Old Fluke Multimeters

[ogdento]

Thanks very much Rod, I appreciate the kind words!  I'll get a few more photos together and probably start a separate topic.  I will have a few for sale but still working out getting more, so I'll let you know.

[NoisyBoy]

I have a 8000A I bought many years ago, it never powered up and I put it in storage for almost 4 years.  I finally got to work on it, and found out the transformer T1 is open on the primary side.  Rather than trying to repair the transformer, do any of you know if there is a modern day direct fit replacement?  It is 115V version of the meter. 

Thanks.

[Paperweight]

I bought my Fluke 8060A new around the year 2000. I still use it frequently as my go to meter. That thing performs like a champ and holds a calibration really well. It's basically all I've ever needed for vacuum tube and solid state audio projects.

[bdunham7]

I have a 8000A I bought many years ago, it never powered up and I put it in storage for almost 4 years.  I finally got to work on it, and found out the transformer T1 is open on the primary side.  Rather than trying to repair the transformer, do any of you know if there is a modern day direct fit replacement?  It is 115V version of the meter. 

Thanks.

I would highly suggest that you verify that your 8000A works properly on a DC supply before bothering to scrounge a transformer.  You need a +/-15V bipolar and a +5V supply, all can be common-ground. 

[NoisyBoy]

Great suggestion, that was my next step. My 3631A, which I never use, may be ideal for the job. While the +5V is quite clear, any suggestion where the +15 and -15 should be connected to on the board? 

[AVGresponding]

The manual for this meter is readily available from the usual suspects online, and contains the schematic and board layout.

[bdunham7]

Great suggestion, that was my next step. My 3631A, which I never use, may be ideal for the job. While the +5V is quite clear, any suggestion where the +15 and -15 should be connected to on the board?

First you have to determine which model of 8000A you have--the 'options' such as Lo-ohms and 10A or even the milliamp-second pulse energy feature all are actually revisions of the entire instrument to varying degrees.  However, if you have a non-battery model, you likely have three larger capacitors on the left rear of the board that all have a common rail on the outside.  The other ends of those--toward the transformer--should be your +5, +15 and -15 rails, in order from the back.

How have you verified that T1 primary is open?  There are two windings used in parallel in the 115V configuration, so it seems unlikely that two windings would both break.

Manual: https://xdevs.com/doc/Fluke/8000a.pdf

Typical PSU: 

[NoisyBoy]

Thank you so much for the helpful response.  I have been working off the service manual on the meter for a couple days now, on page 4-5 step 15, they refer to J4-25 and J4-27, which corresponds to the circled number on the schematics, the challenge is I have no idea where they are referring to on the actual board.  If I apply DC power to the ends of C17 and C18, it appears I have to apply 19-20V instead of the 15V based on step 14 of the troubleshooting guide.  But at least I can find those connection points at the end of the two caps. 

I was able confirm connectivity between the plug to one end of S12, and confirm the fuse F1 is fine, as well as S12 (the power switch) working correctly after I deox it.  But from the end of S12, through the primary to the other end of the plug, it is measured open.  Could the internal thermal fuse cause the problem?  Given the external fuse F1 is intact, I am surprise the thermal fuse would fail on the primary end.

[bdunham7]

If you measure right at T1 what do you get?  They use solder bridges to rewire from 115 to 230V operation, for 115V SB1 and SB3 are bridged and SB2 is open.  On mine if I measure from SB1 to SB3 I get 367.5 ohms.

[NoisyBoy]

Hi, I checked that last night.  My unit matches your picture exactly, SB1 and SB3 are bridged and SB2 is open.  On my unit, SB1 to SB3 is wide open, that's what led me to think the primary failed.  The transformer looks perfect on the outside, no burn mark or sign of overheating.

[bdunham7]

On my unit, SB1 to SB3 is wide open, that's what led me to think the primary failed. 

Yeah, that seems conclusive...

[NoisyBoy]

Thanks, if that's the case, does anyone know if there's a modern equivalent to that transformer for a drop in replacement? 

