[papasweetwd]

I am running a small block chevy with a digital 6 box. I returned the box to MSD for service because I was having mid to top end problems. I was told on the repair sheet diode in5273 was breaking down, and 2 in5279 diode were replaced as well. What problems would those diodes cause if they were not operating correctly?

[Rustydawg]

A quick google for the specs on a 1N5273 diode says it's a 120V zener diode.

The 1N5279 lists as a 180V zener diode.

The diodes are likely configured to regulate an internal power supply to 120 & 180 V or to limit voltages to these maximums. If they 'break down' they won't regulate at the specified voltage (they will conduct at a lower voltage). They could also drain or load the internal high-voltage power supply, leaving less energy available to fire the coil with.

I could see it causing a high-speed problem in the ignition - that's just when you need maximum output from the MSD's power supply.

[papasweetwd]

Thanks Rustydawg;

That the exact problem that I am having. MSD sent the Box back to me. I was told that I would be charged the minimum of $30.00 if nothing was found to be wrong with the box and up to $80.00 if something was found. I was charged the minimum but three problems were found. I thought this was one of MSD standard letters that they sent out after checking your system. I was expecting MSD to switch out my box and send me one that was already repaired. That’s not what happen, to my surprise they repaired and sent my same box back. I was shocked. The lost of power from mid range to top end has been solved.

RIGHT ON MSD!!!!

Thanks Rustydawg for your info, it was helpful. :>)