VHS Pedal, bypassbut no effects

DedSecV

DedSecV

New member
Hello everyone, newbie here :) I got my hands on the VHS Pedal from the german distibutor musikding.de
It was my 5 pedal build and the first with an SMD Chip on it.

Sound comes through in bypass mode, but when I turn it on, only a suuuuper quiet signal comes through. I can barely hear it, but my interface shows that something is coming through. Normally, there should be a faint hiss because the pedal uses the FV-1 digital signal.

I checked the resistor values—they all seem to be correct. Capacitors, transistors, and ICs are all in the right places. The LEDs also light up when I switch on the individual modes. Just to note, this was my first SMD IC. I pre-tinned the board and then soldered it on with a hot-air gun. Just to be safe, though, I heated each pin again with a soldering iron.

Here are messurements from the different ICs:

L78L33:
PIN123
Voltage in V3,300

24LC32A
PIN12345678
Voltage in V00003,33,203,3

TL072CP
PIN12345678
Voltage in V4,34,34,304,34,34,38,6

FV-1
PIN1234567891011121314
Voltage in V1,11,11,203,33,30,03,31,90,9 (crystal)0,00,02,9 (modulated)3,2 (modulated)
PIN1516171819202122232425262728
Voltage in V3,33,33,3003,23,30,03,30,00,01,42,60,7

Here’s the current schematic and pictures of my build:

IMG_7758.JPEG IMG_7760.JPEG IMG_7761.JPEG

I tried Roberts steps mentioned here
The VHS algorithm is on the 24LC32A, not loaded directly onto the FV-1 IC.

Grounding pin 13 disables the external 24LC32A EEPROM and runs the internal programs of the FV-1 IC.

Check for 3.3V on Pin 8 of IC2 and verify continuity between IC2 Pin 5 / IC3 Pin 15, and IC2 Pin 6 / IC3 Pin 14.
Also verify that Pins 1 - 4 of IC2 measure 0V (continuity to ground).

If all of this checks okay it sounds like I need to ship you a replacement EEPROM.
Click to expand...
I grounded PIN 13. But unfortunately, I can't hear any effect. There is continuity between the specified pins on IC2 and IC3 and ground. Is the programming possibly messed up? Do I need a new EEPROM?

I tried bridging PINs 3 and 7 of the Opamp but now only a clean signal comes through regardless of whether on/off

I also tried some troubleshooting with the guys over in the musikding forum, but so far no success...

Thanks in advance!
 
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I've been down this road with another member and ended up having him mail the board to me... His ended up being the incorrect toggle switches... Confirm what toggles you have soldered in... Calls for DPDT ON/ON
 
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You can ignore the EEPROM for now.

Shorting pin 13 to ground activates the internal programs of the FV-1, bypassing the EEPROM.

We haven't guaranteed that it's good without a doubt, but it's not causing the issue at the moment.
 
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RICHB555 said:
Maybe try using the Stomp switch breakout board for input and output connections instead of wiring to the switch lugs?
Click to expand...
It was a test with the wires directly on the lugs, now i use the breakoutboard thats already in the picture. Switch works fine according to my measurements.

jwin615 said:
Just to be sure, you're not plugging you cables in backwards? I.e. guitar to out jack.
Easy to do when the pedal is inverted
Click to expand...
Yes tried it in reverse also :D juuuust to be sure. Still no success, that would have been nice...

I am getting a new FV-1 send now, as there is just no output signal from it wether I connect the EEPROM or not. Any tips how to solder it on? As mentioned initially I pre-tinned the board and then soldered it on with a hot-air gun. Then I heated each pin again shortly with a soldering iron. I am using hot air and solderiron at 350°C and lead solder.

I thought that my job looked quite nice, but it was my first SMD chip :oops:
 
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