Looks like a glorified logic probe with some DMM and basic logic analyzer functions?
What makes it so bad?
I have one too and still consider it useful when no LA or MSO is available. Of course, with the demise of classical digital circuitry, those situations became rarer.
Until the LCD failed on my LogicDart, it was probably my most used piece of test gear. I found it really useful when doing board bring-up or firmware dev, and was really handy to have for any low voltage work when visiting client sites. For I2C or SPI or other protocol decode it doesn't come close to a Saleae or MSO, but it helped me diagnose a huge number of HW & FW issues over the years.
I miss my LogicDart
If we talk about scopes... I would add here HP54601A, it is claimed to be a 4 x 100MHz scope but it's sampling rate is only 20MS/s 
and it has about 4k of memory.
The sampling rate of the HP54600 series is rather poor (even with random repetitive sampling) and the 4kpts of memory are also relatively low (keeping in mind that contemporary digitising oscilloscopes like the Tek 2430 only had 1kpts), but despite all of that, they are a joy to use, relatively easy to work on and quite robust. Typical failure points are two vertical stage CRT caps and the Dallas NVRAM (both easy enough to replace/upgrade).
HP specifically designed the 54600 to introduce analog scope users to digitising ones at a reasonable price while offering a familiar interface.
Not trying to be an HP shill, but I think the 54600 series is far from being one of their worst products.
Until the LCD failed on my LogicDart, it was probably my most used piece of test gear. I found it really useful when doing board bring-up or firmware dev, and was really handy to have for any low voltage work when visiting client sites. For I2C or SPI or other protocol decode it doesn't come close to a Saleae or MSO, but it helped me diagnose a huge number of HW & FW issues over the years.
I miss my LogicDart
The LCD is the same one as that used in an HP48. Prices on those have risen somewhat but they're still pretty common, and some even have the higher contrast black LCD. Maybe you could repair it with HP48 parts. Also, I thiink the HP48s tend to fail with zebra-strip connection problems so maybe the same techniques would repair your Dart.
I always wanted one, just because they seemed to address things that I worked on. But you're the first person I've seen finding them really useful so I haven't been willing to pay the going rate even on the rare occasions that I've seen one for sale.
It makes me wonder, though, if it's a concept that could be revisited. The Saleae analyser, as you say, is absolutely wonderful. That's a combination of a nice bit of mechanical engineering and some superb software. The later analog versions take that to another level. I don't know if it would be so good as a handheld or a phone accessory but .. maybe. The point is, it's relatively low tech (first version was very little more than an FX2 board) but has been designed and refined by someone who really knew what they wanted.
Maybe a thread somewhere else on designing a kick-ass logic probe ? A Flipper-zero for wired signals ?
The LCD is the same one as that used in an HP48. Prices on those have risen somewhat but they're still pretty common, and some even have the higher contrast black LCD. Maybe you could repair it with HP48 parts. Also, I thiink the HP48s tend to fail with zebra-strip connection problems so maybe the same techniques would repair your Dart.
Interesting. I did try swapping in a display from a HP38G and it didn't work. I also have a HP48G which suffered PCB damage from a leaky battery, but the display should be fine. I don't recall if I tried that one... thanks for the tip.
I always wanted one, just because they seemed to address things that I worked on. But you're the first person I've seen finding them really useful so I haven't been willing to pay the going rate even on the rare occasions that I've seen one for sale.
I bought it on eBay nearly 20 years ago for AUD300, and got plenty of use out of it before the LCD went dark a few years ago. I tried to replace the polarizing film in the hope that might help, but I ended up cracking the screen.
For Tektronix, their stuff seems electrically excellent. But mechanically, that is another story. Repair and maintenance of some of their earlier scopes (the 7000 series or the 22xx/24xx series) is a chore. Cam switches, endless brackets and screws, stuff packed into the chassis like sardines, etc. And I am not a big fan of the 500-series mainframe and plug-ins. Although I suppose it is nice to have a 6-bay mainframe packed with a variety of plug-ins, I find the individual plug-ins to be somewhat lacking in performance and I would rather use a dedicated piece.
The mechanics of the 7000 series was bizarre. Who thought beautifully and expensively machined actuators for bottom of the barrel 1 cent consumer slide switches made sense? The reliability was horrendous. Most repairs were things like replacing those slide switches which had been ripped apart by the nicely machined actuator.
If we talk about scopes... I would add here HP54601A, it is claimed to be a 4 x 100MHz scope but it's sampling rate is only 20MS/s and it has about 4k of memory.
The sampling rate of the HP54600 series is rather poor (even with random repetitive sampling) and the 4kpts of memory are also relatively low (keeping in mind that contemporary digitising oscilloscopes like the Tek 2430 only had 1kpts), but despite all of that, they are a joy to use, relatively easy to work on and quite robust. Typical failure points are two vertical stage CRT caps and the Dallas NVRAM (both easy enough to replace/upgrade).
HP specifically designed the 54600 to introduce analog scope users to digitising ones at a reasonable price while offering a familiar interface.
Not trying to be an HP shill, but I think the 54600 series is far from being one of their worst products.
That demonstrates the arrogance of both HP & Tek, when they were pushing their early DSOs.
Although the interfaces were clunky in many such instruments, it was not an "unfamiliar interface", but the poor performance in real world scenarios that put people who normally used analog 'scopes to look at signals like analog video off DSOs.
The attitude was "You are just used to using obsolete methods---get with the future".
Being told that the horrific mess of aliasing on the screen was an equally viable way of displaying the information was insulting to people who used Oscilloscopes every day as part of their job, turning off many who had been enthusiastic about digital instruments.
It seems that was the beginning of the dominance of Sales over Engineering at both companies.
I think its pretty insane to just re write the visual language of the electrical world.
IMO its kind of like pushing for a language change, grunts, faces and hand waving, when people are used to latin. The amsuing part is that like doctors of science were effected. I find it amusing if they switched a surgeons language set to grunts and hand motions. Is he talking about the spleen or a kidney?!
I tried to do a XY plot on a cheap DSO. I felt like I was working with some malfunctioned bullshit. The standard offering is basically something you see on star trek consoles after they get by disruptor fire. Spock might feel like dealing with that bull shit if the warp core is about to explode and it killed the previous operator. Did someone throw a pound of LSD into the ventilation system?
Agilent U1602B, piece of junk:
Slow CPU
Terrible rubber silicone Keyboard, gotta press really hard to switch.
Worst case material in history, brittle polymer, would break at any load.
Please remember that at the time it was introduced, the 500 stuff was leading edge.
Yes, it should have been put out to pasture before the first moon landing, but in the 50s and early 60s it was something else.
If we talk about scopes... I would add here HP54601A, it is claimed to be a 4 x 100MHz scope but it's sampling rate is only 20MS/s and it has about 4k of memory.
The sampling rate of the HP54600 series is rather poor (even with random repetitive sampling) and the 4kpts of memory are also relatively low (keeping in mind that contemporary digitising oscilloscopes like the Tek 2430 only had 1kpts), but despite all of that, they are a joy to use, relatively easy to work on and quite robust. Typical failure points are two vertical stage CRT caps and the Dallas NVRAM (both easy enough to replace/upgrade).
HP specifically designed the 54600 to introduce analog scope users to digitising ones at a reasonable price while offering a familiar interface.
Not trying to be an HP shill, but I think the 54600 series is far from being one of their worst products.
That demonstrates the arrogance of both HP & Tek, when they were pushing their early DSOs.
Although the interfaces were clunky in many such instruments, it was not an "unfamiliar interface", but the poor performance in real world scenarios that put people who normally used analog 'scopes to look at signals like analog video off DSOs.
The attitude was "You are just used to using obsolete methods---get with the future".
Being told that the horrific mess of aliasing on the screen was an equally viable way of displaying the information was insulting to people who used Oscilloscopes every day as part of their job, turning off many who had been enthusiastic about digital instruments.
It seems that was the beginning of the dominance of Sales over Engineering at both companies.
HPs first digital oscilloscopes were a mix of things that looked and felt like traditional analogue oscilloscopes and things that looked and felt like a logic analyser. I loved the logic analyser style ones, but they sunk without trace so badly in the market its hard to even find references to them on the internet. So, they played up the products real engineers put real money into.
RE the 8640B slide switches --- fighting that battle right now - a photo of a replacement metal part will save me some thinking about what might work ---aluminum, brass? bent up out of shim stock?
it looks like these are made out of two pieces somehow molded together based on the different colors of plastic. The key to "experimenting" is that it is so hard to get at these that it's pretty much impractical to try something and fail.
now updating it with some pictures of a kludy but hopefully effective repair - one was missing the handle, one had a broken handle.
.010 brass shim stock and a slice cut from the "handle" part of an old key and we have (see photos)
RE the 8640B slide switches --- fighting that battle right now - a photo of a replacement metal part will save me some thinking about what might work ---aluminum, brass? bent up out of shim stock?
it looks like these are made out of two pieces somehow molded together based on the different colors of plastic. The key to "experimenting" is that it is so hard to get at these that it's pretty much impractical to try something and fail.
Try to replace it with a PCB - DIY from clad, or draw it up and order online. You can solder(carefully!!!) the contacts in place, or, if you find proper rivets, rivet them in place.
thanks - I updated my post just above to include the attempt to repair with shim stock - I'm waiting for the epoxy to finish drying before I reinstall and see what happens. it looks like it ought to be OK, and if so, the metal should last a lot longer than that plastic did... not only is it old plastic, but in a prior life it must have been near a window and the sunlight doesn't help either.
second hint for this signal generator ... there are white plastic gears that make up a differential, and the gears split - I just removed the gear and set the brass insert on my soldering iron and let it heat up, the gear wants to close back to how it was molded and that's what it did, it's all good now. try it.