EEVblog #430 - Fluke 91 Scopemeter Teardown

[EEVblog]

Teardown Tuesday.
Inside a 1994 vintage Fluke 91 Series II Scopemeter.
Extended commentary on PCB Wave Soldering: http://youtu.be/ntxIdJTygIE

TDA8703 http://www.datasheetcatalog.org/datasheet/philips/TDA8703T.pdf
74HC4316 http://www.fairchildsemi.com/ds/MM/MM74HC4316.pdf
TLC27M2A http://www.ti.com/lit/gpn/tlc27m2a
LF453 http://noel.feld.cvut.cz/hw/ns/LF453.pdf
S83C196KB http://pdf1.alldatasheet.com/datasheet-pdf/view/66148/INTEL/S83C196KB.html

Photos: http://www.flickr.com/photos/eevblog/sets/72157632863100548/



Dave.

[nitro2k01]

Actually, I believe a male BNC connector should always have an internal ground sheath as well. So that connector should work just fine with regular BNC connectors.

[alm]

Except that using standard metal BNC connectors on them will cause much more wear and tear on the female connectors. And that they form a safety hazard unless you restrict the signals to SELV (40 V or so).

[Bored@Work]

The ScopeMeters where developed by Philips for Fluke, until Fluke finally bought the T&M part of Philips in 1993. That's why it says Made in Holland on the ScopeMeter 91, and why you have some Philips parts in it.

[c4757p]

Interesting - both HEF4093 and 74HC132 are quad Schmitt-input NAND gates. Why would they use both?

[EEVblog]

Interesting - both HEF4093 and 74HC132 are quad Schmitt-input NAND gates. Why would they use both?

Different schmitt threshold levels perhaps.

Dave.

[justanothercanuck]

Quick question about the wave soldering...  If the solder thieves are meant to keep the trailing edge of a chip from getting too much solder, then how come the leading edge of the chip doesn't get too much solder from having a solder thief on the opposite side?

[BravoV]

Btw, for those who wonder about the strength, that plastic cover at the BNC female connector, although looks soft, it is a very durable and strong material. Have few of the bnc to banana adapter made by Phillips Fluke, they're really good stuff.  Made a thread about this adapters while ago HERE

[EEVblog]

Quick question about the wave soldering...  If the solder thieves are meant to keep the trailing edge of a chip from getting too much solder, then how come the leading edge of the chip doesn't get too much solder from having a solder thief on the opposite side?

Solder thieves are meant to keep the last two trailing edge pins from shorting. The result is that the last pin gets more solder than the pin next to it. This does not affect the trailing edge pin.

Dave.

[dewhite2485]

Would you be interested in tearing down a Tektronix 213 portable scope/dmm? I have one that I got off Ebay many years ago and dont really use it anymore.

[MadScientist]

I have a Fluke Scopemeter 105B Series 2 , dual 100Mhz, on the bench , I still use it every day.

[andersm]

I remember seeing a board (probably an old videogame console mainboard) that had "direction of wave soldering ->" silkscreened in two orthogonal directions. Does it mean the board made two passes through the wave soldering machine? I assume this would be to allow for parts being oriented along either axis.

Anyway, it was interesting comparing this teardown to Shahriar's teardown of the Fluke 196B.

[Flávio V]

I guess that the fluke 97(which i own) is the 2 channel version of the 91...

[Fraser]

I have a 'new in the box' Fluke 97 ScopeMeter complete with all the accessories etc 

It was a backup to one that I have since sold. They still command pretty high priced on eb*y.

The service manual is definitely available for free download as I have it on my PC. Its >20MB though. I will see if I can track down the source.

Update: here is the MkI 93-97 service manual:

http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Philips/pm93_95_97_fluke_93_95_97.pdf


These were state of the art in their day but the more modern units with colour displays make them look kind of boring and the user interface is the most unfriendly that I have used on an oscilloscope.

