Starting an Apple I replica - already in over my head

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CWJ_Wilko's picture
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Not content with 'just' an Apple II, I've looked to the Apple I. I've been looking at Mr Briel's computer as a potential example that I could assemble.

I'm really keen to try putting this together myself, without a kit, hoping to learn something and hopefully save a few dollars. Mr Briel's kit becomes quite expensive for me after international shipping and currency conversion.

I've put together a part list, could someone let me know whether I've made any serious errors in my parts selection? (From Mouser, in Australian Dollars)

https://drive.google.com/file/d/0B4oPoNL3O7UCdmhaN1ZRLXpLYU0/view?usp=sharing

I'm also trying to figure out the best way to get the ROM onto the 28C64. Can I use an original Apple I ROM in place of Mr Briel's ROM? If not, is Mr Briel's ROM available for download somewhere?

I don't have a programmer, so I'm wondering whether it's at all possible to purchase an EEPROM preprogrammed with the required ROM... is that possible? If not it may just be easier to start with Mr Briel's kit.

Forgive my total ignorance on all this, I'm looking forward to trying to figure this all out.

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Re: Starting an Apple I replica - already in over my head

Looking at your parts cost, I think it has to be better to buy a Briel system. You still haven't factored in the lack of a PCB and that you will need to do a whole lot of hand wiring to get it up and running and the potential for human error increases.

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Re: Starting an Apple I replica - already in over my head

Unfortunately, I think the Briel shop is sold out right now... EDIT: Just some Apple II stuff is sold out. Replica 1's appear to be in stock. http://www.brielcomputers.com/wordpress/?cat=30

Still cheaper and more accessible than a "real" replica.

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Re: Starting an Apple I replica - already in over my head

Breaking down the numbers, Mr Briel's system would come to AU$288 including shipping to Australia, whereas my parts list comes to $104.49 before shipping. I'll still need to pick up a proto board and probably a lot of wire, or get a PCB made up.

I still think I'll come in well under the kit price with my system, although with plenty of extra stress in making sure every connection is perfect. But if I can't get the ROM image and a ROM burner then I might be out of luck.

EDIT: I've found someone that can provide 1x EPROM preburnt with the Replica 1 ROM that I have found online. Should be around AU$30.

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Re: Starting an Apple I replica - already in over my head

I don't mind burning you an eprom and mailing it, but I'm located in the states. Maybe someone in Australia could burn you an EPROM. You may want to simply invest in a cheap EPROM burner from China. They aren't that expensive and are useful for things like a replica-1. One thing to comment if you use an eeprom like the later replica-1, you will have trouble with using an Apple ACI. Apparently the eeprom puts too much noise on the bus to get a clean load. I'm sure we could figure out a way to clean the lines up since you are hand wiring up yours. With the replica-1 the only choice is to swap out the eeprom for an EPROM.

Cheers,
Corey

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Re: Starting an Apple I replica - already in over my head

Thanks Corey - wish I had read this before, I've just sent some cash to the USA to get the 8kb ROM burnt onto a 27C64. We'll see how it goes in a few months when I get around to assembling the Apple I.

I went with an EPROM for the moment, figuring that I am unlikely to need to reburn an image if all goes well. And through coincidence that looks like it'll be perfect if I decide to go on to make an ACI.

I'm basing my replica off the original 'Replica 1' by Mr Briel. While the Replica 1 Plus has fewer components, it actually ended up being more expensive to build after picking up a USBtoSerial board, and I don't have any experience in writing to the Propeller chips yet either. Maybe that can be my next project, after all this.

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Re: Starting an Apple I replica - already in over my head

I think I have a decent understanding of the original replica 1 schematic, but can someone tell me what all the bypass capacitors are used for? On the PCB they are scattered all over the place, but on the schematic it seems like all 12 of them are just hooked up to 5v and ground. Is that really all I need to do with those?

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Re: Starting an Apple I replica - already in over my head

Sorry for spamming the thread. I have just plugged all my components into Mouser (minus the EPROM that is on its way) and I came in way under my original estimate, which I'm happy about.

