2020年11月22日 · To avoid solder on such and parts that should not carry any, a solder mask is used. That's essentially a layer of lacquer printed on top of the traces, wherever no solder needs to go. It also helps increasing fine details. In addition the PCBs are preheated, so the solder moves in right away. Naturally the traces heat better than the PCB.

2021年3月18日 · The modern PCB, as we know it, was a war time development and so was wave soldering as a way to lower production cost while maintaining consistent quality. All this predates computers, so when computer production became serious manufacturing, that is more than single unit with special to type board, PCBs and wave soldering was used.

Excess solder on the traces would be removed before the mask was applied, but usually not completely on large traces. So, after being masked, when the board was wave soldered to attach the electronic components, the original HASL solder, now underneath the solder mask, would melt again and reform unevenly under the mask during cooling.

2018年9月6日 · *2 - Wave soldering is a rather secure process and around since at least 1947 (oldest usage I know). It does require to have the whole board plus all of the placed components preheated to 130-160 degree Celsius (depending on the process) for several minutes. In combination with (somewhat) early chips, this may cause failure within the chips.

2018年7月8日 · Put it back together and it works, sort of. I can clearly see the picture that is supposed to be there but the blacks are not black in EGA graphics mode and there is an undulating wave. In non-graphics (text) mode, the blacks are black but the undulating wave is still there. Here's a video. How can I further troubleshoot this?

2020年11月21日 · if every machine will be sold preassembled, the vendor can invest in things like wave soldering equipment that can do the job much more efficiently than a user doing it once on the kitchen table. I think this is a key point. Back in the 1970s, you did not have the super-cheap build-it-in-China and ship extremely inexpensively that you have today.

2018年2月1日 · The main clock output consists of a 4.5V (Vcc @ 5V) square wave at a 33.3% duty cycle, with an additional peripheral clock running at half of the main clock and a 50% duty cycle. Additional logic is provided to accommodate delays to allow for proper system start-up."

2018年11月19日 · Stack Exchange Network. Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

2017年1月3日 · Note that the boards have extensive solder jumpers that can be used to allow it support various sizes of EPROMs and maskROMs. There actually are 2 security chips on a Playchoice cartridge. There is the small serial ROM, and there is also another standard 27C64 EPROM that is used by the Z80.

2019年11月27日 · Each of these is an unprotected point where corrosion can occur. Repeated heating and cooling cycles can unseat socketed components and connectors, or weaken iffy solder joints. Humidity can corrode exposed wire, pins, and traces. Many old printed circuit boards do not have protective solder mask layers, which leaves them exposed as well.