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Waterproofing Detector Circuit Boards?


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I recently sent one of my White's detectors to Centreville Electronics for repair. It is a TDI BeachHunter which has a waterproof case but condensation built up in the control box during a hunt in the cold rain and surf this past month and it stopped working. I believe that if I had taken the time to waterproof the circuit board in my TDIBH that I could have avoided the failure of the detector despite the condensation problem. 

I have been reading up on PCB waterproofing and have found out that it seems to be a growing practice in many do-it-yourself hobby applications such as waterproofing drone controls for wet weather use. There are several specialized products available but even a simple coating of nail polish was mentioned in a number of articles as being a cost effective method.

Has anyone here tried this? It seems like cheap enough insurance to minimize the risk of damage to a detector if it gets dropped in the water, splashed on, spilled on or rained on. I am considering using the product in the attached picture.

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MG is good stuff. I use the 419E Acrylic Conformal Coating Aerosol Spray to waterproof circuit boards with great results. Use it in a well ventilated area and wear a mask, it fairly toxic to breath in.

https://www.amazon.com/419E-Premium-Acrylic-Conformal-Recognized/dp/B07TXWN3V6/ref=sr_1_2?crid=1J3ZUSR84LFCN&keywords=mg+chemical+acrylic+coating&qid=1675115242&sprefix=mg%20chemical%20acrylic%20coating%2Caps%2C106&sr=8-2 

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1 hour ago, CPT_GhostLight said:

MG is good stuff. I use the 419E Acrylic Conformal Coating Aerosol Spray to waterproof circuit boards with great results. Use it in a well ventilated area and wear a mask, it fairly toxic to breath in.

https://www.amazon.com/419E-Premium-Acrylic-Conformal-Recognized/dp/B07TXWN3V6/ref=sr_1_2?crid=1J3ZUSR84LFCN&keywords=mg+chemical+acrylic+coating&qid=1675115242&sprefix=mg%20chemical%20acrylic%20coating%2Caps%2C106&sr=8-2 

Good to know - I appreciate the feedback!

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I've also used the silicon sprays used in the marine industry to protect instruments (like radars and gps) against salt spray.. Good old WD-40 with silicon is also good.. 

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6 minutes ago, Erik Oostra said:

I've also used the silicon sprays used in the marine industry to protect instruments (like radars and gps) against salt spray.. Good old WD-40 with silicon is also good.. 

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Thank you! These look good for the moving parts like switches and pots.

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Has anyone tried to remove the thicker conformal coatings to make repairs to the PCB if a component fails?  

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5 hours ago, PI-Man said:

Has anyone tried to remove the thicker conformal coatings to make repairs to the PCB if a component fails?  

I use acetone to remove the old coating, or a solvent product made by MG that removes almost anything.

Be careful when using it and don't smoke around it. After using the cleaner respray with standard contact MG cleaner to remove more of the solvent. Allow to dry in the open air for a few minutes or put a fan on it.

I will post a link to the cleaner when I can find the product number.

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Update to earlier post:

This will explain more about coatings than I could convey myself, I have used their products in the past and found them very good. Remember that what some people call waterproofing is not really waterproofing with most products.

Here is the link and please check out other links inside the article for more products.

https://www.chemtronics.com/the-ultimate-guide-to-conformal-coating/

 

 

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Valens — good job on the Chemtronics link .  Great link to share with everyone.  Know the link and the products well.  Been doing underwater electrical/electronics engineering for almost 40 years.  Hopefully I get to retire soon.  I was throwing the question about ‘conformal coating PCB repair’ out earlier as food for thought since it is not as easy for some people to deal with removing and making repairs to PCBs.  Especially surface mount components.  Do not want to see some people inadvertently paint themselves in a corner for future repairs if needed that could cost them more.

Coatings can be a real pain in certain applications and from experience on many repairs of underwater electronics a coating can hinder the repair.  Good example is if the PCB is after market coated and a spot is missed during the coating process and water intrusion happens especially at constant pressure/depth/diving.  Well we can only imagine the results.  This can even happen with OEM manufacturer coatings.  Saltwater environment — well once it gets trapped into the boards layers/underneath just throw it away and replace with new board.  Sometimes you can dry the PCB out via soaking in denatured alcohol (yes I know about residue n such it works) for a given period of time then baking board at low temps in an oven, but eventually it will come back to haunt you it always does it’s just when.  Probably will happen when you are having the best day of your life detecting and your machine fails with no spare in walking distance for 6 plus miles — been there before.  Murphy’s Law.  Not saying a good coating cannot be done at home.  

My suggestion as first try if someone experiences condensation/moisture related issues with the TDI BH is to look for any small cracks in the housing, seal issues, etc and try some desiccant packs in the control box if you can fit them in there (you should be able too).  Plenty of different sizes of packs now in the marketplace.  Usually they show up in regular shipments/packaging so you can repurpose them. You do have to change them from time to time they don’t last forever.  I used several in my Whites Surf PI DF over the years and they worked great.  Of course I was very religious about checking seals as well.  It’s amazing how the seal can get compromised with a grain of sand/dirt/hair.  I had a very small hairline crack in the clear housing on my retired Surf PI.  It was actually very hard to find but I found it — Whites replaced the housing and I added the desiccant packs and never a problem again.  

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I was having problems with a circuit board in my Spa or Jacuzzi or whatever you call them in America getting condensation on it from the warm air inside the Spa's housing, it was causing corrosion on the PCB so I was having to reflow solder and do repairs occasionally.  I sprayed it with this stuff and have never had a problem since.  You can also solder right through it should you need to.

https://www.chemtools.com.au/product/our-brands/clearcote/clearcote-lqr-circuit-board-lacquer/

CT-LQR-GROUP_600x600.jpg.c98219d1040dfd81f4428eeb425de4ff.jpg

Clearcote LQR Circuit Board Lacquer

Clearcote Circuit Board Lacquer is an economical general purpose resin conformal coating that provides insulation and protection against environmental stresses and factors. It offers excellent protection in high temperature environments, as well as during exposure to high humidity, shock, and vibration.

Drying quickly, Circuit Board Lacquer leaves a clear and flexible – but tough – high gloss finish which is resistant to moisture, fungal growth, abrasion, and staining.

Clearcote Circuit Board Lacquer has high dielectric strength and promotes extended service life and enhanced reliability for printed circuit board components and assemblies.

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