Again if anyone has the time, can someone check this list for any obvious incompatibilities and let me know? I think I've done a pretty good job with the component selection, with some even coming in over spec.

https://drive.google.com/file/d/0B4oPoNL3O7UCRlYwMjhYd2VBb28/view?usp=sharing

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Re: Starting an Apple I replica - already in over my head

CWJ_Wilko wrote:

I think I have a decent understanding of the original replica 1 schematic, but can someone tell me what all the bypass capacitors are used for? On the PCB they are scattered all over the place, but on the schematic it seems like all 12 of them are just hooked up to 5v and ground. Is that really all I need to do with those?

The way the schematics are drawn for the Replica-1 it's how the bypass caps are documents, but the reality is you need them placed all over the board just like the replica-1 does.

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Re: Starting an Apple I replica - already in over my head

So is it just a random placement between 5v and ground at various points?

EDIT: Just did a bit of learning, so is it enough to place the bypass caps on the vcc and gnd pins of each IC? What other locations are important?

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Re: Starting an Apple I replica - already in over my head

Well it's easier on a PCB to figure this out since you can see where the signal lines are. With a self wired board, I'd start with a cap per chip to be safe, but you may need to add caps as you troubleshoot noise on the board. I could get into a scientific method here, but on a project like this it's not worth it.

Designs like the real Apple-1 don't have caps for every chip, but place them strategically in places to clean things up. Sometimes it's enough to just make the design marginal (the Apple-1 is marginal) sometimes it's not (Sinclair ZX81, ask me why I think this).

Good luck, I think you are going to learn a lot with this project.

Cheers,
Corey

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Re: Starting an Apple I replica - already in over my head

I think so too Corey - I'll start by placing a bypass capacitor between vcc and gnd of each chip to start with, but I can also take a closer look at the PCB design of the original Replica 1 to see where they are best deployed.

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Re: Starting an Apple I replica - already in over my head

Placement will be tricky. You really need 1 every 3 to 5 chips, but because you are hand wiring you need to keep track of how you wire up the power to the chips so that you don't wind up putting 1 next to the other in relation to your wiring. That's why I said it's easier in a self wired system to just put one per chip. There aren't a lot of chips on a replica-1.

On a PCB it's easy, the path is layed out literally so you can put the caps where needed.

I hope that makes sense. I'm trying to keep it simple for you and not overcomplicate the use of caps in digital electronics. Plus .1 caps are cheap.

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Re: Starting an Apple I replica - already in over my head

EDIT: Corey I now get what you mean regarding more specific placement. Instead of placing a capacitor between vcc and gnd of each chip, should I instead be placing one between the 5v rail and the vcc pin of each chip? Or should I just go vcc to gnd for each IC?

I have ordered 11 - enough for each IC, and the same amount that is in the original Replica 1 parts list, so I figured this makes sense. If I need more they're really cheap, but I'll go with the above plan for now and see how it goes I guess.

Mouser is preparing to ship my components this week, looking forward to getting down to business. I'll have to also load the firmware onto each AtMEGA chip, something I didn't realise, but this sounds easier than EPROM programming so should be able to manage.

Lucky I could still even find the firmware. The original Replica 1 itself is now becoming 'vintage' that its documentation and firmware are becoming harder to find.

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Re: Starting an Apple I replica - already in over my head

Hello CWJ_Wilko,

maybe this explenation helps you to understand the topic better:

In any kind of CPU board ( even those by handwiring more than those with etched traces )
there are lines with high frequency ( like adressing or data lines ) and those with low frequency
( like powersupply or reset )...
and depending to the high frequency there are very tiny magnetic fields along the traces ( i.e. wires )
and if they run same way parallel they may pass over some electric "noise" to other wires
by electromagnetic fields...

This causes a noise that engineers call "spikes" ( resulting from the picture given at a oscilloscope that look like
little needles on the signaldisplay )....

the purpose of the filtering caps is to filter that spikes off from powersupply or "noisy" wires and lead them
via the cap to groundline ( you may treat that as a specific kind of "noise-shortcut" ).
It therefor is also recommended to use a thicker wire as "ground"-wire if soldering a board by handwiring
so that stuff may be "easy deported off from the board to the powercaps" to eliminate that kind of noise...

There is a rule: the higher the used frequency in a wire - the more noise it will inject by magnetic field
in a parallel wire....

Therefor it´s recomended to avoid wires running long paths close to eachother parallel.....

and in very long cables that wires are twisted to make antiparallel magnetic fields....

