MeghanIsMe

All the lamps are working on the 2270! I cleaned it too; so shiny! Next I'm going to troubleshoot my 300 disc CD changer while trying not to spill 150-ish CDs all over the floor.

I should get down on top of this thing with my super-wide lens and see if I can make it look weird. Making things look weird is one of my primary photographic motivations.

Analog electronics are beautiful. What do you buy anymore that has physical gears in it?

This is the tuning section of my Marantz 2270. The rows of discs are variable capacitors for tuning. Rotating discs alternate with stationary discs to provide variable capacitance.

I believe the set of three on the left are AM and the five on the right are FM.

Doctor Luke (my work friend) said that someone pointed him at a book from 1971 called Modern Operational Circuit Design. I looked it up and it seemed like it might be helpful so I got it through our iShare program (ILL, but within a network).

In discussing operational amplifiers, the author wrote in a footnote: "A note of encouragement is offered to certain readers: integral calculus is one of the mathematical disciplines that operational circuitry exploits and, in the process, rather demolishes as a barrier to understanding."

I am amused that I am clearly one of those 'certain readers.' Regrettably, I'm not at a point where I want to try to figure out integral calculus right now. It's on my list to be sure; I just don't know if it's high enough on that list for me to ever actually get to...

A number of unrelated things have given me thought about time management lately. I want to devote time to the people in my life I care about (including me!) and the things in my life that matter to me. I get easily distracted by other stuff after work, so I'm going to experiment with deliberate planning of activities. I also talked to Danae about making plans with each other to ensure we both feel like we're prioritizing each other and other concerns in ways acceptable to both of us. Communication is pretty great.

We discussed time specifically in the context of me dating. Because Danae has a lot more experience with poly issues than I do, and because it hasn't really applied to us very much for a long time, I've kind of assumed that its rather easier for her than it actually is. She's socially isolated, and deeply stressed and anxious about her dissertation and job search. I'm a very large part of her support structure right now, and that's very important to me. It also makes me uncomfortable to talk about time in a way that feels like either of us have a claim on the other's time. More Than Two succinctly described the way I feel about allocation of time; that it is a gift, not an entitlement. It's really scary for me to ask for something that feels very important to me and risk being told no, and that's what time as a choice and gift means: the possibility of rejection. I believe that, while it would be fairly easy for someone who knows me to exploit my weaknesses of personality to manipulate my choices, Danae is not someone who would do that. I believe I'll be able to weigh the wants and needs of people I care about and give my time to them in ways that are not equal, but are fair. As long as there's enough communication happening for me to have the necessary knowledge to do so.

I'll have to figure out a good way to manage time commitment to housework too; that bears some thought. I've often done that on weekends, but if my weekends become busier I may have to spread that out. This Friday, I'm driving out to visit Erik. He's never seen Eternal Sunshine of the Spotless Mind so I'm bringing that. We might do some sewing or something to. I'm staying there for the night and getting back home some time Saturday.

Yesterday, I played Divinity: Original Sin 2 with Danae. Today, I'm going to focus on my radio kit. The amplifier is done and the AM detector stage is next. To get all my equipment connected, I'm using a prototyping breadboard. I create a test signal with my signal generator and run it through a pot to attenuate it. The wiper output from the pot goes to one rail on the prototyping board and the ground of the generator goes to another rail. Then I can use hookup wires and alligator clips to get everything else connected to it; my frequency counter, my scope, and the radio kit itself. It works decently well.

Today is the first time I'll be working in the archives here at work after my desk shift and I'm excited about that. I might be cataloging the contents of some institutional time capsules.

I've commented before that different kinds of photography can be essentially whole different skillsets. Architecture vs. portraits for instance. Or even architecture vs. cars and trucks. Basical technical concepts carry over, but the details are nothing alike.

Enter digital vs. analog electronics. I started out being interested in analog, but that's led me into some digital stuff too and they are entirely different worlds. Learning to understand the analog amplifier in my radio kit while also watching Ben Eater's videos about constructing an 8-bit computer is like learning two different languages. Digital feels a little more straight-forward in its basics, but analog has more elegance and beauty, and complexity, right from the start.

Ooooh. I really want this kit to build an 8-bit computer from chips and components. I shouldn't buy it right now 'cause money, but this would keep me busy for ages.

https://eater.net/8bit/kits

I changed some passwords while at work yesterday and put them into my password manager. Then I forgot to send the database to myself so I couldn't get into DW or LJ this weekend. Oops!

Yesterday, I wrote:

I'm not quite sure what to do today. I want to work on my electronics project, but I need to order a socket*. The weather is warm enough that I'm thinking seriously about finally fixing up my bicycle because I'm really tired of not being able to ride to work. But the weather will get cold again. Still, it'll be warm this week, so that's probably what I'll do.

