Black Box Repair

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wippb

Petty Officer 2nd Class
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Dec 3, 2001
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Mr. Schem or others<br />I am curious to know how you get all of the resin out of these black boxes without destroying any of the components inside. I have tried many times. It's a little like brain surgery only just slightly less messy.<br /><br />>Once opened do you then reverse engineer the circuit board and make yourself a diagram? <br />>Are the board circuits similar from different manufacturers? <br />>Do you find that the damaged part is usually the same component and is it evident by blackening as is seen by some failed components on an open PC board? <br />>How do you test to ensure repair is good? <br />>What do you refill the box with after you are confident that your repair is good.<br /> <br />With the price of these "boxes", I would be tempted to open it up to try and repair it myself.
 
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petryshyn

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Re: Black Box Repair

Hello wipper<br /><br />I've done several. Not easy, but rewarding. First off, the majority of electronic failures are solder joints. The components fail from time to time, but bet on the joints. The sealant is tough to get out on most. The trick is to only take out the minimal needed. The packs with clear sealant often expose the circuit board. Get a 7-10X jewellers loop and inspect solder joints through the sealant. Sometimes it improves visability if you spray WD-40 on the sealant first. If you see cracked or burnt joints, thats the area to repair. The sealant can be weakened by the use of a heat gun, then peeled out carefully a little at a time. You must have patience! Don't try to remove sealant from the component side of the circuit board (unless you find a bad component). Thats a sure loss. <br />Old merc's use a friendly sealer. They used a aluminum box and simply submerged the electronics and terminal strip into the box of sealant. I carefully cut the back off of the pack and peel out the soft sealant totally exposing the circuit board. The last merc I did had 10 cracked joints. The change up on these pack were from a soldering defficiency. I've lost on some motorbike packs. The sealant is so tough....gerrrrrrrr! When you've tried and proven your fix, reseal the area. They do make special silicone for electronics, but its extremely expensive. I use a hardware caulk clear SiliconeII, NOT regular silicone!!!!!!! Regular silicone is highly corrosive!!!! It must say on the tube "non-corrosive or metal safe".<br />Be sure to use rosin core solder, and clean off the excess when done.<br /><br />good luck!! :)
 
12Footer

12Footer

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Mar 25, 2001
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8,217
Re: Black Box Repair

Hmm. I got an old Force CD unit out in the garage.I have no idea why I kept it, but I'm gonna 'spearment with that puppy!
 
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woywoyboy

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Jun 2, 2001
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104
Re: Black Box Repair

Hello boys, I am trying to remove the resin on an aftermarket type for a Merc. The stuff is clear/yellow and a bit elastic. Only the component side is visible as the back is and part of the alum case unit. Is there a known solvent to remove this ? I will destroy some components if I try to dig it out.
 
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petryshyn

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Re: Black Box Repair

well hello again woywoywoywoyboy!<br /><br />you don't want to remove the component side sealant. Odds are good the problem is on the other side. Take a hacksaw and cut the back out. Don't go too deep, just through the case. Peel out the sealant and inspect solder joints with a jewellers loop or magnafine glass. Resolder the bad ones. Then reseal case with siliconeII (read above posts)<br /><br /><br />Good luck!!
pack.gif
 
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woywoyboy

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Jun 2, 2001
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Re: Black Box Repair

Thank you again schematic, again you have provided a solution. It's Saturday arvo here and the wreckers are not open until Monday so I will attempt removal as per your instructions. When you are next in Orztrayla you must allow me to introduce you to Wally Grout. Oh yeah, condolences for the skating thingo.
 
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wippb

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Dec 3, 2001
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Re: Black Box Repair

Hi Schem<br />Great post<br />I will assume that a jeweller's loop is that thingy that they put in their eye when they are lookin at diamonds. All clear on the removal procedure and the bad solder joint procedure. Now, after reading many of the posts here about what function the "black box" is performing, I am going to assume that it is some kind of capacitor discharge circuit using SCR's as the firing device. Correct me if I'm wrong please. <br /><br />>Is it the same back removal procedure for boxes that have heat sink fins on them.<br />>If it's not a bad solder joint how do you test for bad components. ie. do you need a scope? <br />>When you have found a bad component is there usually a numbering system readable on the component that you can cross reference for new parts?<br />>Do the manufacturers use proprietory components that sometimes can't be cross referenced.<br />>How do you cross reference your parts, books, internet, or the guy in the parts store.<br />>Where do you buy your components?<br /> <br />I am still planning on building the battery charging project but I haven't gotten my hands on a cross reference book yet.
 
