EEVblog Electronics Community Forum

EEVblog => EEVblog Specific => Topic started by: EEVblog on August 03, 2017, 09:03:14 am

Title: EEVblog #1012 - Ebay Fluke 8842A
Post by: EEVblog on August 03, 2017, 09:03:14 am
Bought as a possible repair video, Dave shows why the Fluke 8842A 5 1/2 digit bench meter is one of the best value 2nd hand bench meters on the market.
Marvel at the LTFLU-1 reference!

Manual with schematic: http://assets.fluke.com/manuals/8842a___imeng0300.pdf (http://assets.fluke.com/manuals/8842a___imeng0300.pdf)

References: https://xdevs.com/review/dcvref_table/ (https://xdevs.com/review/dcvref_table/)

https://www.youtube.com/watch?v=X4_iRB2DIW8 (https://www.youtube.com/watch?v=X4_iRB2DIW8)
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: bd139 on August 03, 2017, 09:04:13 am
And thus the prices have now ascended to the unaffordable. Was just looking at these ;)
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: nixfu on August 03, 2017, 09:17:55 am
I will wait now for everyone else to get one, and then all the prospective buyers in the entire EE community will all have one thanks to Dave, and I will be the only one left willing to buy one and get it for a steal. :)

Always been a big fan of VFD displays myself.
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: calin on August 03, 2017, 09:27:26 am
Phew .. good I got one with all bells and whistles - 70$ "broken". Of course is working and is bang on.


Yeah 70$ ... before Dave's video !!!  :)   
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: alm on August 03, 2017, 09:55:23 am
Having AC (and sometimes even resistance!) optional was actually not that uncommon back then. I have a Keithley 192 that also has AC optional (and does not even have current). The old Fluke 850x meters also had pretty much everything but DCV optional. So it pays to pay attention to the installed options, since this will not be obvious from the front panel (like in this case: it has all the front panel silkscreen for AC). Even the check mark on the back is not 100% reliable because people will sometimes take out the option to move to another meter.
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: AF6LJ on August 03, 2017, 10:01:08 am
This looks good. :)
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: alm on August 03, 2017, 10:57:13 am
Similar units from the same vintage that are less likely to have their prices skyrocket:

Fluke 8840A. The predecessor to the 8842A. I think the only difference is worse accuracy (0.005% instead of 0.003% basic DC accuracy).

Keithley 199. This unit has a nicer display than the Fluke: big LEDs that do not have the same dimming that VFDs suffer from. Voltage only goes up to 300 V. Current ranges are 30 mA and 3 A, which in my opinion is nicer for electronics than 200 mA and 2 A. GPIB and AC are standard ;). Has an optional 8 channel scanner card (card that can connect the DMM to multiple points in the circuit in quick succession through relays). Basic accuracy is 0.007%.

HP 3468A/B / 3478A. These are very similar meters. The 3478A adds GPIB, a lower voltage and resistance range and better accuracy. Current range is limited to 3A. Basic accuracy is 0.018% for the 3468, and 0.006% for the 3478. The display is worse than the Fluke 884x (low-contrast LCD without backlight). I believe some people have added an improvised backlight. AC is standard, as is GPIB (on the 3478A). Current range is limited to a single 3A range. Voltage only goes up to 300 V. Dave did a teardown (and some other videos) a long time ago:
https://www.youtube.com/watch?v=9v6OksEFqpA (https://www.youtube.com/watch?v=9v6OksEFqpA)
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: EEVblog on August 03, 2017, 10:59:45 am
Phew .. good I got one with all bells and whistles - 70$ "broken". Of course is working and is bang on.

Score!
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: Excavatoree on August 03, 2017, 11:47:19 am
Great, I'll never get an affordable parts 8840 now.  The "Dave effect" is again proven.

I still say Dave could make a killing selling "early notifications" of what E-bay items he will be using for videos, so we can buy low and sell high.

Hey, maybe someone will buy one in good condition - working except for 4 wire resistance mode.  (eh, maybe not)
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: EEVblog on August 03, 2017, 12:00:17 pm
I still say Dave could make a killing selling "early notifications" of what E-bay items he will be using for videos, so we can buy low and sell high.

$3507 a month actually:
https://www.patreon.com/eevblog (https://www.patreon.com/eevblog)
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: Excavatoree on August 03, 2017, 12:11:07 pm
I still say Dave could make a killing selling "early notifications" of what E-bay items he will be using for videos, so we can buy low and sell high.

$3507 a month actually:
https://www.patreon.com/eevblog (https://www.patreon.com/eevblog)

Not exactly what I was thinking of, but I suppose it's the same thing.    I was thinking more of just a notification, not getting early access to the video itself.
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: EEVblog on August 03, 2017, 12:20:02 pm
Not exactly what I was thinking of, but I suppose it's the same thing.    I was thinking more of just a notification, not getting early access to the video itself.

I did notify people early on Patreon.
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: Jay_Diddy_B on August 03, 2017, 12:25:00 pm
Hi,
I have a few of these meters, 8840 and 8842A. Although they are 5 1/2 digits they have similar accuracy specifications to some 6 1/2 digit meters.

Be aware that ac volts and GPIB (IEEE 488) were optional on these meters. Sometimes the marking of the ac option is unreliable. If you select AC without the option 09, you get Error 30 on the display.

The ac option board is different in the 8842A than the 8840A. This was covered in this message:

https://www.eevblog.com/forum/testgear/help-troubleshooting-fluke-8842a-ac-board/msg358316/#msg358316 (https://www.eevblog.com/forum/testgear/help-troubleshooting-fluke-8842a-ac-board/msg358316/#msg358316)

The ac option can be moved from 8840A to 8842A if you swap the two signals.

