Keithley 179 bench multimeter

[Zenith]

I found this at a swapmeet about a year back. It was the only piece of TE on a stall selling vintage domestic radios. The stallholder said he wanted £5 for it. It's a Keithley and I thought it had to be worth that, so I bought it.

It's a 4½ digit True RMS multimeter with a crest factor of three, so not great in that respect.

It has the sealed lead acid battery option. The cells weren't leaking, but I assumed they were long dead. I disconnected the battery pack and had no intention of messing with it. It adds to the weight of the unit and helps stop it moving about the bench when the buttons are pressed, so I left it.

On powering it up it came to life and more or less worked. One of the red LED 7 segment displays wasn't working properly, so I replaced it with one from the collection. It's a slightly different style and has a slight slant, but it's not noticeable. There was nothing wrong with the supply lines (-15V, 5V and 15V). I set it up against newish Brymen 867s and a cheap voltage standard based on a Maxim MX485KH reference. You're supposed to use a calibration screen, but the one on this unit was missing. It seemed to work well enough, but offered no particular advantage over the Brymen, so i set it aside.

I came across it again a few days back, and powered it up. The display flashed on all ranges, indicating an overload, I looked on the web and thought it might be the ICL8052ACPD 4½ digit A/D converter.

https://samueldperry.com/2019/01/12/ben ... 79-repair/

These are available on ebay for about £20 each.

Panic subsided and sense returned, and I checked the power lines. The -15V line was wrong. It turned out to be a tant. I replaced both tants in -15V line with higher capacitance electrolytics. Everything was OK for a couple of hours until the display started flashing again. This time it was the +15V line. I looked and one of the tants was a different colour to the others, it was black. It wasn't burned, that was the colour it was made with, so I suspect it was a replacement. I replaced the remaining four tants with suitable electrolytics and everything was back to normal. There's a place in the world for tants, but I don't see it as being across linear power supply lines. It was left on overnight and there were no more problems.

The replacement electrolytics are ringed in red.

DSCN3971A.JPG

View of the unit showing the battery pack.

DSCN3970.JPG

View on the Ohms range connected to a 100K resistance standard.

DSCN3964.JPG

I had a scrambled pile of resistors to sort out. This is a pain since I'm red green colour blind and regard the resistor colour code as an invention of the Devil. I found the Keithley was convenient for that. The display is easy to read and since it's mains powered, it doesn't turn itself off annoyingly, or consume batteries. It seems convenient for some things. I must put an effort into getting my Solartron 7150 Plus to work, or look put for a better bench multimeter. Keithley 179s seem to sell well on ebay.

[AVGresponding]

Nice! Well worth a fiver and the time spent in repairing it imo, Keithley meters always seem to have better low ranges than other brands, and 4.5 digits in LED is definitely a go-to for me too for quick and dirty measurements (Black Star 4503 in my case)

[MED6753]

There's a Keithley 175 on my local CL about 15 minutes away from a seller I've done business with before and he's legit. Price is good and supposedly works. Can't make up my mind to go for it or not. I have plenty of DMM's here but no Keithley's. Did I just say that?

https://hudsonvalley.craigslist.org/ele ... 05797.html

[BU508A]

There's a Keithley 175 on my local CL about 15 minutes away from a seller I've done business with before and he's legit. Price is good and supposedly works. Can't make up my mind to go for it or not. I have plenty of DMM's here but no Keithley's. Did I just say that?

https://hudsonvalley.craigslist.org/ele ... 05797.html

Go for it, you won't regret it.
At least, you can paint it smurf blue.

[Zenith]

There's a Keithley 175 on my local CL about 15 minutes away from a seller I've done business with before and he's legit. Price is good and supposedly works. Can't make up my mind to go for it or not. I have plenty of DMM's here but no Keithley's. Did I just say that?

https://hudsonvalley.craigslist.org/ele ... 05797.html

I'd be tempted. It's autoranging, which is convenient. It looks a step up from the 179. The thing with DMMs is that they are mostly quite small.

Something I forgot to mention about the 179 was that the current range was dead. That turned out to be because of a blown 2A fuse. With that fixed it worked and was in fairly close agreement with the Brymen.

