Fluke 8020B Teardown - 30yo DMM Technology

[LaurenceW]

Nice picture, Modemhead. Nostalgia is not what it used to be, eh?

[Bored@Work]

I just wounder what the deal between Fluke and Intersil was. Fluke claims they designed the IC. And we know Intersil manufactures it, even back then.

If Fluke designed it, they must have agreed to Intersil marketing it under their own name, too. Maybe Intersil was allowed to keep the floor sweeps?

[free_electron]

7106 only has a few needs for accuracy. A short term stable clock, it only has to be stable over under 5000 cycles, nothing more.

correct. the rampup cycle is 2000 counts with the rampdown a maximum of 2000 counts. throw some additional steps in there to do a null check and you end up at about 5k cycles.

You need one good film capacitor to store charge, and all it needs is low leakage and no voltage dependance, easily met by most modern polyester film units.

low leakage and soakage and low tempco is what you are after. pyloester film performs fine. silver-mica if you want it really right.

[SeanB]

Nice is that the chips are now made by many manufacturers, and are pretty much the same performance wise. The original design has held up well, you get improved parts, but they are backwards compatible with the original. Nice is that you can get a 7106 variant that has a full scale of 20mV and is stable at that, the originals did 200mV.

[Rick]

Fluke 27 in awesome nick for $40:
http://www.ebay.com.au/itm/280984986629?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649#ht_5707wt_1397
2 available.

I missed that one.
So I contacted the seller to ask if he had more and he had used ones. The one mentioned by Dave being a "new one without box" obviously it was used very little.
The ones (2) I bought do not have very "sharp" looking displays (they are not delivered yet but I have seen the pics) so may be should I clean the contacts or replace the display ? I wonder if Fluke would sell spare parts such as LCD displays, elastomers and the glass on top of the LCD.
It was not a good bargain either because I got them for the same price as the "new" one.

I beware when a pic shows the meter turned off, like recently a guy from the middle east has told me the DMM works fine (a Fluke 8021b) but it has no battery, so I told him "buy a battery and show me the pic of it and I shall pay you the price of the battery too". But there is no answer yet...   
As it is an international shipment they know you wouldn't send the item back as it is a low cost item.
 

[ModemHead]

Great discussion on the venerable 7106. I am inspired to read up on how it really works.  And thanks to Excavatoree, my 8020B is no longer missing a button and is ready for service again!

[T4P]

Cyrustek themself has a ICL7106 drop in replacement 
http://www.datasheetcatalog.org/datasheet/CyrustekCo/mXrvszy.pdf
Found it on my wavetek DM5XL

[Lawsen]

I used to own a Fluke 8060A, before it broke.  The microprocessor counting display chip needs replacement.  Fluke exchanged it for a Fluke 187.  A Fluke 8060A was sold for $425.00 new in 1989.  My Fluke 8060A stopped working by 2000 and Fluke simply exchanged it for a Fluke 187.  Thanks for posting the Fluke 8020B.  There was also a black color version of the Fluke 8024A.  I did not see much of them.  Surf here for the Fluke 8024A manual.  The old Fluke 8060A came with two manuals, a self service manual with all the parts listed and where to buy them and detailed mechanical and schematic circuit and probing tips and a general users manual.  Hardly any electronics company in the world still practices this much detail.  Fluke 187 multimeter that was exchanged did not has a service manual and the users manual was not much, just simple pictures in different languages, but no details or any use.  I wondered, maybe, I should have repaired the Fluke 8060A myself at the studio than send it in only to be e wasted and traded in.  The bench top equivalent to the Fluke 8060A is the Fluke 8050A and it came with quite a detailed manual in service and using, too.  These are truly classics, both instrument and documentation, never again by Fluke.

http://www.ko4bb.com/Manuals/Fluke/Misc/8024A_Manual.pdf

[rsjsouza]

And thanks to Excavatoree, my 8020B is no longer missing a button and is ready for service again!

Sorry for revamping an old thread, but I too would like to publicly thank Excavatoree for sending me two button caps for a recently purchased Fluke 8060A!

