I’ve begun working on the Shortwave Oscilloclast to install the “Dynamizer/Reflexophone” circuitry into it. The idea is that the removable lid inside the storage section (see this blog post) can be swapped out for a new lid with the additional circuitry built into it, and connected to the Oscilloclast’s circuit.
I’ve installed the connectors to interface the new circuitry, but in such a way that it can be patched in to the existing circuit using terminal clips, so the Oscilloclast can still be restored to “normal” when the Dynamizer/Reflexophone section is not installed.
In the photo, the row of wire resistors across the top (which are behind the front panel selector buttons) are in the circuit path where a Dynamizer (what we now call a witness well) and the tuning potentiometer are usually installed, according to the circuit diagrams of the old Abrams devices. So I’ve installed connector clips on the black wire (upper right) and white wire (upper left) so the new circuit can be “jumpered” into the existing signal paths.
The other new circuit will be the equivalent of a Reflexophone detector (the forerunner of the stick pad), which will be connected to the blue wire (in the center of the photo, coiled up) which taps into the polarity detection test point on the front panel.
I’m not actually using a Reflexophone per se, which was a pretty complicated “tap sensor” device with its own set of resistance dials, but a standard stick pad (a mobius coil layered under a rubbing surface) instead. I’m also using a Hieronymus-type witness well (a tesla coil with a pyrex beaker as a core) instead of the two-probes-and-clamp of the original Dynamizer (more suited to holding the blood sample paper that Abrams used for the witness.) I’m also installing a fine-tune potentiometer, but the installation of the circuit for the fine tuning pot led me to a discovery.
In the Shortwave Oscilloclast, the tuning is done with the row of switches numbered 0-10, so there are only eleven discrete increments of tuning. Each switch additively inserts a wire-wound resistor into the circuit. I wanted to tune “in between” those increments by adding a potentiometer to the circuit to “sweep” through the ranges between the increments. Basically, it was adding another “resistor” into the circuit with the other (switch) resistors. If I keep that dial on “0”, the total switched-in resistance is unaffected, but I can “sweep” through the resistance values in-between. But for this to work, the pot has to match the same value as each individual switch resistor.
I found a website devoted to antique electronics which had a page about the Shortwave Oscilloclast, along with scans of the original user’s manual and a block diagram. But it stated that each switch in an Oscilloclast inserted an increment of 1000 ohms into the tuning circuit, and this has turned out to be false. Each switch inserts only 100 ohms, not 1000, by actual measurement on my meter. The increments are actually pretty accurate, within about a tenth of an ohm.
This is more in keeping with my research on Abrams and his ERA machines. Most of his devices were calibrated in tenths of an ohm; rarely did any resistance dial “Rate” settings go beyond 1000 ohms total. So a 10,000 ohm Abrams device would be unusual – and it turns out that is the case.
So I will be using a 100 ohm potentiometer for the fine tuning control, instead of the 1000 ohm pot I originally planned. Placed in series with the bank of resistance switches, it will add a tunable range between 0-100 ohms to the total, so I can use the witness well and stick pad to fine-tune Rates for specific purposes.
I’m so glad I was curious and decided to check the resistances of the switches! (Never take anything for granted.)
And the machine was badly in need of a refurbish job. Most of the mountings were loose, and the switch contacts were pretty scored with crud. I was able to reach into all the nooks and crannies, and clean out old dust and grime. I was also able to get the old Mark-Time bell timer to work again. The clockwork was all gummed up inside, but a bath of contact cleaner followed by a bath of WD-40 got it running again.
I definitely had to replace the power supply capacitor – it was an old paper-and-wax cap that had begun to leak waxy goo. Replacement paper caps are pretty much unheard of anymore – even if I could find an old part from salvage it might be just as bad, even “new old stock”. So I had to replace it with a modern Mylar cap (which pretty much last forever.) This is much safer, as an old paper cap can melt down and start a fire, and if it shorts internally, it can electrify the chassis! The fuses would probably blow, but still…
Also, I’m doing one little alteration for sheer cosmetic purposes. The circular glass “portholes” in the front panel let you see the glowing filaments of the valve tubes while the device is powered up – obviously they are there not merely to let you see if the tubes are working, but for a bit of a “light show”. However (I’ve noticed this before) the tube sockets are mounted about 3/4″ lower than they should be, if you want the tube’s filaments to be right behind the glass exactly. So I’m going to add some 3/4″ standoffs under the existing ones to raise the tubes up a bit.
More pictures and reports to come, so stay tuned!
Update: The operation was a success! Bolts tightened, caps replaced, jumpers installed, tubes elevated, everything cleaned, buffed and polished! Powered up the box and it ticks, clicks, glows and pulses as it should. Hopefully good for another 70 years!
Update 2: Report on the final modifications here.