Yellow glue, a problem waiting to strike your vintage electronics

Many in the retro-computer community are aware of the dangers of Varta rechargeable batteries found on many older computer mainboards. These permanently soldered-on components have a tendency to leak as they age and wreak havoc as the acidic fluid corrodes and dissolves the copper traces on the board. As I learned today, there’s another hidden foe that may be lurking in some of your devices, particularly power supplies. This evil substance is a type of yellowish glue.

Yellow glue isn’t silastic, the typically white non-conductive silicone-based adhesive found in some higher quality applications. It seems to be possibly some type of neoprene rubber adhesive that is cheap and sets quickly making it a popular choice for low cost manufacturing of electronics. It’s typically applied to glue components in place for assembly, insulation and protection from vibration. The down side is that this material ages poorly, especially in hot environments and becomes hygroscopic. Once this happens, the material becomes partially conductive as it absorbs water which can lead to some pretty dramatic failures, especially if the material is on a mains or high voltage part of a circuit board.

I discovered this issue on some power supply boards I was troubleshooting. I had been going through the process of reworking them and was checking all of the components prior to powering up. One of the probes to my multimeter slipped off the diode I was measuring, but to my surprise I was still getting a reading. I jammed both probes into the browning mess of old glue and what do you know, it was conductive! It measured over a mega-ohm, but it was consistent. I started checking the other spots of glue and any that looked darker and crusty were conductive.

The other downside of this material is that it’s very difficult to remove without damaging components. In my application, I was able to use some stiff plastic spudger tools to scrape it away. It was very labor intensive and didn’t entirely remove it. I may try something like acetone on individual components like inductive coils, (to attempt to dissolve and remove it) but unsure if this would be safe to just douse the board with.

The end of VMWare as we know it

I have to admit the acquisition of VMWare by Broadcom came as a surprise. I had missed the news earlier in the year of a possible acquisition which has now come to pass. This event pulls a younger and more progressive company, VMWare under the umbrella of a more traditionally conservative and cutthroat corporate behemoth, Broadcom. When I first heard the news, I couldn’t imagine why Broadcom, known for their semiconductor manufacturing business would be interested in a software company such as VMWare. As this saga has progressed, it seems Broadcom is wanting to get into the enterprise cloud virtualization space. Unfortunately for VMWare and their employees, what Broadcom CEO Hock Tan has in mind looks very little like the VMWare they’ve known.

Hock Tan has taken Broadcom from a spin-off of HP (Agilent, which formed the basis of Avago) and grown it through acquisitions. In fact, that’s been Tan’s business strategy from the beginning. Tan seems to be more of an acquisitions-focused CEO, concerned only with maximizing profit and has no real concern for engineering or technology innovations. He sees something of value in another company and goes after it, ruthlessly stripping away anything not core to that feature and selling it off post-acquisition. Reading through their history, you’d almost have expected Richard Gere to pull up to VMWare HQ in his Lotus and begin the process of chopping up the company.

In a previous role, I worked with VMWare a lot. The company revolutionized the traditional IT industry by enabling companies to save money and be more fault tolerant all while using less physical hardware to support their services. I remember being excited by the possibilities it opened up for me as the then IT admin for an academic department within a relatively small college. VMWare invested in their customers too, supporting user groups who in turn helped the company through word of mouth.

VMWare has been the victim of their own success to a degree. The technology they spawned is now a base expectation for IT pros. Many other companies make products that compete in the same space, though arguably perhaps not as well. However, despite that dominance, the industry has largely moved beyond full system virtualization to the containerization of individual services with products like Docker and Kubernetes. There has also been a push over the last decade or more to move services onto the infrastructure of cloud providers like AWS, Azure or Google Cloud. While VMWare can have a role in both situations, they aren’t the only game in town and depending on the application, may not even be necessary.

Broadcom seems to be interested in VMWare’s core enterprise virtualization products. However, the move to spin off desktop and other non-core products, dropping support options for existing products and moving to a subscription only model, the harsh requirements ending remote work for employees, and the exodus of talent from the company paints a grim picture for the biggest name in the virtualization space.

Chamberlain Smart Garage Control teardown

With the recent Chamberlain API lockdown, I thought it might be interesting to tear down one of their controllers to see what makes it tick. Thankfully I happen to have a spare unit sitting new in the box. Why do I have a spare unit you might ask? The standard package comes with what Chamberlain calls a WiFi hub and a single door sensor. I have 2 garage doors, each with openers. At the time a spare door sensor was most of the cost of the whole package, so I just bought the whole thing again.

The WiFi hub is incredibly simple to disassemble. There are just 2 screws that hold the faceplate to the frame. Once you remove the faceplate, a single snap lever retains the main PCB. Once I had the main PCB separated from the frame, it was easy to pick out the core components.

The system is based on a PIC18 microcontroller. In this case the Microchip PIC 18F67J11-1/PT. The PIC18 is a 16-bit RISC CPU compatible with the earlier PIC16. It has 128KB flash onboard and 4KB of RAM. While it’s no powerhouse, the CPU does offer 4 interrupt lines, 5 PWM, Parallel and Serial ports with SPI and i2C support.

Linked to the PIC18’s i2C bus is a 24C16K SPI Flash ROM. I had a compatible harness for this and dumped the contents which were mostly empty. I’m assuming this rom is used for configuration data, possibly to store the opener codes programmed in during initial setup.

The remaining modules of interest were an Si4432 433mhz transceiver chip (left) and an Fn-Link 6220N-IS 2.4Ghz WiFi 5 module. (right) These enable comms with your network and most garage door openers.

So, what can we do with this knowledge? Well, given the CPU has a built-in flash, we could attempt to dump the contents of that storage and see if there’s anything useful we can decipher from it. There are test points on the board that appear to be connected directly to the CPU for programming. I’m going to attempt to verify this against the datasheet for the PIC18 and see if that’s the case. To be continued…