Just finishes the A500 ++ project but +5v is pulled to ground

[turrican9]

So I just finished my A500 ++ project. Been transplanting components from a 6A board + some new components.

The issue is that I have a dead short between +5v and ground. Where to even start?

[amiman99]

First, check for solder blobs with magnifying glass.
Second, reversed components or polarity.

[turrican9]

Originally Posted by amiman99

First, check for solder blobs with magnifying glass.
Second, reversed components or polarity.

I have been looking for solder blobs with a magnifying glass. I have also been checking for correct polarity on the electrolyte caps. Could not see anything out of the ordinary. If there is a solder blob under a socket or something then I would have no way of seeing it.

[turrican9]

This could have been really dramatic. I think I found the problem. I unsoldered the linefilter and noticed the short had gone from the rest of the motherboard. However, the short was still present between the linefilter solderpoints and the power connector. So I unsoldered the power connector. Then I noticed the problem...

Turns out the + 5v pad and the ground pad had joined on the upper side of the board. This happened when I soldered the power connector and the solder flows through the via. I removed the solder bridge between the two pads and the short is gone. Will solder the linefilter and power connector back on and report back.

I added some bad pictures that shows the problem. This could have been much worse. I'm glad it was this simple and the fact that I tried to unsolder the line filter which sat me on the right path.

[turrican9]

omg. It's alive! It lives!

[amiman99]

Nice!

[turrican9]

Been doing some testing now. At first the keyboard and the audio filter was not working. But then I realised that U38 and U39 was named 1488 and 1489. I had swapped them around. After fixing that the keyboard and audio filter was working. Strange. I though those were for the serial port. Probably are for the keyboard also. And when they were swapped around the keyboard was stuck, constantly seding keypress signals without it working. That is probably why I couldn't enable the audio filter with the test program.

Still have another issue. Mouse is not moving left. Joystick is working fine. Buttons on mouse is working fine aswell. Have to investigate this. I know that U15 controls the mouse and joystick ports. And U15 are again controlled by Denise.

[turrican9]

I swapped the Denise that came from the 6A board with the Indivision ECS V2 which I had in mind for this build anyway. Now the mouse is working fine.

Building the A500 ++ replica board has been quite the journey. It's a ton of work. Especially considering how many parts I de-soldered from the 6A board and re-soldered onto the A500 ++ 8A replica board.

So much work but a learning experience and worth it.

[amiman99]

It's nice to see that you got it working, considering you soldered everything.

[turrican9]

Originally Posted by amiman99

It's nice to see that you got it working, considering you soldered everything.

Thanks. It's a real nice feeling to see it working after all this work. Another fault I just found was that I had used a 100uF cap at C307 instead of a 1000uF. This probably caused the problem with the A500 Denise and the mouse not working correctly. I had some strange problems with the ECS V2 aswell where I lost colours. After it had warmed up everything was fine. Most likely caused by this cap being way too small. Looks like an important smoothing cap. Will swap it tomorrow.

I guess I was a bit to fast to put the caps on today. Was eager to get it up and running. In the rush I noticed a bunch of 100uF caps in that area and didn't see that extra zero printed on the PCB for C307.