In the mean time, I will also power it up with a bench supply to make sure the rest of the meter is working correctly.  Does applying +/- 19-20V at cap C17 and C18, along with +5V at C19 seem to be the consensus?

[bdunham7]

In the mean time, I will also power it up with a bench supply to make sure the rest of the meter is working correctly.  Does applying +/- 19-20V at cap C17 and C18 seem to be there consensus?

I don't think it needs to be that high, start with +/- 16V.  And use current limiting to about 100mA or so.  Something had to toast that transformer and if the meter came from North America, I doubt it was a 230V input accident.

[NoisyBoy]

Great point, I will give that a try. It is a US model, it would be nice to be able to revive it after all these years if it is just the transformer. As along as I can find a replacement.

I wonder if a power surge might have done the damage to it. The meter is pristine otherwise, I had to break the original Fluke stickers at the screw to open it.

[med6753]

Great point, I will give that a try. It is a US model, it would be nice to be able to revive it after all these years if it is just the transformer. As along as I can find a replacement.

I wonder if a power surge might have done the damage to it. The meter is pristine otherwise, I had to break the original Fluke stickers at the screw to open it.

There are usually several "for parts or not working" 8000A's on Ebay that can be had for pretty cheap.

[bdunham7]

As along as I can find a replacement.

If your meter works on a power supply, I can supply a transformer for postage costs.  I don't have the same nostalgia for mine and I've only pulled it off the shelf to help the guy in the other Fluke 8000A thread.  I've not paid too much attention to it over the years but somehow it never made it to the trash.  If people are fixing these I may as well put its parts to use.  Mine has a bad U3 and I have plenty of meters, including two more 8800As that need attention.

So, Fluke 8000A fans, I think the transformer is spoken for here and I've already removed the current shunts, but if you need parts (other than U3 and there's a U3 kit on eBay right now for $10) let me know.

[NoisyBoy]

Oh wow, thank you so much for the generous offer and all the guidance you have already given me, I really appreciate it. Let me do some testing in the next couple days to make sure the rest of the meter is in working order.

I am restoring the meter for nostalgic reasons, it is my second 8000A, the other one is well used and had been with me for 20 years and still get used regularly.  The 8000A was one of those meters in the EE lab that was always available when I was in college. Instead of queuing up for the newer Fluke and HP Bench DMMs, I often just used the 8000A and bypass the line.  It may not have the high precision and requires some extra effort for manual ranging, but it was good enough to give me the measurements I needed.  Even today, that is still my first go-to DMM purely out of habit.

Again, thanks for everything.

[BeBuLamar]

Does anyone know when was the 8060a in production last? I really want one. I think it's the best of that style with the side swiches.

[Paperweight]

The 8060A was discontinued around the time the 189 came out in 2004. So, somewhere between 2001 to 2004 would be the best estimate of the last production. The final manual for the 8060A has a copyright date of 1997 Rev. 3 11/00 or November 2000. It is posted on the Fluke website.

[NoisyBoy]

Well, if I put the 8000A on life support, it lives!

I finally got to test the 8000A without the transformer and rectifier section, and I was lucky to report that it powered up.  I use my EDC 522A calibrator to apply a range of voltages and current to it, and everything works.  I then connect it with my decade resistor, again all ranges are working properly.  Calibration is off, but it should be a simple fix with the universal counter and the EDC.

Thanks to bdunham7's wisdom, I figure I would share with you how I am bypassing the transformer, and the power parameter the DMM consumes.  Hopefully it will help others with similar issues with testing their units in the future.  If you look at the second picture, you will see how I am attaching the bench supply to the DMM.  The black and red cables are supplying +5V, the meter draws 170mA, the blue/yellow/green pair are set to track each other, I set them to +/- 16V.  On the +16V, it draws a tiny 13mA, the -16V draws 33mA.  So all three together the meter only consumes under 1.6W of power.  And I don't recall the consumption change much as I change function. 

Best of all, I realize it is the earlier version of the 8000A with the tiny LED segments instead of the later 7 segment LEDs.  It will be a nice differentiation from the other 8000A I currently use. 

