Solder Bridge Found...

A few days ago, I noticed that the LED for address line A4 on the expansion card was not illuminated. I removed the expansion card and connected it up to a 5v power supply and probed the header connectors. All of the LEDs were working fine. I figured there must be either a bad chip somewhere or a solder bridge. After poking around for about 30 mins with a magnifying glass, I finally found the solder bridge under one of the 74S257 DIP sockets. After dragging a hot solder iron through the bridge, and powering up the clone again, I had an illuminated LED for Address line A4. Very hard to see! (I need to get some flux remover I guess .... that would probably make things a bit easier to see).

Clock Signal Fixed...

Note the square wave on the scope... I finally have a clock input signal on pin 37 of the 6502 processor. I found that replacing the Philips 74HCT04N with a National Semi 7404N (D12 in the schematic) gave me a square wave. I found this problem by first checking pin 37 on the 6502, then checking the schematic, and seeing that the output from the crystal clock circuit is sent to pin 9 on the 74175 (C13 in the schematic). I then checked pin 9 with my scope and what I saw was certainly not a square wave, so I immediately thought this chip must be bad and replaced it (the 7404). After powering down, then back up again, I was pumped to see my expansion card LEDs flashing away as they should be! Finally. In the image above, you can see the square wave generated while I have my left hand holding the oscilloscope probe on pin 37, and the camera in my right.
The video is still not working, but it is late (5:30 AM) so I will take a closer look at the video issue "in the morning".

-- 9-dec-2009 UPDATE: The video section needs a 7404. 74HCT04 and 74LS04 will not work. I replaced the 7404 with a new one and now have video.

2513 Character Generator

This description of the 2513 Character Generator is from Don Lancaster's TV Typewriter Cookbook. The description explains clearly how this thing works. Compared to the datasheet, I thought this was easier to understand, so figured I'd share it with the community.

I've been spending a bit more time on the video section of my Apple 1 clone, trying to locate the source of the problem (I have a signal, but no video). I re-soldered most of the points on the back of the board thinking maybe I had either a solder bridge or just a bad connection. I pulled and reinstalled the chips. Still no video. I tried removing and reinstalling all RAM chips, still no video. I tried swapping out a few of the chips, still no video. I checked all of the 1404 voltages, and everything looked fine. I'm going to have to spend a little more time with the scope, the schematics and the datasheets to figure out what's wrong here....

On Sunday, Oct 11, 2009 I decided to put together an expansion card to plug into the Apple 1 motherboard. This card provides the ability to send a "reset" signal to the CPU, read the address bus, and provide +5v and ground pins for a logic probe or oscilloscope probe. The above image shows the card with power applied, and the logic probe connected. The card is connected using the exact same 44 pin connector that is on the motherboard.


Lights off, first test. The green LED is the power indicator letting me know the board is getting power from the motherboard : +5 volts




Here you can see the 16 address LEDs, with sibling 300 ohm resistors. Note just to the left of the "+ 5v" label (bottom left) and the ground label (top left) there is a single molex pin. These 2 pins are for debugging the motherboard (i.e. the pins are used to hook up a logic probe).
The LED for the reset will be removed -- mainly because I wired it up wrong, and the signal for reset was blocked. Cool to have, but not necessary. Just above the switch is a .1 uF ceramic capacitor - for debouncing. The cap is connected to each pin on the switch.


Rat's nest on the back of the board. What you see here are the address lines, reset, +5 volts running across the top of the board from connector pin 1, ground across the bottom of the board from pin 20. The reset line is held high with a 10k ohm resistor. When the momentary switch is pressed the line is forced low, sending a reset signal to the motherboard / CPU. Testing with a logic probe shows we are good to go.


I attached the 44 pin header to the card using super-glue and a couple of C-clamps. What you see taped onto the board are (6) 16 pin DIP sockets which were soldered into place later on. These will eventually be used for hex displays.