[YashEE]

I know that I'm rather late to this Post. The pix are a nostalgic delight and are inviting this question:

I have since new (ca. 1979) 8020A model that I managed last week (!) to damage (voltage spike) the input section (over voltage protection portion)  - blowing the R2 (1000 ohm /2 watt) resistor and two of the 430V varistors (RV1 and RV2).

Is there a parts source to get the 'original components' or what would you good folks recommend an appropriate replacement of same

(btw, I replaced the 1K 2W resistor with a 1% metal oxide type -not fusible type as in 8020B)   

[Excavatoree]

The 1K 2W fuseable resistors are getting difficult to find.  There was a replacement I used to purchase from Digi-key, but it was discontinued.  Modemhead mentioned one, it may be available in Canada, but it wasn't available on the US site when I checked.  I wish I had ordered more of them - I'm out myself and all my parts meters have had them removed.

Parts availability may depend on your location.  Where in the world are you?

[MarkPalmer]

Factory new parts should still be available from Fluke themselves, Tucker Electronics or Talon Electronics using the Fluke part numbers.  474080 for the 2W resistor, 447672 for the varistors, both varistors are the same.  But.....

You can probably buy a used 8020A for use or one to scab the parts from for much less than what it will cost to buy new factory parts.  If it's sentimental I understand, I still have my 8020A I bought brand new in 1983.   

-Mark-

[YashEE]

Thanks for such a quick replay -I am in the Philadelphia area...

The fried R2  1000 +/- 10% resistor was not fusible as such (not sure I can tell) so I simply replaced it with a metal oxide 2W type (1%).   

The varistors (430V type) are cylindrical / vertically mounted -need at least two of those or recommended replacement   

[Excavatoree]

I'll check my "junkyard."

[retiredcaps]

The 1K 2W fuseable resistors are getting difficult to find.

The Fluke 8020A manual just says

R2, ww, 1k +/-10%, 2W

Nothing about it being fusible. edit: However the part number for the A and B are identical.

PS. If you need 1K 2W fusible resistors, modemhead got his latest batch from Moyer (part number F2W210)

http://www.moyerelectronics.com/BVModules/ProductTemplates/MoyerProductTemp/Product.aspx?productid=37a1f44f-b860-407d-93b6-a7601a4423d8

NTE Fusible Power Oxide Resistor 2W 1K OHM 5% Fuse.  Data sheet at

http://www.nteinc.com/resistor_web/pdf/1w_2w_fusible.pdf

Shipping, iirc, was a very reasonable $2.50 ish using USPS first class mail for USA customers?

I got 10 even though I personally have never subjected my meters to abuse, but the ones I buy used sometimes requires a replacement fusible resistor.

[Excavatoree]

The 1K 2W fuseable resistors are getting difficult to find.

The Fluke 8020A manual just says

R2, ww, 1k +/-10%, 2W

Nothing about it being fusible.

PS. If you need 1K 2W fusible resistors, modemhead got his latest batch from Moyer (part number F2W210)

http://www.moyerelectronics.com/BVModules/ProductTemplates/MoyerProductTemp/Product.aspx?productid=37a1f44f-b860-407d-93b6-a7601a4423d8

NTE Fusible Power Oxide Resistor 2W 1K OHM 5% Fuse

Shipping, iirc, was a very reasonable $2.50 ish using USPS first class mail for USA customers?

I got 10 even though I personally have never subjected my meters to abuse, but the ones I buy used sometimes requires a replacement fusible resistor.

Thanks for the info.  I  suppose when I saw the older 70 series meters with the same resistor as the 80xx series, I just assumed they were fuse resistors as well because the replacements were.   I know better, but I still do it.

[retiredcaps]

I  suppose when I saw the older 70 series meters with the same resistor as the 80xx series, I just assumed they were fuse resistors as well because the replacements were.

Just to make it more confusing, the 8020B, which is what this thread is based on, does say in the manual, the word "fusible" for R2. 

