Category: making things

Not wanting to sit in traffic I decided to stay at work late and poke around with the Atari SIO connectors from an Okidata printer which sent last week. These parts were desoldered earlier in the week and I think I’ve captured their footprint properly. I just hope that the other SIO connectors out there also fit.

Because this footprint was done in CadSoft EAGLE I can’t easily dimension it, so that might make it a little difficult for other people to reuse. Maybe I’ll try and do a DXF of it or something. While measuring it I came across a couple unexpected (for me) things which lead me to believe that it was hand-designed way back when. For example, the overall footprint seems to be 2:1 width:height ratio (1.86″ x .93″), and the pins have a .14″ spacing between each other, with the pins forming equilateral triangles.

(And yes, I will be CC licensing this footprint once I’ve tuned it to fit all the SIO connector variants that I can find.)

A few months ago I mentioned that I’d like to build an Atari SDrive as an electronics project. Well, one difficulty in doing that was obtaining SIO connectors. Well, thanks to I now possess a controller board from an Okidata printer bearing two SIO ports. Yay! I’ve heard that the Atarimax guy will be selling connectors-only soon, but I’m not sure how true this is, so this will have to do for now.

Since I’m in a posty mood tonight, have a photo of the smallest thing I’ve soldered to date. It’s nowhere near as small as what some folks I know have done, but I’m pretty happy with it. This part, U1D, is a Texas Instruments TPS2115APW, which handles automatically switching the AMB γ1 between wall and USB power, giving priority to USB whenever it is plugged in.

The package of this part is TSSOP-8, which has 0.65mm between centers of the pins, with the pins being 0.19mm – 0.30mm wide. I soldered it with a Weller WES51 with an ETO tip. Kester 24-6337-6417 (Water Soluble 331 Solder Wire, .025″ dia., Core Size-66 Sn63Pb37) solder was used along with a 2331-zx flux pen. Chemtronics Soder-Wick Rosin SD desoldering braid, in size 3, was used for cleanup.

Soldering was done with the iron set at 700°F. The area was coated with flux, a pad was tinned, more flux was added to that pad, then the part was placed. The iron was then touched to the edge of the pad and the part settled into place. Any slight adjustment would be performed by reheating the pad and moving the part slightly with fingers or a pin, but this wasn’t needed. I then fluxed the legs of the part and very quickly tacked each leg with a bit of solder.

The solder braid was then quickly run across the legs to pull off any extra solder. When washing the PCB after assembly the rosin flux from the desoldering braid was first removed with 99% isopropyl alcohol, then while the board was still wet it was washed with hot water.

(Click here or on the image above for a full res copy of that image.)

I’m building an AMB γ1 Modular Miniature DAC and as part of this I had to order a number of components from Digi-Key. Unfortunately, one part was missed. As can be seen above the bag was sent, but there was no part in it. At least it was only a $0.21, 0.1μF ceramic cap.

Even if I had received this cap I wouldn’t be done. It seems that I forgot to order some connectors for mating the two boards and screwed up a tiny SOT23 AND gate, so there’s now a couple other parts which I have to (re)order as well. Missing cap (C3U) and AND gate (U2U) can be seen here and the missing pin receptacles here.

On the upside, I had no problems soldering any of the SMT parts. I just put that aforementioned one in the wrong place and didn’t have any facilities for safely desoldering it. At least it only cost $0.40 or so.

That’s that. x0xb0x #888 is done. Now I just have to sell it.

Part of me hopes that this is the last x0xb0x that I ever build, but not the last 303 clone. More and more ideas have been swimming around my head about making a newer, better version of something similar to, but definitely not, the x0xb0x.

As hoped (and anticipated) the replacement BA6110 sorted out the problems I was having with x0xb0x #888.

Here’s another waveform photo like the one above, and here’s the bottom of the BA6110 with no-clean flux on it. Yes, there is a bit too much solder on pin 5, and possibly a couple others. No, it won’t hurt anything. Now all I have to do is finish tuning / adjusting things and then close it up.

Today I received an envelope containing three BA6110 chips and some mome rath buttons. Hopefully one of these will resolve the problem I had with the bad BA6110 I received as part of the x0xb0x kit.

I’d previously posted about how x0xb0x #888 was generating no audio after powerup, and with Roxie now gone I had time to start digging into what was wrong.

I’d already known that the power supply, digital half (sequencer), DAC, and VCO were working fine, so I set to work tracing things back through the schematic from the headphone out. Eventually I found that I was able to see a waveform on the first half of the BA6110, after the op-amp (pins 6 and 7) but before the buffer. I didn’t see anything after the buffer (pin 8).

So, I think I have a bad BA6110, which is one of the rare / hard to find parts in the x0xb0x. This is just what I was afraid of.

Being typically paranoid of my own work I double-checked soldering, checked for shorts, and all the other normal things like that, but I really think the problem is with the buffer.