Fluke 8050A Repair

[Cigarsnob]

Howdy,

I just picked up a fluke 8000A and 8050A DMM from a surplus store yesterday. The 8050A model is the battery option (Connects to mains, but it comes with recharable bat). Well I knew the 8050A DMM needed some repair and when I switch it on, the "bat chg" LED comes on, but the DMM does not work. No LCD display. Although when I switch through the ranges, I do get a flash on the LCD.

I plan on buying some new batteries to see if that does the trick, but ideally, I would like to save myself the money and remove the batteries and make the 8050A function off the mains directly. I found one thread saying to just remove the batteries and install some beefy caps with a resistor. Does anyone know if this will do the trick?

I found the manual with the schematic and plan on digging into the DMM once I get home after the holiday, but thought I would seek some advise here while I wait.

Thanks in advance for any information.

Phil

[alm]

Some circuits use batteries as crude voltage regulators, in that case a cap wouldn't do. If it's just for smoothing, a cap might work found. This post in the TekScopes Yahoo! group suggests some minor circuit modifications (eg. replacing the voltage regulator and removing some resistors) to get the 8000A/8050A working without the batteries, so just putting in a cap may not be sufficient.

[ModemHead]

The battery-operated 8050A-01 uses an LM317 in current-regulator configuration to supply both charging current for the batteries and operating current for the meter.  The batteries need to be there to regulate the voltage (roughly 5V).  I modified one of my 8050As by removing the batteries and modding the circuit board to use the LM317 as a voltage regulator.  It works fine that way.

If you need more details on how I did the mod, I can provide them but it will take a few days since I am away from home for the holidays.

[Cigarsnob]

Modemhead,

If it's not too much of an inconvinance, I would appreciate more info regarding the mod you spoke of. I don't mind the wait as I'm also away for the holidays.

I should be able to make the mod just by looking at the datasheet of the lm317 and the schematic of the 8050A, but you can't go wrong with having more information.

Thank you,
Phil

[Conrad Hoffman]

I had a similar instrument that was a constant problem because of the batteries. I didn't use it often enough to keep the expensive battery pack in good shape. I replaced the battery pack with a big aluminum electrolytic cap, shunted with some power zener diodes to imitate the clamping action of a real battery. The zeners have to be sized to take the usually minimum charging current. It probably works better now than it ever did with batteries.

[grenert]

Hey, anyone have a spare LCD from one of these?  I've got one where I replaced the batteries with modern NiCd (NiMH self-discharge to quickly), but the display was squashed at some point, and it is "blurry".

Thanks and Merry Christmas to those who celebrate it!

[ModemHead]

If it's not too much of an inconvinance, I would appreciate more info regarding the mod you spoke of. I don't mind the wait as I'm also away for the holidays.

It's now on my to-do list.   

[amspire]

Hey, anyone have a spare LCD from one of these? 

I may have a working display. I have a non working meter I keep for spares. I well power out up and see if I can get any life out of the display.

What country are you in?

Richard.

[amspire]

I decided to look at what was faulty in my spare 8050a, and unfortunately, the only thing wrong is the display.

I think the display is fine, but there is a problem with the conductive rubber contract strip.

The contact with the most problem is pin 1 - the display common.

I do have spare Fluke 120v transformers, so if anybody wants to convert from battery to Mains, it looks like all you need is the transformer and about 9 other standard components. All the locations for the Mains supply part are actually on the board under R&D that is only used for the battery version.

Richard

[amspire]

This is not a bad alternative to sourcing a replacement LCD display for a Fluke 8050A DMM.



http://lous.home.xs4all.nl/fluke/Fluke8050Asite.html

The 8050A LCD does suffer from low contrast.

Richard

[alm]

This seems like an excellent alternative providing you don't care about battery life. In my opinion LED displays are superior to LCD for basic 8 segment displays. Much better viewing angle and contrast.

[ModemHead]

Modemhead,

If it's not too much of an inconvinance, I would appreciate more info regarding the mod you spoke of. I don't mind the wait as I'm also away for the holidays.

I should be able to make the mod just by looking at the datasheet of the lm317 and the schematic of the 8050A, but you can't go wrong with having more information.

Thank you,
Phil

Originally, U26 (LM317) is configured as a current regulator. When the front-panel switch is off, a 137mA charging current (determined by R26) is provided to the 4.8V battery pack. When the meter is turned on, an additional 104mA (determined by R25) is supplied to operate the meter and continue trickle-charging the batteries. As I recall, the meter required about 150mA operating current. The voltage from this arrangement would probably vary between about 4.8V for a discharged-but-healthy battery pack and 5.6V for a charged pack. Note that this Fluke schematic is in error regarding the LM317 input and output pin numbers.



