Is a Fluke 8000A worth repairing?

[Alex Eisenhut]

That's a '70s-vintage DMM I picked up while thrifting, it had 4 D NiCads in it which I recycled. There's a bit of leakage damage and a bit of "green meanies" on the PCB, but nothing huge.
But looking at it, I'm kinda surprised at the cheapness of the thing, I thought Fluke was supposed to be premium stuff or did they really improve in the '80s?
The way it's built it
1) Needs a special AC cord
2) Needs the batteries to work.
3) Uses an incandescent bulb as a current regulator for charging the cells. Clever for the 1930s, but even in the '70s surely there was better?
There is a Northern Telecom sticker on the thing so it must have been considered good at the time?

Is it worth putting in time and effort for what seems like a very basic DMM? Or should I keep it as a display gizmo?

[tridac]

From what i've seen, Fluke are past masters at getting performance out of deceptively simple circuitry. The essence of good engineering. Any fool can throw $ at a problem, but takes a good engineer to get the best out of little. Sure, it's worth fixing, respect, even if only kept as a backup...

[coppercone2]

those switches on it are super annoying

[bdunham7]

Fixing one is certainly a bizarre side trip into some interesting engineering choices.  There's a surprising number of variants of this meter and some came with a few unique options like data output, battery, and  impulse (amp-seconds) for specific purposes.  I think it was less expensive than other digital meters of the era.

I'd bypass the power supply section and power it up to see if it works or not.  If not, these use a rather strange system of converting volts to counts--they have some hybrid ICs with matching resistors and capacitors that were (and still are on eBay) sold as a set.  The meter essentially couldn't be calibrated if these parts weren't matched.  The design was one chip as a 'precision' VCO and another as a gated counter, then some logic for the displays.  So volts-to-frequency, count the frequency and display it.  If those chips are toast--and they often are--there's no fixing it without them.

[zepto]

it's a 3.5 digit bench multimeter with .1% annual accuracy specifications. it has less resolution and worse accuracy than modern high-end handheld multimeters. i've never considered buying one for repair or anything else. maybe you could use it to learn more about multimeters.

8800A's are quite nice, especially the later generation.

[vk3em]

I have one too, rescued it out of the e-waste bin. Works fine - front panel switches are annoying, otherwise OK.
Here is what I have found on it:

Forum Links:
https://www.eevblog.com/forum/testgear/strange-behavior-while-calibrating-a-fluke-8000a
https://www.eevblog.com/forum/testgear/fluke-8000a-dmm-schematic
https://www.eevblog.com/forum/testgear/restoring-repairing-an-old-fluke-8000a

Videos

[joeqsmith]

Personally, I don't see the point of buying such a meter unless you have a love for vintage tech.   Yes, it's a princess and if you look at it funny in the slightest way, you can damage it beyond repair.  Just like so many other modern low cost meters.   Let me know if you need any help with it.   

If it does run and you decide to try an align it, you may want to read this:

https://www.eevblog.com/forum/testgear/strange-behavior-while-calibrating-a-fluke-8000a

[Alex Eisenhut]

Personally, I don't see the point of buying such a meter unless you have a love for vintage tech.

Clutter as a lifestyle? 

[Paceguy]

Don't forget that this is DMM technology ftom the early to mid 70's, before Fluke started making it's 8XXX series handheld meters. If you intend to use it as a bench meter and power it only on 120VAC, I would suggest that you remove everthing that's related to operating it on batteries and re-configure the power supply as per the AC only unit power supply referred to in the service manual. That involves adding some electro caps, diodes and maybe cutting some pcb tracks and adding some jumpers. You won't need to keep that filiment bulb.

These were very much the industry standard meter back in the 1970's in Canada. Northern Telecom, CAE, Pratt & Whitney Canada, and others all used these and the Fluke 8600A.

