These days, oscilloscope hacking is all about enabling features that the manufacturer baked into the hardware but locked out in the firmware. Those hacks are cool, of course, but back in the days of analog scopes, unlocking new features required a decidedly more hardware-based approach.

For an example of this, take a look at this oscilloscope beam splitter by [Lockdown Electronics]. It’s a simple way to turn a single-channel scope into a dual-channel scope using what amounts to time-division multiplexing. A 555 timer is set up as an astable oscillator generating a 2.5-kHz square wave. That’s fed into the bases of a pair of transistors, one NPN and the other PNP. The collectors of each transistor are connected to the two input signals, each biased to either the positive or negative rail of the power supply. As the 555 swings back and forth it alternately applies each input signal to the output of the beam splitter, which goes to the scope. The result is two independent traces on the analog scope, like magic.

More after the break…

If you’re wondering how this would work on a modern digital scope, so was [Lockdown Electronics]. He gave it a go with his little handheld scope meter and the results were surprisingly good and illustrative of how the thing works. You can clearly see the 555’s square wave on the digital scope sandwiched between the two different input sine waves. Analog scopes always have trouble showing these rising and falling edges, which explains why the beam splitter looks so good on the CRT versus the LCD.

Does this circuit serve any practical purpose these days? Probably not, although you could probably use the same principle to double the number of channels on your digital scope. Eight channels on a four-channel scope for the price of a 555? Sounds like a bargain to us.

If you’re a fan of vintage electronics and DIY tinkering, you’ll find this teardown by [Thomas Scherrer] fascinating. In a recent video, he delves into a rare piece of equipment: the Data Lab Transient Recorder DL 901. This device looks like a classic one-channel oscilloscope, complete with all the knobs and settings you’d expect.

The DL 901, made by Data Laboratories Ltd., is a mystery even to [Thomas], who couldn’t find any documentation online. From the DC offset and trigger settings to the sweep time controls, the DL 901 is equipped to handle slow, high-resolution analog-to-digital conversion. The circuitry includes TTL chips and a PMI DAAC 100, a 10-bit digital-to-analog converter. [Thomas] speculates it uses a successive approximation technique for analog-to-digital conversion—a perfect blend of analog finesse and digital processing for its time.

Despite its intriguing features, the DL 901 suffers from a non-responsive analog input system, limiting the teardown to a partial exploration. For those who enjoyed past Hackaday articles on oscilloscope teardowns and analog tech, this one is a treat. Watch the video to see more details and the full process of uncovering this vintage device’s secrets.

Modern computers are so fast and complex that we would seldom try and fix them on a component level with simple DIY tools. Working on an early 1980s computer is much easier by comparison, with the fastest signals often in the single-MHz range. [Sayaka] demonstrates this by using a cheap $20 oscilloscope to troubleshoot and repair a Commodore 64.

After powering it up for the first time, the C64 displays a BASIC prompt, but none of the keys seem to work. [Sayaka] did what good hackers do, and immediately disassembled it to try and figure out the problem, suspecting the CIA chip as a likely culprit.

[Sayaka] elected to purchase a cheap DS0138 oscilloscope kit to help troubleshoot the C64. It’s not the most capable thing, with a bandwidth of just 200 KHz, but it’s enough to do some work on an old retro machine. After probing around to check a number of signals, she noted that the CIA’s pins seemed to be very oxidized and suffering poor conductivity. All it took from there was a resolder job, and the computer was repaired.

We’ve seen other cheap scopes with altogether more impressive specs, too. Video after the break.

[Adrian] had a Commodore computer to fix and decided to see how his latest tiny portable scope would work. He paid $57 for the tiny little test instrument although the current price seems higher. It claims to have 120MHz bandwidth along with 500 megasamples per second. There are several versions with different claimed specs, but we did find a similar device for under $60. You can see the unboxing and how it worked in the video below.

Of course, these kinds of instruments often overstate their specs, and [Adrian] was also suspicious. One odd feature of the device is it can echo its output to an NTSC video output so you can send the screen to an external monitor.

If you want to skip the scope unboxing, forward up to about 19 minutes to see the inside of the Commodore 64. The scope was easily sufficient for scanning the chips in the computer and revealed a suspicious address line. The line went to a PLA and a mux chip, neither of which were in sockets. He clipped the PLA out of the circuit, and the address line started looking normal. So the conclusion was the PLA was dead.

