Author Topic: Old Fluke Multimeters  (Read 190525 times)

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Offline DarthBubba

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Re: Old Fluke Multimeters
« Reply #225 on: July 26, 2015, 06:53:43 am »
Welcome DarthBubba, I've repaired 4 8060A meters at this point. I replaced every aluminum electrolytic with modern 105 C rated parts of the same physical dimentions. I think I used Panasonic parts. It's amazing the amount of damage these spewing caps cause! Is your meter in working order, or does it need repair?

It was starting to get "funny" with the display - segments not going full "On," and sometimes it would just die for no reason.  I opened it up and looked around a bit, nudged a few parts here and there; no actual, intentional repair was done.  Now my 8060A seems to be working normally.  I hooked it up to a wall socket and monitored the ACV and frequency for over an hour without a hiccup.  Beginner's luck, I guess.

Anyway, I was specifically wondering about replacing the old aluminum electrolytics with tantalum capacitors, as the Tants are usually more stable and have a tighter tolerance (most are 10% vs 20% or worse for aluminum caps). That, and I can usually place a higher voltage unit in the same physical space vacated by an aluminum electro.
 

Offline DarthBubba

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Re: Old Fluke Multimeters
« Reply #226 on: July 26, 2015, 07:02:19 am »
Quote
would it make sense to go ahead and replace all the caps Mr. Modemhead specified with tantalum devices of the same, or slightly higher voltage, rather than use current aluminum electrolytics (even though the new ones are superior to the original caps)?
Quote
Just use high quality Nichicon, Rubyon, United Chemicon or Panasonic aluminum electrolytic capacitors for replacements.  Replace all the old ones regardless if they test or look okay.  All the old ones will eventually leak.

As above I wrote to @vindoline above;  I was specifically thinking about replacing the old aluminum electrolytics with tantalum capacitors, as the Tants are usually more stable and have a tighter tolerance (most are 10% vs 20% or worse for aluminum caps). That, and I can usually place a higher voltage tantalum unit in the same physical space vacated by an aluminum electro.  Is there any reason for preferring aluminum electros over tantalum caps?  I already have a supply of new, low-ESR aluminum electros on hand, so getting good grade aluminum electro-caps is not an issue in this case.
« Last Edit: August 06, 2015, 03:44:00 pm by DarthBubba »
 

Offline ModemHead

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Re: Old Fluke Multimeters
« Reply #227 on: July 26, 2015, 01:56:13 pm »
I don't have enough design experience to say for sure whether tantulum caps are appropriate in the 8060A. Personally, if I had another one to repair, I would just get top-brand aluminum electrolytics like in my original BOM, except this time I'd go for 105° temp rated ones, as others mentioned.

If your intermittent issues return, carefully disassemble the LCD/microprocessor board assembly, and clean the elastomeric connectors with IPA.
 

Offline DarthBubba

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Re: Old Fluke Multimeters
« Reply #228 on: July 28, 2015, 12:49:20 am »
I don't have enough design experience to say for sure whether tantulum caps are appropriate in the 8060A. Personally, if I had another one to repair, I would just get top-brand aluminum electrolytics like in my original BOM, except this time I'd go for 105° temp rated ones, as others mentioned.

If your intermittent issues return, carefully disassemble the LCD/microprocessor board assembly, and clean the elastomeric connectors with IPA.

Thanks for the reply.
 

Offline drtaylor

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Re: Old Fluke Multimeters
« Reply #229 on: December 17, 2015, 06:00:02 pm »
I was PM'd about repairing an 8060A. I thought the information might prove useful to other owners of 8060s.

Bob in Port Coquitlam BC wrote:
"I recently pulled an 8060A out of non-function land back to life.  Thanks to Mr.Modem-head, a 7660, and a bunch of electrolytics its now working again  ... except the ohms range.  A little troubleshooting revealed a broken RT1.  A quick 1k resistor in place of it proved the ohms is working.  I have sourced out the 446849 Fluke part but the greedy people on Ebay and other places want outrageous amounts to ship a few $ part across the 49th parallel.  Is there any source you know of (Digikey, Mouser etc) that would have a suitable 1000v PTC thermistor substitute?  Or am I stuck looking for an affordable Fluke part?