Though it looks much nicer to arrange "parallel running bundles" of wires that habit also causes trouble....
so it´s in fact better to use "non parallel wiring" though that looks to outside view more "ugly"....

and the filtercaps of course only can serve their duty, if they are located close to the input power pins of the chips
where they shall keep the noise away from.....

In etched PCB´s it often is more easy, because there is quite space between noisy lines and powerrails
and often engineers even place "phantom"ground traces between noisy lines and sensitive lines to supress
that kind of anoying disturbances....

hope this helps you at correct strategic placement of that caps....

speedyG

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Re: Starting an Apple I replica - already in over my head

I was trying to avoid the technical explanation, but Speedy you have said it much simpler than I every could.

Thanks,
Cheers,
Corey

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Re: Starting an Apple I replica - already in over my head

Hello Corey,

i just watched the postings and recognized that in this case it might be usefull
to explain why someone is doing something and not only how to do it.....
specifically i was missing the hint with the more thick wire for ground....
thats in 70% of handwired boards a endless source of trouble if not soldered well...
and i believe that after this posting CWJ_Wilko will be able to make better decisions
because he now should be able to unterstand whats going on in the board...
at least i hope so... and besides i also bear in mind that this thread is read also
by other users working at a repilca....

speedyG

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Re: Starting an Apple I replica - already in over my head

Thanks speedy, that was a great explanation. So in summary for my project:

- Place bypass capacitors near the vcc input pin for each IC and take the shortest path to ground (usually the gnd pin of the same IC?)
- Do not run data lines near power lines when possible (avoid parallel and keep it 'messy')
- Use thick ground wire to soak up more electromagnetic noise

Would this project noticeably benefit by running phantom ground lines in various places on the board, as you pointed out sometimes happens on PCBs?

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Re: Starting an Apple I replica - already in over my head

speedyG wrote:

Hello Corey,

i just watched the postings and recognized that in this case it might be usefull
to explain why someone is doing something and not only how to do it.....
specifically i was missing the hint with the more thick wire for ground....
thats in 70% of handwired boards a endless source of trouble if not soldered well...
and i believe that after this posting CWJ_Wilko will be able to make better decisions
because he now should be able to unterstand whats going on in the board...
at least i hope so... and besides i also bear in mind that this thread is read also
by other users working at a repilca....

speedyG

Good point about the ground wires. I usually get the PCBs that have a thick ground and power that run around the edges of the board when I'm doing point to point soldering. So they usually are already thick and I just jump off those runs.

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Re: Starting an Apple I replica - already in over my head

Hello CWJ_Wilko,

yep you got everything correct in mind....
the explenation about the phantomlines is only valid to etched PCBs.....
- at handwired PCB´s that´s not possible .....

but you should pay attention that the powerwires are ordered in "star topologie"
and avoid under all circumstances making a so called "closed loop" ( a common
mistake done with ground wires ) because such loops are very sensitive in catching
high frequency noise and collecting so called "humming" from the powersupply
( typically in the frequency of the powersource from the AC supply: 50 Hz or 60 Hz )

sincerely
speedyG

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Re: Starting an Apple I replica - already in over my head

Been thinking about that today speedy. Would it be best to have a GND rail at the far edge of the board, and the GND connector for the power supply at the very corner of the board?

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Re: Starting an Apple I replica - already in over my head

If you perform handwiring another rule is:
keep wires as short as possible....( and at practical execution add up about 5 % to 10 % of length
as spare reserve for moving wire while working and soldering.... )
to match both rules it´s better to keep a clean area at the center of the board
with the powerconnector located in that centered area....
layout for etched PCB is not matching best layout for handwired PCB.
speedyG

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Re: Starting an Apple I replica - already in over my head

Hmmm okay I'll try get it in the middle. I'm working on a very small board already figuring that short wires are better, its 9cm by 15cm and will be a really tight fit.

All my components arrived today bar just a few, so I'm going to start assembly soon!

I'm actually going to be using a //e power supply, I've jumped on Digikey and bought the power socket, pretty happy with that.

