Tuesday, March 6, 2012

A friend has a Fender Twin sized road case, and would like to trade it for an oscilliscope. Time to dig through the pile and assess workability.

First up is a Heathkit IO-104. When I first tried to search the internet for this guy, I misread the model as "10-104", which resulted in some confusion. The difference between I and 1 now seems pretty obvious, but to be fair the difference between 0 and O in the chosen font is only one of magnitude.

Simple, and attractive. Unfortunately, this model is single trace, so it probably won't be a trade candidate. Already on the desk, and extremely easy to open up (facilitated farther by a missing chassis screw), so let's see what's going on inside.

Quite clean, for something that was probably built as a kit. The electrolytics are clearly past their prime, although there's no actual leakage or burnouts to be seen. This came from a school with some money, so it's probably been sitting on a shelf for quite a long time. I've chosen not to apply power today.

This certainly tells a story. I don't know the storage history of this particular unit, but I do know that they built a new science building around the turn of the century, which probably meant some time spent in some kind of storage container during construction.

Either way, this particular brand of corrosion is everywhere, including on actual components. I've never seen this sort of thing on ceramic resistors like that, so I guess that tells a bit of a story. I can't imagine its good for the casing on those caps.

Although I love the color of copper oxidization, it's a bummer to see this happen to such a beautiful piece. Either way, this is quite an expensive way to shield a transformer - I'm not sure what inspired them to do this.

All in all, while I think this unit would be pretty easy to get running (new power supply caps would be a fine minimum, although I suspect it would need more work in order to stay calibrated), this guy is destined for some more time in storage.

Next up: Tektronix 561B. Blurry photo, oops.

Cosmetically, a work of art. Some strange design decisions though; this is a modular scope, and although the 561B was the first solid state design in the series, no solid state modules were ever designed. Apparently the design features amplifiers living entirely on the plug-in units rather than on the frame, which results in a direct tie-in to the CRT. The result is a scope which must be calibrated at every use.

Tubes in the dual-trace plugin. Lots of dust. This was after compressed air.

This got me pretty excited - these electrolytics, just short of socketed on their ceramic rails, were clearly designed for replacement. I realized soon after that based on their even 1.0, 0.1 and 0.01 values, they exist for calibration, not for any power purposes. Still a useful feature, but nothing that will help me get this beast running.

You can see the real power supply caps in the side shot above - multi-cap cans, everybody's favorite. This is a 60's unit which basically guarantees dry capacitors = no power until that's sorted, so back into the heap she goes.

A quick glamour shot of the onboard circuitry...

And a comparison of the connector pins on the two modules - after all these years, the modules slide in, connect and lock without a hitch, which is great overbuilt design - but why is one connector super grimy, while the other is spotless and shiny?


krivx said...

This was interesting, you should post more often.

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