Understanding the La Marzocco GS3 Level Detect Circuit - Page 3

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AssafL

#21: Post by AssafL » Aug 13, 2019, 10:56 am

Looking at the capacitor above - it seems there is the sort of tin oxidation as well.

I'd IPA it as well to get it bright and shiny. No need to trap all these oxidizers under the acrylic coating. And then dry it well - a well regulated oven is best.

Oh - And I bet Pat is happy he has that thick track to connect the replacement chip to....
Scraping away (slowly) at the tyranny of biases and dogma.

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Jake_G
Team HB

#22: Post by Jake_G » Sep 13, 2019, 8:36 am

I thought I should update this for posterity.

Pat repaired my board and had it back to me remarkably quickly. I got it back and was pulling shots within a week of identifying the failure. Communication throughout the process was excellent and his price was very reasonable. I am a happy customer. :mrgreen:
AssafL wrote:Looking at the capacitor above - it seems there is the sort of tin oxidation as well.
Yes. It was replaced as well. Pat found that it had DC resistance and took care of it.
AssafL wrote:I'd IPA it as well to get it bright and shiny. No need to trap all these oxidizers under the acrylic coating. And then dry it well - a well regulated oven is best.
Yes, but which IPA?

We have so many microbreweries in Pacific Northwest. Is a hazy IPA best? Maybe a double IPA or Imperial? Too many choices :lol: Personally, I prefer browns, porters and stouts over the fruity and stanky IPA craze we're in the midst of right now. 3rd wave beer?
Yes, I know you were referring to Isopropyl...
AssafL wrote:Oh - And I bet Pat is happy he has that thick track to connect the replacement chip to....
Oh, you bet!

Here's close up of the finished repair:
Image
Image: Repaired Schmitt Oscillator with solder bridge to Vcc trace

Luckily the STO chip only uses 4 of the 5 traces, so Pat was able to jump to the test point of the NC terminal to get the bridge over to the missing solder pad on the Vcc terminal. Pat was able to test everything at his shop before sending it back, so there was no question of whether or not it would work. This is a huge advantage to having folks like Pat in the community.

Here is a shot of the board to show just how tiny this repair area is:
Image
Image: Repaired 3D5 board with solder bridge by my thumb

Thanks to all for helping me demystify this circuit and to Pat for making stellar repairs. A week without spro was tough, but knowing that these logic boards can be resuscitated after significant water damage is worth it.

Also note that it is my opinion that this damage was well underway for longer than I've had this machine. I do believe that the water in the electronics case was from my sloppy boiler drain activities, as I've had the covers off since getting the board back and there is NO evidence of leaks. I suspect that the damage was done when I got the machine and it just took a while for the compromised solder pad and terminal to continue the degradation caused by subsurface corrosion beneath the chip. This is likely an indication that I was unsuccessful in ridding the board of moisture when I cleaned it up upon receipt of the machine, but such is life. Now I know. Now you know. :wink:

Cheers!

- Jake

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AssafL

#23: Post by AssafL » Sep 13, 2019, 9:51 am

I was drinking Sierra Nevada. Gives the board a lovely brown tinge valued so much by the dilettantes.

(Oh - and lovely work by Pat; mine would have less finesse...
and Oh2 - Conformally coat the board. You'll sleep sounder AND have more caffeine...)
Scraping away (slowly) at the tyranny of biases and dogma.

jpboyt

#24: Post by jpboyt » Sep 13, 2019, 12:57 pm

It doesn't show too well in the photo but I coated the repaired area with clear fingernail polish. One of the few useful things I got out of the divorce...
Two pair of cheater glasses job.
jpboyt

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AssafL

#25: Post by AssafL » Sep 13, 2019, 3:56 pm

And the soldering iron. They never take those. No way she takes the Metcal
Scraping away (slowly) at the tyranny of biases and dogma.