I changed the LM317 configuration to regulate voltage at 5.5V, as follows:

• Cut two traces at the points indicated.
• Replace R25 with a wire jumper.
• Replace R26 with a 150R 0.25W resistor.
• Add wire jumper from R26 to U26P1.
• Add 510R 0.25W resistor from U26P1 to C23-neg.

This shows the mods from the solder side of the PCB.  The upper cut trace is obscured by the resistor lead.



Optionally, you can remove the red "Bat Chg" LED DS1, because it will still illuminate when the power switch is off.  Note that when the power switch is off, the transformer, rectifier, and regulator are still energized, and will consume some power (but much less than if batteries were installed.)

Re-installing batteries after these mods may lead to unfortunate consequences, so you may want to remove the battery pins or somesuch to prevent that.

[ModemHead]

This is not a bad alternative to sourcing a replacement LCD display for a Fluke 8050A DMM.

<snip>

http://lous.home.xs4all.nl/fluke/Fluke8050Asite.html

The 8050A LCD does suffer from low contrast.

Richard

I've done that one too, but the back side of that LED display is a labor of love.  Eh, some people climb rocks for the heck of it, I play with old gear. 

[Cigarsnob]

ModemHead,

Great description. Thank you very much. I will do this mod soon.

But before I do, without knowing anything else, do you think the batteries is causing the DMM to not function properly? I had it plugged in for a couple of hours when I first got home and switched the thing on. It worked at that point, but the low battery indicator on the LCD was always on. Then I noticed last night that it worked for a bit and then when I switched it off and back on again, I would get the low battery indicator on the LCD again along with a "1" and then the LCD would fade out. After switching the thing on and off again several times and sweeping through different ranges and voltage/resistor setting, the same result would occur. All of this after the DMM has been plugged in for the past 48 hours.

Well thanks again and I really appreciation the tutorial you provided. Hopefully this will get my DMM running again and consistently this time.

[ModemHead]

ModemHead,

Great description. Thank you very much. I will do this mod soon.

But before I do, without knowing anything else, do you think the batteries is causing the DMM to not function properly? I had it plugged in for a couple of hours when I first got home and switched the thing on. It worked at that point, but the low battery indicator on the LCD was always on. Then I noticed last night that it worked for a bit and then when I switched it off and back on again, I would get the low battery indicator on the LCD again along with a "1" and then the LCD would fade out. After switching the thing on and off again several times and sweeping through different ranges and voltage/resistor setting, the same result would occur. All of this after the DMM has been plugged in for the past 48 hours.

Well thanks again and I really appreciation the tutorial you provided. Hopefully this will get my DMM running again and consistently this time.

You're welcome, happy modding/repairing.

Your problem sounds exactly like a dead battery pack.  Bad cells will pull the voltage on this 5V nominal supply down far enough that the meter will not operate, or won't operate for long.

An alternate, even easier fix, is just to solder in any working sub-C NiCd cells that you have. If you're not concerned about actual battery operation, four 1.2V cells of just about any size will allow the meter to work fine on AC power.  Until the cells go bad, as they all do.  Smaller cells may get warm on the 140mA constant trickle...

[Cigarsnob]

You're welcome, happy modding/repairing.

Your problem sounds exactly like a dead battery pack.  Bad cells will pull the voltage on this 5V nominal supply down far enough that the meter will not operate, or won't operate for long.

An alternate, even easier fix, is just to solder in any working sub-C NiCd cells that you have. If you're not concerned about actual battery operation, four 1.2V cells of just about any size will allow the meter to work fine on AC power.  Until the cells go bad, as they all do.  Smaller cells may get warm on the 140mA constant trickle...

I don't have any C NiCd cells so I'll just stick with the mod you provided. Thanks again for all your help. I'll post my results in a day or two.

[ModemHead]

Since the transformer and regulator are energized as soon as you plug the meter in, 5.5V or so should appear across U26P2 to C23-negative even before turning the power switch on.  You can check your work this way without possibly damaging the rest of the meter if you make any mistakes.

[amspire]

This is not a bad alternative to sourcing a replacement LCD display for a Fluke 8050A DMM.

<snip>

http://lous.home.xs4all.nl/fluke/Fluke8050Asite.html

The 8050A LCD does suffer from low contrast.

