New to me Fluke 8502A.   Thoughts? - Page 1
Forum section: electronics / testgear

author: Stray Electron
author_rank: Super Contributor
timestamp: June 04, 2022, 04:00:17 pm
content: Yesterday I went and helped clean out the storage shed of an old friend of mine that is getting out of electronics. Among the boat anchors was a Fluke 8502A that we had picked up in a pile of surplus equipment 15+ years ago and put in a corner and forgot about. I don't think that we ever even turned it on :-/This came from a large US government contractor and has options; 02 Ohms Converter, 04 Cal memory, 05 IEEE-488, 06 RS-232, 09 RMS Converter and 16 Switchable Front/Rear Inputs. It'd dirty but appears to be in good condition but I have not tried to power it up yet.The questions are; is this worth keeping? And should I try to revive it and is there anything I should check before I try to power it on? I already have three working Keithley 196 meters and a working HP 3456.OK, Go!

author: AVGresponding
author_rank: Super Contributor
timestamp: June 04, 2022, 04:07:41 pm
content: Definitely worth keeping!It's mainly worth checking for bad caps before turning on, ie ones that have obviously spit their electrolyte out, or cracked casing on mains input filter caps (RIFA madness).Also probably worth checking for damp damage, vermin, loose debris inside.

author: Stray Electron
author_rank: Super Contributor
timestamp: June 04, 2022, 05:59:45 pm
content: A quick update: I got the unit out of the truck this AM and cleaned it up and took a closer look. It has option 08 (Isolator)) and not option 06. The warranty seals on the case are (were) still intact so no one has been monkeying around it :-) I pulled the top cover and all of the modules that are supposed to be in it are there :-) and it's clean as a whistle insideNo signs of water, moisture, rats, mice, roaches or corrosion of any kind :-) I knew that the Cal Memory option used a battery so I pulled that module and opened it and checked it. I was expecting to find battery leakage and corrosion but nope, everything is clean. It looks like new inside :-) I was surprised to find that it uses a 6V Lithium Sulphur Dioxide battery in it. I checked the battery voltage and it reads 0.5 millivolts! So it will need a new battery.I read on the AntiquesRadio.com forum that these typically have shorted tant caps so I will check those and the large electrolytics before I try to power it up. And I will probably just replace the mains filter without even checking the current one.All in all, so far, it looks like a keeper! Now I just need to decide if I want to make room in order to keep it. I brought home 9 other large rack mount sized boat anchors with it and I don't have room for ANY more stuff so I'm going to have to make some though choices.

author: bdunham7
author_rank: Super Contributor
timestamp: June 04, 2022, 06:34:34 pm
content: I would just plug it in and see what you have. If you have a variac, you can bring it up over a 10-15 second period while watching the current, but other than that I wouldn't bother or worry. Once you see that it functions you can start thinking about tantalum caps and so on. And if something does pop, just fix it.If you have a complete set of modules and can get everything working, they're a pretty decent meter, but the performance-to-space ratio is moderate at best.What else did you lug home?

author: m k
author_rank: Super Contributor
timestamp: June 04, 2022, 07:08:46 pm
content: And what you're gonna sell.(since we now have an idea of net expenses)

author: Stray Electron
author_rank: Super Contributor
timestamp: June 05, 2022, 02:25:48 am
content: Quote from: bdunham7 on June 04, 2022, 06:34:34 pmTwo HP 8165a Programmable Signal sources, a really old HP Nixie tube voltmeter (I don't recall the model), an HP 5335a Frequency Counter, an Elgar 251 AC source, three racks of AC/DC EL300 Electronic Loads (6 per rack) and a few other things that I don't recall at the moment. I left a rack mount Tek scope (a 7903 IIRC) and several other big items.I bought the Nixie tube meter myself about 30 years ago (used) and it dates from 1966 IIRC. it still worked great when I got it and was still working when I parked it and I'm eager to see if it still works.I was offered an HP 34401 meter and two HP 4 channel color DSOs and some other late model HP items but I think that the owner might change his mind and will want them back so I told him to just hold onto them for the time being. The owner has had serious vision problems lately and is almost completely blind and very depressed about it and has about given up on life and is dumping everything.

