VHS, no sound, FV-1 issue? (SOLVED)

irvmuller

irvmuller

Active member
So, I built a 2 in 1 pedal. It’s a VHS going into a Phase II. I’m getting clean signal though the pedal. The Phase II works perfectly. The VHS, when I engage it it gives me a hiss sound and no bass signal. I notice when I switch on the Chorus or Reverb there is a loud pop. No pop when I switch on the Boost. There don’t seem to be any power issues. All the LEDs light up perfectly. I accidentally ordered Film Caps for 1u instead of Electrolytics and just used film. The Film Caps were too big to be on top and so I connected them from underneath.
Any input is helpful.

2654031A-C4B4-4218-8697-1BC983C001AA.jpeg
 
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Went through ALL my pieces last night: resistors and caps just to make sure EVERYTHING was the right value. I also added extra solder to a few pieces that I thought might need it. No luck.

I'm starting to lose hope on this one and am wondering if I need to start over or just move on. I've built over 15 pieces and this is by far the most trouble I've had and might be my first failure to work. I just can't figure this one out.

I did not socket parts this time and I usually do. That's on me.

Gonna try to check continuity later today. Not sure how that works with the FV-1.
 
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irvmuller said:
Gonna try to check continuity later today. Not sure how that works with the FV-1.
Click to expand...

Just put one probe on an FV1 pin, and the other to a resistor/cap that's supposed to connect to it. See if there's continuity everywhere.

Maybe @p_wats could help, he seems to have doing quite a bit of troubleshooting around FV1 builds these days! :)
 
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Boba7 said:
Just put one probe on an FV1 pin, and the other to a resistor/cap that's supposed to connect to it. See if there's continuity everywhere.

Maybe @p_wats could help, he seems to have doing quite a bit of troubleshooting around FV1 builds these days! :)
Click to expand...

Ha. That I have, though not by choice. ;)

Nothing special about continuity checking with the FV-1, just follow the schematic and check that the right pins show continuity to the right components (ie, pin 13 should connect to one side of R5).

I recently ran into a bad noise issue that turned out to have been caused by a tiny lifted trace near lug 2 of the mix pot. All the jostling to get the board in/out of the enclosure put pressure on the board-mounted pots and cut off VREF from where it needed to go next.

To that end, if I were you, I would follow the schematic and make sure continuity is right for each component connection. The good news is that if I can fix my ailing build then you definitely can too!
 
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Here are some other things you can check:

Make sure the value for C11 is correct, since that pot connects the audio path to ground.

You can also check to see if your audio probe picks up any signal on pin 27 of the FV1 (it is an audio output, but not actually connected to anything in this case). If you had sound on pin 27, you might be getting output to pin 28 that is being shunted to ground. Check to see if you have any unintended ground connections to the audio path between the FV-1 pin 28 and the connections all the way to the output jack. The only parts that are supposed to connect to ground are C11 and R4.

If you are not getting any audio signal on pins 27 or 28, you could also try using a jumper wire to connect FV-1 pin 1 to pin 28 to see if you get a clean signal going through to output. if so narrows your troubleshooting down to the FV-1.

At that point, if you have a spare crystal, go ahead and replace the one on the board to see if that brings your FV-1 to life.
 
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zgrav said:
Here are some other things you can check:

Make sure the value for C11 is correct, since that pot connects the audio path to ground.

You can also check to see if your audio probe picks up any signal on pin 27 of the FV1 (it is an audio output, but not actually connected to anything in this case). If you had sound on pin 27, you might be getting output to pin 28 that is being shunted to ground. Check to see if you have any unintended ground connections to the audio path between the FV-1 pin 28 and the connections all the way to the output jack. The only parts that are supposed to connect to ground are C11 and R4.

If you are not getting any audio signal on pins 27 or 28, you could also try using a jumper wire to connect FV-1 pin 1 to pin 28 to see if you get a clean signal going through to output. if so narrows your troubleshooting down to the FV-1.

At that point, if you have a spare crystal, go ahead and replace the one on the board to see if that brings your FV-1 to life.
Click to expand...

So, C11 is correct.

No sound out of pin 27.

When I jump pins 1 and 28, no signal passes... which is confusing to me.

I'm going to go ahead and change out the crystal. I happened to order an extra one and so am lucky to have it on hand.

Thanks for all the suggestions.
 
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Big news today.

I tried jumping pins 1 and 28 before but no signal passed. HOWEVER, I jumped pin 1 to C8, the first cap after the FV-1, and signal passes!

So, the issue must be with the FV-1or the way it was soldered on. At least I think. I already changed the crystal so it's not that.

Moving from here, I want to hear what possible solutions you guys might have. Please holler back guys.

I'm hoping to be able to fix this one. I did finish checking continuity and couldn't find any issues with that. I've never had to solder a chip that small before so if I have to do that it'll be something new for me.:oops:
 
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irvmuller said:
Bigger news! I grounded pin 13 and the signal passed through perfectly. This means the issue is with the eeprom!

Next steps anyone?
Click to expand...

Good progress! When you ground pin 13 does it produce an effect (the internal FV-1 programs should be on at that point---the first one is a reverb with modulation, if I recall)?
 
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you have already verified your connections between the eeprom and the FV-1, so there is a chance you have a blank (or defective) eeprom. (just to be sure -- did you verify connectivity from the pins on the eeprom to the FV-1? if not -- give that a quick check to make sure it is not just a bad socket)

assuming your eeprom is in contact with the FV-1, you should get another eeprom and give it a shot.
 
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zgrav said:
you have already verified your connections between the eeprom and the FV-1, so there is a chance you have a blank (or defective) eeprom. (just to be sure -- did you verify connectivity from the pins on the eeprom to the FV-1? if not -- give that a quick check to make sure it is not just a bad socket)

assuming your eeprom is in contact with the FV-1, you should get another eeprom and give it a shot.
Click to expand...

The eeprom in this case is programmed by pedalpcb into the FV-1. That's why when I ground pin 13 signal finally passes. Something must have gone wrong in programming it.

If you're talking about IC2(24LC32A), that kicks in at pin 14 and is allowing signal to pass.
 
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the eeprom holds the programs for the FV-1 and are loaded in every time the pedal is powered on or when the program knob is changed. that is why you can order different eeproms to change the programs that run on the FV-1. the programs that are in the internal memory are part of the FV-1 chip.

you can ask to get a replacement eeprom mailed to you to see if that solves the problem. someone else also had a bad or blank eeprom for a build a couple of months ago, so that seems to be the case here as well.
 
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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.
 
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Robert said:
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 just checked all of that and it all checked out...
 
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