Also, should I worry about a ratio check that starts at 10025 and settles to 10015?  More cleaning maybe?"

DRTaylor reply:
Regarding the PTC. The original part was made by a company no longer in existence. There are many candidates that would do the job. The 8060A was designed before the international safety rules went into effect, and the ohms protection wouldn't pass todays tests. That being said, the ohms protection is pretty simple in the 8060A. It consists of two selected 2N3904 transistors in BC to E diode mode. The resulting zener diodes are connected back to back. This yields a very low leakage Zener Diode clamp (leakage typically <1pA) that will clamp at around ±6.4V. Having a low leakage clamp is critical to making accurate measurements in the higher ohm and nS ranges. The current rating of these zeners is around 100mA. So the trick to this protection circuit is to have a PTC that reduces the current well below 100mA in time to keep the clamps from burning up. The initial resistance of the PTC is important in that it is in series with the reference resistor. But only the 200 and 2k ohm ranges have any worries about the series resistance. The max current through the PTC will top out at around 1.6mA.

BTW, the overload protection in the ohms range is rated to 300V, not 1000V. This is due to the breakdown rating of the PTC. So a cheap alternative that will not compromise performance is the Epcos B59885C0120A070. This is a PTC rated at 500V. These are in stock at DigiKey. However, it is bigger than the original part and you'll have to find a place to tuck it in. This is insulation coated which helps when you have to kinda fold it in. PTCs are noisy devices, but in this case it is just in series, and no precision measurements include the voltage across the PTC.

As far the ratio test failing, the most likely reason is board contamination, probably from spewwed (sic) electrolyte from the old Electrolytic caps. This requires a thorough cleaning. You should immerse the entire board (but not the switches) in IPA. Let it soak, then give it a good brushing with a stiff acid brush. Ratio error is can also be caused by DA in the integrate cap or by leakage current. It is probable you have a contamination under one or more of the critical A/D converter caps, or in the MAC chip socket. Usually the film caps do not degrade with time, so I would put that at a distant possibility. The ratio test shows that you probably have turnover error. Try putting 1V in and then reverse the leads. If all is well it should read exactly the same.

 
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Offline ModemHead

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Re: Old Fluke Multimeters
« Reply #230 on: December 19, 2015, 03:41:04 pm »
Thanks @drtaylor for sharing that information!
 

Online rsjsouza

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Re: Old Fluke Multimeters
« Reply #231 on: December 19, 2015, 09:02:58 pm »
+1. Thanks for the information. It is really nice to see the developer's inside scoop... :)
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 

Offline retiredcaps

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Re: Old Fluke Multimeters
« Reply #232 on: December 20, 2015, 06:44:11 am »
Regarding the PTC. The original part was made by a company no longer in existence.

BTW, the overload protection in the ohms range is rated to 300V, not 1000V. This is due to the breakdown rating of the PTC. So a cheap alternative that will not compromise performance is the Epcos B59885C0120A070. This is a PTC rated at 500V. These are in stock at DigiKey.
In my research over the last couple of years, the only PTC that is rated at 1000V and 1.1k ohm is the YS4020.

http://www.cdiweb.com/datasheets/ge_thermometrics/ys4019.pdf

Unfortunately, no one stocks it.
 

Offline rrinker

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Re: Old Fluke Multimeters
« Reply #233 on: December 24, 2015, 02:44:45 am »
Great thread to run across. I have an 8012A that I snagged on a dumpster dive some 10 years ago. Currently my only bench dmm, and it gets used regularly. So far no troubles but I suppose it's only a matter of time before some capacitors call it quits.