I added the IN914 diode previously mentioned to protect the Apple 1 from unwanted external video surges, and I also added a "power on" LED indicator just for kicks.

On October 6, 2009 I built this external circuit to bring the video, ground and +5v out to a separate PCB with an RCA jack. Eventually I'll add an LED and I should have included a diode to protect the Apple 1 from any surges coming from the video terminal. It's on my list.
In any case, I did not see anything on the video monitor other than a gray screen. I don't have a keyboard set up yet, with reset and clear, but I was thinking I might at least see random characters.

Miscellaneous images while populating the PCB

More power supply images...

Above: prepping to solder the ON/OFF switch.

Above - prepping to solder the female connector to the power supply lines. I don't know why I waited so long to buy "Helping Hands"... let's see how long it takes before I finally break down and purchase a solder-sucker...


Above: soldering the molex housing pins, one at a time.

Above is the completed power supply. At some point the transformers will be bolted to the floor of a home-made case, or maybe just a piece of plywood...
BTW, that is a 0.5 Amp 250v fuse.

Building the Power Supply

Note that the 4 pin header looks a little rough, because it's actually a cut down version of the 6 pin header. If I took crapier pictures you wouldn't notice :D.



Today I pulled out the 2 Stancor transformers and put together the power supply. I didn't have all of the parts. After spending too much money on hard-to-find chips and carbon composite resistors, I decided it was time to do what we all should do, a little spring cleaning!
So I dug through the basement and garage and found a decent 2 prong power cord, and a fuse housing wire (from an old Panasonic car stereo equalizer) . There were also 4 nice nuts and bolts probably for mounting the stereo equalizer that I snatched out of the equalizer box to use for mounting the (2) Stancor transformers. While digging around I also found a brand new 125v ON -OFF toggle switch that was perfect for this project, in one of my parts bins down in the basement. I grabbed a handful of various old male/female wire connectors I thought I'd find useful as well.

I first started with assembling the 6 pin Molex connector housing and pins. I soldered each connector pin to each of the corresponding Stancor transformer wires after crimping them. I added wire connectors between the fuse wires and also for the ON/OFF switch. Every minute or so I referred back to the Apple 1 manual I had displayed on my computer screen just to make double sure I wasn't screwing up. I had never built a power supply before, so I was a little worried I was either going to hurt myself or fry the board. I took my time, and everything came together just fine. I powered up the board (after soldering the 6 Pin and 4 Pin headers to the board) with the supply and checked a few points to make sure I had the expected voltages (-5, +5, -12, +12). I did this using 3 tools:

1) Oscilloscope
2) Logic Probe and
3) Multimeter set to measure DC voltage

Everything looked OK to me except for one area, which I am still confused over....
The Apple 1 schematic (drawing 101 - Power Supply) shows J3 pins X, Y, and Z where X = GND, Y = +12v and Z = -12v. I measured 22.5v and -22.5v for both of these points. However, the manual said that these 2 pins should not be used, and if they are used need to be regulated (the voltage is not regulated as is).

After cleaning up a bit, I went ahead and soldered the jumper points above the 74154. I used a combination of the Apple 1 manual - schematic notes, and the scant instructions (from the web) from Obtronix. They are slightly different, but I don't know why:

Apple 1 Manual (schematic notes) jumper connections:
Y => CSF
Z => CSD
W => CS1
X => CS0 (zero)

Obtronix:
Y => F
Z => D
W => E (Note Apple jumps W=>CS1)
X => 0 (zero)
R => C

I took a look at a few Apple 1 images, and found a couple with jumper wire from W=>E so that is what I went with as well.

I powered up the board again and checked a few more points. I shut everything down, cleaned up a bit more, then proceeded to install the chips. After installing all of the chips, I powered up the board again looking for smoke, arcing, fire, flames, explosions, and nothing happened. But this time the board started producing heat. The 74154, the ROMs and the LM323k were all generating heat. The 6502 was not, however. I checked the voltages for 5v on the 6502 and everything looked fine.

