Seq v4+: Left LeMec board troubles

[geekraver]

Hi all

I am having a very hard time making any progress with a problem with my left LeMec board. When I first assembled the JA and LeMec boards and tested them, everything was working on JA board and the two LeMec boards except:

- encoder 3 on left Lemec board was not registering depress events
- encoder 8 on left LeMec board was generating garbage counter values when rotating. 

Since then I have gone backwards and been stuck for over several weeks with no progress. I first tried to solve the issues above with reflowing the ICs on left LeMec board but that didn't help. I then reflowed the ICs on the core, and after that, I am in this worse state with left LeMec board

- encoder 8 does not register turns

- none of the encoders are registering push events

- 4 leftmost buttons on are not registering push events

- 12 of the 16 LEDs light up immediately upon powering up as seen in attached pic

I haven't bothered testing the Matias switch events as this is enough wrong already

I have reflowed the ICs, diodes and transistors on that board multiple times, and on the core board too, and nothing is changing. The only advice I get from Midiphy is to reflow/check for dry joints/shorts which I have done over and over. It would help to have proper circuit diagrams to try to chase down likely culprits instead of messing with everything all the time.

If I just connect the JA board to core and run the seq_l test, that is still testing fine for everything. The right LeMec board is out of the picture for now; I think it was all working well at least.

Any help will be most welcome as I am close to assuming I just have to abandon this and write it off as a very expensive exercise in frustration and futility.

Thanks

Graham

 

 

 

 

 

[forestcaver]

Hi -

1. Midiphy people will send you snippets of the schematic if you ask (sub-optimal, I know, but better than nothing. When I built mine, the lack of schematics was a major concern for me too. Looking at the midibox schematics can help understand the midiphy reworking - look at the DIN shift registers and anything in that chain first for the inputs - it should be pretty solvable). (For background - I’ve built a midiphy seqv4+ and two seqv4s, one of which is very fully loaded)

2. There are issues with your soldering (sorry !) but even in that one photo there are loads of suspect solder joints. Type of solder, heat, flux, technique, etc can all contribute ! (Sorry to be negative!)

3. Do you have any magnification ? (Seeing what you are doing makes a massive difference - I use a stereoscopic microscope with a decent working distance - it’s pretty essential for me to build things reliably)

4. Where do you live ? (Your online accent implies UK !)

Edited May 19 by forestcaver

[geekraver]

At this point I don’t think the solder you see is representative of where I started. I have reworked the board at least once, in some cases multiple times, over the past 3 weeks, and yesterday before taking this photo just fluxed everything and retouched it. It’s looking much worse than when I started, but I am just throwing stuff at the wall at this point to see if anything sticks.

Right after this I decided to replace the ICs on the core and one of the tabs got damaged so I now need to replace the PCB and rebuild the core before doing anything else.

And yes, I am working with a microscope.

I live in Seattle, not sure what that has to do with anything though!

 

Edited May 19 by geekraver

[forestcaver]

12 minutes ago, geekraver said:

At this point I don’t think the solder you see is representative of where I started. I have reworked the board at least once, in some cases multiple times, over the past 3 weeks, and yesterday before taking this photo just fluxed everything and retouched it. It’s looking much worse than when I started, but I am just throwing stuff at the wall at this point to see if anything sticks.

Right after this I decided to replace the ICs on the core and one of the tabs got damaged so I now need to replace the PCB and rebuild the core before doing anything else.

And yes, I am working with a microscope.

I live in Seattle, not sure what that has to do with anything though!

 

Ah, ok - apologies - was just trying to help with some suggestions and was commenting on the shared photo. As I’m sure you know, you can often reroute lifted pads by using kynar wire or similar....

Reason I asked where you lived was that I was going to offer to look at it for you if you lived near me and wanted to drive over (shouldnt need to be said, but for clarity, not for any remuneration - just to be friendly. I have no interest in taking money for any DIY stuff - it’s just a hobby). I was making a (very) wild guess that is completely wrong that you were in the UK - again, apologies for any assumptions.... good luck.

Edited May 19 by forestcaver

[geekraver]

Thanks, perhaps I'll shoot over to the UK ;-)

I've rebuilt the core board now and I'm back where roughly where I started. At least I feel confident I have eliminated the core as a possible cause; the problem must be with my LeMec board.

Done some more reflowing on that board and now:

 

- just 4 LEDs light up on power up now

- all encoders generate counts when rotated but not depresses

- botton left 4 buttons generate no events; bottom right four are working

- mattias switches generate events for the four that have illuminated LEDs but not the rest 

[geekraver]

Reflowed the ttasnsistors on the top side and now I am back to 12 LEDs on. I'm assuming the LEDs shouldn't be on, but otherwise that feels like an improvement as it means I get mattias switch events for 12 of 16. I'm also getting events for depresses on the right 4 encoders although they seem a bit random in the actual event details.

I've also replaced IC2, IC3 and T3 based on advice from ChatGPT but that made no difference.

Edited May 24 by geekraver

[geekraver]

II replaces the remaining ICs and its working! Woohoo!

 

[forestcaver]

20 hours ago, geekraver said:

II replaces the remaining ICs and its working! Woohoo!

 

Excellent ! Great news ! :-)