Fluke 8050A - MPU failure

Mostek 3780 is the single-chip version of the F8 (3850); a very strange device indeed.

If it were a 37P80 you could have an external EPROM and you'd have a fighting chance. It isn't so you're screwed.

No & no. It's dead; let it go.

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Typo. It's a Mostek 3870. I worked on a radio that used one in the late 1970's. It took me years to recover from the brain damage caused by the weird programming (and I wasn't even the programmer on the project).

Note that there are different 3870 mutations with varying amounts of RAM and ROM.

The big problem is that the 3870 is mask programmable. Unless a Fluke

8050A chip can be found, a random 3870 chip won't work. There are a few for sale on eBay, but I'm sure they won't play.

Even the EPROM version has mutations. There are some for sale on eBay, but make sure that it's the same mutation as in your Fluke:

How you're going to extract the Fluke programming out of your blown chip, and into an EPROM is unknown.

Note that many companies in the late 1970's shipped their products with the EPROM version. They were making so many firmware changes after shipping, that the mask programmable version wasn't practical.

Typo again. The piggy back EPROM version of the 3870 is a 38P70. Another version is a 97400R. I may actually have one of these in the Mostek dev sys, but a quick search didn't find it. I'll try again later:

e-Waste or sell for parts on eBay.

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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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I have less than $50 in the dead meter.

That's about what I have in the meter. I bought three for about $100, one with the Ni-Cad option. Considering some places still want $450 for one meter, that's not a bad deal. Two of the cases are in good condition, and cleaned up nicely with household Ammonia and a Scotchbrite pad.

I have three Fluke 8050A. I was wondering about trying to read one of the good chips. I am aware that it's mask programed, and that '3870' is a family instead of a single device. I tossed some of the EPROM piggyback versions about 15 years ago, rather than try to clean and tin the badly corroded pins. They were in some new 9 track computer tape drives I had. I couldn't track down any interface data and junked them. for the motors & drive circuits.

The unit works fine with a borrowed chip. Maybe I'll luck into another working meter, with a damaged case or someone with a used chip at a reasonable price

That's rather high, even for a 4 1/2 digit meter. Checking the eBay completed listings, I found about 8 meters had sold for about $40 including shipping. One went for $50.

Probably not. There was a bit that could be set to make the ROM section excute only. I suspect this is the normal shipping condition. I could try to find all the pieces of my F8 dev sys, and try to read it, but I really don't want to burn the time. Sorry.

Nothing on eBay. However, a parts meter went for $25 including shipping:

"The secret to engineering (and repair) is knowing when to give up." (from one of my mentors years ago).

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Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

No big deal. I know several used test equipment dealers, and one who owns a cal lab. He offered me a couple truckloads of equipment to salvage, but I have no way to get it here.

That meter is sitting here beside me. I won it, and repaired it in under ten minutes. It will need new batteries to use as a portable meter but that's under $10 I need about 36 C size Ni-cads at the moment for various items.

Hi Mike,

You could try here in hopes that someone has a parts unit:

Thanks. If I don't find one before long, I'll part it out. It'll end up in my boneyard.

Not much in it, at the moment:

The only thing that can replace it is another 3870. Freaky weird uP that

3850 which uses it.

?-/

I bought another 8050A meter, for a total of five, and was able to repair four of them. Two had bad NiCad batteries, which kept them from working. So, one of the first four worked, and the fifth.

I will leave the AC powered on my workbench, and take the battery powered units with me for other work. I have under $100 in all five.

For $50, I just bought a large box of junk that includes some allegedly defective Fluke meters. Two 8000A with leaking D batteries, rotten battery contacts, blown Amps fuse, and covered with difficult to remove calibration stickers. One 8030A with some of the segments dead but otherwise ok. One 8010A with leaky batteries, a very dim LCD display, and which looks like it's been under water for some time.

Two 8050A with missing Amps fuses, dead sub-C batteries, and difficult to read LCD displays. The problem is that the stock 8050A will not work without the batteries. However, there is a modification to fix that: I want battery power, so I ordered some sub-C cells on eBay. I'm also tempted to modify the 8050A display:

That should keep me out of trouble for a while.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

If you have a good 3870 then you can get Ed of DataSync to read it, then track down a MK38P70 (eBay) and burn an eprom for the piggyback EPROM spot.

Reading these is a trick, you have to send code to the CPU to extract one byte, then increment the counter and tell it to skip one space and extract the next byte, and so on. This involves the "TEST" pin being set to a particular voltage (track down documents) and a PIC or similar to talk to the CPU with a bunch of code to get it to count correctly...

Not sure what Ed charges to read these...once read if you want to send me the code I'll host it on the TTL FTP site so others can find it.

(Tech Tools mail List)

John :-#)#

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I have the databook on those chips, so I might be able to read one here. I'd have to build a fixture to read it, but it would be in line with the work I used to do at Microdyne.

Who knows? With the code, it might be possible to make a header to use a newer and easier to find IC? 25 years ago I wrote sofware to read the OS in Commodore drives, and updated the orignial 'Disk Doctor' to identify & read newer drives. That was fun, writing machine language to disk one byte at a time, to modify the program I was using to do the work. I also changed the user interface to make it easier to use. :)

I think I have an 8000 in the garage in the pile of equipment I couldn't find parts for, 20 years ago.

The manual shows the minor differences in the two versions.

That would be an inderesting module to make availible for repairs.

YOU? HAHAHAHAHAHAHAHAHAHAHAHAHAHA!!! ;-)

I bought 50 subc on Ebay that just arrived a few days ago. Eight for the two Fluke 8050A meters, the rest for other test equipment. If anything else fails, I'll have to order more.

There is a pile of damaged Fluke meters out in the shop that accumulated over the last 25 years.

OK, I made it out to the shop & found a pair of Fluke 8000A meters along with a lot of water damage. There is smashed & rusted stuff all over the floor, an interior door fell apart, and the wood floor in part of the shop collapsed, leaving the shelving leaning against each other. I think it would be easier to write it all off, than to try to clean it up. Anyone have a spare bulldozer & a half dozen construction dumpsters?

Save the Fluke meters and trash the rest. Probably too wet to burn down the building. You could claim that the building was used for soldering with the dreaded leaded solder and that chlorinated hydrocarbon solvents were used and stored in the shop. That way, it will be declared a toxic waste dump or superfund site which various government agencies are obligated to clean up. Your government at work (for you).

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

It's a pole building with a steel roof and aluminum skin. Nothing much to burn.

Florida would condem the property and I'd be homeless.

One of the earlier fluke meters (I don't remember which one) had a battery that was required to be installed in order to regulate the power supply. If you took out the battery pack and tried to operate the meter on AC power, you'd blow the damn thing! Was the 8050A that meter?

They don't work without the battery, but it didn't appear to damage them.

I have a 8000A that uses four 'D Cell' nicads, but they leaked so bad that I may not be able to repair it. BTW, I see these with really high serial numbers on Ebay.

One 8000A has a SN of 1702 and has an extra set of jacks for 10A which would make it option -05. It has a bad Siliconix SC522 A/D converter.

The damaged meter is SN 65187. The A/D is good, but the circuit board is damaged from the bad NiCads.

The power transformer is larger in the battery version, and it has a large light bulb in the DC supply. The battery operated version has a small DC-DC converter to power the meter. A manual is on BAMA: