Friday, November 21, 2008

x0xb0x SS#01. Component Log

All components in bold are considered important to optimize the x0x.

2SA733P hFE ratings
  • q8: 225
  • q9: 220
  • q10: 218
  • q27: 198

x0xb0x SS#01: Day 2. VCO

Since the PSU went relatively quickly, I went ahead and started on the VCO as well. Overall this was a much bigger task. While I'm not entirely new to electronics, I also don't have expert ... or even real intermediate skills doing this. A good chunk of my time in this phase involved troubleshooting, trying to get my homemade probe to work with the software scope (unsuccessfully), and trying to follow the steps and instructions really carefully. Total time spent was about 10 hours, four of which involved the above. I also socketed all the ICs and 'rare parts' and made my own cabling as per subatomic's x0xl0g. That also added to my overall time.

Because the scope never did fully work, I had to go the headphone route to test the VCOs. Again - a bit more time was spent on that. Thankfully I got to hear a saw wave before calling it quits for the night. I was quite thankful for that :) I slept better for sure! One unfortunate aspect in this is that the 2SA733Ps I have are all really low hFE. The highest ones I have are 225 so q8 has one of them in there now. I'll certainly be replacing these. It'll be interesting to hear what such low hFE will sound like though. So just as a note:

  • q8: 225 hFE
  • q27: 198 hFE

Day 2 was spent troubleshooting some more and filling out the rest (i.e. majority) of the VCO section. I continued to use the headphones as my 'scope' but I don't entirely trust the results. It really would be nice to see it on the scope just to be sure it's working as it should and that the frequencies are set just so. My multimeter and variable PSU have been quite good but I will need to get the scope up and running to really get the results I want.

One thing that baffled me was that the instructions for the VCO section are also not entirely complete. I had to double check the last round of resistors, caps, and ICs that would have to be added. I learned that I've been relying too heavily on the images at the site. I was a good exercise to have to track things down on my own and place the components correctly. These first two section taught me to have a clearer strategy before embarking on upcoming sections. I can see where I can be more efficient in this process.

All in all it was really nice to hear both the square and saw running. They're tuned quite well so far. Once the scope is up and running I can fine tune them some more.

x0xb0x SS#01: Day 1. Power Supply

I finally had a chance to get things started yesterday. Pulling parts on a per-section basis has been a little more finicky than I had hoped. I may still go ahead and sort sections after all.

Building the power supply unit wasn't too tough. I spend 4 hours building it. I have been working on it cautiously though so despite being a bit slower than I had originally thought, the results have been quite satisfying. I was interrupted numerous times as well so having to walk away so much meant that I'd have to review where I stopped before picking up again.

All the tests outlined in the instructions went just fine. I was able to dial in the correct voltage without any fuss. I did omit the power switch at this stage but after doing so many tests with the VCO I'm just going to add it in before I start the next round. It really *is* a pain to keep pulling the jack out every time.

Tuesday, November 18, 2008

x0xb0x SS#01: Day 0. Parts & Sorting

Very, very excited! Today the last set of parts arrived.

It was among the more important shipments: all the resistors as well as sockets for all the rare parts and a few other bits. Futurlec had the best prices by far, where 1/4W metal film resistors were $0.02 a piece, sold in quantities of 10. I decided to make the purchase worth my while so I picked up enough resistors for three units. If I decide not to make three I can just sell a round to another x0x builder for a good price. I also picked up a power switch from them ($0.65) but I'm pretty disappointed by the quality. It feels loose, flimsy, and cheap. I'll keep it around for breadboard tests but it looks like a bit if a waste of $. I won't rule it out yet but I think a nicer quality switch is in order.

My first statement wasn't quite true. There is actually a very small handful of parts I need to have everything on hand. I still need the following:

  • 74HC126 Quad Buffer IC
  • all the screws, washers, and standoffs
  • IC Socket strips (which are ordered but being shipped direct, so there's a slight delay)
  • knobs
The IC was the one thing I missed. The error was nothing more than me passing over it in the xls sheet. A1 Parts, a shop that's relatively close to me, has it for $0.99 so I'm not too worried about it. They also have some knobs and switches so I may be able to fill those gaps there.

I'm pretty critical about the knobs. It irks me that there isn't a supplier for really cool options. Most are pretty standard black knobs with or without a cap, maybe a line. I'd like something much more unique but it just seems like no one wants to stock any of them. Manufacturers make 1000 or 5000 minimum runs so that's out. There has to be a good source out there. I'm still looking and am prepared to hold out until I find it. It obviously won't affect the x0x's ability to function.

I also now have flat LEDs in white, blue, and UV. They look really good. I just need to work out what the appropriate resistance will be for them. I'll get to that soon.

So - the big task today was to test all the resistor values and sort all the parts into general categories. (Done! and Done!). x0xlog has everything neatly sorted on sheets. I considered doing that but frankly all the parts are already labelled. I'm going to leave them as is and see how I do.
I did bag them into groups though:

  • Adafruit parts
  • Rare parts
  • Chips & ICs
  • Resistors
  • Capacitors
  • Sockets and connectors
  • Pots, trimmers, encoders, switches
  • LEDs and LED standoffs
  • Miscellaneaous parts: switch caps, wall wart, wires, etc.
Obviously it's a very general grouping structure. It all lands into a bag or box each so it's quite manageable thouhg. If it becomes tedious I'll group them the same way it was done on x0xl0g. That's certainly well organized. I can't argue with that.

So - without a further delay - it's time to start! I couldn't be more excited.