No effects out of arachnid. Bypass signal only

[Milos38]

Hello, I have build the arachnid Multi-fx platform and am not getting any effect out of it except for plain amp audio in bypass. I have changed out the TL074, EEPROM with no change. I have two sets of EEPROMS which are the module 8 and custom loaded ones I purchased. Changing these did not make a difference. Is it possible there is something wrong with the crystal or the FV-1 chip itself? My solder work is good and I cannot see any shorts or problems otherwise. Loyal customer and this is the first problem I have ever had with a PedalPCB build. Have built about 7 prior.
Cheers,
Andrew.

 

[Milos38]

I have changed the crystal and again no effect present. Beginning to think I may have a faulty FV-1. If anyone has expected voltages for pinouts it would be much appreciated. That way I can try and figure it out.

 

[Robert]

What happens when you turn the Mix control all the way up? Do you get silence, or clean signal?

 

[zgrav]

For a problem like you are describing you need to look at the circuit diagram to find the audio patch from the input to the FV-1 chip, and then from the FV-1 chip to the output. I suggest using an audio probe to see if you an audio signal reaching the FV-1 chip on pin 1 (check the circuit diagram). If you have audio going in to the FV-1, check and see if you have audio coming out of in on pin 28. If you don't have audio reaching the FV-1 you use your DMM and audio probe to find out where the signal stops in the circuit and troubleshoot your connections. If you have audio leaving the FV-1 but not reaching the output you check that part of the circuit.

 

[Milos38]

What happens when you turn the Mix control all the way up? Do you get silence, or clean signal?

Hi, the mix control doesn’t change anything, just silent when the 3pdt is depressed. I am about to make up an audio probe. But will check the voltage regulator out put and the 3pdt and see how I go.

 

[Robert]

Ahh I misunderstood the issue you were having.

If you have no audio when you turn the mix control down, the problem is not the FV-1. The Arachnid uses an analog dry path, so unless the Mix is turned all the way up you should have a clean signal. It would pass a clean signal when you turn down the mix even if the FV-1 wasn't installed at all.

 

[Milos38]

Hi all, thanks for ideas. Found a loose output cable. Got sound coming out now but seems not all effects fire on respective rotary positions. I have reflowed rotary switch solder joints and will test again. I have also checked continuity for the switch positions after reflowing and each spot is short when selected as it should be.

 

[Sbeblis]

I have the same problem, must be a faulty board or chip..

 

[phi1]

Same problem as in the patches don't seem to work correctly on the rotary positions?

Try checking the voltage at pins 16, 17, and 18. The FV-1 will read these three bits as high voltage or low voltage (0 or 1 if you're thinking in binary). The 3 bits of 0 or 1 form 8 possible combinations.

More precisely, these FV-1 pins should either read near 0v (low, 0) or near 3.3v (high, 1). From the schematic, it should be clear which pins should be 3.3v at which rotary positions. It works out that positions 1-8 are just counting up from 0 to 7 in binary. Then, if there's a problem with the voltage on some of the pins you could backtrack from there.

Happy to add any clarification if needed.