Lowrey Micro Genie V-100
Made by the Victor Company of Japan, i.e. JVC, the Lowrey Micro Genie V-100 is a modified version of the JVC KB-500, and was introduced in 1982 and produced until 1987 (the latter date according to usedprice.com). It is capable of many unique sounds, thanks to its custom JVC digitally-controlled tone generator chip, extensive analog tone-modifying circuitry, as well as analog rhythm generation circuitry. Differences between the V-100 and the KB-500 include changes to the wording of the applied text, and possibly some changes to the way the accompaniment recognizes chord fingerings. It also has black plastic side pieces of the top case instead of the white of the KB-500.
This example of a V-100 was picked up at a local music store, where it had been stored almost inaccessible among a pile of other equipment. In fact, I had passed it over at least three times before, thinking it was yet another cheap modern digital unit. Of course, upon further inspection, I discovered this was not the case. After testing it, I decided to take it home.
It had certainly not been well-treated or well-maintained. Apart from being dirty, two of the keys—the lowest C and third-from-lowest D#—were broken such that they rested slightly sideways, and would stick when pressed down. In fact, when received, around half of the keys triggered no sound whatsoever when played, which is apparently a common problem with these keyboards. The rectangular buttons had a tendency to stick, and with especially the "Piano / Organ" preset button having an intermittent contact problem. Especially on the left and right sides, there were some deep scratches in the plastic, the kind that would occur from scraping against a concrete floor. As well, the original keyboard stand was (and still is) missing, which would have had screws to attach to eight mounting points in the bottom. Two other parts are also missing—the transparent plastic piece that would have served as both a dust cover for the unit's controls and as a music stand, and the battery cover. Here are pictures of the instrument pre-repair:
The first things repaired were the non-sounding keys. Since there were so many, I removed the board with all of the key buttons, called the "MKM Ass'y." Each key button is an independent sealed unit with a silicone dome, instead of the more typical arrangement of having a strip of silicone domes resting on a board having all of the contacts on its surface, which would be much easier to clean. It is impossible to clean the actual contacts directly without surgically removing the silicone domes, but they can nonetheless be returned to functionality by applying "contact cleaner" to every button along the edges of the domes, so that it would seep onto the contacts inside, and then repeatedly "massage" the contacts for about a minute each, doing four at a time. In this instrument's case, this process fixed all but one, which I had to massage once more after I had reinstalled the MKM Ass'y.
Broken plastic at the pivot points near the back was the cause of the two slightly sideways keys. Luckily, the broken-off chunks were still within the case, otherwise the repair would have been much trickier. Another key—the D directly beside the broken D#—was just starting to crack at the same point, so this was also repaired in the same way. In order to remove the keys, the entire keyboard assembly had to be removed from the rest of the case, which involved removing a number of screws. I was able to figure it out on my own, but there are instructions in the service manual (available at the bottom) if you have difficulty. Here are the C and D keys prior to repair:
A little bit of thin cyanoacrylate glue got the keys back in working order.
Having the keyboard assembly out gave a good opportunity to thoroughly clean the keys and keybed, which were certainly in need of cleaning.
Another repair came in the form of this broken plastic mounting post, which was one of four attaching the back of the metal keyboard frame to the top plastic piece. This was also repaired with cyanoacrylate glue, once the keyboard assembly had been reattached to the top section.
At this point, the instrument was completely functional, but...
Every single 220uF 10V and 10uF 25V capacitor had corrosion on one or both leads, due to leakage of the electrolyte, which I've found is common on these Matsushita CE series from the 80s. I decided to replace all of them, which was pretty straightforward; eleven 10uF and eleven 220uF capacitors were replaced, as shown below.
One final note, and that is that initially, I thought the Mach III sequencing/"recording" feature was not working, since I could not get any of the LEDs to respond no matter what I pressed. It was only after I received a copy of the service manual (see link at bottom) that I figured out how this is supposed to work; it is really quite unintuitive. Page 8 indicates that the instrument must be in Music Chord mode and with the Auto Start switch pressed, with the rhythm running, and then will you be able to press the Record button, making the record light and one of the channel lights turn on, select the channel, and then play the chord progression and have it recorded.
Let's start with the bottom, on which there is not a whole lot to see. The battery compartment is shown, missing the cover unfortunately. It takes eight D cells, which the service manual states will last only 3 hours at full volume! There is also the label giving the specs and serial number.
Opening it up can be done fairly easily by the removal of 13 screws on the bottom, which the service manual gives instructions for doing. Unless you have a very large workspace where the bottom piece will not get in the way, it's best to disconnect the three cables joining the top section to the bottom. This unit, at least, has hand-written numbers that can assist in connecting the cables' plugs back to the correct sockets on the power supply board. The bottom piece itself doesn't have much mounted to it except for the power supply circuitry and a foil-coated-cardboard ground shield:
Looking at the top piece, it becomes clear that there is not a great deal of free space inside this unit. It manages to fit a remarkable amount of electronics: 13 circuit boards in total, of varying sizes. The two largest and most obvious boards are boards 1 and 2 (in the SM) which are the "Central Processing System" and "Quality Control" boards respectively. On the actual boards, they are marked as the "D1 Ass'y" and "AN Ass'y" respectively. In any case, these are mounted on a metal bracket on a hinge, which can be moved upwards 90 degrees into servicing position after the removal of four screws.
Another large and obvious board is mounted directly on the top case towards the back. This is Board 3, the "Rhythm Instrumentation" or "RH Ass'y" board.
As for electronics, the V-100 uses an interesting mix of analog and digital circuitry, with many functions performed by ICs. There are three LSI chips, which are a microcontroller, RAM/IO chip, and a custom JVC tone generator chip. The rest are mostly 4000 series CMOS logic and various linears (4558 dual op-amp, MN3204 bucket-brigade device, LA4125T power amp, etc.) typical of early 80s designs such as this. All components are through-hole, with all boards being single-sided and made of phenolic paper.
The microcontroller chip used is an OKI MSM80C49-21RS (or MSM80C49RS as specified in the service manual). This is supported by an OKI MSM81C55RS, which contains 256 bytes of RAM as well as some I/O circuitry. These do not do nearly as much as the microcontrollers in typical modern digital keyboards, which often are used for tone generation through DSP software and prerecorded samples. Rather, in this case, these chips are used for interpreting the keyboard and some switch settings, triggering the rhythm generating circuits and beat LEDs, providing the Mach III sequencer function, and controlling the tone generator chip. Thus, this keyboard can be thought of as digitally controlled, but with mostly analog tone generation and processing, and this is certainly reflected in its sounds.
Responsible for generating the tones (except rhythm) is the "Programmable Tone Synthesizer" chip: the JVC VC4050BL (or VC4050BH as specified in the service manual). It is in a pretty nice socket. Based on various input control, it produces square, triangle, and sawtooth waves of various octaves/"footages" that go on to be filtered by additional (analog) circuitry.
The rhythm sounds are generated completely seperately from the tone generator chip, with circuits using discrete transistors and opamp ICs as the active elements. This is done on the "RH Ass'y" board shown previously, of course.
Something interesting to notice near the tone synthesizer chip is a 0.047F (i.e. 47,000uF) capacitor that is used to retain the contents of RAM for "up to fourteen days with the organ power turned off," according to the service manual.
Like many keyboards of the 80s and beyond, the V-100 has a large variety of sounds it can produce. It would take a lot of text to describe all of them, and it would be ambiguous no matter what, so I will skip the description this time. There are already some videos and sound samples of the keyboard online, especially on the KB-500 page of the website dedicated to JVC keyboards, a link to which is at the bottom.
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