IMac Repair Update

December 14th, 2017

My previous post on a couple of attempts at an IMac repair was here:

I glad to report that I’m convinced that the problem is resolved, as the unexpected power off issue has completely vanished.

Modern Views of the City Point and Army Line Yard Location

December 12th, 2017
Taken November, 2017, This View From the Bluff Views the Location of the City Point and Army Line Engine House

Taken November, 2017, This view shows where part of the City Point and Army Line yard was located

This picture was taken from the bluff, where the impressive row of barracks were located. The First Baptist Church of City Point is located there now. The bluff at the far side of the picture is where the railroad hospital was located. After taking this and several other pictures, a resident asked me if I was with the company that was planning some development there. I said no, I was interested in Civil War history. He said that was understandable. Maybe I should have asked him what was up, but felt that I didn’t want to disturb the residents any more than I already had done.

Here is a famous view taken from the same general location during the Civil War.

Water tanks and bluff where railroad hospital was located

Water tanks and bluff where railroad hospital was located

Here is a modern view of the cut leading to the yard.

Cut leading to City Point Termnial

Cut leading to City Point Termnial

The US Military Railroad laid 3 parallel tracks in this cut.

My overall impression is that there wasn’t a lot of extra space at City Point. Everything seems like it must have been squeezed pretty tightly together.

Another Book about Lincoln at City Point and a Correction

December 3rd, 2017
two Lincoln at City Point books

two Lincoln at City Point books

The book, “Abraham Lincoln At City Point” was written by national park historian, Donald C. Pfalz and published in 1989. My new book, “Lincoln’s Greatest Journey” was written by Noah Andre Trudeau and published in 2016.

Both books contain a remarkably similar account of Lincoln’s stay at City Point in late March and early April of 1865. I would say that Pfalz’s book is a bit more scholarly in nature. Trudeau’s book is written more for general consumption and contains more background information about what was happening with the war in general and at the Petersburg front in particular.

Despite the duplicate subject matter, for someone modeling City Point during this period in time, I can’t imagine not picking up both volumes. There aren’t really that many books that use so much ink describing what was going at at City Point, at the time.

Now, for the correction. A while back, I made this post describing a theory I had about about Lincoln’s travel to the front on March 25th.

Though I still think that Mr Pfanz was wrong in his assessment that the train took them to Patrick’s station, I was missing some information, and didn’t read the train reports closely enough.

My assessment was also wrong. I should have investigated further, but it turns out that Meade’s HQ was near the Aikin’s house, which was near Parke’s station. Here is crop of Michler’s map of the Petersburg fortifications, showing the area from Meade’s HQ to Fort Wadsworth, the area that Lincoln’s party visited. I have labelled the area of Parke’s and Warren’s station, which are not noted on Michler’s original map.

Lincoln's Visit to the Front

Lincoln’s Visit to the Front

It’s interesting that the train report that Bernard Kempkinski found in the National Archives doesn’t list a Parke Station at all. I suppose it was more of whistle stop, rather than a regular station. I now believe that Lincoln’s party probably left the train at Parke Station and went directly to Meade’s HQ, which would have have been proper protocol for a commander visiting his subordinates army. However, if Parke Station didn’t have the facilities to unload the horses that were brought along, the most logical first stop would have been Warren Station.

Meade’s HQ area is where Lincoln’s party saw the prisoners from the fight for Fort Stedman. I finally realized why there would be prisoners so far from where the fighting took place, which was part of my confusion in the past. Meade’s army would have had provisions and procedures for handling prisoners. During the Civil War, the army’s provost guard HQ was usually near army HQ. Most likely, all prisoners the army captured, were sent to a holding area somewhere near the provost guard HQ for processing. This is why the prisoners from the fight at Stedman were marched to near the Aiken house.

I don’t believe that Lincoln actually saw the battlefield around Stedman, itself. Since they were so far from the big fight at Stedman, I’m not really sure how many dead and wounded that Lincoln saw that day. However because of all the fighting going on across the front that day, it’s very likely that some wounded and perhaps a few men that had expired from their wounds were in the area that Lincoln visited.

