Fluke 8060a meter interconnect strip

I have an old IBM labelled Fluke built DMM (8060a equivalent) that hasn't w orked in years for reasons I don't recall exactly, but seem to think it was stone dead. I had it apart and left in a box and, since my last 87 crappe d out a few weeks ago, I needed the low ohms feature of one or the other so I took another look at the old IBM.

I found just about every electrolytic on the board physically leaky, and mo st down in value and ESR, some considerably. I replaced them all but when assembling the meter, I checked the two flexible rubber interconnect strips . One of them is round and reads zero ohms all across it's length, so that one's good.

The other is a flat rectangular piece, and I cannot get any kind of resista nce reading *anywhere* across it. I've cleaned it several times including using an abrasive last time and cannot get a whiff of conductance, and I've put considerable pressure on the test leads. I guess it being unassembled and sitting in free air must have poisoned it somehow as I don't recall it having any issues with erratic segments before the meter died.

It will be easy to hard wire this but was wondering if this is a low ohm tr ansfer strip of something maybe a few ohms to a few thousand. If it's low ohms, I'll just hard wire it. If it's something other, there's plenty of r oom to put in 1/8 w resistors of appropriate value.

Anyone know the approximate resistance of the strip?

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ohger1s
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with the answer from Jack on August 18,2014 near the end

Wolfgang

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Wolfgang Allinger

It would not be in the best interest of any (legitimate) manufacturer to bu ild a precision-resistance into an interconnect strip. As you have discover ed, they can be volatile, and any actual planned resistance will necessaril y generate heat - leading to even quicker failure.

Hardwire it - and if it works properly (and it should if this is the only p roblem), you are done.

Peter Wieck Melrose Park, PA

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pfjw

build a precision-resistance into an interconnect strip. As you have discov ered, they can be volatile, and any actual planned resistance will necessar ily generate heat - leading to even quicker failure.

problem), you are done.

Thanks Peter. I don't think any resistance (assuming there is any) would b e a problem. The strip in question feeds the LCD display glass and the dra w would likely be few micro amps at 5V. I was thinking in terms of the con ductive pads used to active scan lines in cheap keyboards. Those measure f rom a few dozen ohms to a few K ohms and work properly.

In any case, I'll take your advice and hard wire it when I get to work tomo rrow and see what happens.

John

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ohger1s

Some photos of the insides of an 8024a, which is fairly close in construction to an 8060a. The ribbon cable: The ribbon cable between the two boards is made from screened graphite, which tends to crack if flexed. I found a similar ribbon cable, but made from flattened copper wire that looked more reliable. I removed the original ribbon cable, clamped in the new cable, and after a bit of jiggling, got it to make a connection without soldering. Once it was working, I used hot melt glue to hold it in place. I suppose soldering would have been easier, but at the time, I didn't want to wreck the meter.

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Jeff Liebermann

Other than the shape of the boards, they're not much alike. The 8060 has n o flexible membrane circuit.

For the heck of it, I took a straight edge and a sharp razor and removed ab out a 16th from both sides of the rubber conductive strip, and still no con tinuity whatsoever, so I hard wired the display.

It now starts, boots, and passes the power up test. The display is clear a nd has full contrast.

The problem is that it's reading voltages and resistances that don't exist, even though it does read my test voltages and resistances. I guess I have to take this apart again and do a better job of cleaning the electrolyte o ff the board.

The link posted by an earlier poster shows problems with leakage below the main chip/socket only. If I knew that would be the only problem to address , I'd pull the socket and try it. The problem is is that every individual solution requires undoing the display hardwire, so I'm trying to formulate a plan to effectively clean this in one shot.

John John

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ohger1s

Other than the shape of the boards, the 8026 and 8060 are not much alike. The 8060 has no flexible membrane circuit.

For the heck of it, I took a straight edge and a sharp razor and removed ab out a 16th from both sides of the rubber conductive strip, and still no con tinuity whatsoever, so I hard wired the display.

It now starts, boots, and passes the power up test. The display is clear a nd has full contrast.

The problem is that it's reading voltages and resistances that don't exist, even though it does read my test voltages and resistances. I guess I have to take this apart again and do a better job of cleaning the electrolyte o ff the board.

The link posted by an earlier poster shows problems with leakage below the main chip/socket only. If I knew that would be the only problem to address , I'd pull the socket and try it. The problem is is that every individual solution requires undoing the display hardwire, so I'm trying to formulate a plan to effectively clean this in one shot.

John

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ohger1s

e main chip/socket only. If I knew that would be the only problem to addre ss, I'd pull the socket and try it. The problem is is that every individua l solution requires undoing the display hardwire, so I'm trying to formulat e a plan to effectively clean this in one shot.

I pulled the main IC/socket and there's no sign of leakage on or under the socket pins or board. The capacitor leakage seems to be contained under th e switch assy.

I removed three variable caps which hugged the board and removed the power switch. Every other part is either high enough off the board not to be tou ched by a very shallow bath or would not be unaffected by one. Next plan i s to give it a hot shallow bath of distilled water followed by a wash of IP A and a few hours in the hot box. I have other things on my bench right no w so I won't play any more with this for a few days at least.

John

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ohger1s

Oops. I couldn't find any decent 8060a photos other than the repair article, so I guessed that they were the same from memory. Sorry for the misinformation.

Well, I may join you on this repair. I just found my long lost Fluke

8060a. About +1.5mv of residual reading on the 200mv scale. I'll drag it to my office, take some photos, and measure the Zebra strip resistance for you (probably tomorrow). Meanwhile, this might offer a clue as to the resistance;

Unrelated dumb question. The three case screws for this Fluke 8060A seem to have walked away. What's the thread designation so I can buy some replacements? There's plenty similar screws on eBay: but none specifically for the 8000 series DMM. $1.50/ea including shipping. I'll probably do better at the hardware store Never mind. I found the type in the user manual on Pg 6-5 in: SCREW,PH,P,THD FORM,STL,7-19,.750

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Jeff Liebermann

You lost the screws, somewhere along the way I lost one of the push buttons. Too bad I can't get one of those in a hardware store! :)

John

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ohger1s

I several large candy jars that are full of random hardware. I probably tossed the screws in one of them. It's easier to buy replacements than to excavate them from the jars. Needle in haystack. The local Ace hardware store didn't have any plastic screws.

You can get another carcass on eBay. Or buy one from the test equipment cannibals: Notice that the LCD display is starting to turn black along the bottom edge. Most of my various Fluke meters have the same problem.

I tore my 8050a apart and tooks some photos and measurements:

This Zebra strip measures about 1K ohms:

while this one measures about 5 ohms:

Measuring the resistance was a PITA. The problem was determining whether I was measuring the resistance of one contact, or a bunch of them in parallel. I didn't want to drag out the microscope, so I resorted to a trick. I placed the flat side of one DVM probe across a section of the strip so that it would connect to a large number of conductive strips. I then used a very sharp needle tip to make contact on the other side. It wasn't perfect, but I think it was good enough.

More photos when I have time. Anything else you want photographed or measured?

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Jeff Liebermann

Curses, foiled again. While tearing apart the meter, taking photos, and putting it back together, I managed to transfer enough blood, sweat, and tears onto the PCB and components to wreck the calibration and add some more leakage. Instead of +1.5mv of residual junk on the

200mv scale, I now have about -7mv of leakage. The next time I work on this meter, I'll remember to use latex or nitrile gloves. 90% alcohol and bake dry scheduled for next weekend.
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Jeff Liebermann

The conductors are *very* dense in this particular zebra strip and I'd gues s that there's at a minimum 10 conductors presented across the large pads o n the boards they make contact with, so I'd venture that if they're 5 ohms each and 10 or more are paralleled across the pads, a wire jumper is just f ine.

No, I think I'm OK at this point. After it takes it's IPA bath I'll reasse mble and see where I'm at. Thanks for the information!

If the meter turns out OK, I'll probably pick up a DOA meter on ebay for pa rts, including the missing button. If the meter still is a bit wonky, I'll remove the switch pack and give it an ultrasonic bath.

The bottom of my display looks exactly like yours. Are you sure this is ab normal? The bottom edge is where the round zebra strip contacts the LCD el ectrically on the back side, so maybe that thicker area is normal. The bord er around the entire LCD display is black although much thinner.

John

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ohger1s

Yep. I can measure the resistance from PCB pad to pad in that area if you want. However, it will need to wait a few days. Bizzeee.

I had quite a struggle reassembling the LCD display. The LCD glass fits into a slot of sorts in the plastic frame that requires the Zebra strip to be compressed. Insert just the glass LCD plate first and use brute force to compress the Zebra strip. Then, slide in the plastic screen protector and frame. If anyone has a better way, I would be interested.

The article at: (near the bottom) says to let it dry for a few hours after an alcohol bath. I've had the same experience. Alcohol absorbs moisture from the air and will dump this moisture onto the PCB during cleaning. It takes a while to evaporate.

I've destroyed a few two-way radios using a 10 watt ultrasonic cleaner. It tends to kill semiconductor devices with unsupported wire bonds to the chip. I suggest using a brush instead. A brush doesn't get under IC sockets and overhanging components, so I like flood the area with alcohol, let it sit for about 30 seconds, and blow it out with compressed air. Not the best way, but better than shaking the meter to death. I haven't done too many DVM's so I don't know what a solvent bath will do the rotary switch.

No, I'm not sure. My eyesight isn't that great any more. I've seen a much more extreme black edge smear on other Fluke LCD displays. Here's an 8020A display disassembled: It has a black border, but it's very different from the 8060a:

You might be right as the black line seems rather consistent instead of the creeping black blob caused by case leakage. I'll put it under the microscope later and double check. This is what it *MIGHT* look like eventually:

Still looking for the missing case screws. No luck so far.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

worked in years for reasons I don't recall exactly, but seem to think it w as stone dead. I had it apart and left in a box and, since my last 87 crap ped out a few weeks ago, I needed the low ohms feature of one or the other so I took another look at the old IBM.

most down in value and ESR, some considerably. I replaced them all but whe n assembling the meter, I checked the two flexible rubber interconnect stri ps. One of them is round and reads zero ohms all across it's length, so th at one's good.

tance reading *anywhere* across it. I've cleaned it several times includin g using an abrasive last time and cannot get a whiff of conductance, and I' ve put considerable pressure on the test leads. I guess it being unassembl ed and sitting in free air must have poisoned it somehow as I don't recall it having any issues with erratic segments before the meter died.

transfer strip of something maybe a few ohms to a few thousand. If it's lo w ohms, I'll just hard wire it. If it's something other, there's plenty of room to put in 1/8 w resistors of appropriate value.

