Simpson 260 repair

Bakelite, if it's an old one. Use epoxy.

John

There are two basic types of plastic, and thermosetting (sed for this type of a box) has no solvent. Use epoxy after cleaning and roughing up the bond surface (J-B Weld comes to mind).

I would have guessed Cycolac, but if that were true, then the ABS solvent should have worked. My Simpson 260 has a yellow case, so definitely not bakelite here! :)

Robert Baer wrote in news:mJednYE59s0GnOHTnZ2dnUVZ snipped-for-privacy@posted.localnet:

I believe the Simpson cases are Bakelite or similar. Ditto on the epoxy,but too thin a glue line makes for a weak epoxy joint. you need to drill some holes or cut grooves,and leave a thick fillet on the back side,possibly even reinforce it with glass cloth. Leave enough time for the epoxy to REALLY cure,a week or more,before putting stress on it.

Or,Perhaps you could buy a new case from Simpson? Or find a junker on Ebay with a bad meter movement but a good case.

Yes, most of the 260 cases are phenolic (bakelite). There are some models of the later series that have plastic cases. I've never had to repair one of those, but if your case isn't bakelite, I would think that a solvent type glue would be the best solution. Look for Weld-On plexiglass or acrylic glue. Any place thst sells plexiglass should sell it. Clear epoxy works quite well on bakelite cases. I've repaired many 260 bakelite cases with epoxy. JB Weld works great too. When bakelite breaks, the edges are usually quite rough, and bond well with the epoxy. If the edges have been allowed to acquire dirt, be sure to clean and dry them well before applying the epoxy. If you do opt for a junker to salvage the case from, make sure htat you get one of the same series as yours. The external of the cases are identical, but the internals are very different.

Devcon plastic welder is about twice as strong as epoxy and doesn't soften when it warms up. It can be filed and drilled after its cured - about 24 hours. Color is like cream Very sturdy stuff.

G=B2

Devcon plastic welder is about twice as strong as epoxy and doesn't soften when it warms up. It can be filed and drilled after its cured - about 24 hours. Color is like cream Very sturdy stuff.

G²

At first I thought you meant the hot air/filler rod type of plastic welder so I tested the case and it doesn't melt when touched with a hot soldering iron. Then I googled the devcon. That's a new one to me and it looks like a good prospect so I'll give it a test. Thanks.

Additional info re ID'ing the plastic: the cracked surface appears rough like broken cast iron and not at all like a usual plastic fracture. Art

That's because it's Bakelite.

John

And I still have a 260 Bakelite unit, and it was kind of old when I got it 30 years. I also still have this (TI-30);

which was my first calculator which I used while I was in the last year of Tech school, and it's in great shape, it was used a lot and I guarded that like it was my life. I keep the batteries out of both of them of course.

Later on, I did inherit an HP RPN calculator of that time, I don't use that any more.

Jamie

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What model? I might want it, for use.

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I had a somewhat different outlook for my TI-30. It screwed me over during an AP Physics exam - it just completely wigged out, numbers flying everywhere. So, my buddy had a 302 Ford Maverick with big tires on the back and plenty of horsepower to burn some rubber. We were expecting a spectacular "explosion" of calculator guts, but it was pretty much a let-down. As I recall, the TI-30 only had one integrated circuit inside.

I then (or shortly thereafter) purchased the HP-41CV and fell in love. Eventually that died (natural causes), and I reluctantly got a HP-48 since the 41 was no longer in production. Counting the TI-30, that's three calculators in nearly 30 years. I can not say the same for desktop PC's!!

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I would be willing to sell my yellow Simpson 260. Complete with bright yellow fabric case and test probes with alligator clips. It is in practically brand new condition - I never use it. (I prefer my Fluke 77, or any of several combination clamp-on's, like my Fluke

Make me an offer.

-mpm

I have followed this thread, now I have to give my hints regarding plastic and epoxy repair. I use *Araldite epoxy, which changed to Huntsman Fastweld 10, then to Vantico Fastweld 10. This is 5 minute epoxy, rock hard when cured. I have 0.025" and 0.035" steel rod and same size drill bits. On some repairs I put the two parts together and find a solid place to put a pin or two. I drill the holes, then apply epoxy to the pins and holes and put the assembly together. Some repairs are stronger than new. If I were repairing the 260 case I would use a cut off wheel in my Dremel and cut 3 slots (~3/4") across the crack, deep enough to hold a pin and epoxy. I would fill the slots with epoxy and lay in the pins. (These slots would be on the inside.) Mikek

Can't remember the model, I would have to dig it out, it's the one before the RESET button came out on it.

And no, you can't have it :)

Jamie

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Hmm. A Simpson 260 compleat is worth maybe US$12 to me, split the shipping. I don't figure you are going to let it go quite that low, but you might surprise me.

I figure that you knew i was after the calculator.

?-)

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Well you know, there are some "tricks" you can do with certain analog meters that you can't really do with digital ones, like my Fluke 77,

For example, on some model 260's you can turn them into a quasi RF millivolt meter. I forget exactly how to do this, but it's something along the lines of using one of the low amps scales, and then looping the probes though the output port. You just dangle the black lead over your circuit (not DC connected to anything!), and then probe with the red lead. It's not terribly accurate, but it will give you a relative indication

- and still useful for seeing if some RF circuits are working.

Someone here will know that "trick", and possibly others, and will post it here.

-mpm

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Plus mechanical analog meters will show you some things that even the finest DMM cannot.

?-)