From Meade’s HQ, it would have been a fairly short ride by horseback to review part of the fifth corps and then on to Fort Wadsworth. There, the party could have obtained distant views of fighting going on in the area. From Fort Wadsworth, the group could easily have proceeded down the line to Patrick’s station, before returning to City Point on the train.

I think that Trudeau’s book describes this trip to the front, pretty well, though I’m kind of skeptical about how many dead and wounded men were seen by the group.

City Point Rail Yard then and now

November 28th, 2017

Here are a couple of views of the US Military Railroad Yard at City Point.

Rail Yard at City Point circa 1865

Rail Yard at City Point circa 1865

This one was probably taken in the winter of 1865.

Former Railyard at City Point Nov- 2017

Former Railyard at City Point Nov- 2017

This is the approximate same view in November of 2017.

Apple II rev 0 reproduction gerber and CAD files available for download

November 8th, 2017

I have made available Apple II rev 0 reproduction gerber and CAD files freely available for download. I actually put these files online a little while back, but didn’t make any announcement. I’m making this announcement, so that people will be more aware of the increased possibility of reproductions being passed off as original units. I.E. the possibility of fakes is increased.

Here is the link:

I believe that several people may already be making some new Apple II reproductions using these CAD files. If you are interested in having one, your best bet would be to make some queries in the more popular forums.

PS/2 keyboard adapter calibration notes.

November 2nd, 2017

I put the design files for my PS/2 to parallel ASCII adapter online when I ran out of PCBs. I get an occassional question about programming the AVRs. Mostly it is straight forward, however for the RS232 port to work properly, the internal RC-oscillator must be calibrated. Here are some notes about the calibration procedure.

Calibrating and programing is a four stage process. The calib and operation FW are built from the same source. Look in the source for a .IFDEF CALIB to see the difference.

When booting the calib image, it will output a 4Khz square wave out port B.

The calibration is done by connecting a terminal to the serial port and typing one of the following 4 commands.

I – this increases the calibration frequency
D – this decreases the calibration frequency
W – this neither increases or decreases frequency
Q – this quits the calibration process, displays the calibration variable, writes it to the last location of EEPROM and exits the calibration process

You need to connect a frequency counter or scope to one of the “B” port outputs and either increase or decrease the frequency until it is as close as possible to 4Khz. These days, many inexpensive meters have frequency counters that will be accurate enough for this job.

The AVR will not echo the correct character to the RS232 port, when it is out of calibration. The calibration routine will default to decrementing the calibration value if it receives a character that it doesn’t understand. Just keep typing and eventually it will wrap around into a good range, at which point you can fine tune it.

So the four steps are:
1) First load the calib file (AVRPS2_keyboard_calib.hex) and run it to adjust the frequency, as described above. When you have the frequency in a good spot, type Q and the the controller will output the calibration value and also writes it to the last location of the EEprom. For record keeping purposes, it is a good idea to write the calibration value with a marker on the underside of the chip when you are done.
2) I have an AVR dude script that reads the EEPROM – I would run this to get the calibration value into a hex file.
3) Now you can program the regular firmware (PS-2keyboardv3.0.hex). Unfortunately, with AVRdude, this process also erases EEPROM, so you need to reprogram the calibration value into the last byte of the EEPROM.
4) Reprogram the calibration value into EEPROM using the AVRdude script provided, using the EEPROM file you read from the system in step 2 and you are done.

If you are doing a batch of them, once you get things set up, it takes only about 30 seconds or so to go through the scripts, to calibrate and program, each part.

In this design, it would have been nice to use a crystal for clock generation to avoid the calibration hassle. However, that would take two pins of the AVR, which I didn’t have available. I could have freed up a couple of pins by configuring the settings with the keyboard or serial port. It would have taken time to write the software that I didn’t have available, as, at that point, I was in the middle of the inital Apple 1 cloning effort for Mimeo.

