Mysterious spark disappearance (MSD) not working

My '73 is suffering from mysterious spark disappearance. Car always ran great but seem to have died over winter despite being on a trickle charger. Wiped out the odessey 925 battery also. Have another 12V battery hooked up for now but the car will not start (starter turns over fine) as the MSD box does not generate a spark. I have checked all wiring and it seems to be okay. To be sure I hooked up the wire coming from the ignition switch directly to the 12V battery. When rubbing it against the battery terminal the box makes a sound (not when just touching) and appears to generate a spark when starting the engine but only intermittently when rubbing and not continuously. Electrics are not my forte. It looks like I have an issue with the MSD unit itself, anybody out there have any pointers before I take the plunge and spend the $500 on a new one?

TIA,

JK
P.S. have also tried a new coil, did not make a difference

I would verify voltage at the box and check all connections.


If you have the old analog MSD box, Having low battery voltage will increase the Amperage draw and potentially damage the box.

I would always suspect the ignition trigger first. Points, Pertronix etc. G

Thanks for the pointers. I have bypassed the ignition trigger per MSD testing instructions and still no spark. Have a fresh battery on order and will see if that makes change. So far all signs are that I am having a problem with the box.

@Aaron, going to call you soon to talk Solex