*The project includes a discrete transistor amplifier on it's own board. That board has headers that slot into the 8-pin socket for the LM386 amplifier. I tried to insert the headers into the socket and mangled a couple of pins. Now it doesn't work with the chip either."

At first I wasn't sure what to do yesterday, but then a number of things came along!

The most fun of the day was watching the Puppy Bowl with Danae and Lisa. There was a capybara! Capybaras are so cute! Not as cute as all the puppies though. Puppies! The Dog Bowl highlighting some older dogs was great too. I am a fan and will be back for it next year. If I can be organized enough, I'll make cookies shaped like dog bones. Maybe other food and treats if I can think of them.

Someone on Evanston Freecycle had two Ikea bookcases to get rid of so I drove over to get them. They were near us, in a beautiful late-1800s house on Orrington. The owner thanked me for being careful with the woodwork on the way down the right-angle stairs, and I said that it's such beautiful wood that I'd feel like a terrible person if I scratched it. Danae helped me get them upstairs using the dolly I trash-picked in the fall, I wiped off the water and grime from setting them down outside the car, and they're now waiting for assembly in our little hallway. The blood from my finger that I cut on one of the nails didn't wash off as easily though.

I got my studded tire on my rear bike wheel. I left the smooth Gatorskin on the front since it's still serviceable and roads aren't that icy right now. The chain, having been outside and unused since December, was rusted badly enough that I walked to the bike shop for a new one. Lastly, I adjusted the front derailleur again (it keeps rotating slowly around the seat tube, eventually making it impossible to shift to the smallest chainring) and all seemed well. I rode to work this morning and it was wonderful! The weather was Spring-like and halfway there, I took my vest off.

I'll need to buy a cassette of gears for the rear wheel. I do 80% of my riding in gears 2-5 and 2-6, and the teeth on those sprockets are worn down enough by the old chain that the new one is skipping significantly on them. I did most of my riding today in 3-2 and 3-3 and the lack of range was a bit hard on my leg muscles.

I've been mathing and some of the below doesn't make sense. I forgot about the 50k pot the signal goes through to get to the amp. In theory, I should be able to drop the signal amplitude to 0. I'll have to do some poking when I get home. I'll figure this thing out yet!

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I soldered together the first stage of my Elenco radio kit last night; the amplifier that ramps up the demodulated radio signal to drive the speaker. It passed the static tests from the instruction book like checking current in the circuit with no input, so I moved on to the dynamic tests.

I set my function generator to 400hz and attached it to the amp input. I set my analog VOM to 3 volts and turned the circuit on. Whack; the needle pegged and I jumped to disconnect it. The movement seems ok, but I will remember in the future to start at higher ranges regardless of what the *expected* value is.

I think the problem is not my circuit, but my function generator. The instructions say to set it to the minimum amplitude and I did that, but I think the circuit is expecting millivolts and my generator stops producing below 2 volts PtP. The amplifier took those two volts and shot the output right up to the positive rail of 9+ volts (a fresh 9 volt batter), which is over three times the range on that VOM scale. Oops.

In fact, the instructions say to raise the volume slowly until the amp output is 2 volts PtP, which was what I was already feeding to the input. The gain in this circuit as configured is supposed to be between 100 and 180, so the amplifier was trying to shoot 200 volts minimum into the speaker, stopped by the fact that it can't get more than 9 out of the battery.

So....I might buy myself a nicer function generator and put that together next. This one for instance; that should do the job a lot better. One reviewer mentions using it at 200mv, so it will go at least that low. Hopefully it'll step down below 100. Maybe I'll ask on Amazon.

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Ah-ha; here's the full manual. The amplitude resolution is 0.1 volts. With an amp gain of 100, it would step from 0v to 10v to 20v so I think this still wouldn't allow me to do the gain test. Oh well. I think it's safe to assume it works and move on to the next stage.
https://jyetech.com/Products/085/Manual_085F.pdf

My middle-to-long term goal is to have what I need to do high-quality repair work on vintage audio gear. Double-bonus if I can build some of my own test gear and learn a lot on the way. Building something like this may be in my future.

http://www.cordellaudio.com/papers/thd_analyzer.pdf

Two kits to build are arriving today! One of them is a cheap function generator, which will be nice for really basic testing at least. The one I'm *really* excited about, though, is an AM/FM radio kit that comes with a 56-page book that covers theory of design and operation. An Amazon review fully sold me:

"If you want to learn radio electronics, really learn what is happening inside a radio and why (to the greatest detail). If you want to learn how to optimize (tune, calibrate) a radio receiver. If you want to learn to use your test equipment, your frequency generator, your oscilloscope, then this is an outstanding kit! I have learned a great deal from this kit even after fifty years. In fact, the most I've learned from a kit in many, many years!"

I'm so excited to start on it! I want to really understand this stuff for when I work on vintage receivers.

(Here's the function generator I bought.)