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Is this a counterfit IBM 5150 board?

Andrettigto said:
... you can solder thru acrylics if rework is ever required.
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Have you ever actually tried? Acrylic sealants clog up a desoldering tool in no time. They insulate the solder and have to be almost totally removed around a component to keep from tearing pads and runs from the board.
 
Yup. I have to scrape the stuff off where I'm putting my iron. Otherwise, it's a mess. Maybe a decent nitrocellulose lacquer might work better...
 
I've never actually tried it as the two I've done haven't had any failures requiring repair. I'd read forum posts where it was used on DJ electronics and users reporting board repairs being performed without any prior chemical treatment. With the ones I've done, after cleaning I applied a single spray coat. It doesn't appear to be too thick so when the time comes where I'm faced with a repair, I may attempt it as is. Good point though about the desoldering tool getting plugged up.
 
Its pretty common waterproofing technics 1200 turntables and mixers, as you perform outside alot. Most my gear is been waterproofed with a thin layer of silicon spray, and the speakers are waterproofed with truck bedliner.
 
I had to repair the computer and a few sensor/controller modules in my 1989 Acura Legend recently. The boards are all coated in something I have never seen on a commercial electronic PCB before. Like a thick clear glaze the board was dipped in after it was assembled. IT also had electrolytic capacitors which looked normal till I saw the bottoms where the rubber boot would normally be but they were epoxy potted. They still read correct but I replaced them anyway.
 
I think the stuff in computers is boat grade resin for fiberglass hulls. Would make sense , and it was pretty cheap.
 
Not trying to extend the diversion from the OP, but there's some stuff I repair for car wash systems (yes, high-humidity environment) where I work that's from the late 80's/early 90's. The (acrylic) conformal-coat is literally just like a heavy varnish and is sometimes over 1/4" thick in spots. I always hate to see those come in. On the production schedule you're allowed around 2 hours per board...and I always lose time on them.
 
T-R-A said:
Not trying to extend the diversion from the OP, but there's some stuff I repair for car wash systems (yes, high-humidity environment) where I work that's from the late 80's/early 90's. The (acrylic) conformal-coat is literally just like a heavy varnish and is sometimes over 1/4" thick in spots. I always hate to see those come in. On the production schedule you're allowed around 2 hours per board...and I always lose time on them.
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So you chisel away this stuff to get to the components..? How awful.
 
More like chisel and burn (with a soldering iron). Afterwards, I need a new tip. It's pretty pathetic, especially when a DIP-40 in its' socket is completely encapsulated in the crap. Fortunately I haven't seen many of them lately and there's only one customer in Texas still dedicated to maintaining that type of system.
 
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