Restoring vintage electronics along with designing and building new circuits. One eye looking into the past, the other looking into the future.
I finally decide that I had pushed my luck far enough with my battery backed NVRAM in my Tektronix TDS 380 oscilloscope. The specifications for the Dallas Semiconductor DS1644-120 Timekeeping RAM state that it is good for at least 10 years at 25°C, and mine had just turned 28 years old.
I decided to take a gamble on purchasing a Power Designs Inc. TP330 triple output power supply. It was a bit rough looking with a bunch of stickers on the front panel, but no scrape marks from past sticker removal visible. The seller stated that the bottom analog meter was non-functional, but the output terminals measured voltage that changed with the voltage knob.
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 was generously donated three Nakamichi BlackBox series units, by the same person who donated the “System One” rack from a previous post.
The units were in great condition, and more than likely could have been used as-is. They also surprisingly came with their original owners manuals, which usually get misplaced or lost over the years.
I found a great deal on a Hewlett Packard 3314A 20 MHz function generator that was non-functional, but overall looked to be in good shape. It arrived in great condition and was well packed for a nice change. The seller clearly stated the issues with this unit such as errors when started up cold, which worsened over time until it finally lost the display and LED’s.
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 did not take any pictures of the initial refurbishment of the Nakamichi 610 control preamplifier as it was mainly cleaning and capacitor replacement. But as soon as I thought the work on all the components of the System One rack had been completed, one of the dB meter lamps failed in the 610 preamp.
Included in the rack of Nakamichi “System One” equipment I recently acquired was a 600Ⅱ two head cassette console. This is the same rack that was involved in a building fire and the previously repaired Nakamichi 620 amplifier.
I was kindly donated a Nakamichi “System One” rack of audio equipment recently. Overall the equipment was in good shape, but had been in a building fire and suffered from significant smoke damage. There was not any detectable heat damage and only minor water damage.
After successfully repairing the 610 FM Tuner / Preamp I decide to tackle the model 620 audio power amplifier next.
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..