Richard

I've done that one too, but the back side of that LED display is a labor of love.  Eh, some people climb rocks for the heck of it, I play with old gear. 

Thanks for the photo's.  It turns out my spare parts 8050A has a dud LCD - the backplane connection is open circuit internally. I have 3 other working ones (got four of them for $25 each), so I am going to do the LED display mod, so I have one meter that works in poor lighting.

After seeing your photos, I will make a custom PCB and find a way (I hope) of connecting to the LCD contact row, rather then all that wiring to the display driver IC's.  I should be able to salvage some SMD resistors and transistors, and I have ordered the displays and some acrylic filter sheet. Total cost will be about $20. 

Main reason for doing the work is that in debugging the LCD display, I found out that the rest of the meter works perfectly (I swapped display boards with a working 8050A), and I don't really need a 4th working LCD display at a cost of a new display - something like $50. To get one with with a LED display makes it worth the effort.

Richard.

[amspire]

I don't have any C NiCd cells so I'll just stick with the mod you provided. Thanks again for all your help. I'll post my results in a day or two.

If it were me, I would spend the $7 for a set of 4 NiCd cells.

http://www.ebay.com.au/itm/4-Sub-C-SubC-Tab-2500mAh-NiCd-Rechargeable-Battery-B1-/130617181876

They will die eventually, but you then get another set, and you can run the meter on battery power for a day's work. It is not just the portability issue, then meter has a higher safety rating when running from batteries. Running off battery also eliminates the 40pF Common Input-to-Mains capacitance that might cause a problem while measuring switching circuits.

Richard

[Cigarsnob]

Since the transformer and regulator are energized as soon as you plug the meter in, 5.5V or so should appear across U26P2 to C23-negative even before turning the power switch on.  You can check your work this way without possibly damaging the rest of the meter if you make any mistakes.

Hey ModemHead,

I am having an issue with the mod. I performed the steps that you listed, although my PCB was slightly different than the picture provided. When cutting the trace that connects to U26.1, I had multiple traces (3) ending at U26.1 besides the battery pack. These multiple connections was the transformer, T3, C22, and C34. The cut disconnected those components from U26.1. I take it this is correct, no?

Also, after adding the 510 ohm resistor from C23 (negative pin) to U26.1 and plugged in the power cord (after all other steps were performed), I only got a voltage of 4.5V when probing U26.1 and C23 (negative pin), so I ended up upping the resistance to ~650ish ohms to get 5.5V. At this point, I turned it on and nothing appeared on the LCD.

I checked my work a few times and I'm fairly certain I did the steps correctly. When I checked the voltages at TP2, 3, 4, and 5, I don't get the voltages as described in the schematic. I was checking these voltages when having one probe placed on C23 (negative pin) and the other on the test points. The voltages observed were roughly 6V (6.5V on some). But then I thought that I may be placing my other probe, (that connects to C23 negative pin) incorrectly so I placed in on the front panel common plug and the voltages on the test points were in the mV range.

I don't know if any of what I said provides any insight as to what I did wrong, but any advise would be appreciated.

I'll have another crack at it in the morning.

Thanks

[ModemHead]

I am having an issue with the mod. I performed the steps that you listed, although my PCB was slightly different than the picture provided. When cutting the trace that connects to U26.1, I had multiple traces (3) ending at U26.1 besides the battery pack. These multiple connections was the transformer, T3, C22, and C34. The cut disconnected those components from U26.1. I take it this is correct, no?

Yes, the cut should simply disconnect U26.1, leaving the rest of the circuit intact.  I've attached a diagram which I hope makes clear exactly how things should be connected before and after, regardless of PCB layout.

Also, after adding the 510 ohm resistor from C23 (negative pin) to U26.1 and plugged in the power cord (after all other steps were performed), I only got a voltage of 4.5V when probing U26.1 and C23 (negative pin), so I ended up upping the resistance to ~650ish ohms to get 5.5V. At this point, I turned it on and nothing appeared on the LCD.

The 5.5V should be from U26 pin 2 to C23 negative pin.  That is the voltage regulator output.  The voltage from U26.1 to C23-neg should be about 1.25V lower than 5.5V, or 4.25V.  Your measurement sounds like it was OK to begin with.  There should be no need to raise the resistor value, which would lead to an output voltage that is too high.

I checked my work a few times and I'm fairly certain I did the steps correctly. When I checked the voltages at TP2, 3, 4, and 5, I don't get the voltages as described in the schematic. I was checking these voltages when having one probe placed on C23 (negative pin) and the other on the test points. The voltages observed were roughly 6V (6.5V on some). But then I thought that I may be placing my other probe, (that connects to C23 negative pin) incorrectly so I placed in on the front panel common plug and the voltages on the test points were in the mV range.