author: m k
author_rank: Super Contributor
timestamp: June 05, 2022, 01:03:40 pm
content: Sources and counter you obviously keep, if not too many already.TEA oldies will evacuate your nixie things, if you come to that.Reasonable electronic load seems to be a constant shortage item.R7903 is sort of a collector item and no matter what is your location, +1 collector should be around.For 8502A,listen to its relays.Ohms and currents continue internally to RT1.DC Signal Conditioner and AC/DC RMS take in RT1 or input jacks and continue to RT6.Maybe easiest it to take modules off and hear the difference.Plastic can be crispy.

author: Stray Electron
author_rank: Super Contributor
timestamp: June 05, 2022, 03:27:18 pm
content: Quote from: bdunham7 on June 04, 2022, 06:34:34 pmI went out and took a look at the HP Nixie tube voltmeter this morning. It's a model 3440A and the date code on it is 1966! 637-070xx serial number. It has a HP 3443a plug in and it was formerly property of the US AF and has an inventory tag from Philco SRS (Space and Recovery Systems) and a Philco SRS calibration sticker. I'm going to have to dig out a power cord with the oval connector before I can power it up.Philco and the US Space Program <https://corporate.ford.com/articles/history/ford-philco-and-the-mission-control-center.html>

author: VE2UM
author_rank: Contributor
timestamp: January 20, 2024, 01:40:34 pm
content: Definitely worth working in...I have bought three (one incomplete) 8502's at an hamfest, let them acquire some dust before opening them...First thing: You'll definitely need the service manual. Some guys sell Fluke manual collection CD's on FleaBay..These multimeters are pure FLUKE. Extremely well built !!!!Some weird design though... The DC conditioner (DC volts input) has a BIPOLAR input !!! (No FETs)Probably that, back in 1978, BJT's were better than JFETs for matching/nulling... but what's singular is that the input diff pair is emitter-biased by a 1 MEG resistor and a "bias" adjust sends a nulling voltage to the input via a 100 MEG resistor !!!But FLUKE didn't neglect JFETs at all... they're everywhere... as analog switches.The ADC is a "Fast RR ADC" (RR for Recirculating Remainder) is kinda weird, but it is working !!! I still have some reading to do...Important: Keep your screwdriver far from the trimpots until you fully understand their purpose. ESPECIALLY the Fast RR ADC module. Some of them are in the heart of the Fast RR thing. You do NOT want to to tweak them!!!First thing first, remove the power supply and test it. (Power switch comes with it). Hold the supply by the main transformer, not the heatsink. The 90° fixations / PCB will flex, possibly damaging the three Controller regulators on the heatsink.The Power supply has two distinct output sections: Guarded (for analog sections) and Unguarded for logic/controller. The Power switch and largest capacitor are in in the Unguaded section.Three supplies (+30V, -30V and Logic return, all in the Guarded section) are ladder-mounted on other (guarded) supplies.Particularly, the Guarded 5v2 supply positive is ladder-mounted on the -15 Volts, hence, the Logic return (5v2 negative) will read -20.2 Volts.Trimpots:- R9 for +15V,- R5 for floating 5v2 guarded supply- R6 for unguarded 5 volt supply.Be careful if you remove the power supply. The main power transformer fragile windings are directly soldered to the PCB.Then, the first range you want to test is the 10v DC volts range. In it, the DC conditioner's attenuator is not used and the amplifier has unity gain.For vintage processor lovers, the 8502 controller uses a genuine Intel 8080 !!!!!!BTW, the FLUKE 7600 is a copycat of the 8502 (or reciprocal)73 de Normand VE2UMMore news later...