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Old 07-06-2021, 12:38 PM   #1
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Can you repair your old circuit board? ...yes you can!

Over the last 4 years I have paid a TV-Satellite repair in Montana total of $300 ($100/visit) to diagnose my circuit boards; and every time he did I saved me thousands of dollars in return, because I did not take my RV in for service, and I was back in business 3-days latter.

What could be easier, cheaper or faster than repairing our circuit board yourself? ...Nothing.

One time I took my whole Dimensions Inverter/Charger to this TV-Satellite Repair Shop in Montana, and for $100 he fixed my the charger side of the Dimension unit when everyone else said, "Get rid of it!" And these same types told me I needed a pure sine wave inverter for my residential refrigerator, or else it would fail inside of 2 years. ...No it didn't. ...I still have my wonderful residential refrigerator 5 years latter; and that $100 circuit board repair to my Dimensions Inverter saved me thousands!

The next year this same shop repaired my Vehicle Data Computer (VDC); and that was after Freightliner quoted me $2,200 to replace one of my dash instrument gauges; and get this, that was not the problem.

I.e., Freightliner misdiagnosed the problem and this shop in Texas charged me $500 just to wrongly diagnose the problem. ...But that's another story I may tell you more about later. The point here is that I did another happy dance after I got my VDC circuit board repaired for $100.



This year the TV repair shop fixed some cold solder joints on the back of my Ventline Holding Tank Sensor board. ...You know the one. ...This is the CB that drives the LEDs to light up when you press the black and gray holding tank button inside your coach and outside in your water service bay.

FACT: I saved thousands of dollars by repairing the old circuit boards, and now I'm learning that sometimes, the only problem with these CBs are cracked solder joints -- and this is a repair almost anyone can fix with a $10 soldering iron from Walmart and a pair of reading glasses. So that is why I posted this thread.

HOW TO SPOT A COLD SOLDER JOINT

* Simple. Just flip the CB over, and with a pair of high power reading glasses or magnifying glass... you just need to visually inspect the back of the CB for cracks.

* In particular, you should look where the power and ground pins are, and then find some diodes. These are called Suppressor Diodes, because they block AC transient spikes.

* Apparently, these diode solder joints crack over time due to vibration. Why, I do not know for sure, but you don't really have to know to fixt your CB problem.

* Moreover, when you have a cracked solder joint it will eventually become an "open" circuit and that's when your device will stop working. Until then, it may work sometime and then other times not work. So I would say, if you have an appliance that sometimes works, all you might need to do is to pull the CB and inspect the back of the board for cracked solder joints. (Aka "cold solder joints.")

* Just use a simple solder iron -- AND FOR FREE -- you can re-flow the existing solder on the pin of the device that has the crack, and that's it. The existing solder will melt and reform a new, tight solder joint. And you really can't hurt the board, unless your solder touches the pin next to it, but that's pretty hard to do.

* You can also do a continuity check with your multimeter if you have one.

* Now just return you board to service and maybe you can do your own happy dance.
https://www.winnieowners.com/forums/...lies/dance.gif

Below are some pictures of the circuit board repairs I discussed above; and in future posts I will provide you with links on where to get more information.

==> If you have any similar stories, about how you or your local TV Repair Shop fixed your old circuit board, then please post some picture and tell us your story.

It does not matter if you have new or old RV, we all have circuit boards in every appliance; and they all fail sooner or later.

Note: Older circuit board are also subject to corrosion and so you might want to watch a YouTube video on how to properly clean corrosion off your circuit board, or you can just sync-up with a good TV Repair Shop in your neighborhood and bypass the RV service shop all together.
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Old 07-07-2021, 07:03 AM   #2
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Yep, sometimes the fix is easy. My philosophy is, if it's already broke, (and not covered by warranty) no sense in not trying to fix it. You'll either be successful or it will still be broke when you've finished. I can't count how many circuit boards I've "repaired" by simply re-seating the IC's that are in sockets. Breaks the oxidation build-up between the IC legs and the socket connection. Learned that one working component level repair on graphic workstation mini computers in the late 80's which then carried over to my industrial career. I guess that's why you don't see too many sockets used anymore, that along with flat pack technology.
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Old 07-07-2021, 07:44 AM   #3
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One of the most common points of failure in old circuit boards are electrolytic capacitors. They can often be identified by swelled cases or actual leakage. In the third photo above, the blue component at the upper right is an electrolytic capacitor. Note that they are polarized with a + and - end.

I once talked to a guy who worked for a company that repaired office telephone systems who told me that electrolytic capacitors were the most common point of failure.
Replacements are usually easy to come by online. Mouser Electronics is a good source:

https://www.mouser.com/?gclid=CjwKCA...xoCbU4QAvD_BwE

You may have to buy more than one, but they're cheap. You may or may not be able to find an identical part number. They're rated in farads or fractions thereof (and voltage. You'll need to match the farad rating but the voltage rating of the replacement can be higher than the original.