The test point voltages are referenced to the meter ground, which is TP1.  The front-panel common input is also tied to the meter ground.

[matt09]

Not meaning to drag up a dead topic but I've just spent AGES trying to get this seemingly very simple circuit to work. I had no problem with getting the correct voltage out the regulator but the other board layout is deceptive. It appears very similar so you break the tracks to find that because of different spur off layouts on the pcb things don't join up anymore as they should.

Got there in the end.. 

[eugenenine]

I did similar with mine after the second set of batteries died.  Since its a simple charger it will wear out the batteries every few years.  IIRc I desoldered their regulator and mounted my own 7805 with a jumper wire so it didn't require cutting any traces.

[matt09]

I came close to doing the same but my stubbornness prevailed. 

[eugenenine]

Mine would never work and charge the batteries at the same time.  So I'd be in the middle of something and it would die.

[emptech]

I purchased my 8050 brand new when it first came out, I think I paid over $500 for it.  Through the years, had the same issue, the ni-cads would die,would usually short circuit.  I've replaced them from time to time.  Looking at the original circuit, I see it is a constant current source, with two settings.  What it needs is constant voltage, which your mod does, and current limiting.  I see as a constant current source, it is eventually going to cook the batteries.

What was so unique with that meter, the low ohms scale.

I like to keep old equipment alive too -

Jim

[Bassblaster505]

I am having an issue with the mod. I performed the steps that you listed, although my PCB was slightly different than the picture provided. When cutting the trace that connects to U26.1, I had multiple traces (3) ending at U26.1 besides the battery pack. These multiple connections was the transformer, T3, C22, and C34. The cut disconnected those components from U26.1. I take it this is correct, no?

Yes, the cut should simply disconnect U26.1, leaving the rest of the circuit intact.  I've attached a diagram which I hope makes clear exactly how things should be connected before and after, regardless of PCB layout.

Also, after adding the 510 ohm resistor from C23 (negative pin) to U26.1 and plugged in the power cord (after all other steps were performed), I only got a voltage of 4.5V when probing U26.1 and C23 (negative pin), so I ended up upping the resistance to ~650ish ohms to get 5.5V. At this point, I turned it on and nothing appeared on the LCD.

The 5.5V should be from U26 pin 2 to C23 negative pin.  That is the voltage regulator output.  The voltage from U26.1 to C23-neg should be about 1.25V lower than 5.5V, or 4.25V.  Your measurement sounds like it was OK to begin with.  There should be no need to raise the resistor value, which would lead to an output voltage that is too high.

I checked my work a few times and I'm fairly certain I did the steps correctly. When I checked the voltages at TP2, 3, 4, and 5, I don't get the voltages as described in the schematic. I was checking these voltages when having one probe placed on C23 (negative pin) and the other on the test points. The voltages observed were roughly 6V (6.5V on some). But then I thought that I may be placing my other probe, (that connects to C23 negative pin) incorrectly so I placed in on the front panel common plug and the voltages on the test points were in the mV range.

The test point voltages are referenced to the meter ground, which is TP1.  The front-panel common input is also tied to the meter ground.

I think my board is different than both of yours. U26P1 connects to 4 points and i have no clue what i need to do here. my board is Rev R model 8050A-3001

[MickM]

https://www.amazon.com/gp/product/B01N4476AK/ref=oh_aui_search_detailpage?ie=UTF8&th=1
They are slightly smaller than stock, part of a paper napkin stops the rattles.
They work fine, as a bonus it is now portable, and two spares.

Mick M.

[ModemHead]

Pardon my bluntness, but if modding the circuit board presents a challenge, it would be best to solder up a couple of pairs of new NiCd cells, as suggested already.  Sub-C, AA, just about anything will allow the meter to operate normally.

[randalstout]

Wow, thank you so much for this one!  I was about to pull my hair out on the issues.  Power supply, power supply, power supply... 

[kelchm]

Can anyone identify the connectors used on the batteries in the 8050A? I'd like to order some new ones for when I replace the batteries in mine.

[xwarp]

When I replaced the batteries on mine, I just soldered the wires to the tabs on the cells.

[Electro Detective]

Please excuse the Off Topic question:

My 8050A (non battery version) works great at all settings, and agrees with other meters,

except when measuring AC 240 volts mains voltage on the 750V AC Range 

It displays a few volts difference compared to handheld 87v, 8060A and other TRMS meters which all closely agree amongst each other. 

