Barbouri's Electronics Projects
Restoring vintage electronics along with designing and building new circuits. One eye looking into the past, the other looking into the future.
This time I am working on another radiation scaler/counter which is quite a bit different than the last one. This one is a decade newer from 1975 and was built by NMC (Nuclear Measurements Corp.). It has a built-in proportional counter, but has external inputs for Geiger-Mueller, Scintillation, and other sensors.
Something a bit different than my usual test equipment and calculator projects is this Picker Nuclear Compact Scaler built by Intertech.
Quite a few people may be wondering. What is a “Scaler” and what is it used for?
A “Scaler” is a counting device that totalizes the events detected over a period of time. Typically used with a Geiger-Muller tube or scintillation detector for measuring ionizing radiation. It is often referred to as a nuclear scaler.
Several decades ago I owned two Beckman / Berkeley model 7360–20 Universal EPUT® and Timer’s. Because of their size and weight and an upcoming move, I gave them away to a friend. In the past few years I have somewhat regretted that decision, even though it was probably for the best. So when I saw this 7360 up for auction, I decided to make an offer on it. I was able to purchase it at a reasonable price, but as expected the shipping was a bit high due to it’s size and weight.
I again wasn’t looking to start another calculator project when this Burroughs C5155 calculator showed up in one of my automated searches. The price including shipping was a bargain, so I purchased it.
I managed to snag a Monroe 430 calculator that was in good condition and a reasonable price. The Monroe 430 is 14 digit four-function calculator with memory, percent, and a few other extras. I have worked on a model 425 and 420 in the past so I kind of knew what I was getting into, especially the lack of documentation.
Welp, another calculator tale of woe. This time it is a Monroe 650 calculator found on eBay. The 650 is the top-end model of Monroe’s 600 series calculators. It is a 16 digit Nixie tube display calculator with addition, subtraction, multiplication, division, square root function, and two memories. It operates in fixed decimal or floating point modes, and has 5 changing indicators spaced every increment of the base-10 exponent of three from the decimal point.
The price was right and included free shipping.
During my wanderings on eBay I came across this 12 digit display Digitronic‑M calculator. It was an auction listing starting at $0.99 with a really low shipping cost, and the seller listed it as “works great!”. I put in a very low bid on it, not expecting to win it, but it turned out I was the only bidder. That was the good part of the transaction.
An early handheld calculator from 1974, with a 10 digit Panaplex display and rechargeable battery.
As I continue searching for Monroe 400 series calculators, I came across this Monroe model 40 calculator at a reasonable price, with a few small issues.
Normally I don’t have an interest in handheld calculators as most are too new. This one caught my eye with it’s unique styling and 10 digit Neon Panaplex II display.
Another bargain price purchase of an Eico Unitrex 1200M calculator. This model also uses the same CT5005 LSI calculator on a chip IC as the APF Mark XII Calculator, but is noteworthy because of the relationship of Eico with Cal-Tex Semiconductor, Inc., the manufacture of the IC chip. The 1200M was the first calculator to use a single LSI IC with integrated memory. It also has a beautiful 12 digit Neon gas-discharge display.
The APF Mark XII (12) is an interesting calculator. It is based on the Cal-Tex Semiconductor Inc. CT5005 FlexiChip, which was developed in 1972. The calculator is a four function with separately addressable memory register, all on a single IC.
A recent addition to the desktop calculator collection is the Canon Canola L100A desktop 10 digit gas discharge display calculator. This unit was purchased as a working calculator, and was in good shape except the heavy yellowing of the beige upper case..
It wasn’t the exact calculator that I was looking for, but the purchase was well worth the price paid for it. The model 425 from Litton Monroe is a 12 digit Panaplex display with memory calculator.
I decided to see what I could do about the temporary modification to the Burroughs C 3207 multiply key indicator, before it became a permanent modification.
Well I just finished working on the APF Mark 1 calculator so I wasn’t looking for another calculator project right away, but I stumbled upon this Burroughs C 3207 calculator with several issues for a price that was too good to pass up. And it’s a vintage 14 digit Nixie tube calculator Built in late 1969.
The newest addition to my small calculator collection is an APF Mark 1 desktop unit. I found it on Ebay a few dozen miles from where I live. As usual it was untested, as it did not have a power cord, and other than being dirty it looked in good condition.
I have had my Nakamichi 420 audio amplifier since the late 70’s, and have used it with no issues since it’s purchase. Recently I was listening to an album, when it quit producing any sound, and shortly after produced that burnt electronics smell we know so well.
