Fluke 77IV and 179 differences with teardown photos

[bigsky]

The simple answer is firmware only. (EDIT: see correction in post #3). In particular, both models contain an AD737 true RMS converter, which is unusual as the 77IV is average responding. The 77IV seems to sell for about 20% more than the 179 and I guess it's a specialised product for those who must have an average responding meter, so build price is less of an issue.

Here's some pics:


The left hand PCB is a 77IV stamped rev 022, the right hand PCB is a 179 stamped rev 020. The board itself is rev 015. The load appears to be the same other than date codes and the colour of some caps.



Rear of both.


Top part of 77IV


Top part of 179


Close up of 77IV


Close up of 179


Rear of 77IV. Note the 1608 at top right which might be a date code.


Rear of 179. Note the 1907 at top right which might be a date code.

[rsjsouza]

Hi,

Thanks for the pictures. A few years ago I posted a teardown of my Fluke 179 and it is interesting to compare the two.

By the way, the datecode theory seems sound: mine shows 3611 (I bought mine new in early 2012).

A few interesting differences:
- both 179s have yellow capacitors, but in the 77 they are black.
- mine does not have a stamp of close to the REV sign, but it has a sticker on the opposite side which says REV 025 (firmware perhaps)
- Despite this, both PCBs have the same REV 015
- The Fluke part has a distiguishable date code on all pictures. The AD737 has datecodes as well, but my pictures don't show its datecode of 21st week of 2011.

[bigsky]

- both 179s have yellow capacitors, but in the 77 they are black.

The cap to the left of the AD737 in the 77 is yellow, and I just noticed there is an extra cap in the 179 to the right of the AD737 (also in yours). I wouldn't read anything into the colours - perhaps Fluke use two cap suppliers - but the extra one is curious.

Also, there is a datecode on the piezo sounder, consistent with others.

[bigsky]

And, of course, I had to try them with my Chinese voltage reference:

[retiredcaps]

Thanks for sharing the comparison pictures.  The 17x and 77IV series have undergone a lot of internal pcb changes, some quite radical, since they were introduced.

The 77IV doesn't get a lot of love and thus, with patience, can be found for $35 USD used. 

[Robomeds]

I have to say the PCB looks quite different than the 177 I've been trying to fix.  I suspect the one I have is a much earlier date code.  I do wonder why Fluke has run some of these same but different number meter families.  I can see something like the 87-IV where they decided to keep the older 80 series design and thus the 87-IV became the 187.  However, we also have examples like the 25/27/8025A/8025B.  Based on the component date codes I've seen these were meters that were all being made at the same time.  We also have the boxy 23/70 series meters and then the tapered meters (which also used 23/70 series numbers in the earlier versions and then 70/170 series numbers in the later versions).  Again, if the 77-4 was replaced by the 177 I would totally get it... but why keep the 77-4 around after the 177 is released?  I'll have to get around to posting the interior of mine one of these days.

[rsjsouza]

Robomeds, depending on where you are located, there is a 177 for a somewhat inexpensive price here.

Just like you, I don't quite get Fluke's idea of having overlapping meters in production. I can only wonder if the 77IV is part of a large government contract that must have guaranteed supply until %DATE%

retiredcaps, I've also seen several 77IVs go for ridiculously low prices... Too bad, given they are built like tanks.

[retiredcaps]

Again, if the 77-4 was replaced by the 177 I would totally get it... but why keep the 77-4 around after the 177 is released? 

Just like you, I don't quite get Fluke's idea of having overlapping meters in production. I can only wonder if the 77IV is part of a large government contract that must have guaranteed supply until %DATE%

Dave speculated that since the government/military had so many non True RMS meters and written procedures that they asked Fluke to continue to offer one.  At today's MSRP prices, it makes no sense to buy the 77IV when the 175, 177 and 179 are available.

retiredcaps, I've also seen several 77IVs go for ridiculously low prices... Too bad, given they are built like tanks.