I removed the switch assy, the main IC socket, and the variable capacitors from the board. Several rounds of 91% IPA bathing has not cleaned the stick y electrolyte off the board, except where I could get an acid brush in to s crub. Two remaining options are to remove every other part off the board a nd scrub with a fiber brush or go to a more aggressive cleaner. I'm going w ith option two and see what happens.

John

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ohger1s

Older electrolytic capacitors used ethylene glycol and boric acid for electrolyte. Later versions used dimethylformamide, dimethylacetamide, or butyrolactone. If you look these up on Wikipedia, the table on the right includes solubility: I would try detergent and water first, followed by a distilled or deoinized water rinse. If that fails, start up the ladder of chlorinated hydrocarbon solvents, starting with alcohol. I wouldn't go much past trichlorethane or trichlorethylene which will probably peel off the PCB printing, labels, and maybe the silk screening. Some of these will also attack the epoxy that holds the PCB together. Be careful and good luck.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

I have seen references to mixing IPA and acetone 50/50 to do some PC board cleaning. Any thing good or bad about doing that ?

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Ralph Mowery

rs from the board. Several rounds of 91% IPA bathing has not cleaned the st icky electrolyte off the board, except where I could get an acid brush in t o scrub. Two remaining options are to remove every other part off the boar d and scrub with a fiber brush or go to a more aggressive cleaner. I'm goin g with option two and see what happens.

That makes a lot of sense. As I was unsoldering all the leaky caps, I never once got a whiff of low tide. When I was rebuilding Sony and Canon camcor ders in the 90s most of them needed 40 or 50 smd caps, and my bench smelled like catch of the day. Clearly the formulation is different for the caps in the Flukes from what we see nowadays.

Anyway, your advice to avoid ultrasonic cleaners made way too much sense so I went ahead and soaked the board with my favorite circuit board cleaner; Fantastik. After a few soaks and rinses, the board looks, well, fantastic. It's clean as a whistle and all the goo is gone, including the crap under the inline packages and ICs. I rinsed in distilled water and now it's getti ng it's last IPA bath. I'll let it dry and reassemble in a few days and ho pe for the best.

And if that's your ground mail, I can send you two screws I have off a non- working 85 that I think needs a main chip. This meter crapped about 8 year s ago and I misplaced one of the screws, but if you want the other two, the y're yours. I'm on the east coast so it'll be a week.

John

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ohger1s

Yep. Lots of changes in electrolyte. I really don't know what Fluke was using.

Ugh. I use Formula 409. I had some issues with Fantastik leaving some residue that didn't evaporate. Fortunately, most seemed to wash off with deionized water, so it wasn't fatal. Residue was easy enough to detect by leaving a blob of Fantastik on a microscope slide, let it evaporate, and inspect the bathtub ring. There wasn't much, but there was enough to make me worry.

Fantastik has changed their formulation over the years. This should be the latest (Formula 35*19431): I have a small problem with the oily fragrance, which does evaporate, but very slowly. The stabilizer and dye also might leave a residue, but I'm not sure. Both 409 and Fantastik are highly alkaline (pH=10.5 to 11.5), which should not be a problem. The grease was cleaned by the inclusion of ethyl alcohol.

Sounds good. Check the residual voltage displayed on the 200mv scale to see if the PCB is still leaking. I know mine is leaking from all my unprotected handling.

Thanks. The address is my palatial office. I could use the screws to finish my 8060A. However, if you think you're going to eventually fix the Model 85, I suggest you keep them. I'll eventually find where I misplaced my screws or find replacements.

Also, I'm still not sure about the black line at the bottom of the LCD. However, I'm inclined to believer that you're correct and that mine is normal. When reassembled, the screen does not show the black line and everything else looks normal.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

No. Bad idea. Don't do that.

Acetone will attack many plastics (ABS, polycarbonate, polystyrene, polyethylene, vinyl, etc). Before you use ANY manner of solvent, do some research on a "chemical compatibility chart" for the materials you expect to be using. Be sure to check compatibility with epoxy, as that's what the PCB is made from.

For example: shows that: ABS plastic and acetone = "Severe Effect" ABS plastic and 50% acetone and water = "Severe Effect"

Also, I guess I should mention that there are many different types of alcohols (amyl, benzyl, butyl, diacetone, ethyl, hexyl, ibsbutyl, methyl, octyl, propyl, etc). Characteristics vary so don't assume that some random alcohol is safe just because isopropyl alcohol didn't destroy some plastic. I had to learn that lesson when I switched to the "alcohol" sold by the local hardware store, and found it far more aggressive than the 91% drug store variety.

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

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