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Re: Starting an Apple I replica - already in over my head

Ben Heck did a couple of videos that appear to me to be rip off's of Vince's design (without giving Vince any credit). You might check out his UTube channel for construction ideas.

regards,
Mike Willegal

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Re: Starting an Apple I replica - already in over my head

Hey Mike, yeah I caught those videos, actually started watching them before I even realised I wanted to build one myself! They were great for a bit of an overview but it wasn't enough to get me started, no parts list etc.

It was only later I put two and two together and realised that Ben Heck's board was pretty similar to Vince Briel's. I've given Ben the benefit of the doubt since he seems to know what he's doing already, and there's not that many different ways to wire up an Apple 1 (or is there? Mike your board is very impressive, something that maybe I'll have to look at down the road?)

I do feel a twinge of guilt about not buying Vince's latest iteration of the replica, and basically scavenging all the important information for free while he's done all the hard work more than ten years ago. But like I said above, I've cut the cost down by half once shipping is included, and I'm looking forward to the extra challenge of assembling the board myself.

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Re: Starting an Apple I replica - already in over my head

There are about a thousand different ways to reproduce the Apple 1 video section. In fact, at one point, Vince completely redesigned this part of his implementation to use a Propeller chip. He originally used AVR microcontrollers to implement video.

While you are at it, I would design in an ACI. Without the ACI, you are missing a big part of the original Apple 1 experience.

Regards,
Mike W

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Re: Starting an Apple I replica - already in over my head

Thanks Mike, I'm actually working off Mr Briel's original design using AVRs as this ended up being marginally cheaper than using a Propeller (somehow). Plus as I mentioned above, this original iteration is itself becoming rare and vintage, it's twelve years old this year!

I have included a 40 pin expansion port. Do I need a specific ACI design for my replica or will any do? It's something I definitely want to include, especially since I don't have Mr Briel's serial board schematics (later revisions of the Replica 1 used the Propeller for serial communication - something I wish I had known before buying components).

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Re: Starting an Apple I replica - already in over my head

Hello CWJ_Wilko,
there is no need for use of a serial chip.....
if you view the original design schematic of the original ACI you will recognize,
that input as well as output is handled by only few chips
( 1 x 74LS02, 1 x 74LS10 a FlipFlop 1x74LS74 and 1x 311 Comparator ) and 2 ROM-chips with 1 kB.
Even the 2 ROM-chips ( each handling only 4 bit of the byte ) can be replaced by
one ROM to handle the entire byte with 8 Bits.
Schematic at:
http://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Interface%20Cards/Apple-1/Apple-1%20Cassette%20Interface/Manuals/Apple-1%20Cassette%20Interface.pdf

If you have the 40pin signals availiable you only need to search for the signal
that shall replace the selection signal from the 74LS154 to enable the correct adressing
and code adressing of the ROM by the activation of the select/enable line which is
in original design of the original board used for activation of the E000 adressblock.

sincerely speedyG

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Re: Starting an Apple I replica - already in over my head

For your approval: a few images of progress thus far. Please excuse some of the poor soldering, it's been a while and I'll make sure everything is looking neat before completion.

http://oi64.tinypic.com/xcoyvm.jpg
http://oi66.tinypic.com/s42grp.jpg

This board was the biggest proto board I could buy locally, I bought two but found that I can -just- squeeze everything onto one. Obviously this presents some massive challenges for a beginner.

I can just barely fit an RCA female, PS/2 and an Apple II power socket onto this board, but I'm now thinking I'll run wire off the board to these points fitted externally to a case that I have found. It's a model car case with clear plastic cover which fits this board just perfectly. The board will sit inside the case on four large rubber feet with plenty of clearance for the wiring on the back of the board.

So far I've soldered a few resistors on there and most of the bypass capacitors. As discussed the bypass capacitors are directly wired to vcc and gnd on every IC. Most of them are on the back!

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Re: Starting an Apple I replica - already in over my head

In that case i´d use the area marked at that board between marking of 40 and 45
for input of the volatge wires - the bottom row ( located the side where the gnd-pins
of the 40 chips are located and the positive voltages at the side located to the Vcc-pins
of the 40 pin sockets )..... abd starting from that points towards the corners....
by that selection the wires will keep short and in star-topology.

at the moment it´s not the time to judge the soldering joints.....
at the moment most of them only fix pins.
The joints can only be judged After the wires have been attached by soldering....
at the moment it seems that good portion of the floating fluid has allready left "the scene"....
it might be therefor usefull to apply some additiv at the moment of soldering to solve that problem:
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2094258_-1
but one advice: train use of the aid first at other board to learn how to apply and
how much to apply ( by dipping in the wiretip just before soldering )

speedyG

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Re: Starting an Apple I replica - already in over my head

Ahh some flux. Yes I'll pick some up, good idea.

