Greetings to all,           First of all,  let me apologize to the group for an un-finished, un-edited post that I accidentally just sent to the group.  At 82, I find Touch screens are wonderful devices, as long as you don't touch them.  I will try again to sent a readable post below. Greetings to all,             I have been keeping these wonderful "old" units running for about twenty-five years.  These units are old a should be approached with old technology, not new  technology, from a trouble shooting approach,  A power supply with any type of current limiting shield be avoided.  Especially if the Z3801a not powered continuously.  At turn on, quite minor current surges often turn the power supply off, adding confusion to the trouble shooting process.  A simple linear power supply will avoid this very common issue.           Again, in 25 years of maintaining Z3201's, I have never encountered a power supply problem, with the single exception  of the  small, 1 ohm, green, fuse resistors.  There are two of them.          Remember, there are, at least, three versions of the  power supply module.  They look exactly alike, with the exception of model nomenclature, in very small print, on the side of one of the small black boxes on the power supply module.  Be sure that your power supply module is correct for the power supply module in your Z3801a.   When these units came out of the factory, the required power supply voltage information was silk screened on the  back of the box.  If your unit has been modified, or serviced, in past years, this formation may not be correct for your Z3801a in 2023.        Remember,  the Z3801a was intended to run continuously.   My advice is to turn the little beauty on and hope for a lockup to 30 minutes to 4 hours, depending on how long the unit has been turned off, a where (position) it was last locked up.  Then enjoy.        As a trouble shooting issue, I have found the oscillator double oven assembly to be the most common problem.  Articles have been published about trouble shooting and repairing these ovens.   I have found it much simpler, and quite cost effective, to simply pick one up on eBay, or from this list. 73 de Lon, K5JV 281-795-1335