No wet signal from older Arachnid board

[p_wats]

After finishing a double Arachnid using the newer boards (with rotary switches, etc.) I figured I'd go back to an older Arachnid I haven't had time to box up.

I got this one a while back with the FV-1 pre-populated, but I'm getting no wet signal. Here's a rundown:

• The mix and volume controls operate as expected (with is zero output when the mix is fully clockwise)
• The 78L33 measures fine and the FV-1 is getting 3.2v where needed (voltage readings match my other boards)
• I tested all the ICs (aside from the FV-1) in a different build and they all work fine
• The only change I made after populating the board was to replace the 220nf coupling caps with 1uf MLCC caps to get closer to the latest board revision (as per this thread)
• I've triple checked all component values and orientation as well as reflowed the solder joints

I'm hoping to rule out a dead FV-1, as obviously that's the most expensive part that's also the biggest pain to replace. Any tips?

 

[p_wats]

Is it possible changing the 220n caps to 1u has had an adverse effect?

 

[Robert]

No that shouldn't have had any affect, unless a through-hole pad was damaged when replacing them?

 

[p_wats]

No that shouldn't have had any affect, unless a through-hole pad was damaged when replacing them?

Thanks. It looks fine, but I'll do some tracing and audio probing when I'm back at my desk later.

The 78L33 gets hotter than the one in my other old Arachnid, but seems to measure fine.

How hardy are the Fv-1 chips?

 

[zgrav]

did you have a wet signal on the board before you changed components?

 

[p_wats]

did you have a wet signal on the board before you changed components?

Never got the board totally finished prior to making the changes. Once the newer boards were announced I stopped this one and worked on a few of those while switching out the 220n caps on this one.

 

[zgrav]

you might have a good fv-1 and spotty eeprom chip to run it. check out this thread to see how to test your fv-1 to see if it will use the internal programs on the chip. https://forum.pedalpcb.com/threads/kaleidoscope-troubleshooting.332/

 

[Robert]

Thanks. It looks fine, but I'll do some tracing and audio probing when I'm back at my desk later.

The 78L33 gets hotter than the one in my other old Arachnid, but seems to measure fine.

How hardy are the Fv-1 chips?

I've only had one FV-1 fail in all of the years I've been using them, and that was because I installed the 3.3V regulator backwards.

 

[p_wats]

you might have a good fv-1 and spotty eeprom chip to run it. check out this thread to see how to test your fv-1 to see if it will use the internal programs on the chip. https://forum.pedalpcb.com/threads/kaleidoscope-troubleshooting.332/

Thanks. I was able to test the eeprom and all other ICs in another working Arachnid, so I know they are fine. I'll check that link for tips just in case though.

I've only had one FV-1 fail in all of the years I've been using them, and that was because I installed the 3.3V regulator backwards.

That's good to know! Thanks

 

[p_wats]

Got home and was able to do some continuity testing around the caps I replaced. C8 was making the connection to the pin 24 of the FV-1, but the other side wasn't passing connection to the R6/IC5 junction. Hardwired that connection and now it's all working as expected. Thanks for the help!

 

[the_grumpy_gnome]

I've only had one FV-1 fail in all of the years I've been using them, and that was because I installed the 3.3V regulator backwards.

I recently killed one of these doing exactly that. The second attempt was an excellent success.