All’s Well That Ends Well

This is a little embarassing, but I don’t think that there was ever anything actually wrong with my JH Living VCO module. I think it was all my error.

I exchanged a few messages with Herr Haible on the electro-music.com forum. He was able to rule out my theory that the substitution of the transistor array was the source of the problem. Once I learned that I went back to basics and checked the value of every component and every solder connectionon the PC board. I completely disassembled the PCB from the panel and tested each oscillator individually, adding connections as I went. I also tested the master section separately. In the end I was able to properly set the 1V/Oct scaling for all three VCOs, with no changes to my original assembly. read more

Let the Children Do Dangerous Things

Some years ago I posted this essay about being a kid in the mid-20th century, and reflected upon it later in this post. I think it’s a dreadful mistake that in an attempt to protect children from injury and disappointment we’re preventing them from learning skills with basic tools, learning how to explore without specific goals, learning how to deal with the unknown without fear, and learning how to overcome obstacles on their own. Hence I was both happy and sad when I ran across this video: read more

ExpandOS!?

No, ExpandOS is not a new operating system. It’s a packing material system. (Okay, yes, you probably have to either be in the mail-order business or be slightly strange to get excited about packing material. I qualify on both counts.) We just found out about them because they were used to pack some printer ink cartridges which just arrived here. They’re little wedge-shaped things made from thin, folded cardboard. According to the ExpandOS web site, they consume 1/25 the volume of pre-expanded packing material. They’re made from 100% post-industrial waste and are reusable and recyclable. In other words, they appear to be what everyone should start using to replace EPS packing peanuts. read more

Aha (No More Phooey)

I found the cause of the 1V/octave scaling problem I mentioned in my previous post. The problem was that I substituted a CA3086 transistor array for the CA3046. This is listed as a substitution on Dave Brown’s Mouser BOM. I probably chose the CA3086 because that’s what Bridechamber had in stock at the time, or something.

At first glance the two parts are viable substitutes for audio applications. Even looking at the Intersil web pages for both parts does not reveal the difference. The difference is in the HFE current gain parameter; the CA3086 has a gain of 100, while the CA3046 has a gain of 110. The Intersil web pages actually have a typo; HFE is stated as 100 for both. It wasn’t until I did a parameter-by-parameter comparison of the PDF data sheets for the parts that I found the difference. read more

Well, Phooey

I started to calibrate my JH Living VCOs on Saturday and quickly discovered that I can’t complete the 1V/oct scaling adjustment. Even at the most extreme setting of the trimmer potentiometer they go up by less than an octave per 1V change in input CV. Grrr.

This is a puzzler. All three VCOs exhibit the same problem, and all three of them appear to operate correctly otherwise. The obvious answer is that I put the wrong components in somewhere, but I’ve now verified the values of all of the resistors and capacitors in the first VCO and found no errors. The only component substitution I made was to use a CA3086 transistor array instead of a LM3046. This substitution was suggested on Dave Brown’s Mouser BOM. As far as I can tell from looking at the data sheets, the two parts should operate identically in this context. read more

No New Tale To Tell

I realize that it’s been quite awhile since I’ve posted anything of note here. This post isn’t going to change that. It seems like there isn’t much in the way of noteworthy news, but here is some somewhat inconsequential news:

Widget is still with us, somewhat to our surprise. (That’s not inconsequential news, but it’s not really news as such either.) She took a sharp turn for the worse Friday before last. We got her into the vet that afternoon, where she received an injection of fluids since she was badly dehydrated. She hadn’t improved noticeably by the time we went to bed, but she seemed much better the next morning and improved steadily after that. It’s very much a day-by-day thing now, though. Day before yesterday she seemed to be slowing down again, but yesterday and today she seems to be doing fairly well. read more

20 Years Passes Like Nothing

Well, maybe not quite like nothing, but it does rather amaze me that it was 20 years ago today that the Berlin Wall came down.