So, enjoy the photos, and tomorrow after work maybe I'll see if I can knock out the keyboard and video.

oops...

I just realized all four of the A14F are installed backwards...

OK, so it took me about 2 hours to fix this major screwup. The A14Fs are back in business.

LM323K Voltage Regulator Installation

UPDATE: Feb.17.2010 - Please note that the A14F recitifier diodes are installed backwards in the above and below images.

I fixed this soon afterwards, before I applied power. See my later posts!

Tonite I installed the LM323K voltage regulator (5v / 3a).
A pair of magnetized wire strippers came in handy to drop the screws into place. Needle nose plyers would have worked fine too I guess. I used a tiny amount of masking tape to tape the washers to the screws so that I could drop them into place easily. The area is too tight to get your fingers into (maybe you can, but I could not).
This was a bit more frustrating than I thought it would be, but everything is now soldered into place. There are 2 insulating washers in the upper left of the image above. You do not need these insulating washers - Just bolt the LM323K as is, to ensure a good grounding connection to the PCB.

Soldering resistors and ceramic capicitors

So today I got a package in the mail from Surplus Sales.... which contained all of the carbon composite resistors (EXCEPT for the (12) 3k ohm), the ceramic caps, the 47pF capacitor, and the 100 ohm video trim potentiometer. I soldered the A14F rectifiers, the MPS transistor (video signal), the .1uF, .01uF and .001uF ceramic disc capacitors, the 47pF dipped cap, and the 14.138 Mhz crystal.
In the image at the top, you can see that I shorted the (2) "6502" bridges, as well as the No DMA bridge. I used wire that was trimmed from the resistors to short the (2) "6502" bridges.
(The No DMA short only has one hole in the PCB, not sure why?)

Anyhow, here are a couple of things that I learned tonite:

1) The MR501 rectifier diodes have wire leads that are too big for the holes in the PCB so I used A14F rectifiers instead. (A friend of mine sent me these from Ca. as I could not find them anywhere -- apparently they are only 15 cents each at the electronics shops in the Bay Area)

2) If you are working with ceramic caps with really short leads, make sure that you tape them to the PCB before you solder them. Otherwise they might fall out when you turn the board over. And if they do fall out *while you are soldering*, as did for me, you will be swearing for the next 15 minutes trying to get the solder out of the holes so that you can start over. Luckily, it only happened once. I didn't have much luck removing the solder using copper braid. So I ended up using a piece of trimmed resistor wire and a pair of plyers to hold the wire (so I wouldn't burn myself). I reheated the solder in the hole while plunging the resistor wire into the hole until it came loose. After a few tries I was able to remove enough solder to get the capacitor back into place AND TAPED to the PCB before attempting to solder. (I will purchase a solder sucker soon...)

3) If you use too much solder on resistors, caps and diodes, the solder will seep through to the other side and "ball up", creating small BB like balls of solder on the top of the PCB. (Maybe my iron is a little hot?)

4.) I am finding that a setting of about 3.4 on my soldering iron is a good heat to work with.
I let the iron heat up for at least 5 minutes before using it.
(Model = Weller WLC100)

Today a package arrived from Jameco.com, more parts for the Apple 1 clone! So tonite I soldered the 1N4001 diodes (4) and the (3) voltage regulators (-12v, +12v and 5v).
My Apple 1 board stencil was not readable, so I broke out the other board I have which does have a readable stencil around the regulators, so I've included a picture.

So today I finally took the plunge and started soldering IC sockets, diodes and axial capacitors onto my Apple 1 clone. I guess it took about 3.5 - 4 hours total. I took my time in effort not to screw up. I taped each IC socket to the front of the board with masking tape, one at a time, as I soldered them so that they were nice and flat against the circuit board. After soldering all of the IC sockets, I soldered the IN914 diodes, then the 22uF axial capacitors. Then I did the large cap, and then the (2) 2400 uF caps.
Note the 11000uF 25v capacitor to replace the impossible to find 5300uF cap. ( Tip from a former Apple Engineer )

Interview with Monroe Postman, Original Apple 1 owner

Monroe Postman Interview
=======================

Sep.2009

Hello everyone, I am here speaking with Monroe Postman, one of the few owners of the original Apple 1 computer.

Hi Monroe, can you tell us about your background, and what sparked your interest in computing?

I got my Bachelor of Electrical Engineering (BEE) before schools were offering Computers as a Major. My long term interest in computers turned professional when I joined the UNIVAC 1 staff at New York University in the early 1950s, which led eventually to a career in designing digital computers. I also taught microprocessor equipment design in the 1970s under a National Science Foundation grant.

What can you tell us about your experience as a HomeBrew Computer Club member?

I attended The Homebrew club after it started meeting at the Stanford Linear Accelerator (SLAC) and stayed until it left that venue. I was not an "active participant;" I just listened with rapt attention as the revolution got under way.

Is it true the Lee Felsenstein thought he was in charge, but wasn't really?
Was it a free for all?

My recollection was that Lee did keep order, but wasn't "bossy." There were at least 100 people at a typical meeting, but it was hardly a free for all. And there were plenty of disagreements, but the atmosphere was generally civil.

Did you ever get to meet Steve Wozniak? If so, what can you tell us about that encounter?

I only met Steve Wozniak briefly, years later, when I asked him to sign my Apple 1, I believe at the Computer History Museum in Mountain View. He was very cordial.

Did you ever see Woz demo the original Apple at the club?

Yes, I recall seeing a demo in the lobby of SLAC. I think that he was also at the First West Coast Computer Faire held in 1977 in San Francisco. That was very exciting!

Where and when did you purchase your Apple 1?

I bought it at an estate sale, in around 1980.

What made you decide to put your Apple 1 up for sale?

I guess as a collector, my interests have evolved over time. And there are so few of these Apple 1s out there, it’s time for someone else to enjoy it.

If you could give any bit of advice to people just getting into computers, who might be interested in either software programming or hardware design what would you tell them?

I've been a hardware engineer, using a bit of programming or machine code to modify and test my designs. If I were just entering graduate school, this time I would opt to study bio-engineering which is an exciting mix of many engineering disciplines. Every engineer should know which end of a soldering iron is hot! I know that is so 20th century . . .

It seems we’re always at the end of one exciting era in the history of computers and at the beginning of another. Leave it to Apple with the iPhone to have introduced one of today’s most interesting computing platforms, with wifi, location awareness, color touch screen, video and all of its other features it is changing the way people compute.

In my own life, I have recently been working at the Department of Veterans Affairs, using sensors, hydraulics and computer control to build solutions that provide rehabilitation and assistance to stroke victims, paraplegics and quadriplegics.

Monroe, thank you very much for your time, it has been a great pleasure.

Please visit: http://apple1forsale.com

An Apple 1 will soon to be for sale...

Please visit: http://apple1forsale.com

Newsflash: This Apple 1, (number 49 sticker on back) SOLD on Oct 3rd, 2009 in the middle of the night, not too long after being posted to ebay!

Apple 1 ROM sets - 3 left

Apple 1 ROMs for sale. I have 3 sets left.

(1 set = A1, A2, A3, A4)
I am dropping the price to $40 USD which was pretty much my cost.

(In fact, they were $10.00 per chip in 1977! Same price today.)

These are all ceramic DIP 6301-1J chips.
I accept PayPal.

Apple 1 Interface Age October 1976

Apple 1 ads first appeared in the October 1976 issue of Interface Age magazine.

(Hmmm... or did the ad first appear as text only, in the September 76 issue?)
"Apple Introduces the First Low Cost Microcomputer System with a Video Terminal and 8K Bytes of RAM on a Single PC Card"

UPDATE FEB.10.2010: It turns out that the September 1976 issue of Interface Age is where the first Ad for the Apple-1 appeared, not the October issue. I will have images on the way soon. Stay tuned!