vendredi 18 novembre 2011

It's christmas day

I just received my PCB prototypes they look nice and good quality. :

So quickly let the iron warm up and start to solder 1st prototype.

I soldered only the important parts, because it is the first prototype and you know the murphy's law.
Let's go for the first tests, add S&S power and test some voltage, Guess what .. IT DOESN'T WORK
I got very strange voltage on the output for the speak and spell bus, it's time to start debugging.

After several tests i found why .. all transistors are inverted ..  but strangely i didn't mounted then wrong, the error comes from Eagle. it seems that Eagle got several the BC558 part and one of this part the collector and emitter is inverted and of course i choose the wrong one ..

Next step, remove the transistors and resolder them in the correct way (what a pain to unsolder them on a double side pcb) and re-test. OK now i got the correct voltages. (-18 or 5V). (not with fresh batteries, problem explained in previous post)

midi optocoupler seems to be working right.
Didn't get time to check other part of the pcb for the moment.

Things to change for the next revision :

- correct silkscreen for transistors
- connect transistor emitters to the regulated 5V supply
- correct the input zener input regulation (put resistor in serie)
- check resistors value to limit the schield current
- remove the -18v / gnd selector jumer (default -18V)
- add a jumper to allow power via arduino.

2 commentaires:

  1. Donn't worry it will come soon, i'm currently busy to solve all the design issues with the hardware.