Progress log: Building the Xagdin prototype board v1.1

I am currently assisting with the development of the new 68030 SBC project by building one of the Xagdin prototype boards. Yoda (one of the principal designers) is building one as well. His build log is available here:

https://www.retrobrewcomputers.org/doku.php?id=builderpages:yoda:start

Initial board:

Memory SIMM installation - Pin one goes to the left. There is an alignment key on the pin 1 side of the SIMM socket to ensure the memory module is correctly installed.

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The schematic called for a 2.5K resistor for R44. As this is a non-standard value and was quite pricey from my usual sources, I “created” one from a pair of 5.1K resistors. Yoda found a source and is sending one to me, so I need to de-solder this one. Ugly, but should work just fine!

Yoda uncovered a problem with the switching diodes in the VGA subsection being reversed. Apparently they are wrong in the design documents from the chip maker. This will be fixed in the next release of the board. Unfortunately, I had already soldered them in before he found the issue, so I have some fixing to do.

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There was some confusion about the installation of J1, the 5V power jack. This is the correct alignment to ensure the board receives 5V and not 12V when plugged in to a standard PC power supply accessory cable. The board also includes an ATX power connector, so J1 will probably only be used for initial testing purposes.

One build tip I adhere to is using sockets for resistor networks. The breakable SIL sockets are available at low cost on eBAY. Resistor networks are a pain to de-solder when you accidently install the wrong one. It is also useful in some instances (such as when the resistor network sets LED brightness) to be able to change the network value for testing purposes.

The Xagdin board uses several high density surface mount chip packages, namely the CPLD, ethernet and VGA video controllers. To simplify installation, the use of SMD to through-hole adapter boards was employed. Below are the PQFP-100 and the TQFP-128 adapter board prototypes.

Checking the fit: Perfect! Now to solder the SMD chips on.

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Partial success. I was finally able to solder the CPLD onto the adapter, but the Ethernet chip is a bit trickier.

I have redesigned the adapter boards to make them easier to solder by using longer pads under the chip as shown below. This is the PQFP-100 board. The TQFP-128 has been similarly redone. These adapters will be included with the final release boards if they are still needed . (And yes, the pin number for the start of the fourth port should read 81, not 71. I made a little mistake with the numbering.)

Current status: All sockets are installed. Almost all resistors are installed. VGA, keyboard and mouse adapters are installed. I am soldering in the last few items, then I will run a voltage check across the board to ensure no solder bridges or shorts, burn the firmware and start the process to bring it up.