It's not a deal breaker, as a few volts here or there when verifying the mains power is ok, and the 8050A is consistent

I'm just wondering whether that particular AC range is out of calibration,
or 8050A implements a different measuring system,
influence from the high AC bandwidth response,
mains/earth/neutral powered influence
 
or perhaps the 8050A is more on the money with such a measurement 

or maybe it's tweak time...     

   

[kelchm]

When I replaced the batteries on mine, I just soldered the wires to the tabs on the cells.

The connectors on mine are already shot.

I'm sure I could come up with something that would work well, but it would be nice to just be able to buy the correct connector.

[amspire]

It displays a few volts difference compared to handheld 87v, 8060A and other TRMS meters which all closely agree amongst each other. 

When you say a few volts, an error of 2.4 volts is still within the accuracy spec for the 8050A's first year. Given all the decades since then, it could now be a little further off. Get the 8050A manual pdf and if you want to tweak the 750V range to make it the same as the other meters, go for it. I seem to remember there are adjustments to the RMS converter - don't touch those. For most settings, the 8050 stays very accurate over time.

[kelchm]

Can anyone identify the connectors used on the batteries in the 8050A? I'd like to order some new ones for when I replace the batteries in mine.

To answer my own question, the connectors are classified as 1.47mm barrel/bullet connectors.

I can confirm that both of the following from TE Connectivity work well:

• 60940-1 (Digi-Key Part Number A111354CT-ND)
• 60888-2 (Digi-Key Part Number A100338CT-ND)

[kelchm]

I began taking a look at one of my 'broken' Fluke 8050A's tonight and was disappointed to find quite a bit of damage. I think this one will be relegated to the parts pile. At least I got a good LCD out of it.

My question is wether this damage was caused by the caps leaking their guts or by some foreign substance (water?). I ask because I'm wondering if I should proactively replace all the caps in my working 8050A's.

Photos

[Electro Detective]

Open them all up asap, put them side by side for comparison and take PHOTOS,

may as well deal with it     while it's fresh in your mind

Mine is a mains operated unit (non battery model) and last time I looked about 6 months ago everything looked like new inside, no weird caps, smells, or leakage,
everything still in spec 

It may depend on the board revision as to whether some had leak prone caps, or perhaps the internal batteries spewed out clear stuff,
or heat, humidity and moisture issues where the units are parked, or a beer session gone ouch!   

Same deal with the handheld 8060A, later revisions had better or reputable branded capacitors 

[lowimpedance]

Indeed it does look like electrolyte from the nearby cap. Most certainly replace the same caps in your good 8050s as a proactive step.
Perhaps the damaged one can be cleaned up and repaired and join the line up again.

And now you have got me worried, will go and check my 'crew' out right away.

[kelchm]

Open them all up asap, put them side by side for comparison and take PHOTOS

Will do!

I have five of the 8050As, so it will be interesting to take a look at the differences side by side.

[Bashstreet]

That one sure knew how to puke up...

It is hard to say from photos how bad the corrosion is but you might be able to clean it up worth a try any case before you junk it.
If you have same units i would replace that cap on them and maybe recap them fully for peace of mind.

[kelchm]

Wanted to share something I started working on last week. I've been fascinated with the various 8050A display mods since before I even owned one. There's something really cool about taking an old, reliable piece of gear and putting your own spin on it by replacing the entire display.

I've decided to take it one step further and use a 2.4" display rather than the 2.2" Adafruit display that others have used. It's a very snug fit, and I did have to shave about half a millimeter off the bottom tabs on the panel. It's still the same resolution, but I think the end result is going to look great.

Edit: The display in the photo is made by New Haven Display (NHD-2.4-240320CF-CSXN#-F). I really like how solidly built the display is. It even has a metal case/backing which I've never seen on a lcd this small.

[kelchm]

Anyone have any thoughts on what brand/series of capacitors to use when replacing the capacitors on my 8050A's?

I'm considering the Rubycon YXJ series currently since they offer very long life but are not low ESR, which I think would not be desirable in this case.

[marcuswilson007]

I have 3 8050As and none of them will work withot batteries.
When turned off the batteries charge and when turned on they run on the batteries, the batteries do not charge when the meter is operating.
I assume that is to reduce the mains noise getting into the meter while measurements are being made.

[lowimpedance]

And now you have got me worried, will go and check my 'crew' out right away.

