[time-nuts] Fixing an HP 5370A with a missing ROM board

[Mark Sims]

For some strange reason,  5370A's with missing ROM boards seem to be more common than one would expect.  I now know there are at least two others...

Another question to ask is how many 5370's are out there without the oven oscillator option?  It  might be worthwhile doing a small run of oven oscillator power supply boards.  
I also noticed that the 5370 drives the oven with unregulated power.  I suspect one could get better performance by using a regulated power supply.  The 10811 spec is 2.5e-10 for a 10% change in oven voltage so the improvement would not be a whole bunch,  but is noticeable.  I did a test with a variac and could see the effect over what my normal line voltage daily range is.  The oven power is generated via a bridge rectifier / 16V transformer winding which generates a nominal 22V,  not much headroom to meet the 20V oscillator spec,  but doable...  I see another pimp 'yo 5370 project coming.

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While I don't have a need for your mod...
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