[retiredcaps]

The varistors (430V type) are cylindrical / vertically mounted -need at least two of those or recommended replacement   

Looking at "my always open" 8020A, there seems to be enough room to use the radial disc varistors (if I'm using the correct terminology)?

For example, this random one that I chose at digikey

http://www.digikey.com/product-detail/en/ERZ-V05D431/P7245-ND/162591

is 430V and 5mm.

[MarkPalmer]

The resistor was the same fusible one in both the 8020A and 8020B, part number 474080.

-Mark-

[retiredcaps]

The fried R2  1000 +/- 10% resistor was not fusible as such (not sure I can tell) so I simply replaced it with a metal oxide 2W type (1%).   

reply from drtaylor

https://www.eevblog.com/forum/testgear/old-fluke-multimeters/msg515471/#msg515471

Now you see what I mean about information spread all over the place...

[retiredcaps]

The resistor was the same fusible one in both the 8020A and 8020B, part number 474080.

Yes, you are correct.

In looking how I made that error  , I see the Fluke 8020B manual at

http://exodus.poly.edu/~kurt/manuals/manuals/Fluke/FLUKE%208020B%20Instruction.pdf

has the BOM sideways and the 8020A manual at

http://exodus.poly.edu/~kurt/manuals/manuals/Fluke/FLUKE%208020A%20Instruction.pdf

has the BOM vertical.

While looking at the 8020B sideways BOM, the part number is not in the screen so I didn't notice they were the same part number.  I will correct my posts above to reflect this.

[Excavatoree]

Thanks for such a quick replay -I am in the Philadelphia area...

The fried R2  1000 +/- 10% resistor was not fusible as such (not sure I can tell) so I simply replaced it with a metal oxide 2W type (1%).   

The varistors (430V type) are cylindrical / vertically mounted -need at least two of those or recommended replacement   

PM sent - hopefully these parts can remain  useful by allowing another 8020 to keep running.

[drtaylor]

Just for the record... This excellent tear down by ModemHead had one misleading comment ("Probably very similar to the ubiquitous ICL7106"). The 429100 is NOT the same as a ICL7106 (though it is indeed similar). The Fluke part was the basis for the ICL7106, but the 7106 lacks one key feature. The 429100 chip can digitally switch between a 200mVFS and 2VFS range. The ICL7106 requires part changes to accomplish the same thing. I wrote more on this topic in the forum subject titled "Old Fluke Multimeters."

If you sub an ICL7106 into a Fluke 802x series DMM, it will not work properly.

I have a small stock of 429100 chips if anyone needs one. They have been in antistatic foam for >30 years, so I don't know if they function. I could try them in one of my vintage Flukes to see if they're still functional.

[YashEE]

Thanks to Excavatoree, the 8020 lives / works again...most generous to send a full complement of original 430V veristors including the classic R2 befitting the ca. 1979 DMM. Had some pangs of nostalgia and trepidations replacing the fried components but all went well and functioning as per specs (!)

Much appreciated advice from the Board.
 

[lowimpedance]

Just for the record... This excellent tear down by ModemHead had one misleading comment ("Probably very similar to the ubiquitous ICL7106"). The 429100 is NOT the same as a ICL7106 (though it is indeed similar). The Fluke part was the basis for the ICL7106, but the 7106 lacks one key feature. The 429100 chip can digitally switch between a 200mVFS and 2VFS range. The ICL7106 requires part changes to accomplish the same thing. I wrote more on this topic in the forum subject titled "Old Fluke Multimeters."

If you sub an ICL7106 into a Fluke 802x series DMM, it will not work properly.

I have a small stock of 429100 chips if anyone needs one. They have been in antistatic foam for >30 years, so I don't know if they function. I could try them in one of my vintage Flukes to see if they're still functional.

 I think many including me had just assumed it was just a 7106 but thanks to you we know its not a substitute. From my perspective having come across quite a number of meters employing this IC , not one of them needed that part replaced, so its quite a reliable component.
I wonder just how many have had to replace one ? not many I'll bet.