Just checked all my 8050's and an 8012 and a 8010.
Of the 3 8050's two are mains only , and I found the
22 uF/16 V caps were just starting to leak. The  220 and 470 microfarad caps
did not show sign's of leakage. I have not investigated the battery model yet as it
contains many more electrolytic's than the mains version.
 As for the 8010 and 12 models both are battery versions and use the same  caps and
I found in both the small 22uF/16 V are also starting corrosion on their pads too.
Note that despite the same value they are not of the same series or manufacturer !.

So this has been a timely reminder to  check old gear with these damn little electro's
otherwise the little bastards will be happily chewing through your favorite gear.
 Many thanks to kelchm for bringing this to our attention, all be it at the expense of one
Of his "50's" (hopefully still salvageable).
 BTW interesting to see the display mod up and running, will look cool I'll bet.

[kelchm]

Just checked all my 8050's and an 8012 and a 8010.
Of the 3 8050's two are mains only , and I found the
22 uF/16 V caps were just starting to leak. The  220 and 470 microfarad caps
did not show sign's of leakage. I have not investigated the battery model yet as it
contains many more electrolytic's than the mains version.
 As for the 8010 and 12 models both are battery versions and use the same  caps and
I found in both the small 22uF/16 V are also starting corrosion on their pads too.
Note that despite the same value they are not of the same series or manufacturer !.

So this has been a timely reminder to  check old gear with these damn little electro's
otherwise the little bastards will be happily chewing through your favorite gear.
 Many thanks to kelchm for bringing this to our attention, all be it at the expense of one
Of his "50's" (hopefully still salvageable).
 BTW interesting to see the display mod up and running, will look cool I'll bet.

Have you begun to pick out replacement caps yet? I’ve been struggling with how to narrow down down what specs I should be looking for beyond the basics.

[lowimpedance]

Have you begun to pick out replacement caps yet? I’ve been struggling with how to narrow down down what specs I should be looking for beyond the basics.

Looking at the schematic only C21 and 24 could be low ESR types, and the rest could be general purpose electrolytics. No need to over analyze it. Just upsize the voltage rating a little since modern
equivalents in the same voltage rating will be quite a bit smaller and the physical mounting may not match the hole spacing.

[Barrelshifter]

I want to describe how I modified the 8050A Revision 3001 PCB for using only with AC Power.
The rev. 3001 board is different to the board showed here to convert the LM317 from current source to regulator mode (5V).
Even the replacement of the LM317 to a LM7805 could not be done directly in the 3001 revision board. This is because of the different layout the pcb has.
The easiest way is to remove the LM317, the batteries and their compartments completely. You do not need them anymore.
The 7805 needs a small heat sink.

It is important, that you place the +5V wire from the 7805 to pinhole 1 AND 2 (bridge). If you miss pin 2, than the meter will not be functional.

I mount the 7805 on the place where one of the batteries was installed before.

See attached schematic for details.

[weejag]

Thank you to Modemhead for posting the best way to modify the 8050A from battery to mains.
The conversion can be done with the other board version.

I have three of the battery versions (two of which are fixable) that require new LED's and which I wish to convert to mains.
The motherboard versions are the 8050A-3001 types so I thought that it might be a help to post pictures of the mod for that particular version.

I have carried out the mod and confirm that it works and gives the required voltages. 
Testing the voltages: test point 1: ground,  test point 2: 13v (actually 14), test point 3: 6v, test point 4: -5v, test point 5: -10v

The mod is the same as ModemHead posted:


R25 does not require removal. Simply short the pins on the solder side.  R26 is replaced with a 150 resisitor.
The 510 resistor is placed on the solder side as shown. Be careful not to short this or the links to anywhere undesirable.

[WimWalther]

Old topic.. but if you landed here, you might just need to know that the battery-option Fluke 8050A will NOT operate with a bad battery pack - even IF it is connected to the AC mains.

If the display just flickers a bit and goes quiet, replace the NiCd batteries, it should fix it.

[Twinsig]

Thanks yall (weejag) for this version update..! Needed the help on this version.

[Twinsig]

Mod completed. And although my voltage and resistance input tests look good (my fluke 87 for comparison) TP-2 is reading 9.54v as opposed to the stated 13v.
IF, anyone is still out there, do you have any experience with this issue?
Any suggestions?

EDIT: I thought C21 may have been dragging it down, but no. No issues with that & C24. They old ones tested fine but i HAD to replace them with new of course.
TP2 remains @ 9.5-ish.
I'm going to tap-out on it for now and use it for a while. hopefully it will meet my needs.