[daisizhou]

It seems there is nothing special about Fluke 8000A.
If it is a FLUKE 8920A it is worth repairing because it is special

[Alex Eisenhut]

I was a little taken aback by the thing, very rudimentary, and now I see how easy it is to blow up the unobtainium front end.
Batteries are out, I'll remove corrosion, and use it as a display piece.
Too many little useless projects going on at the same time...

[bd139]

You can stuck an LM317 in instead of the battery stack like the 8010A.

Horrible DMMs though. Hate the things. The display board falls to bits, it's full of ASICs which are unobtainium and the board runs live mains right to the front panel next to all the signal lines. Fzzt.

[edavid]

That's a '70s-vintage DMM I picked up while thrifting, it had 4 D NiCads in it which I recycled. There's a bit of leakage damage and a bit of "green meanies" on the PCB, but nothing huge.

It will probably work even if you don't put much effort into cleaning it.

But looking at it, I'm kinda surprised at the cheapness of the thing, I thought Fluke was supposed to be premium stuff or did they really improve in the '80s?

The most I ever paid for an 8000A was $10, so I guess I had lower expectations    I do like the 8600A quite a bit better though.

1) Needs a special AC cord

Not really, you just need an IEC cord with no shoulder on the socket.  I'll bet you have something suitable.

2) Needs the batteries to work.
3) Uses an incandescent bulb as a current regulator for charging the cells.

As someone else mentioned, you can replace this stuff with a 1000uF capacitor and an LM317.  I've found the DC-DC converter is usually happier with 5.5-6.0V rather than 5.0V, so use a trimpot.

Clever for the 1930s, but even in the '70s surely there was better?

There was an almost complete lack of cheap but effective NiCd charger circuits at the time.  It didn't help that the 8000A is in a sealed case and gets quite hot inside, so sensing the battery temperature probably wouldn't work.  If you were a business and had it cal-ed by Fluke, they would just replace the NiCds as a matter of course (take that, Mother Earth).

Is it worth putting in time and effort for what seems like a very basic DMM? Or should I keep it as a display gizmo?

If you like the look, a sort of fun thing you can do is stick a microcontroller inside and use it as a clock.

I was a little taken aback by the thing, very rudimentary, and now I see how easy it is to blow up the unobtainium front end.

I've never managed to blow one up though.

the board runs live mains right to the front panel next to all the signal lines. Fzzt.

Not on OP's battery version - the transformer primary is unswitched.  Of course that's not so great since it's a crappy little transformer with a lot of leakage current.

[J-R]

Some 8000A units have slightly interesting LEDs where each segment is made of multiple tiny dots, but otherwise it's meh.  There are plenty of them for sale on eBay, I assume waiting for someone looking to re-live a prior time in their life: "Here's what I used at work 50 years ago!"

But regardless, tinkering a little bit with vintage gear is always a learning experience IMHO.

[bd139]

Some 8000A units have slightly interesting LEDs where each segment is made of multiple tiny dots, but otherwise it's meh.  There are plenty of them for sale on eBay, I assume waiting for someone looking to re-live a prior time in their life: "Here's what I used at work 50 years ago!"

But regardless, tinkering a little bit with vintage gear is always a learning experience IMHO.

Inevitably at least one segment is burned out on those because they had to stuff quite a bit of current through them to get them to light up brightly. This has the side effect of heating and slowly knackering the displays and that crappy bent PCB.

[Alex Eisenhut]

Yeah well it's not a big loss.
I don't expect to find electronic test equipment at the Value Village and Renaissance stores here, so when I see some, I swoop down like a seagull that spotted a french fry, and do my thinking (and regretting ) later...
The prices aren't that great either, but anything under 25$ I generally snap up on the spot, unless it's in pitiful condition.

[bdunham7]

Yeah well it's not a big loss.

When I parted mine out I found there were a decent selection of useful precision resisitors for current sensing and voltage division as well as a very nice capacitor or two for use as test standards.