So I bought one of the last Ambika kits many years ago and lost my bottle after soldering a resistor network the wrong way round so left it until I got better at soldering (on smaller projects), I had to replace the motherboard pcb in the end trying to remove that resistor network resulting in removing a pad.
I’ve managed to get it all working and passing the checks apart from one voicecard (unsurprisingly the first one I made) which is much louder, to the point of distorting. Lots of the previous posts have been resolved after incorrect resistors, I’ve checked against a working voicecard and I can’t see any difference (it doesn’t help of course that I wasn’t consistent with my resistor orientation at this point).
I’ve pulled my scope out. So I’ve got the faulty one and a working one and I’ve got the ambika in mono with one oscillator playing a sine.
Here’s the output of the working voice card
Here’s the output of the faulty one
I went looking through the pins and I’ve found that pin 13 on ic4 (LM13700N) on the faulty voice card had a sine
while the working voice card didn’t (or at least it’s very quiet)
I then noticed that it seems like R29 (10k) on both have a sine going into it but on the working voicecard the resistor brings it down to the previous pictures but on the faulty voicecard it stays the same.
I checked the soldering, the voicecard with the green band and the awful soldering is the faulty one, I’ve not managed to find any bridges or shorts, just this gunk (is it flux?)
Here’s a close up of the pins of that resistor and IC (might be a red herring)
Let me know if there’s any more photos I can provide, sorry if this is a really dumb mistake I’ve made that I’m not seeing.