Classic Hifi Care

I have pictures, so please stand by for those. I have two of these small PB radios, one with a power transformer, one with series filaments. The model with the PT has a fairly heavy chassis, particularly on the end with the PT. The cabinet on the PT model was cracked. Just a simple crack, running from the screw that holds the chassis in to the front of the cabinet. No big deal, right? Well, not for me it wasn't. I glued the original crack, then reinforced it with epoxy on the inside. All was well until I used a furniture clamp to hold it together like I wanted. When I tightened the clamp, a huge chunk broke out of the middle and fell out. So, now, instead of having a cracked cabinet, I had a busted cabinet. This time, I glued and reinforced the second repair, then omitted the clamp. So far, so good. I need to use some body putty and glazing putty so my repairs won't show, then I'll repaint the entire cabinet. It is tan now, the wife likes a light green, so we'll shoot it with that. The cabinet with the series string chassis is really nice, dark brown bakelite. The chassis with the PT is a better performer than the other one. One of them has the wrong dial pointer, so I reckon I should see if I can find the correct pointer at some point.

I worked on this stupid cabinet all afternoon, but am not further along than when I started....

I have no idea what material the cabinet is made of, but Elmer's Construction glue won't stick to it. Nor will epoxy. I had the cabinet all fixed, looking pretty good. I started spreading Bondo on the cracks when the cabinet split in three pieces again. I can just peel the glue off in strips, the epoxy comes off in chunks prodded by a screwdriver bit. It must be some kind of plastic. It's not bakelite. It doesn't scratch easily. I plan to try model car cement to see what that does. Lacquer thinner doesn't hurt it, nor does acetone, nor does alcohol. I've never had this trouble before. Elmer's is what I have always used.

Try "superglue" (cyanoacrylate)? Or a urethane glue like Gorilla Glue? The latter is moisture-curing and tends to foam and expand when it cures, so afterward you'll need to do some cleanup. But the urethanes are tenacious as all get-out. 3M makes a marine adhesive called 5200. It is permanent, full stop. There are release agents you can buy but I have not had good luck with them. The permanence of the stuff means it is banned from my boats, but I buy it for gluing boot soles back on. The glue always craps out first on my boots, so I have been using 5200 to make repairs with great success.

With the urethanes, wear rubber gloves. Get it on your skin and its there until the skin cells slough off. The spray insulating foam you can buy is a urethane and it's equally permanent on the skin. I've been using a marine underwater urethane primer designed for ferrous metals (Pettit's Rustlok) but it works equally well on aluminum (or anything else it gets on).

Chris Campbell

One more thing. Epoxies don't need clamping like wood glues. They are very effective gap fillers, and only need enough clamping force to keep things in place while the glue cures.

Be careful about larger quantities of mixed epoxies. They are exothermic--give off heat as they cure--and the extra heat accelerates curing. It can lead to thermal runaway: smoking and bubbling. Ask me how I know. When using them, you can extend working time buy cooling the glue container, or buy using a large shallow container so there's lots of surface area to shed heat.

Chris Campbell