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HW-16 Circuit Board Restoration (Part 1)

 

HW-16 Circuit Board Restoration (Part 1)

Last Spring, I started working on the circuit board for the Heathkit HW-16. Even after its bath with soap and water, it was very grundgy, with lots of old rosin on the bottom (foil side) of the board.

I decided to remove the board from the chassis, in order to get better access for parts replacement. I suspected that many of the old carbon-composition resistors had changed value significantly over the years.

I started by photographing the connections from the chassis to the circuit board. This should help me get it back together once I have finished restoration.

 
Bottom of circuit board

Once all of the wiring was documented, I started off by simply scraping the worst of the old rosin off the board with a small screwdriver tip.

 
Scraping flux off the board

As I did this, I followed up with rinses of soap and water to wash away the loosened particles. But there were still a lot of spots that I couldn’t get the flux cleaned from effectively. I tried using Isopropyl Alcohol, which was ineffective. Next I tried mineral spirits, which was also ineffective.

Finally, I read somewhere that someone had tried paint brush cleaner on their boards with success ( hackaday article ). So I went to Home Depot and found some in the Paint Area.

 
Paint Brush Stripper

Now, I have to tell you. This is some nasty stuff… I wore latex gloves and eye goggles while working with it. I was outside, in an open area. And I still felt sick after working with it for 15 minutes or so. The fumes are really bad. I’m pretty sure it causes cancer.

But, given all of that, it worked wonders on the grungy old board. Where I couldn’t get the rosin to chip off before, it came out clean.

Here is a before picture of one of the tube sockets:

 
V3 – Before Brush Cleaner

And here is the same area after using the brush cleaner, and flushing with water:

 
V3 – After Using Brush Cleaner

 


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