MT not triggering during Build [SOLVED]

I don't know that it will solve 'the' issue but R12A is supposed to be connected to IC22 pin14 right?

Yes ,R12A is connected to IC22 pin14.
You can use the original TR909 service manual, schematic are exactly the same for the analogue section.

Best regards,
e-licktronic

Ok, so I fixed the connection between IC22 pin14 and R12A.

I also found another trace that was broken (I've switched away from the flat head solder tip now... I like them but they don't work on this PCB...) and fixed that, it was connecting IC20 pin7 and R126...

MT Voice still sounds like a heavy click....

IC22 pin14 voltage is now +1.665v to +3.51v.

IC22 pin2,4 and 8 now just has flat line and no wave while scoped at about.

Voltage on those pins is about +3.5v

Voltage on VR13 pin2 with your DC Multimeter is almost +1.665v to +3.51v with and without IC20 in place.

Any ideas?

Try to replace IC22

Best regards,
e-licktronic

e-licktronic wrote:Try to replace IC22

Best regards,
e-licktronic

Just before you posted this I found the connection between 2 & 12 on IC22 was not complete. The culprit was the IC socket!

The clips that hold the IC pins were not making contact...

How much can be wrong with one voice!?

So the MT is not working totally but the tuning pot now works. So it kinda sound like a double attack, like there are 2 clicks for every one hit.

Any ideas?

I will also continue to test connections with the rest of the circuit. These PCB's are very fragile....

Thanks

Ok, so went through the rest of the Circuit and checked ALL connections between components. In total I found 3 broken traces and a dodgy DIP14 IC Socket. This is down to a flat tip soldering Iron and small fragile solder pads on the Nava.

From my last post when the MT wasn't working properly, all I have done is take the IC's out of the sockets and go through the circuit. Thats it!

NOW; the MT is working!

So after 13 days working on and off on this I'll continue the build (Id probably be finished by now!)

IC 22 Pin 2

IC 22 Pin 4

IC 22 Pin 8

Hey Hofmann25,

Ive been reading most of the posts on this thread to gather as much info before i start mine.

Are you saying the traces are prone to failure due to the size of tip you are using?

Any advice on best size tip to use and safe heat level on iron?

Thanks

Demos

I would say, use of of light and place the iron on the opposite side as the trace connected to the pad. Use a pointed tip even if you have the smallest flat one (like me).

The pads are very small and I managed to break 3 traces (so far) and I'm ok at soldering.

Take your time.

Best of luck

Thanks for the info.

I put my x0xb0x together with no problems but i am guessing the pads are more of a pain on this build going by some of the threads i have been reading.

Yep.

Take care.