. Sometimes it’s easy to over-loosen the sockets when assembling. If pin 2 (the plate) wasn’t making good connection then the screen (attached to the 2k2 resistor) would start drawing too much current. So tighten all the tube sockets.
…But I’d start by turning on the amp without the tube in the socket to see if the problem is just related to the tube and/or socket.
Keep me posted on what you find.
Good luck.
-BrachWhat is your Quaverato’s serial number?
Just as an experiment, try to use a linear power supply instead of a switch mode power supply. In the past we’ve had good luck using liner power supplies or even a battery (with a barrel-to-9v-battery-snap adapter) to get rid of noise issues. If the noise changes when using a different power supply it will help with troubleshooting.
-BrachDid you build this from a kit or was it built by us, at ZDL? What is your serial number?
Just to be clear, you are saying that the pedal works fine, when it is either bypassed or engaged, but when it is engaged the effect doesn’t seem to be working (there is no tremolo), just a louder guitar signal. Is this correct?
About the volume issue, set the volume knob in the center and adjust VR10 until the gain is set to unity.
-BrachDoes it respond to the tap foot swtich?…(with the multiplier knob set to 1:1) Can you tap out a tempo?
-Brach25K is not enough resistance to stop the signal from getting through the high frequency signal path. But you wouldn’t get an accurate reading anyway unless you unsoldered the jumpers…the dc voltage from opamp pins will skew the reading of your ohm meter. The most likely cause is a bad solder joint somewhere. Make sure everything is soldered correctly…including the jumpers. You can double check that the high frequency optocoupler led is being lit up by making a tiny incision with you xacto knife (about 1mm long) on the heat shrink on the back side of the led (close to the led’s leads). That way you can see if the led is actually bright when it’s supposed to be bright (when the depth knob is at 0, for example…or when in calibration mode on the high harmonic mix setting).
If the LED is turning on then the problem has to be in the high frequency signal path somewhere…most likely a bad solder joint. Use the schematic to trace out the components in the high frequency path and then look for bad solder joints in those areas.
Let me know what you find.
-BrachSo that’s good that the FET fixed the no signal issue.
Now it sounds like something is wrong with the high frequency signal path. We need to know if the problem is with the digital control (as in the high optocoupler’s led isn’t lighting up) or if the problem is in the audio signal path.
With the depth knob at 0 (fully counter clockwise) what DC voltage do you get on the square pad of the high side optocoupler (opto1)…from ground (black lead on ground, red lead on the square pad)? It should be about 1.8V dc.
-BrachYes, that would do it. Good job noticing it was backwards. That is a FET (field effect transistor) which is responsible for momentarily muting the audio signal while the relay is switching to keep the relay click out of audio path. Since it’s backwards it might be constantly keeping the signal muted, so that’s why everything is really quiet.
Email us at info “at” zeppelindesignlabs.com and we’ll explain how to get a new FET.
-Brach
