Did I fly to close to the sun (and fry my FV-1)?

[p_wats]

I posted this build of an old Arachnid board with some mods and everything was working perfectly, until I tried to push it a little further. I wanted to build a little daughter board to sit in the EEPROM socket and switch between 2 EEPROMS (as per this post), but needed to adapt the layout in that thread to fit the older board (EEPROM on the opposite side of the board).

Something appears to have gone wrong, as now the circuit in general doesn't work (I've removed the EEPROM daughter board).

I didn't find any shorts in my daughter board that would have sent 3.3v to the wrong spot, but I now get no output from the FV-1 (not even using the internal programs).

• Using my audio probe I get sound at pins 1 & 2 of the FV-1, but nothing at pin 28.
• I've got 3.3v to all the correct pins and also ground where required.
• Mix and volume controls work as expected, reinforcing that maybe I somehow killed the FV-1 itself.

Anything else I should check for?

I've got a rework station, but I doubt it's going to be easy to get this FV-1 off the board and replace it without doing some damage.

 

[zgrav]

You can ignore my prior post. I was measuring the wrong pins on the eeprom. I will check them again after I learn to count to 5 an 6. : ^ )

 

[zgrav]

I also get 3.5v on pins 5 and 6. if you use your DMM to check the resistance between pin 13 and ground on the FV-1, what are you getting?

 

[p_wats]

I also get 3.5v on pins 5 and 6. if you use your DMM to check the resistance between pin 13 and ground on the FV-1, what are you getting?

With power disconnected I measure 12k between pin 13 and ground (same on two other working circuits---I also found an even older Octagon board that measures 20k to ground).

 

[zgrav]

Ideally you would find something on the board you could fix, but it might be that the FV-1 is damaged and won't load any external programs now. The FV-1 runs the internal programs when pin 13 is grounded, and your chip seems to think it is grounded in its present state. Seems like a long shot, but when the pedal is powered, try grounding pin 13 for a few seconds, and then un-ground it to see if it loads the program from the eeprom. If possible have something playing through the pedal at the time to see if you get any change in the wet signal when you ground and un-ground pin 13.

 

[p_wats]

Ideally you would find something on the board you could fix, but it might be that the FV-1 is damaged and won't load any external programs now. The FV-1 runs the internal programs when pin 13 is grounded, and your chip seems to think it is grounded in its present state. Seems like a long shot, but when the pedal is powered, try grounding pin 13 for a few seconds, and then un-ground it to see if it loads the program from the eeprom. If possible have something playing through the pedal at the time to see if you get any change in the wet signal when you ground and un-ground pin 13.

No luck, unfortunately. I have a test rig with an oscillator tone I can run through pedals and grounding pin 13 for any amount of time has no effect (neither does applying 3.3v to it).

I'll likely try removing the EEPROM socket, just in case, but I doubt that will do anything either. It would be great to rule out either the board or the FV-1, so I know which can be salvaged, but worst case I'll ditch them both and just repopulate the enclosure with the other older board I have sitting here.

Thanks for your help so far!

 

[zgrav]

It sounds like you have connectivity to the right pins on the eeprom. you can check the empty socket to make sure you don't have any extra connections between the pins. probably no need to remove the socket if those things check out OK.

At this point the FV-1 seems to be the prime suspect. If you are tired of dealing with this right now you might want to set it aside and build something else. Or you could keep it as is to use the internal programs.

If you are up for more tinkering, consider using a nondestructive method like the low-temp solder to remove the chip and do some more tests on the board to see if the parts and connections are all good. If the board looks OK you could try another FV-1 chip in it. If you instead find a problem on the board you would still have a (presumably) good FV-1 chip.

 

[p_wats]

Thanks @zgrav.

I'll probably switch gears to putting the other old board in the same enclosure with similar mods, as I liked what it was doing when it was working.

Do you think it would be possible to remove the chip without damaging it using a hot air station and some kapton tape to protect the center from too much heat (as I don't have any low-temp solder and doubt it's something I'll end up using much of if I go ahead and order it)?

 

[zgrav]

I have never used a hot air station, but it should do the trick. Much more focused than a heat gun, right? Sometimes putting more solder on the pins can also help since all of them could react together. Good luck!

btw -- the chip quick stuff can come in handy in other tasks, and the 18 inches of it you get will last a long time. I was able to use it to remove an 8-pin 2P4T rotary switch without damaging it after I inadvertently put it in the wrong way on a board.

 

[p_wats]

I have never used a hot air station, but it should do the trick. Much more focused than a heat gun, right? Sometimes putting more solder on the pins can also help since all of them could react together. Good luck!

btw -- the chip quick stuff can come in handy in other tasks, and the 18 inches of it you get will last a long time. I was able to use it to remove an 8-pin 2P4T rotary switch without damaging it after I inadvertently put it in the wrong way on a board.

I think I'll order some anyway--sounds useful. Thanks!

 

[p_wats]

Apparently I'm too impetuous to wait for the low-temp solder to arrive and I've removed the chip with the hot air station. It was my first time trying something that large, so the board didn't really survive very well (my fault). The chip came off well enough, so I'll save it in case I ever get another Arachnid or similar.

Thanks again for all the help @zgrav! I'm still going to order some low-temp solder anyway, as it sounds useful.