For most applications, the farad is an impractically large unit of capacitance. Most electrical and electronic applications are covered by the following prefixes:

1 mF (millifarad, one thousandth (10−3) of a farad) = 0.001 F = 1000 μF = 1000000 nF
1 μF (microfarad, one millionth (10−6) of a farad) = 0.000 001 F = 1000 nF = 1000000 pF
1 nF (nanofarad, one billionth (10−9) of a farad) = 0.001 μF = 1000 pF
1 pF (picofarad, one trillionth (10−12) of a farad)
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Old 07-07-2021, 07:27 PM   #4
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I should add that older printed circuit boards using "through hole" mounting are fairly easy to repair with basic soldering skills since the wires go through holes in the board where they're soldered. Newer boards that use surface mount technology (SMT) where components (often very tiny) are mounted to very small solder pads on the surface of the board. As a result, they are much more difficult to repair, requiring specialized techniques and equipment.

The photos in post #1 are examples of through hole printed circuit boards. The boards in our computers, cell phones, and most modern electronic devices etc. utilize surface mount boards. The link below shows some photos and additional information.

SMT Vs Through Hole Technology - Advantages and Disadvantages
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Old 07-12-2021, 11:43 AM   #5
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As an electronic tech, I have to disagree with the fact of just "reflowing" the existing solder. Solder is a mixture of tin, lead, and nickle. Over time, the solder absorbs moisture and becomes contaminated. Just reheating the solder is a band-aid. The existing solder should be removed using copper braid or a solder sucker and then new resin core solder should be used to remake the connection. A reheated joint might last a year or so, a newly soldered joint will last many years. The failure is caused by moisture penetrating the solder joint and vibration on the board causing the weight of the component to form a hair line crack in the solder. This is why you see many high reliability boards potted with an epoxy or polyurethane covering, to prevent the oxidation.
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Old 07-12-2021, 11:50 AM   #6
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Good point.. I had all my circuit boards repaired at a TV-Satelite shop so I missed the process they used to clean and re-solder.

Here's a picture of a solder sucker on Amazon.

jimkamery: What process do you recommend to remove corrosion from the circuit board?

Also, when we don't have the special electronic polyurethane spray to coat the new solder pins, can we instead use a drop of "super glue" on them?
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Old 07-12-2021, 12:28 PM   #7
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I use trichlorethylene 1,1,1 for cleaning PC boards and an old toothbrush. If you use this stuff be very careful. It is a known carcinogen and should be handled and used with the respect it deserves. But there really isn't anything that cleans as well as it does. As far as super glue goes, that's an interesting question. The way cyanoacrolate adhesives cure usually requires moisture to bond the glue to the substrate and has poor electrical insulating qualities. I would be more inclined to use JB Weld 5 minute epoxy. The only problem with potting the board terminals is that you would most likely never be able to repair it again. Typically I will use potting on a board when it is used in a very corrosive environment and when a replacement board is readily available. I would much rather be able to repair a board every 10 years than to have to throw it away because it can no longer be repaired due to potting.
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Old 07-12-2021, 12:43 PM   #8
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Thx. I had to google "Potting Circuit Boards" to know what you are talking about and this is what I found:

Potting is the term used for insulation electrical components on a PC motherboard, as well as other circuit boards. During potting application, key components are coated with a putty-like material that protects them from moisture and electrical charges and prevents them from overheating. Potting compounds are typically made from epoxy, urethane or silicon. Although applying potting compound is extremely easy, removing it takes quite a bit of patience so as not to damage any critical circuit components.

The TV Repair Shop suggested I use superglue to protect the new solder joints so I did and after 3 years I have not had any trouble. Of the potting material listed above, I would think applying RTV Silicon would be a good choice to protect the new solder joint from future corrosion when nothing else is available. (Just a guess.)
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Old 07-12-2021, 01:54 PM   #9
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Yes, RTV Silicone would work and in most cases would be easier to remove than the others should the board ever need to be repaired again.
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Old 07-16-2021, 08:31 PM   #10
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Over 17 years of full timing in two RVs, I've only had a few problems with bad cards and except for a corroded generator board, and a defunct gas furnace board problem, I've tended to shrug and buy new cards. I've the skill, equipment, and onboard parts to fix nearly anything electronic but sometimes a CC is the best tool I have to save time and headaches.

Recently though, I had a great time completely designing and building a substitute timer card for the not working gas furnace card. It would spark and the gas would light but then it would go out in 2 minutes and shut down 2 minutes after that. All that I read said to replace the card. And since it was $300, I just designed my own replacement. Works like a charm on cold mornings. Not now of course since it's summer, but last winter it worked fine.

So yeah, give it a go repairing cards, but I'd wager you'll not find all that many poor solder joints. More likely female terminals that get loose over time, or wire nuts that walk off the twisted wires and short to nearby metal. Stuff like that.
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