First Pass of a Mantua General Repaint

October 22nd, 2017

First see this old old blog post about the remotoring and change to the drawbar that I did a few years ago.

I am not a master modeler, but more recently, I’ve been working on changing an old Mantua General Locomotive over to the paint scheme of a US Military Railroad Norris type locomotive. With City Point being my main area of focus, I found some really good images of the Govener Nye, and decided to use that locomotive as my prototype.

The original paint job was severely chipped and probably not very great to start with. I stripped the old paint off with lacquer thinner and then repainted. Here is the result.

Generic USMRR Locomotive - paint based on Govenor Nye, a Norris built 4-4-0

Generic USMRR Locomotive – paint based on Govenor Nye, a Norris built 4-4-0

I used an ancient can of Humrol #96 RAF blue that was left over from my days as a wargamer for the Russian iron, and am very pleased with the result. Other paints were from what I had on hand. I’m not all that happy with the green, but it will do for now. Decals are from Microscale’s Eastern USMRR set.

Besides the repaint here are some other things that I have done with this locomotive.

I added a DCC decoder using a Digitrax DZ-123 Z scale decoder, which can handle the 1 AMP motor. At this time, I don’t plan on adding sound to my Civil War locomotives, thinking that an external sound system will be more impressive. For example, I’m contemplating having an actual whistle that will be controlled with the DCC throttle, just like any other locomotive with a built in sound system.

I also added an engineer to the cab, but he is not very visable.

After mucking around for a bit trying to make the Matua supplied wood pile look more realistic, I ended up replacing the wood in the tender. I scored the sides of some round toothpicks with a fine tooth metal cutting sabre saw blade. Then I stained them and then cut them to size using a end cutting pliers. After positioning them losely on the tender, I used diluted elmers glue to attach them to the top of the tender.

What’s up next? I will add a line so the miniature engineer can ring the bell. I’m considering adding a working headlamp, but that may wait for a later date. I also need to program the speed tables for the DCC decoder. I will probably add a small magnet to the smoke/steam, so it can be removed when the locomotive is shut down, yet be a little more firmly attached when the locomotive is in motion.

IMac repair

October 11th, 2017

I have a 5 year old IMac that recently started to act up in a most annoying fashion. Every couple of hours it would shut itself off, with absolutely no warning.

Right from the first occurrence, this felt like a power supply issue. I could power it back up, simply by unplugging the unit, waiting a few minutes, and turning it back on.

Research on the internet, revealed that others had similar issues, and also how to get inside the unit. One symptom of this failure is that the sys log showed the last restart was done to loss of power, not some kind of crash.

Knowing how expensive Apple service would likely be, I decided to look into fixing it myself. I carefully worked a putty knife between the display and the chassis to get it open. What a horrible design, it’s so bad that it’s hard to comprehend that Apple would ship something like that. I managed to crack one corner of the glass getting it open, but it wasn’t a fatal crack, and the display remains perfectly usable.

Anyway, I removed and examined the power supply, looking for the telltale signs of a damaged component, but couldn’t find anything obviously wrong. I decided to reassemble the unit, hoping that perhaps one of the connectors was intermittent. I decided to use duct tape to reattach the screen, in case I might need to attempt something different, like replacing the power supply, altogether, in order to get the system fixed.

IMac held together with duct tape

IMac held together with duct tape

After powering up and running for a few days, the problem returned, so I knew it wasn’t a faulty connector. I decided to take one more look at the power supply before ordering a replacement. This time, I repeated the scan for obviously fried components, but found none. I did notice that the soldering on a few of the through hole components, just didn’t look that good. The solder job looked like the heat wasn’t enough to draw the solder down into the holes, so the solder was kind of balled up on the legs of these parts. Getting the heat right on a board like this, probably isn’t easy, as it contains a mix of small surface mount parts and through hole parts, that are connected to relatively large heat sinks.

I decided to reflow the solder on the suspect components and see if the system would work more reliably. I went ahead and took a shot at it and put the system back together (with duct tape). I’m still not sure if I fixed it, but three weeks later, I haven’t seen a reoccurrence of the random power off. However, it wouldn’t surprise me at all if putting up this post doesn’t cause an immediate reoccurance of the issue!

