The lowest-priced item that has been used or worn previously. The item may have some signs of cosmetic wear, but is fully operational and functions as intended. This item may be a floor model or store return that has been used. See details for description of any imperfections.
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Welcome, Guest. Please login or register. Did you miss your activation email? This topic This board Entire forum Google Bing. Print Search. The attatchement: The calibration module. Believe it or not, pointy haired people do exist! Nice teardown! This HP Journal issue which discusses the design of the A is also an interesting read: www.
I have here also a A but it's defective. There are two version of reference PCBs. I have attached some pictures of the B Version. JPG Vgkid Super Contributor Posts: Country:. Very nice teardown the analog side reminds me of my , but that uses no custom components at all. If you own any North Hills Electronics gear, message me. TonyGreene Contributor Posts: The HPA is an economical precision meter. For 6 digits The fan is a problem, when it goes.
And the fan is not made any more. I found a small 12V DC fan from a power supply that fit the hole, but I had to mount it on the outside of the case.
Also when it ran off of 12 volts, it was loud. I ended up mounting a T voltage regulator inside and feed the fan, and it moves enough air and is quiet now. This unit can see down to the microvolt level at 1 volt range, and my unit appears to have about a 3 microvolts noise, so it bobbles 3 digits. This depends on how clean the voltage reference is. Also as old as these units are, the voltage references have burned in and the drift will be minimal. I had my unit calibrated 4 years ago, got before and after data, and then I had it calibrated in April this year.
The 1 volt range had changed by 8 microvolts - so I seen a drift of 2ppm a year! That fan appears to be the same unit used in the A, which I just tore down. No longer active here - try the IRC channel if you just can't be without me. What kind of resistors are those?
I've never seen a resistor package like that. With the low tempco, I figure they are probably wirewound. All of the round precision resistors would most likely be wirewound. I will check, and update this post in a few minutes. I acquired it for around EUR. A bargain, considering the parameters. The only thing I regret is that it does not have current measurement :- Quote. Quote from: kilobyte on November 06, , pm. I bought this as defective with the hint that all LEDs are on after power on.
The first issues are dried out electrolytic capacitors of the voltage regulators. So far i had no time to continue repairing that big monster DMM. Nice teardown. Your unit is sooo clean. Its technology was building block for the a, 57a, and finally the 58a.
I would argue the A is a direct successor to the A. Which might be related to the A plug-in DVM. However, I don't think there was an HPIB bus then so 'system' use would be whatever ad-hoc network one used to control these devices. Also, this DVM was hard wired, rather than use some early microprocessor. But my criteria considers the existing top DMM today, the a, where did its technology evolve from?
What models preceded it that help make it what it is today? Per the HP Journal, the core of a, its accuracy, began with the a. Quote from: alm on November 08, , am. There was an error while thanking. SMF 2. EEVblog on Youtube.
Showing Results for Keysight Technologies (Agilent HP) 3455A
3455A 5 or 6-Digit Digital Multimeter/Voltmeter
HP 3455A Operating And Service Manual