      --Randy
 

Offline billfernandez

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Re: Old Fluke Multimeters
« Reply #234 on: December 24, 2015, 06:47:57 am »
Greetings all.  It's wonderful to find this thread.  I bought a Fluke 8060A in 1983 when I was working on the Macintosh at Apple.  IT was expensive, but I wanted a really good meter that would last a long time, and it has!  It's been a real workhorse, and as far as I know still works perfectly (though I've learned from this thread that it would be prudent to replace some caps). 

I just recently bought a modern meter (Extech EX540) to replace it, but I still like my 8060A better -- and have always appreciated and benefited from the fast continuity response!  The Extech sucks at this simple function.

I used to work at Siliconix (a now defunct semiconductor manufacturer) and when there I learned that we were making a custom chip (I think a hybrid analog/digital A/D converter) for Fluke meters.  I had thought they were for the 8060, but I guess not.  DRTaylor, do you have any recollection of what I'm talking about?
 

Offline gearhead

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Re: Old Fluke Multimeters
« Reply #235 on: December 24, 2015, 06:28:21 pm »
I have an 8020B that I got about 15 years ago, works like new. And I have an 8000A, 8600A, and 8050A benchtop meters. The 8000A was a new unused military issue unit that I use as a reference. The 8600A works like a champ. I've had to replace the NiCad batteries twice. The 8050A has an issue with the RMS converter. I'm about to unsolder it from the main PCB and check the components on it. I can get everything except for the Fluke IC. Maybe I'll get lucky?
So here's a pic of them
 

Offline eugenenine

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Re: Old Fluke Multimeters
« Reply #236 on: December 24, 2015, 06:42:40 pm »
I have an 8050a like the bottom one.  I've replaced the batteries a long time ago and just recently pulled them and wired a 7805 in place so its just line powered.
 

Offline gearhead

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Re: Old Fluke Multimeters
« Reply #237 on: December 26, 2015, 06:07:39 am »
I have an 8050a like the bottom one.  I've replaced the batteries a long time ago and just recently pulled them and wired a 7805 in place so its just line powered.
I really like that 8050A, good units. But I LOVE the red LEDS on the 8600A. Can see it from across the room.
I''m hoping I can narrow down my RMS Conv. issue and repair it. Everything works but AC volts and mA.
 

Offline IconicPCB

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Re: Old Fluke Multimeters
« Reply #238 on: December 26, 2015, 07:01:10 am »
Is there a specification on the battery option toroidal transformer?
I would like to implement it.
 

Offline gearhead

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Re: Old Fluke Multimeters
« Reply #239 on: December 27, 2015, 03:08:33 pm »
Is there a specification on the battery option toroidal transformer?
I would like to implement it.
I haven't seen that, but there is a thread here thats shows how to delete the battery option.
https://www.eevblog.com/forum/repair/fluke-8050a-repair/
 

Offline IconicPCB

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Re: Old Fluke Multimeters
« Reply #240 on: December 27, 2015, 10:30:50 pm »
Gearhead thanks for Your consideration.

I have a NOS 8050 bought on ebay with 120V transformer.

Am looking for a 240V transformer to replace the 120V option. I understand the transformers are like hens teeth.

If the transformer based powersupply were to be replaced by a battery pack what would be the appropriate voltages coming from the battery pack.

I can not measure the rails in the 8050, no way to power it up at the moment.

 

Offline edavid

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Re: Old Fluke Multimeters
« Reply #241 on: December 28, 2015, 12:22:44 am »
If the transformer based powersupply were to be replaced by a battery pack what would be the appropriate voltages coming from the battery pack.

5V, but why not just buy a small transformer?

http://www.ebay.com/itm/Hot-220V-240V-to-110V-120V-Step-Down-Voltage-Converter-50W-Transformer-Adapter-/351444718689
 

Offline IconicPCB

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Re: Old Fluke Multimeters
« Reply #242 on: December 28, 2015, 12:57:04 pm »
VotlageS..plural.

The meter operates on a few rails...  so what would they be?+/-15?+5?
 

