10 December 2009

PC Function Generator (Part 1)

The last Velleman kit that I'm building for now is a Function Generator that can be controlled by the same software that came with the PC Oscilloscope. They can also work together. The Function Generator will do a frequency sweep and the oscilloscope draws a nice graph of the result. In this way you can test a filter for example and get a nice graph of the filter response. Even though I also have a hardware function generator this one is also capable of generating much more complex waveforms that are very suitable for error tracing and testing audio equipment.

The kit looks a lot like the PC Oscilloscope. It actually has the same enclosure, just with different front and back panels. I started inspecting if I had all the parts and it looked OK. The first thing I noticed is that this thing has a lot of power regulators and that all the resistors are of the 1% type. Further more nothing special. The PCB layout is quite neat, but when I started soldering I found out soon that the ground isles are very big. I needed to heat the parts that are connected to ground way longer than I'm used to before the solder started to flow.

I started building this PCB today. Here is a picture where you can see the documentation in the back. It is very clear and again most components are on a roll in the right order. Even though I managed to solder R14 in the place of R41. They were actually next to each other. I took a lot of trouble to desolder the resistor and put the new one in place when I found out later that R41 had the same value. A lot of work for nothing. Well I learned one thing. Next time first check if it really needs to be taken out when I make a mistake.

And here is another picture with all the IC sockets in place. I decided to deviate from the instructions here and solder them before the capacitors. If you look closely at the picture you will see that there are two very odd size IC sockets on there. I never saw those before. But they will hold two IC's as well that I never saw before. Well so far it is all very straight forward and I hope it will work. I'll try to finish it as soon as possible because I can't wait to get it finished. Somehow after the problem with the oscilloscope I lost confidence a bit and I'd like to prove it wasn't me I guess ;)

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