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Re: Starting an Apple I replica - already in over my head

Speedy would this be an appropriate way to provide power? +5v is red and GND is black, and obviously all connections are underneath the board.

(Edit, obviously the 6502 pins aren't correct but you get the idea)

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Re: Starting an Apple I replica - already in over my head

Yes thats the core of the idea.

But pay attention !
At the moment there is a potential danger in your soldering !
It´s not a good idea to keep that wires of the capacitors blank / uncovered !
I´d recommend to use either shrinking hose or plastic coating to protect
that wires from unwanted shortcuts by touch !
While preparing to solder handwiring - you allways have to strip off plastic coating from wires.
It´s a good habit not to throw that coatings away to the dump - but instead
collecting some off that stuff in a small box besides for later use.....
then in such cases like at the present moment - you may pick out some of that
coatings and use them by pushing them over the blank portion of wire at the caps in correct length to
cover the blank area just leaving a small portion left blank for the soldering of the end of the wire
and thereby protecting / isolating that wires from shortcuts. And their wires should be bent
small part "inwards" like in the sketch to keep them away from the neighbor pins. i´ve marked the picture
related to this topic with light violett color !

mark up that at the 6821 the supplyvoltage is not at the usually used pins !

The following picture is a recommendation:

speedyG

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Re: Starting an Apple I replica - already in over my head

Thanks again speedy, I'll make the necessary adjustments. I'll most certainly be covering those bare capacitors with something, probably some heatshrink material. For some points I was thinking about finding some kind of insulation 'goo' or just plain wax to make doubly sure.

I've wired up three data lines so far between the 6502 and the 62256, extremely short. I have got those 'curves' you suggested on the data lines and everything looks good, although the cheap rubber covering keeps getting melted by the soldering iron, not even with direct touch. I'll have to be careful about how quick I solder wire to pin.

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Re: Starting an Apple I replica - already in over my head

Hello CWJ_Wilko,
the way you mention your soldering iron leads to the question what kind of iron you are using.... ?
The quality of work is upmost dependent to the kind of tool you use !
It seems you are using a soldering iron
a) without good temeparture regulation
b) without very tiny pinpoint tip
c) the tool would in ideal case have a heating unit with 50 Watt to 70 Watt ( more than 80 Watt will be hazerdous )
short explenation :
if the tip is too hot it will start very fast to scale and the tip will not melt correct the soldering lead
resulting from oxydation and the fluid resin evaporates too fast not giving the soldering lead time to flow and
make a perfect connection....

the perfect temperature for wirebased soldering is 360 degrees Celsius
and it´s upmost important that this is concentrated very constant at the tip

the soldering tip schould have (depending to the soldering iron you use ) a shape similar to this one:
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_35115_-1

cheap soldering station ( cheaper than 30 bucks ) don´t regulate that precise enough
good soldering station cost in general at least more than 50 bucks

just for orientation:
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_2193782_-1

sincerly speedyG

speedyG

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Re: Starting an Apple I replica - already in over my head

At the moment I am using a very cheap soldering iron with a poor tip, I have a spare tip that should improve things quite a bit for this project.

To be brutally honest I think much of the melted rubber is because I'm leaving the soldering iron on the wire for too long and too close, this is just a technique that I have to practice a lot more (and boy, do I have a lot more soldering to go on this...) I have to get in quick then get out.

I wired up some ground cabling today, looks okay, it looks very.... Apple 1 prototype, if that makes sense. I never expected a polished product though.

I have just rediscovered a whole tin of liquid electrical tape that I used to insulate the CRT on my Apple II monitor, so I'm probably going to reuse it for this project to cover up some of the more vulnerable points on the board. It's red liquid though, which isn't the best aesthetically - but then again, it's a hack!

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Re: Starting an Apple I replica - already in over my head

Progress has been steady but slow. I have a day off work tomorrow so I'm hoping to get right down to it and finish it off. The ROM arrived in the post yesterday so keen to get it finished.