[MED6753]

Decided to make an offer. We'll see.

[MED6753]

Rather than start a new thread I'll continue here.

The Keithley 175 is here. In VG condition and initial checks of DCV and Ohms shows that it's spot on. I'll be doing my usual clean up and re-cap. While I'm not thrilled with the brown case it will remain as is. At least it's much better than the awful Fluke beige.



Internal view.

[Zenith]

Excellent! Although I must say I prefer LEDs to an LCD.

Bench multimeters have never been things that registered and I only bought the 179 because it was cheap, but I've since come to realise its delights.

BD139 and tggzzz have been fully into these things for a long time. I feel ashamed at the way I haven't got that Solartron 7150 Plus on song yet. My antennae are twitching for more and I'm even looking at ebay.

This TEA thing.......

[tggzzz]

I had a 7151 once. Perfectly good, but it irritated me. I can't explain why I didn't like it, and that irritates me even more!

Anyway. Let me know when you want to calibrate and/or adjust it.

[BU508A]

I assume, this is the voltage reference (the red diode)? Looks like an 1N82XA type.

Edit:
I'm a bit confused. The subject is saying "Keithley 179" but then you are showing us a Keithley 175?

Screenshot_20240810_131716.png

Seems, it is a 1N4577:

Screenshot_20240810_133529.png

[MED6753]

Excellent! Although I must say I prefer LEDs to an LCD.

Agreed. And no backlight is provided which makes it hard to read in low light conditions. I have the same complaint with my Fluke 8010A and 8050A.

[BU508A]

Sorry, seems I have taken a wrong turn (179 vs. 175)

Summertime needs to be ending, it is too hot.

[MED6753]

Sorry, seems I have taken a wrong turn (179 vs. 175)

Summertime needs to be ending, it is too hot.

Since both are Keithley's I decided to add to this thread rather than start a new one.

[25 CPS]

Excellent! Although I must say I prefer LEDs to an LCD.

Agreed. And no backlight is provided which makes it hard to read in low light conditions. I have the same complaint with my Fluke 8010A and 8050A.

Hewlett Packard also had a line of bench meters in the 1980s that were the same. No backlight made the LCD displays on the 3478A and 3457A tough to read under anything less than ideal lighting conditions.

It's interesting how so many (all?) of the big manufacturers jumped on the LCD with no backlight bandwagon in the early 80s after they all used LEDs after they all used Nixies, but before they all moved to VFDs. Nobody, not one that I know of dissented and decided to sick with LEDs over the ease of readability concerns with non-backlit LCD displays. In portable battery powered applications like calculators or handheld DMMs, it makes sense given the power consumption and battery life difference but that's not an issue with line powered bench equipment, and yet, nothing but LCDs across the board whether they were needed and desirable or not from that time period.

[AVGresponding]

The 175 can probably be modded like the 197 for backlighting. I don't know if you need to use the screen out of a 197A to do this though

[MED6753]

The 175 has been re-capped. Reassembled and will burn in for 24 hours then verify calibration.



The banished to the trash.

[Zenith]

One nice point about it is that it accepts shrouded leads, which are the easiest to get these days.

Last year I bought a Micronta (Radio Shack) FET analogue multimeter, in its original box and with the leaflet/manual, but with no leads. I cut the shrouds of an old pair of leads which were becoming stiff, and so were definitely for occasional use. I don't think it would have been possible to fit shrouded sockets to the Micronta, and they would almost certainly have cost more than I paid for it.

[MED6753]

Finally got around to checking the calibration of the 175. It sat for 3 days straight powered up due to a distraction of working on Blondie's Honda Accord. It had an electrical issue which took some time to fix. I'm getting too old to be bending under the hood of a car and my back is letting me know it ain't happy.

Anyway, the calibration procedure of the 175 is closed case via calibration constants loaded into EAROM. No trimmers. I'm familiar with this mode of calibration as the DMM option on the Tek 2465 DMS uses that same method.



