Stripboard ADA flanger

[uncle boko]

As I mentioned a week or so back over in Ampage, I decided to solder up an ADA flanger clone on stripboard of a size that would squeeze into sensibly sized stomp box. A proper PCB was out of the question as I neither have the time nor the patience to draw one up, although after reading Mark Hammer's procedure of drilling the holes first, I was tempted to try.

I reported earlier that the unit I built a couple of months ago took up a piece of stripboard 11" x 4", but everything was given plenty of space to allow for trouble shooting, which funnily enough didn't amount to much, apart from the couple of strip tracks I forgot to cut causing havoc in the input section. I drew up an area of holes on Excel representing the size of stripboard I wanted to use and overlaid component shapes to give me an idea of how small I could go. That seemed to indicate that I could go to 4" x 4", using 2 MC3403 for the audio path and the manual sweep amp, LM324 for the LFO and other CV processors, 4007, 4047, 4049 and BBD. The 3403s are on top, 4049 and BBD in the middle and LM324, 4007 and 4047 at at the bottom.

I have now built the input section, LFO and clock generator up to the 4047 and sod's law has already crept in because I hadn't allowed space for power lines and decoupling capacitors, so I'm now looking at a board 4" x 5.25" which isn't too bad. Now, I've also built this beast twice on breadboard so you would think that any potential problems would have reared their ugly heads by now - wrong! I had extreme difficulty in getting the LFO to work, in fact the first time I looked at the LFO output my digital multimeter read 0v. I already had the input section working OK at the top of the board, using incidentally the passive limiter from Rev3, so I decided to desolder the LM 324 and try another - but tired eyes managed to desolder the 3403 instead! It's easy to take out the wrong chip when the board is upside down - I tend not to use sockets for opamps although I do for cmos and BBDs. I then checked the 324 on another board and found that it was dead - a brand new chip. So with another 324 in place which I knew was working, I tried for LFO voltage again but this time a static voltage, so some progress. I then replaced each component making up the LFO and it was not until I replaced the 33uf capacitor (again brand new) with an old 10uf,that it worked. I then tried each of 5 other 33uf caps I bought at the same time recently and none of them worked!

Upward and onward, the clock generator came next and I copied the layout from my other board. The 4047 is positioned 1 row below the 4007 so that pin 12 of the 4007 lines up with pin 2 of the 4047. I also managed to get a 22p - 65p variable capacitor from Maplin Electronics (wonders will never cease!) which will allow me to play around with the max and min delay. This worked first time, giving out roughly 6.4v at each of pins 10 and 11 of the 4047. If the voltages at those output pins are not the same, the BBD will not work - believe me.

That's as far as I've got folks - one thing to remember when designing stripboard layouts is to allow plenty of space for electrolytics, unless they are very small you need to allow an area of at least 3 x3 holes, and preset pots take up more space than you think.