Ahhh, memories of the 1990's 

Fraser

[chicken]

How are the SMD pots managed with wave soldering? I'd imagine they'd get clogged up with solder if run through the process as is. Do they come with a cap that's removed after soldering?

[PA0PBZ]

How are the SMD pots managed with wave soldering? I'd imagine they'd get clogged up with solder if run through the process as is. Do they come with a cap that's removed after soldering?

It certainly looks like they could have been capped, otherwise I don't know why they are constructed as they are, see
http://www.flickr.com/photos/eevblog/8509778996/#in/set-72157632863100548

Otherwise they had to be hand soldered after the wave soldering, and it certainly doesn't look like that.

[RoelA]

I still have a fluke 99 scopemeter series 2, and the screen is as bad as this one.

Fun thing, except one of the marker-move buttons is broken, the go left on the most left marker. Have to use the right marker to push the left one more to the left.. :-)

[Cones]

Excellent tear down as usual. 

I've just bought a Fluke 123 20Mhz scopemeter from ebay for a VERY good price. 

It needed a new battery (£15 which was also wired incorrectly from an Amazon seller. Good job Fluke do a nice service manual!).

A bit of a clean and I have my very first oscilloscope, that I am pretty pleased with. For less than the cost of a set of Fluke scope probes!

It does have three or four horizontal lines on the display due to a know fault with the heat bonded ribbon cable. I may investigate this further and see if I can repair it. I've seen an article where someone used a travel to to gently iron the cable down. The fact it trend logs and acts as a DMM as well is a bonus. It may be useful for looking at some Profibus communication wiring at work later this year as well.

Thanks

Mark

[Spawn]

You ask in the video about the contrast Dave, I have seen couple of these back in early nineties and those where Philips / Fluke branded, can’t remember the model number since it was 20 years ago, my electronics engineer colleagues where using these, since I am electrics engineer I didn’t "play" with these but the contras was still bad on a new unit from what I remember, and my colleagues where handling like it was their child and where very proud to own one at work 

[grenert]

With regard to the battery pack. It is nothing special. Just four C cells with a contact from the positive nipple down to the charging contact at the bottom of the cattery compartment. Many users just fit four individual rechargeable c cells with a metal strip connecting the positive terminal to the charge contact.

I believe the 123 Scopemeter uses Sub-C cells.  Not sure about the 9X series.

[free_electron]

the D-asic is indeed the display controlle.r the lottle tssop above is the frame buffer for the display.

the Masic is a memeory controller.
the 196 cpu interfaces with 1 ram ( the mitsubishi part in the middle. the two flashes ( 010 and 020 hold the firmware.

the 83c193 means it is a mask ROM version so not an OTP or eprom or flash
80 is romless 83 is mask rom 87 is eprom (otp if windowless package)

the 196 only has 8 k of rom so it probabjy only holds a bootloader that can reflash the real firmware in the external flash memories.

the masic switches the 196 form internal rom to external rom. when the thing comes out of reset the rom code in the 196 is run. if there is no reflash requested the 196 writes a register in the masic that pulls the EA pin low of the 196 and invokes a reset of the 196.
at this point the 196 cannot execute itsinternal rom because the EA pin is forced so it executes from flash.
simple but effective mechanism. this is some hardware trick because it makes writing code easier. you don't need to take overlays or offsets into account. the entire memory space is swapped out.

the masic serves another purpose : DMA. when sample data is coming in the masic streams that straight into the frame buffer without passing through the 196 space. essentially the 196 write 'one plane' " grid, text , cursors while the incoming data is catapulted directly into trace memory. it's a kind of bus arbiter.

[fleuroman]

a few pics from the 91 Service Manual
pic 1 description of the display operation

[fleuroman]

digital board layout

[fleuroman]

it wont let me upload schematic pictures.. too big

[justanothercanuck]

it wont let me upload schematic pictures.. too big

you could always try throwing them up on imgur.