Author Archives: Mike

Automobile design for serviceability

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After several years of being broken, I finally took the time to repair the remote starter on my 2004 Malibu.

Based on internet searches, I had a pretty good idea that the problem was in the switch that detects whether the hood is open or closed. This switch is designed to protect anyone that is working under the hood from harm due to a remote start event.

The first step of this job is to remove the hood latch, since the switch is integrated in with it. This wasn’t too difficult, but disconnecting the remote release cable was tricky and the connector for the switch harness was underneath a plastic bezel that couldn’t be removed. However one side of the bezel was bolted down. I unbolted it and pried the bezel up so I could get at the connector, which was underneath.

I now had the latch out and examined the integrated switch, which was riveted on. Testing the the three leads coming off switch with an ohm meter revealed no connection, no matter what position the switch was in. I wondered if it could be fixed, so I decided to drill out the rivet and remove it from the latch assembly. Then I cut off the plastic rivets that held the sides of the case together to get a look inside.

The mechanism was rather interesting, it held two sealed magnetic switches mounted on small PC board. One of the two switches was activated at any time by a magnet that moved with the latch mechanism. The sealed switches were defniately designed for the hostile environment at the front of my car. However, the weakness of the design was that traces on the PCB were exposed to whatever could get into the switches. They had corroded to the point of failure.

Well I got out my soldering iron and soldered some wire where the traces were supposed to go. Then I attached the switch to the cars electrical system and sure enough, the remote starter came to life for the first time in a number of years.

With the fix proven, I used crazy glue to put the switch case back together and attached the switch back to the latch with a small screw and nut, dropping a bit a glue on the exposed threads so it wouldn’t work loose in the future. I then reassembled everything and successfully verified the fix.

Now what about the title. I have several complaints about this design in terms of servicability.

Though removing the latch was not that difficult, it was made more difficult by the limited space available to access the three bolts holding the latch to the car. Getting under the plastic bezel to access the electrical connector was also a pain. Riveting this switch to the latch ensures that normal people will have to replace the latch with the switch, increasing cost of repairs by quite a bit.

All in all this isn’t too terrible a repair job. It just took longer than it should have, because the overall design wasn’t optimized for serviceability.

Interesting city point photo

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While investigating maritime actives at City Point, I discovered an image of an apparent blockade runner at City Point. Here is crop of that image.

USS Banshee

USS Banshee

I think it is the USS Banshee, which was a captured blockade runner put to use by the US navy.

City Point web pages reorganized

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Note that since the proposed City Point layout involves a busy maritime port, I’ve been investigating Maritime activities. Though I’ve been reading about the Civil War for many years, I just discovered how little I knew about the war on the water. My revised City Point web pages now include the beginnings of a “maritime” page.

Let me know what you think.

Mimeo 1 iPhone case spotted

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Mimeo 1 iPhone Case

Mimeo 1 iPhone Case


I have nothing to do with this, other than the business stole the image off my website. This net thievery normally annoy’s me, but this time, I’m just amused. There are plenty of authenitic Apple 1 images floating around the web that could be stolen, instead of an image of a Mimeo 1.

http://crankcases.co.uk/iphone-cases-2.html

P.S. If someone asks to use an image or article, I almost always say, just credit the source and I’m fine with it.

Craftsman Structure Convention in Mansfield, MA

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Spent some time Friday Evening building a Alkem Scale Models water tank and Saturday where I learned about backdrop painting, visited the vendors and heard Bernie Kempinski give his Civil War talk. I enjoyed meeting and talking with Bernie and the other modelers present. Building the Alkem water tank was a lot of fun. I learned quite a bit from everyone.

Yesterday I painted and completed assembly of the water tank and I think it turned out great. This is probably the best looking structure I’ve ever built.

Water Tank

Water Tank

This will certainly help to inspire me to get moving on the City Point model. The first part of the City Point layout I’m planning to do will be the lead in tracks. This area is probably the most basic and will allow me to experiment without having to redo a lot of structures and details. I ordered several flat cars from Bernie, as several images show flats cars parked there.

Going to this convention might be the trigger that gets me off my butt and going on the City Point model.I have torn a Mantua General all apart for a planned rebuild, I just need to figure out how to mill down the flanges on those drivers.

Brain Board 74LS244 Grounding Issue

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The Brain Board review in Juiced GS included a description of a bad 74LS244. I have had one other report of problems with the Brain Board in an Apple IIe. In that second case, I had that person send back his board, twice. Though I wasn’t able to reproduce the problem in my Apple IIe with his board, I tried two different repairs, the second of which seems to be successful. The first was a simple swap of the 74LS244, which helped, but didn’t completely eliminate the problem.

After further analysis, I determined that the grounding of the 74LS244 is less than optimal on the Brain Board and switching on of the 74LS244 causes a lot of noise on the ground. Apple boards that use a similar data bus driver circuit (Apple FW card & Super Serial) also exhibit this switching noise. The stock Brain Board is somewhat worse in this regard. I found that adding an additional ground wire on the 74LS244 reduces noise to levels lower than the Apple FW board and appears to solve the problem.

This intermittent operation is typically seen as random characters input while at the console prompt, while not actually typing on the keyboard. If you notice this problem, add a wire between the ground pin of the 74LS244 and the ground lead of the decoupling cap near the other end of the edge connector.

Here is an image of a board with the fix applied.

brainboard 74LS244 ground wire fix

brainboard 74LS244 ground wire fix

One more word about this problem. Though I didn’t know of any issue with the ground, when laying out the production Brain Board, I considered shortening the ground connection to the 74LS244, running it across the center of the board, instead of the top. This change might have prevented this issue. However, I decided that, since, in several years of operation of the prototype “Brain Board”, I had seen no issues, that it was unnecessary. This is a case where the “if it ain’t broke, don’t fix it” approach, was the wrong approach. For now, the one wire fix will have to do. If I make another run of these boards, the ground trace will be widened and rerouted using the shortened path I considered before.

Also because of this issue, I’m going to have to make major changes to the layout of the protoboard that I have described earlier in this blog.

One project complete – Datanetics PCBs sold out

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Finally, I sold the last of the 10 Datanetics PCBs that I had made last year. I don’t expect to make another run of these since the market for them is so tiny. I guess about the only way that that another run would happen, is if someone is willing to buy an entire batch and finances the whole thing.

I am glad I did this project, as now I have a nice matching keyboard for my personal Mimeo 1.

The one thing that surprised me about this project, is that no owners of original Apple 1s that needed a matching keyboard bought a PCB to build up. Original keyboards appropriate for Apple 1’s are extremely rare and a number of the original Apple 1s don’t have the original keyboards. I’m learning that many people get enjoyment out of owning, admiring and preserving original artifacts, without the risk of operating them. Other people, like myself, get more satisfaction out of operating the old style gear. I think that there is an important place for both types of people in this hobby.

Though the Datanetics keyboard project was a money loser, I am really glad that John Calande talked me into doing it. He also lent me the original Datanetics keyboard he owns, which greatly facilitated this project. Also thanks to Mike Gregory for fabricating the brackets and stiffeners.

Scelbi Layout Started

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It looks like I’ll be putting the per cycle Scelbi emulator on hold for a while, since I just started on this:

first draft of IC, resistor and cap placement

first draft of IC, resistor and cap placement

This is what the first rough draft of IC, resistor and cap placement for a replica Scelbi CPU card looks like. In the past, once I’ve started on layout, everything else usually goes on hold for a number of months.