After that, it was straightforward to remove the chip and replace it. Well, technically, replace it with a socket to make a future repair easier. Will a $57 scope replace your big benchtop instrument? Maybe not. But it was a useful tool for troubleshooting.

Even if you don’t want a cheap scope, you can learn a lot from [Adrian’s] thoughtful troubleshooting and analysis if you are faced with any digital repair project. We do like cheap scopes around here. It is amazing how much scope $100 will buy now compared to just a few years ago.

One of the best things about the Internet — especially the video part — is that you can get exposed to lots of things you might otherwise not be able to see. Take oscilloscopes, for example. If you were lucky, you might have one or two really nice instruments at work and you certainly weren’t going to be allowed to tear them open if they were working well. [The Signal Path], as a case in point, tears down a $30,000 MSO6 8 GHz oscilloscope.

Actually, the base price is not quite $30,000 but by the time you outfit one, you’ll probably break the $30K barrier. Compared to the scopes we usually get to use, these are very different. Sure, the screens are larger and denser, but looking at the circuit boards they look more like some sort of high-end computer than an oscilloscope. Of course, in a way, that’s exactly what it is.

The real trick to building an expensive 8 GHz is the signal integrity. But the most visible part of the design is thermal management. The entire box is full of heat sinks and other thermal management gear.

The board inside actually can accommodate six inputs, even though the scope was only set up for four inputs. No software hack here, though. The boards are lacking the connectors and the special ICs that manage the front end.

The video is nearly an hour long, and goes into a lot of detail. Looking at the analog front end design is surprisingly enlightening, especially since there are two unpopulated sections so you can deduce the wiring easily without removing any parts.

We used to think we were in clover buying surplus Tektronix or HP scopes from the 1970s back in the 1990s. We wonder how long it will be before these become staples at hamfests and on eBay?

If you want to contrast that to a more common scope, look at the insides of this OWON.You can also shop for something more affordable if you are in the market. Just don’t expect it to look or perform like this scope!

In the world of oscilloscopes, as in the rest of the test equipment world, there’s always some trickery afoot. Companies will often offer different models to the market at different price points, in an effort to gain the widest possible customer base while also making the most profit. Cheaper, less capable models are often largely identical to more expensive hardware, save for some software or a couple jumpers that disable functionality. [Alexandre] found just this when working to repair his HP 16533A scope card.

Work began when [Alexandre] received his HP 16533A in the mail after a long wait, only to find the trigger functionality was inoperable. This is crucial on a digital scope, so this simply wouldn’t do. After some research online, a post was found discussing which signals to probe to troubleshoot the issue. It noted that corrosion is a common problem on these units, and that occasionally, a certain resistor goes open circuit and causes problems. Initial measurement showed there was still resistance there, but reading closer, [Alexandre] noted this fateful line:

You might not be able to measure it accurately in circuit. 

Removing the 100K resistor from the board, the part was indeed open circuit. After replacement with a new component, the trigger circuit was again fully operational. With the scope still open, it was then a simple job to execute a further resistor swap which gives the 16533A the functionality and range of the higher-spec 16534A model.

It’s very common for oscilloscopes and other test hardware to be configured this way from the factory. Rigol scopes are particularly popular with hackers for this very reason.

[Thanks to jafinch78 for the tip!]

It’s that time of year again, and the Christmas hacks are flooding in thick and fast. To get into the Christmas spirit,  the FoxGuard team wanted a custom ornament to hang from the tree. They may have gotten more than they bargained for.

It’s a simple build that demonstrates the basic techniques of working with DACs and scopes in a charming holiday fashion. A Tektronix T932A analog oscilloscope is pressed into service as a display, by operating in XY mode. A Teensy 3.5 was then chosen for its onboard digital to analog converters, and used to output signals to draw a Christmas tree and star on the screen.

Old-school coders will appreciate the effort taken to plot the graphics out on graph paper. While the hack doesn’t do anything cutting edge or wild, it’s impressive how quick and easy this is thanks to modern development methods. While the technology to do this has existed for decades, a hacker in 1998 would have spent hours breadboarding a PIC microcontroller with DACs, let alone the coding required. We’ve come a long way.

It’s a bit of fun, but we highly recommend you don’t try and hang an analog scope off your tree at home. These WiFi-controlled ornaments are perhaps more suitable. Video after the break.