Electrical help

[JAM1777]

I took your guys advice and got my drum brake system repaired till i could afford disc brake conversion, and it was a well spent $400!! Truck stops excellent! Now i have another problem, when i drive the truck all the power goes out.....sometimes in the middle of a busy intersection. I put the truck in park and when i turn the key the engine will turn over but takes a few turns of the key to start. I told the mechanic that fixed my brakes about this problem and it happened to him too when he was test driving after he fixed the brakes. So he changed the coil and igniter, thinking that would fix the problem.......and he also checked all my connections and he said some were loose. He said he hopes that fixed the problem but he didn't know for sure. When i picked up my truck today i drove from the mechanic hoping it was fixed, and as soon as i got close to my house I was waiting at a red light and it died again! It started right up when i turned the key. Im not sure what to do or check?? Any troubleshooting ideas or advice would be very appreciated