A few years ago, I alerted members here about 40 (forty) Fluke 77IVs selling for $35 BIN.  Some called it risky and stupid when you could buy another brand new meter for the same $35 USD.  After that incident, I decided to keep quiet about any good deals.

[rickselectricalprojects]

whats the difference between the 77IV and the 179?

[Robomeds]

Robomeds, depending on where you are located, there is a 177 for a somewhat inexpensive price here.

Just like you, I don't quite get Fluke's idea of having overlapping meters in production. I can only wonder if the 77IV is part of a large government contract that must have guaranteed supply until %DATE%

retiredcaps, I've also seen several 77IVs go for ridiculously low prices... Too bad, given they are built like tanks.

Thanks for the link.  I've actually ordered a replacement for the bad ASIC in mine.  I bought it for $30 so if I can't fix it, not the end of the world.  If I do, well for less than $60 I'm up and running.  Sometimes it's the challenge of the repair that's worth more than the working meter

Rick, based on the pictures above I would say the 177 and 77-4 are the same meter.  The 179 adds temperature measuring but I'm not sure what, if anything, else. 

[ModemHead]

I guess it's worth mentioning, the advertised DCV accuracy for the 177/179 is 0.09% but the 77-4 is 0.3%, even though it runs on the same platform.  Also the 77-4 is missing the 600mV AC range.  The 77-4 is an odd creature, considering it's retail price.

[rsjsouza]

A few years ago, I alerted members here about 40 (forty) Fluke 77IVs selling for $35 BIN.  Some called it risky and stupid when you could buy another brand new meter for the same $35 USD.  After that incident, I decided to keep quiet about any good deals.

I remember that. As with everything left for public scrutiny, good deeds do not go unpunished.

Thanks for the link.  I've actually ordered a replacement for the bad ASIC in mine.  I bought it for $30 so if I can't fix it, not the end of the world.  If I do, well for less than $60 I'm up and running.  Sometimes it's the challenge of the repair that's worth more than the working meter

Yep, that is surely fun. I do love to fix things around, even if they are not terribly worth the effort.

Rick, based on the pictures above I would say the 177 and 77-4 are the same meter.  The 179 adds temperature measuring but I'm not sure what, if anything, else. 

That is pretty much about it. In the same family, the 175 has a bit less DC accuracy and lacks backlight.

[retiredcaps]

@bigsky,

Can you list the part number on the precision network resistor from both meters?  It would be curious to see if they are the same despite the 179 having superior accuracy specs on paper.

If you have already closed them up, don't worry about it.

[Robomeds]

What are the odds the 77-4's accuracy is the same as the 177/179 but they just rate it the same as an older model?

[Paul Moir]

The DC accuracy on the 175 is 0.15%.  It is also built on the same platform.  If you add LEDs and the pushbutton the 177/179 backlight even works.

Very strange that they populate the TRMS converter and not use it.  The capacitor next to it is missing, and I'm thinking that's the Cavg for the AD737.  Fig 26 on the datasheet suggests disconnecting the Cavg capacitor will turn it into normal averaging.  So perhaps if you add this capacitor in, you get TRMS?

(rickselectricprojects:  a bunch of small differences, but one big one is that the 77 is not true RMS while the 17x is.)

[bigsky]

@bigsky,

Can you list the part number on the precision network resistor from both meters?  It would be curious to see if they are the same despite the 179 having superior accuracy specs on paper.

If you have already closed them up, don't worry about it.

I have put them back together but I'll open them up again to check - I wasn't aware that the 77IV had a worse DCV accuracy so I think it's worth checking this out. I'm working away at the moment so it won't be until the weekend.

[Deckert]

The 77IV has slightly lower DC accuracy, but better accuracy in the ohms range (going by the specs). The 77IV also has double the battery life of the 177/179. From the manual, the 77IV has a 400 hours battery life and the 177/179 lasts 200 hours. Maybe the difference is due to the RMS converter chip?

