Assembly

2011-05-19T18:50:00.003+01:00

Well I'e done most of the assembly on stripboard - I decided to use a piece I had that is slightly bigger than the case I'd bought, because everytime I try to squeeze everything up together it always goes wrong!

I'm looking forward to testing the circuit, but there's a few things left to do, namely:

1) Get the chip onto the adapter board - I had a go but failed miserably - since the chip is SSOP, not SOP, the pin pitch is ridiculously small and there's no chance of doing it without the proper tools. I just hope I didn't cook the chip when I tried to do it (they are about £5 each...) Hopefully I have arranged to get it done at work, there are a couple of places that can do it.

2) Do the breadboard design for the op-amp - currently I am planning to test a simple buffer and the single sided circuit I posted a while back on breadboard, and then the winner will make it onto the stripboard. Thanks also to industry standard wiring layouts for dual op-amp chips, I can test both the TL072 and LM833 by just swapping the chips over :)

There were a couple of design issues with the trackboard, most notably with the 1uF caps - I assumed they would have a 0.1" pitch, but they are actually 0.2" - not too much of an issue, but they aren't as tidy as I'd like (and I'm glad I didn't design a PCB with 0.1" pitch holes for them)
Similarly, the electrolytic caps aren't the neatest ever, but originally I was worried about height clearances in the case, not that that's really an issue anymore...

I also made a noob mistake with one of the caps - I cut the track and then soldered the cap, which lifted the track under one of the pins. Thankfully the leg (which is a ground pin anyway) was long enough to reach a nearby joint, but I'd rather not have to do that if I can help it!

I bought some silver solder to do the board with, but it's quick thick and doesn't have much flux in it, so wouldn't recommend it for future projects. I'm used to the thin stuff we had at uni which is better - although if you can get your hands on some proper lead solder, it's millions of times better!

I'd like to get it finished soon, and test it works ok - I'd really like to be able to justify building a PCB and making a couple (was thinking of potentially selling some to cover the cost of the PCB manufacture) - I recon I could fit four on a eurocard (4x 40x100mm) without many issues - possibly even smaller if I went to surface mount components on the digital side...

Incoherent Mumblings

Assembly