MSD or Mallory?

[machoneman]

Since my ancient MSD-7A box died last week, I've looked at a new -6 box or the Mallory equivalent, also a -6 box. Any users of the Mallory unit? It's a toss up methinks between the two.

On perhaps a related issue, I have note my LCD dash voltmeter on start-up latety has been as high as 15.5 and sometimes pegs the meter (reads 'high' as apparently the voltage has spiked the upper end of the units range). In the past, it would hit 13.7-14.4 and then settle down to 13.5 or so.

Now it seems to hit the upper limit all the time and it makes me wonder if this smoked by MSD box. Any ideas on why the recent high readings? I did check all the +/- coil and battery wiring for tightness and all seems fine. Could my voltage regulator be going bad?

[jayb]

FWIW I have never smoked an MSD box on the dyno, and I regularly run the battery charger at boost voltage levels (16V-19V) to start a high compression engine, or just get the engine spinning faster.  I doubt that the voltage smoked the MSD.  Also FYI the magnetic sensors that our company specifies for the automotive market are required to withstand voltage excursions up to 40V without damage; I imagine that MSDs are specified similarly.

Your voltage regulator may be going bad, but also the MSD could have started to draw a bunch more current than normal en-route to failure.  This would require more alternator output, and therefore result in a higher voltage in the system.  I'd hook up the new MSD (my choice would be a Digital 6), and see if the voltage doesn't come back down to normal.  If it doesn't then try the regulator.

[rcodecj]

I would suspect the voltage regulator. I would use a 2nd volt meter to double check before buying parts though.

[machoneman]

Hey fellas, thanks for the super fast replies!

Hadn't thought to check the in-car gauge after bypassing the MSD which of course told me it failed. Did so just now (in between posting and 2 replies!) and the voltage has come down to 14.9 and an occasional drift up to 15.4-15.5,  much closer to the pre-MSD box failure readings. I'll charge up the battery (had the flashers on for a long time while awaiting the flatbed!) tonight and fire her up tomorrow and see if it drops below 14.0 as it had before.

Appreciate the voltage note too Jay as I could not find any MSD note on how much was too much. Knowing that some racers use more than standard 12V batteries, I kinda suspected this did not cause the box to fail but hey, had to ask as they aren't really giving away those spark boxes, LOL!  And yes, I was leaning towards the digital 6 MSD as heck, the old unit survived way over 100,000 street miles in 2 cars over about a 30 year span, plus MSD did rebuild it even though is was long obsolete.
 
I think I have the original regulator (now 42 years old!) in a box rcodecl. Good idea and I'm not adverse to even buying a new one if the voltage (sans any CD box right now) doesn't come down as noted above...or I can't find the old one.