This blog post describes how I repaired the board and explains a bit about how the Alto's groundbreaking Ethernet worked. Unfortunately, there was about one bit error per word, making it unusable. I'm moderately optimistic that the system will come up successfully, but there could be more hardware problems waiting for us. According to Bill Wall, technical director for subscriber networks at Scientific-Atlanta, a leading maker of equipment for cable television systems, limitations in these amplifiers were a significant issue for cable system designers in the next three decades. Finally the transmitter and receiver can then be linked using standard Cat5e or Cat6 cable. Strung about 6 feet above ground, on the azimuth of your intended receiver target, this antenna can make a big difference. This method of testing is highly accurate and sometimes the quickest, but it should be used only after you make certain that there are no circuit defects that might damage the replacement transistor. Mini flashlights family with wide or narrow focus, some with SOS mode are available online or you can just go to a nearby gadget store and enquire about the details according to your specifications.

The board was receiving the input okay, but a few gates later the signals looked kind of sketchy, as you can see above. When I powered up the Alto, I didn't get anything from the Ethernet board: it was not sending or receiving successfully. Thanks to Josh Dersch and the Living Computer Museum for their debugging help and sending out a boot disk. After plugging the connector in, I saw that the Alto was sending packets successfully, but still wasn't receiving anything. My emulator almost worked; by using the logic analyzer, I saw the Ethernet microcode was running and the Alto was receiving data from my board. I built an Ethernet emulator using a BeagleBone Black, allowing me to send Ethernet boot packets to the Alto. The Alto's chassis slides out of the cabinet, allowing access to the circuit boards (see above). The Ethernet board is hanging out the right side of the chassis because I used an extender board. The board applies an R-C filter (green) and then the signal edges are detected (blue). Yellow is input data, green is R-C filtered, blue is detected edges.

While the input (yellow) is a clean signal, the green signals only go up to about 2 volts, not the expected 4-5 volts. Concurrency is a special kind of analog circuit parallelism that uses a single circuit with necessary bandwidth to process multiple signals at the same time. So one of the RPI engineers fixed the bugged kernel, I updated to this one and I performed again the same test as earlier. But one of its most important contributions was Ethernet, the local area network that is still heavily used today. They both partially worked, but still have some bugs. These new technologies have been integrated into LGs latest module design, which has been highly capable of future IC (Integrated Circuit) fabrication to help ease the path towards future commercialization. This is a similar circuit to that of the front end amp. A crimped on terminal lug at the end of the wire finishes it off nicely. The problem is probably interference due to the sketchy wiring I used; I'll try shielded wire next session. These locations are sometimes referred to as wiring closets. The Ethernet signals to and from the Alto are 5V TTL. The photo below shows the BeagleBone, along with a chip (74AHCT125) to convert the BeagleBone's 3.3V signals to 5V TTL signals.

Even worse, the blue waveform is irregular and low-noise amplifier has "runt" pulses-short irregular signals that don't go all the way up. Based on the spec sheet, it looked like a really good backup controller for my Midnite Classic - if something goes wrong, I can bolt this in and go on my way. Note that there is a transition in the middle of each cell that can be used as a clock. One note is that this takes a very, very long time to start up, especially on a slow internet connection. One of these address pools (which typically corresponds to a single subnet) is called a scope. For example, all the top-most segment pins would be connected to each other, and connected to only one pin on the microcontroller. The board had a couple straightforward problems-a chip with a bent pin (which I straightened) and another chip with broken pins. This energizes the optocoupler, providing current pulling the FB pin lower. Measuring the power consumption of a charger is tricky because the charger doesn't use power like a normal resistive load, but uses a nonlinear part of the input current. Because the extra current is diverted into the MOV and to ground, the voltage in the PCB power supply line returns to a normal level, so the MOV's 'by-pass' resistance shoots up again.