I have both the 77IV and the 177 (both 'used' from our local version of eBay, Gumtree) - paid less than US$160 for both.

--deckert

[retiredcaps]

The 77IV also has double the battery life of the 177/179. From the manual, the 77IV has a 400 hours battery life and the 177/179 lasts 200 hours.

The 77IV has better battery life than the 170 series depending on which 170 pcb you are using.  I posted this in another forum.  See below.

http://www.antiqueradios.com/forums/viewtopic.php?f=8&t=264761

== snip ==

BTW, it looks like the Fluke 175 that I measured with a 2.5mA current consumption or less is consistent with this datasheet from 2000 and the claims for 200 hour battery life (assuming a new 9V is 500mAH).

http://www.mantech.co.za/Datasheets/Products/FLUKE17X.pdf

The OP's manual that states 300 hours battery life suggests the manual was printed in 2003 as per link below.

http://www.produktinfo.conrad.com/datenblaetter/100000-124999/120556-an-01-en-Fluke_179_Multimeter_Kalibrieranl.pdf

So for the OP, I would expect current consumption on his 179 to be 2.5mA or less for all functions and obviously 0mA when it is turned off.

The latest Fluke 170 (circa 2008) series manual states 400 hours on Fluke's website.

I know that the Fluke 170 has at least 3 pcb revisions: 7, 12 and 15. So it is possible with each revision or firmware changes, they have optimized battery life.

== end snip ==

That is what I referred to earlier of the radical pcb changes internally while the front facing user interface/model number stayed the same.

[CosPhi]

The newer 170 meters measure resistance also with a higher voltage than the old models. As far I remember the older models used always a voltage lower than 2V as far I remember. I just checked my 175 at home. The voltage goes up to 7.3V in the lower Ohm ranges.

[bigsky]

@bigsky,

Can you list the part number on the precision network resistor from both meters?  It would be curious to see if they are the same despite the 179 having superior accuracy specs on paper.

If you have already closed them up, don't worry about it.

Same part number - 1780017 - on both. I'm not surprised.

[bigsky]

Here's a couple of close-ups - the third digit is definitely an 8

[bigsky]

I've also checked current draws and they are the same on both the 77 IV and the 179.

VAC 1.25mA
VDC 1.10mA
mVDC 1.10mA
ohms 1.55mA
continuity 1.97mA
mA 1.24mA
A 1.24mA

Backlight adds about 9mA

(measured with a Fluke 187)

The ohms ranges outputs 2.75V on the 60M range, 5.30V on the 6M, 3.50V on the 600k range, and about 7.3V on all other ranges inc continuity and diode check

[retiredcaps]

I've also checked current draws and they are the same on both the 77 IV and the 179.

VAC 1.25mA
VDC 1.10mA
mVDC 1.10mA
ohms 1.55mA
continuity 1.97mA
mA 1.24mA
A 1.24mA

Your readings above suggests your meter will run around 400 hours (with no backlight) assuming a 9V is around 500 mAh.

[retiredcaps]

Same part number - 1780017 - on both. I'm not surprised.

Thanks for the extra pictures.

It is probably cheaper and easier logistics wise for Fluke just to stock one network resistor divider than multiple ones.   I suspect the 77IV real world accuracy is much better than the paper specs.

[bigsky]

Your readings above suggests your meter will run around 400 hours (with no backlight) assuming a 9V is around 500 mAh.

Fluke specify 200 hours typical without backlight.

Energizer say their alkaline 9V battery is 600mAh at 25mA discharge rate, so I'd expect the capacity to be even higher at <2mA discharge. But that's to 4.8V which I'm sure is a lot less than the meter's minimum battery voltage. Given the 7.3V output on the ohms range, I'd be amazed if the meter will run on less than 8V, and it wouldn't surprise me if it needs more.