Operating an Original SCELBI 8B

September 26th, 2017

I recently spent a few hours with Mark Arnold and his original SCELBI 8B. This is the very machine that Mark used to develop SCELBAL with, way back, in 1975. Towards the end of our debug session, we had the machine in a largely working order!

Mark Arnold with his SCELBI-8B

Mark Arnold with his SCELBI-8B

We spent a lot of time, troubleshooting what appeared to be an intermittent EPROM issue. Finally we discovered that that the edge connector on the EPROM board wasn’t making reliable contact with the connector. After examining the board in detail, we noticed tarnish on the edge connector contacts. We used a soft pencil eraser to clean the tarnish off of the contacts and the intermittent operation completely disappeared. Fixing a computer with a pencil eraser was a first for me, though I expect others have done the same. Once the repair was done, Mark was able to reliably run a variety of MEA operations without any problems.

With only 4K of SRAM installed, we were unable to load the full floating point SCELBAL, but we were able to load tiny SCELBAL using a simple bit-banged RS232 port. Once loaded, Mark successfully entered and ran some small BASIC programs. Weeks later, I understand that Mark still has the system powered on and it responds to MEA commands, without any need to reset or reboot.

In order to declare that the machine is in 100% working order, a few things still need to be checked out. We had only 4K of SRAM installed, the other 8K should be added back into the system. We used a modified version of MEA with the page 76 EPROM changed. I created a version of page 76 EPROM with a 2400 baud driver, but we were having some issue with corrupted serial output characters. We don’t know if that was a ground loop problem or a baud rate problem with the modified page 76 driver. Serial input at 2400 is working perfectly, but the timing for output is done differently, so it could be either.

Finally, the cassette interface needs to be connected and tried out. I don’t really expect any issues with that, as I have used that particular cassette interface with a reproduction SCELBI 8B, back when I was first troubleshooting my reproduction cassette interface.

Repairing an Old Automobile Tape Deck

September 24th, 2017

Quite of a bit of the stuff I own and use everyday is, let’s just say old. This includes a 1988 Mustang convertible that sometimes becomes my daily driver. This car is what they call “bone stock”, and I like to keep it that way, though there can be challenges with it. One of the challenges is the sound system that gives you the option of a FM/AM radio or cassette tapes. Lately I’ve been relying mostly on the cassette tape player.

The problem with the cassette tape player is that after so many years, the pinch roller losses it’s grip, and the tape plays at too high a speed, giving you awful Donald Duck sounds. The last time that happened, I found an exact replacement tape deck on eBay and simply swapped it in. Well, eventually the replacement deck started exhibiting the same issue. This time around, though those decks can still be found on eBay, I figured that I would try to fix it. This became a multi-week adventure, as I stripped down both decks, swapping the best components of the replacement deck onto the original deck, which I had kept stashed in the attic. In the end, I ended up with a pile of parts and a working deck, but it wasn’t easy.

Radio in Pieces

Radio in Pieces

Here is some of the stuff that I did to get a working tape deck.

  • The original deck had chipped corners on the front bezel, so I swapped in the bezel from the replacement deck. In doing this swap, some of the wires on the flat flex cable connecting the front PCB to the main PCB were damaged, so jumper wires had to be added to repair this.
  • The backlight for the original deck’s display was gone, so I had to swap in the backlight from the replacement deck. This might actually be the light that was originally in that deck.
  • A power supply trace on the main PCB was found to be broken and had to be jumpered over.
  • I’m not sure, but I think the original tape deck had an issue with a switch, resulting in the tape playing at fast forward speed, similar to the slipping pinch roller sound. Rather than troubleshoot, I ended up swapping in the replacement deck, after cleaning the pinch rollers, which is was next step.
  • The pinch rollers on the replacement deck were cleaned, as best I could. In fact, if I had done this in the first place, that is all that I would have had to do.