[NoisyBoy]

Thanks to bdunham7's generous T1 transformer, the transplant was performed, and another 8000A is back in action!

While the meter works, all the readings are slightly off, so I performed a full calibration today.  For those who plan to calibrate the 8000A, the hardest part is the period adjustment (the first step).  It requires 100ms +/- 5us for the "positive waveform", which really is the "more positive part of the waveform".  The waveform is an unsymmetrical square wave, the lower edge is at about 1.2V, the upper edge is 5.7V with ripples.  What they want you to adjust is the duration of the upper square wave, mine was about 102.87ms.  Most scopes do not have enough precision or accuracy for the adjustment, I use the time interval measurement of my counter driven off of the lab master GPSDO amp, which offers much better resolution and accuracy.  I set it up to trigger to start at the rising edge at 2V, and ending at the falling edge at 2V. 

After that, it is the routine adjustment for each function using a calibrator.  In my case, each pot required tweaking.  But when it is done, the meter was working well within spec.

Note this meter is one of the earlier design, using the 14-segment vs. 9-segment LEDs in my other later 8000A along with a zeroing pot.  A nice addition to the lab.

Again, a big shout out to bdunham7 for helping me out with the transformer, and bringing another vintage Fluke back to full working order.  Thank you!

[bdunham7]

Glad to help, and I've also managed to clear up 18 cubic inches of storage space!  For those with an unrepairable 8000A, or one that needs the U3 set like mine, I'll point out that scrapping out an 8000A yields a surprising haul of potentially useful parts.  So far I have:

A nice 0.1R kelvin-connected (properly) resistor, 1 loop of manganin on a mica card
A set of current shunts 1R, 9R, 90R, 900R that seem pretty accurate.
Some nice precision resistors in possibly useful values for a voltage divider--9.9M, 100K, 90K, 10K (several)
A small assortment of mica capacitors
Some vintage op-amps (LM301A for example) and other miscellaneous obsolete semiconductors
A few fairly low quality banana jacks, but they seem to be reusable.

I also have a few interesting capacitors, but the most interesting is from the U3 set, a 0.22uF hermetically sealed type that I couldn't identify.  It has a similar appearance to the integrating capacitors used in other models, but here it is used as part of the circuit that sets the period for U3.  The manual just calls it "Capacitor, poly".  It is labelled "MIDWEC M8-26  .22uF +/-5% 50VDC 415".  I haven't found type M8, although other Midwec offerings seem to have been polypropylene.  Any ideas?

[Gyro]

...

I also have a few interesting capacitors, but the most interesting is from the U3 set, a 0.22uF hermetically sealed type that I couldn't identify.  It has a similar appearance to the integrating capacitors used in other models, but here it is used as part of the circuit that sets the period for U3.  The manual just calls it "Capacitor, poly".  It is labelled "MIDWEC M8-26  .22uF +/-5% 50VDC 415".  I haven't found type M8, although other Midwec offerings seem to have been polypropylene.  Any ideas?

That's funny, I have one just like it somewhere!  It's the integrator capacitor for the A/D, low leakage and DA. I think mine says it's Teflon but it will be plypropylene at worst.

[NoisyBoy]

And the components in it all held up very well, I checked all the eletrolytic caps in my earlier 8000A, they were all within spec, and looked perfect on the outside. 

Granted it is low power application, but having components that lasted nearly 50 years is a testament to its build quality. 

[adinsen]

I have an issue with the elastomeric between the display controller PCB and the LCD on my Fluke 8060a. It has deformed/softened over time so it doesn't conduct. The result is missing segments. Unlike most elastomerics this one is cylindrical. I can rotate it by a quarter of a turn to solve the issue for a while, but it rotate back in the old position and then I loose the segments again. I have not seen anyone experiencing this. It seems defective LCDs are more common, but mine is actually fine. I may have missed a post here, though!

Update/edit: I have attempted a repair by inserting a piece of wire in the elastomeric hopefully forcing it to be a bit more round. Pictures attached