Roy, The 3458A is quite the instrument. I'm not familiar with the latest 'plug-in/power-up' devices of which you speak. I suspect you have Rev 9.2. Mine have the single chip EPROM, through-hole, A5 board. I suspect yours has the SMT version. If you have just had Agilent calibrate the meter, it is now eligible for the Repair Agreement for $178.68 per year. You can buy up to 5 year's worth and get a slight discount, 4% or so, IIRC. Might be worth considering. Gary Bierman at Agilent Loveland told me about that. When I called Agilent to purchase that, they were a bit skeptical. However, when I told them that Gary Bierman told me it was possible, they got on the phone to talk to someone and then readily sold me the agreement. Not a bad price to cover a potentially expensive repair, especially if you plan to leave it on 24/7/365 and you don't know it's history. Good luck. Joe -----Original Message----- From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On Behalf Of R.Phillips Sent: Saturday, June 14, 2014 4:00 AM To: 'Discussion of precise voltage measurement' Subject: Re: [volt-nuts] A Fluke 732A: Return it or keep it? Joe, Bill and Charlie Thank you all for your advice, and for the short term I will leave the 732A as is. Like you Joe, my 732A arrived with a set of 'dead' SLA batteries - these were replaced, and its been powered 24/7 since last October, again it came with no history. I bought mine from a dealer on the West Coast who had a batch of 14, so I guess that they came from a lab. Its stability is impressive, and the Thermistor reading is currently 4.5194 K ohms, with only small variations over time. My 3458A had a new processor/RAM/ROM board fitted by Agilent - so it has the latest 'plug-in/power-up' devices which I understand are a great improvement, and was calibrated just about six weeks ago. I take your point that the 3458A should be power continuously, but of course the display is of the fluorescent type which deteriorate over time. This is now less important, as I have had a new display installed, and the improvement is great. I certainly agree that the 3458A is very sensitive to temperature changes and as you advise, I frequently run 'Auto Cal' . I consider the cost of its refurbishment/calibration to be well worth while, considering the cost of a new instrument. Best regards. Roy