Offline wiss

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Re: Old Fluke Multimeters
« Reply #243 on: December 28, 2015, 03:42:14 pm »
If the transformer based powersupply were to be replaced by a battery pack what would be the appropriate voltages coming from the battery pack.

5V, but why not just buy a small transformer?

How about hacking in a USB PowerPack? and a 5V regulator for charging?
 

Offline ModemHead

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Re: Old Fluke Multimeters
« Reply #244 on: December 28, 2015, 04:56:39 pm »
The meter operates on a few rails...  so what would they be?+/-15?+5?

I assume you have a line-powered model.  The battery-powered model (-01 option) has a multi-tapped transformer and runs from a 4.8V NiCd pack via a DC-DC converter.

According to the text of the instruction manual,  the transformer has to be replaced in the line-powered model.  Oddly, the schematic shows a multi-tapped transformer, but I checked a 120V unit that I have here and the 100V and 240V pins are indeed no-connect.

I measured this unit and marked the readings on the attached schematic section.  All readings are relative to ground (TP1).  It looks like a small 24VCT transformer would be a reasonable substitute.  For a direct DC supply, I would guess that anything from a +/-12V to +/-15V would probably work OK, since those rails are unregulated and seem to vary widely.  The positive rail load averages 23mA, the negative rail load averages 60mA.  The assymetric load is probably due to powering the CMOS logic between -5V and ground.
 

Offline eugenenine

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Re: Old Fluke Multimeters
« Reply #245 on: December 30, 2015, 01:27:45 am »
Mine seemed to be a little different from that thread.  Mine would only power the meter from battery even with good cells.  The charge circuit went to the battery packs when the meter was off and when on the battery was connected to the meter.  So after a few hours of use the batteries would get drained and you had to switch off to charge.  Reading the other thread it seems that theirs would still charge the batteries while the meter was in use.

I just pulled out their regulator and batteries and soldered in my own 5v regulator going into the switch where the batteries used to be connected.
 

Online tautech

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Re: Old Fluke Multimeters
« Reply #246 on: December 30, 2015, 07:14:44 am »
A reply in another thread by drtaylor that should be linked to from this thread:
https://www.eevblog.com/forum/testgear/fluke-8060a-dual-fuses-bad-design/
Avid Rabid Hobbyist
 

Offline drtaylor

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Re: Old Fluke Multimeters
« Reply #247 on: December 30, 2015, 07:16:37 am »
I used to work at Siliconix (a now defunct semiconductor manufacturer) and when there I learned that we were making a custom chip (I think a hybrid analog/digital A/D converter) for Fluke meters.  I had thought they were for the 8060, but I guess not.  DRTaylor, do you have any recollection of what I'm talking about?

Bill, I believe that Siliconix supplied a custom chip used in the 8050 A/D. It had a lot of low leakage analog switches and was used in conjunction with external Op Amps. If I come across any proof of this I'll post it. But this is just a vague memory. I do know that we used a lot of discrete Siliconix J-Fets for low leakage analog switches. Siliconix was another victim of the Vishay plan to rule the world (of discretes)!
 

Offline billfernandez

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Re: Old Fluke Multimeters
« Reply #248 on: January 01, 2016, 04:56:11 am »
Bill, I believe that Siliconix supplied a custom chip used in the 8050 A/D. It had a lot of low leakage analog switches and was used in conjunction with external Op Amps. If I come across any proof of this I'll post it. But this is just a vague memory. I do know that we used a lot of discrete Siliconix J-Fets for low leakage analog switches. Siliconix was another victim of the Vishay plan to rule the world (of discretes)!

That sounds vaguely familiar.  It's kind of nostalgic thinking back to those days  :).
 

Offline eugenenine

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Re: Old Fluke Multimeters
« Reply #249 on: January 01, 2016, 03:55:40 pm »
Is there a specification on the battery option toroidal transformer?
I would like to implement it.

I wouldn't bother duplicating Fluke's design, they used a simple trickle charger which is why the batteries die after a few years.  Design a proper charger if your going to do it.
 


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