Once again, I was donated a pair of Infinity Infinitesimal speakers by the same generous person, who donated the “System One” rack and three Nakamichi BlackBox series units from a previous post.
Infinity Infinitesimal Speakers
HP 5005B Signature Multimeter cleanup
I have been looking for a Hewlett Packard signature analyzer for many years, but until I found this one they have either been in good shape and really expensive or in poor shape and really expensive.
Nakamichi 620 Amplifier Repair
After the restoration of the Nakamichi 620 amplifier last year, it had been working great for 6 plus months. Then one day I turned it on and there was no sound output. Luckily the speaker protection circuit did it’s job and no speakers were damaged. The right channel had it’s output shorted to B+ (53 volts).
Tektronix TDS 380 NVRAM Replacement
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.
Power Designs TP330 Power Supply
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.
Beckman 7360R Universal EPUT® and Timer Restoration
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.
Nakamichi BlackBox Series Refresh
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.
HP 3314A Function Generator Repair
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.
Burroughs C5155 Calculator Refurbishment
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.
Nakamichi 610 Control Preamplifier Lamp Replacement
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.
Nakamichi 600Ⅱ Stereo Cassette Deck Repair
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.
Nakamichi 620 Amplifier Repair
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.
Monroe 430 Calculator repair and cleanup
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.
Monroe 650 Calculator repair and cleanup
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.
Digitronic‑M Calculator Repair
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.
Monroe 40 Calculator Refurbishment
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.
