Troubleshooting a semi-working board

Hardware questions and issues with the FV-1

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the_frey
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Joined: Sat Jun 04, 2016 9:56 am

Troubleshooting a semi-working board

Post by the_frey » Mon May 08, 2017 3:28 am

I've already implemented a board using the FV1, but it was super hard to solder in a logical order, so I redrew it. Just finished putting together the revision and I have a weird issue - I get audio through (both dry and wet - I've got a mix pot) but the signal keeps flashing out to a kind of static noise, at which point the clip LED lights. The static noise manifests sort of like the patch you're currently using from the EEPROM - i.e. on a pitch shifter, it has a differnt quality to a reverb patch, etc, which makes me think that there is a clean path from FV1 output to the output jack.

The weird thing is that if I push against the FV1 with my thumb, the signal resolves and the glitching over to the static either disappears or becomes much more infrequent.

That sort of suggests to me it's the opposite of a ground as it's not them touching the case or something like that.

I've checked the continuity of the pins on the FV1 and there are no shorts. The connections look okay with a magnifying glass, but maybe there are some dodgy connections, it's possible. I've checked the voltages and they seem in-line with the previous revision of the board, which I know works fine.

Could it be that I need to reflow the connections on the FV1? Maybe it's intermittent?

Is there anything else I should try?

frank
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Post by frank » Mon May 08, 2017 8:34 am

Indicates an issue with the soldering of the FV-1, reflow the pins and make sure to clean any flux residue from the board.
Frank Thomson
Experimental Noize

the_frey
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Joined: Sat Jun 04, 2016 9:56 am

Post by the_frey » Mon May 08, 2017 9:27 am

Ah okay, at least that validates my suspicion. I'll give it a clean to make sure flux isn't the issue too, and report back. Thanks!

the_frey
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Post by the_frey » Tue May 09, 2017 12:38 am

Reflowed all the pins and added a bit more solder and it sprang to life. Thanks again!

the_frey
Posts: 13
Joined: Sat Jun 04, 2016 9:56 am

Post by the_frey » Tue May 09, 2017 3:14 am

One last thing - I'm finding that PROG 4 is running my program from PROG 6 - I take it the only explanation for this is that I've got the wrong voltage being delivered to the pins right?

I've got a 1p8t switch and some diodes in place in a similar way to some of the implementations I've seen on here, and it worked previously. I'll re-check the diodes to see if any are duff, but I think they are fine, and they're definitely the correct orientation, so it does make me wonder what I've done wrong, heh.

Maybe it's just a solder bridge, the diodes are placed pretty close to one another on the PCB.

Reprogrammed a fresh EEPROM and it definitely seems like it's a hardware thing as switching it out to the other pedal the PROG 4 patch behaves as expected.

frank
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Post by frank » Tue May 09, 2017 8:50 am

Check the voltage levels at the S pins to see if they are getting the proper level, if they are not then back track from the pin to see where the issue is. I would guess that S1 is not seeing the proper level when selecting program 6 and that is why it is running program 4 instead.
Frank Thomson
Experimental Noize

the_frey
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Joined: Sat Jun 04, 2016 9:56 am

Post by the_frey » Wed May 10, 2017 2:39 am

Yeah S1 and S2 are both getting the same voltage for each, after checking again with the DMM. Must have misread it the first time. I've checked the schematic, diodes (on this board) and traces (on a fresh board), so it looks like I'll have to do a bit of digging to work out why there's a connection.

DMM says there's no continuity between S1 and S2 so it's not a solder bridge (and the other positions wouldn't work in that case I guess). Looks like the PROG 4 should not give a path to ground for S1 but it does, meaning it's the same on both pins as PROG 6. Weird!

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