Tools used. Home built DCV reference of 190mV, 1.9V, and 19V. Home built 190V reference. I don't have a 1000V reference so that wasn't checked. Home built Ohms reference. I don't have ACV references other than 1.00V so that's all that was checked.





Keeping everything honest by cross checking with the hp 3456A.



Results. No adjustments were required. Every parameter checked was in spec. The furthest off was +1.8998VDC vs. +1.9000VDC. Not a big deal. This project is complete.

[tggzzz]

Tools used. Home built DCV reference of 190mV, 1.9V, and 19V. Home built 190V reference. I don't have a 1000V reference so that wasn't checked.

My Fluke null volunteer has in inbuilt 1kV supply; it has to, how else could it measure a 1kV input voltage with zero current at null?

I wonder if that could be "additionally purposed"?

[Zenith]

Well you know the way it is. The technical guys have produced this thing as good or better than the opposition. The sales and marketing guys have to sell it and it's obviously not a nail. Most of them are not technically illiterate, but there are reasons they are in sales rather than R&D, and there are questions it's better not to ask, or must be deflected, if they want to make their quota. This 1000V business, well it's more or less bound to be done by extrapolation but our guys are constantly in contact with the NIST etc. Basically, who's interested in measuring anything like 1kV to anything like the precision expected at less than 20V? If they were, they'd be building their own gear and in any case, there aren't enough to launch a class law suit.

I wonder if that could be "additionally purposed"?

That has a ring to it, along the lines of "our classic models and now our enhanced models for those customers demanding more than merely the best".

[MED6753]

I'd rather find a precision ACV cal source at a reasonable price. Good luck.

[tggzzz]

Well you know the way it is. The technical guys have produced this thing as good or better than the opposition. The sales and marketing guys have to sell it and it's obviously not a nail. Most of them are not technically illiterate, but there are reasons they are in sales rather than R&D, and there are questions it's better not to ask, or must be deflected, if they want to make their quota. This 1000V business, well it's more or less bound to be done by extrapolation but our guys are constantly in contact with the NIST etc. Basically, who's interested in measuring anything like 1kV to anything like the precision expected at less than 20V? If they were, they'd be building their own gear and in any case, there aren't enough to launch a class law suit.

The metrology guys are always interested. My KVD is 100kohm input at up to 1kV. The first resistors are in an oil bath, to minimise heating effects and maximise transport costs (and increase the chance of a hernia)

My Datron calibrator is also 1kV; I've yet to pluck up courage to work on it, since no manuals are available.

I wonder if that could be "additionally purposed"?

That has a ring to it, along the lines of "our classic models and now our enhanced models for those customers demanding more than merely the best".

You are too kind. I was thinking of "bodged".

[Zenith]

You are too kind. I was thinking of "bodged".

"bodged" is not a marketing term. There isn't a single word that would fit, but phrases occur; "stretching hitherto accepted limits of performance" and "adventurously designed". "Value engineered" has an appeal, but there are obvious limits, e,g, the luxury yacht of bullshit could too easily be wrecked on the rocks of reality, when messing with 1kV.

[tggzzz]

You are too kind. I was thinking of "bodged".

"bodged" is not a marketing term. There isn't a single word that would fit, but phrases occur; "stretching hitherto accepted limits of performance" and "adventurously designed". "Value engineered" has an appeal, but there are obvious limits, e,g, the luxury yacht of bullshit could too easily be wrecked on the rocks of reality, when messing with 1kV.

True, but using an internal (1kV) voltage reference as an external voltage source/reference is, I think, serious hillbilly engineering.

In the null voltmeters case, the KVD is 1Mohm, the KVD (or fingertip) only takes 1mA. OTOH, that is supplied from a 470nF capacitor via a 10k resistor, so that could give a noticeable belt for a short time!

That capacitor: ~1mJ.
Pacemaker: ~0.2mJ
External defibrillator: 10-100J

So, how lucky are you feeling today (punk).

[AVGresponding]

My Datron calibrator is also 1kV; I've yet to pluck up courage to work on it, since no manuals are available.

Send it to Chris to fix it; he never reads manuals (deliberate out of context quote from Discord chat, that we're beating him over the head with)