The 8840A has a lower grade divider resistor and lower grade reference than the 8842A.

The 8842A one year accuracy specification is 0.0035% on the 20V range (35ppm)
The 8840A one year accuracy specification is 0.006% on the 20V (60ppm)

The 8840A does not have the 20 \$\Omega\$ Resistance range.

Both are great meters.

Regards,

Jay_Diddy_B


Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: Excavatoree on August 03, 2017, 12:35:50 pm
Not exactly what I was thinking of, but I suppose it's the same thing.    I was thinking more of just a notification, not getting early access to the video itself.

I did notify people early on Patreon.

I thought it was just early access to videos.
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: LazyJack on August 03, 2017, 05:00:47 pm
Oh, good I have already scored such a beautiful item before the prices will skyrocket after this video.
Got it for 70 bucks with AC and GPIB option and a failed solder on the mains transformer.

https://www.eevblog.com/forum/repair/yet-another-fluke-8842a-transformer-solder-fail/msg986417/#msg986417 (https://www.eevblog.com/forum/repair/yet-another-fluke-8842a-transformer-solder-fail/msg986417/#msg986417)
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: Raj on August 03, 2017, 08:54:48 pm
Don't the super fast changing digits make you think, traditional symbols fire numbers are obsolete? Specially for computer generation
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: xwarp on August 05, 2017, 07:18:26 pm


Hey Dave, I think I might have an extra AC board somewhere around.
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: hendorog on August 05, 2017, 08:36:27 pm

HP 3468A/B / 3478A. These are very similar meters. The 3478A adds GPIB, a lower voltage and resistance range and better accuracy. Current range is limited to 3A. Basic accuracy is 0.018% for the 3468, and 0.006% for the 3478. The display is worse than the Fluke 884x (low-contrast LCD without backlight). I believe some people have added an improvised backlight. AC is standard, as is GPIB (on the 3478A). Current range is limited to a single 3A range. Voltage only goes up to 300 V. Dave did a teardown (and some other videos) a long time ago:
https://www.youtube.com/watch?v=9v6OksEFqpA (https://www.youtube.com/watch?v=9v6OksEFqpA)

FWIW my HP 3478 has (IMHO anyway) a horrible right angle zebra stripe connector between the main board and the display board. Held in place by a little plastic bracket which also takes the load of holding the front panel relative to the main board.
This is easily damaged during disassembly, and because it has to hold the zebra stripe precisely it is difficult to repair.
I'd avoid getting one with a bad display for that reason.
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: pelule on August 06, 2017, 04:07:07 am
2007 I bought the 8840A, my 1st higher resolution Bench DMM - fully equipped with option -09 (AC) and option -05 (IEEE488/GPIB).
It had unbrocken original Fluke Cal sticker (1993).
Price ~$95 (including manual, power cable and 1m GPIB cable) and shipping - a real bargin.

In 2014 I got my 3458A and checked the calibration - it was still inside spec, after 21 years - the drift is far less the spec.
It is still the main part of my bench, it's my daily working horse (beside my 87s) and for low resolution logging.
Would never sell it...
Spec of 8840A is similar to the 8842A.
/PeLuLe
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: n3vti on August 06, 2017, 08:03:56 am
I love that meter! I have the older and cheaper brother, the Fluke 8000A, which is a 3 1/2 digit meter. Loved the red LED 7 segment display on it. Unfortunately the calibration is way off... haven't had a chance to calibrate it since I bought it... doh! (Mainly because I bought it right before I knew I was moving and now all my equipment has been sitting in storage since I have no room for a bench in the apt I live in... ulgh.)
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: Dr. Frank on August 06, 2017, 11:44:52 pm
Nice video & teardown.
However, the LTFLU has no oven, so the accuracy/stability is on par with the 731A, or the 343A, only.
Latter also use non ovenized Reference Amplifier SZA263.
So temperature stability and timely drift is quite good, like these, perhaps.
Frank
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: BobInOhio on August 11, 2017, 07:33:02 am
I picked up one of these on ebay last week after seeing this video (for well under a hundred bucks  ;D ) and interestingly my unit does NOT have the LT FLU-1 voltage reference, but instead is marked with the Motorola logo and has the following part number: SZA 2638 K8850.  I could not find anything online about this part and I'm curious if anyone knows anything about it relative to the LT FLU-1.   Meanwhile, this unit of mine does not power up, and there was a hand written note adhered to the Z8 microcontroller chip indicating it was no good. So I have lots to sort out!?  :-/O

Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: alm on August 11, 2017, 08:09:08 am
For information between the LTFLU and SZA263, see here (https://www.eevblog.com/forum/metrology/the-ltflu-(aka-sza263)-reference-zener-diode-circuit/msg608888/#msg608888) for some information about the relation and differences between the SZA263 and LTFLU. They are very similar.
Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: ptricks on August 16, 2017, 11:47:15 pm
I have this meter on my bench, bought it on ebay for $60 as-is
Everything worked , sort of. The keypad for the ac button wasn't working, used automotive rear window defogger repair paint to restore the keypad.
I use it almost every day .

Title: Re: EEVblog #1012 - Ebay Fluke 8842A
Post by: sorenkir on August 20, 2017, 11:24:24 pm
Mine had a Schaffner mains filter that decided to release its magic smoke a few months ago...
Easy fix but unpleasant smell!
Michel.