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petryshyn

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Re: Black Box Repair

Hi wipper<br />In answer to your questions....<br /><br />>Haven't tried one with fins. If its broke, what do you have to lose? There are some sealants which conduct head readily. Its a roll of the dice when repairing them as the components will overheat if the proper sealant isn't replaced.<br />>Odds are its solder joints. Testing components can be done somewhat from the solder joint side.<br />>I can't speak for all modules, but in most cases manufacturers won't go through the hassle of house numbers (or removing numbers)if the comonents are potted in tough sealant.<br />>any major city will have electronics suppliers. Radio-shack is lame for most parts. We have many suppliers here. Just look in the yellow pages under electronics. Sometimes I order from the U.S. A place called Digi-key. Awsome service....good prices. If you order from them, make it a large order, as the shipping is high.Digi-key Online<br />>almost all parts can be crossed. Just search the part number on the net. Google is a good search engine. Once you find the specs, any manufacturer can help you. Or, you can try a direct cross over from NTE. They have an online cross-reference, or a down-loadable one. If after a honest try you can't find a cross, just ask! Yes, sometimes the manufacturer will scratch off the common part number and put his own boggis number on (house number). That can fowl you up. They usually do this on open circuit board that are easily worked on. Car manufacturers are bad for this.<br />>if you are referring to the charger project from GE, all those numbers are GE numbers which are crossable common components.<br /><br />Since you're an electronics buff, check out this <br />web site for some neat stuff.<br /><br /><br />Hope this helps. Sometimes you will ruine the first pack you open, but you'll be better prepared for the next one.....<br /><br /> :)
 
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wippb

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Re: Black Box Repair

Hi Mr Schematic<br />Thanks for the info. I use google religiously, I guess I just didn't add in the right search words. I checked out the NTE site and I was able to cross all parts for the charger. I plan on starting that project soon. The other hobbyist site was cool too. Thanks again.
 
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Franki

Lieutenant Junior Grade
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Feb 16, 2002
Messages
1,059
Re: Black Box Repair

Has anyone tried this on the Johnson ESL series powerpacks? when mine died, I took it off, got the resin coated pcb out of the alloy casing, and tried to get the resin off the back, I had very little luck, its green, its hard and you can't see through it at all.<br /><br />Everyone I spoke to said it can't be done, and that I should just buy a new one or convert to points and a car coil. I ended up buying a brand new one, cost me 400 bucks, the engine is running now, but if it happens again, I'd like to be in a position to see if I can do something about it.<br /><br />rgds<br /><br />Frank
 
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petryshyn

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Re: Black Box Repair

I haven't tried that style, but.....<br />Don't try removing the sealant from the component side. Try heating the sealant on the PC side with a heat gun. Get it good and hot, then try peeling it off. Let us know how you make out....<br /> :)
 
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wippb

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Re: Black Box Repair

Mr. Schematic<br />I crossed all the parts for the charger and found a local dude for parts. The cost of these is not a problem but when it comes time to making up a board the etch and resist is mucho expensive. This would make this simple charger worth a lot af bucks. When you build up a board do you go with the etch and resist method or do you use the less expensive "perf" boards and just wire in your traces.
 
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petryshyn

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Re: Black Box Repair

If your refering to the GE charger, there is so few parts actually on the board, I'd use a perf board or terminal strip. Just to make sure you're not being ripped on the components, what are they charging you for the SCR's? Remember, substitutions are expensive, while originals are not. The large SCR may be $8 from NTE, but if you get the specs and buy it from IR or texas instruments, it may be $2 as an example.<br /><br /><br /> :)
 
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wippb

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Re: Black Box Repair

Mr Schem<br />I got a price of $6.95 for the SCR1. I figured this will be the most expensive of all the parts. The rest are smaller and cheaper parts. Perf board will probably be the way I'll go. I can get a piece 8"X 12" for $5.00. I'll just solder the links with wire. <br />Thanks :)
 
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