As a recap, I'm going off the original schematics for the Replica 1, designed by Vince Briel in 2004. In a post from a few years ago I noted an amendment to this schematic, specifically that SH/LD on the 7474 should be wired to PB0 of the Atmega8. The original schematic was never updated.

So my question is, are there any other amendments I should be aware of before continuing? Would hate to finish this up only to have screwed up because the schematic wasn't correct.

http://www.applefritter.com/?q=node/6950 <<<< This was the post in question. It also covers some problems with the firmware which I'm hoping to not encounter in 2016 (but we will see!)

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Re: Starting an Apple I replica - already in over my head

Hello CWJ_Wilko,

just an advice for ordering the soldering task in blocks for better tracing of / avoiding mistakes....

1st task:
soldering all power lines
then proff of connections

2nd task:
soldering all data lines
then proof of all that connections

3rd task:
soldering all adressing lines
then proof of all that connections

4th task:
soldering all protocol and remaining signal lines
and then proof of all that lines for correct connection

5th task:
inserting all parts related to the oscillator and the powerup only oscillator
and check oscillator frequency present at related lines

then proceeding with the next steps....

nothing can become more boring and frustrating than an error in wire-buildup
and hunting for the source of trouble and repair of such a mistake
( specially if several other wires are crossing a damaged line or connection....)

so it´s a good behaviour to make several precise testings in different steps of the task
to keep error trace and repair in a mantainable range....

sincerely
speedyG

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Re: Starting an Apple I replica - already in over my head

Here is a pic. Before anyone else says it I would like to acknowledge that this is one nasty looking replica, and frankly I'm a little embarrassed to share it here, where pretty much everyone would have done a better job than this. This was a huge undertaking for me, and perhaps I didn't realise the scale of what I was getting myself into, but overall I'm very satisfied with progress so far. And most importantly, pin-to-pin it all works well, I've been testing as I go. While there are a lot of joints close to each other, there are no short circuits.

Thanks as always speedy, in fact that's exactly what I've done. Laid down the power cabling first, then started with data and address bus.

I ran into trouble completing just one bus at a time, as my design had a lot of overlapping points, so I found myself working on both the data bus and address bus at the same time.

Data and address buses are now complete, and most of the protocol wiring is done. I'm currently working on the video and keyboard buses.

If I had to offer myself advice, I would have gone with a bigger board. While I felt it was admirable to shrink everything down into such a small space for aesthetics, it doesn't look good when you start seeing burnt rubber all over the place.

speedyG's picture
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Re: Starting an Apple I replica - already in over my head

Wiresoldering allways results to wierd view at the final end......
i just marked 3 points of possible trouble to pay attention.

if you take a look at my prototype of the Apple-1 diagnostic - it also looks wierd - but it works.
At that prototype you see the use if schrinkhose well at the resistors:
http://www.applefritter.com/?q=content/mysterious-sync-apple-1-manual-diagnostic-card-apple-1

sincerely
speedyG

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CWJ_Wilko's picture
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Re: Starting an Apple I replica - already in over my head

Thanks speedy, yeah those were all easily fixed.

I'm currently stumped trying to assemble the firmware for the Atmega microcontrollers. Thought this would be as simple as dropping Mr Briel's firmware into AVRStudio and compiling, but I'm getting hundreds of errors and I'm not really sure what I'm doing wrong.

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Re: Starting an Apple I replica - already in over my head

Hello CWJ_Wilko,

well i´m not sitting besides while running the compiler....
- but what kind of error messages are you getting ?

In general spoken : often missing defs result from missing library.....

just as hint.....
maybe there is some more info, that you might discover by research in the related thread at
briel within the old parts of postings:
http://www.brielcomputers.com/phpBB3/viewforum.php?f=3&sid=6f1bbe67a5d27ed5c19d98725dca75e8

sincerely speedyG

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CWJ_Wilko's picture
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Re: Starting an Apple I replica - already in over my head

I did get there in the end by removing the comments at the start of each .asm file.

Unfortunately I had my 1mhz oscillator rotated 90 degrees around, so the first test gave me nothing at all. Subsequent tests give me static garbage on the screen, so I'm fearing that I have fried some poor chips with errant volts. Not much I can do at this point - a bit of a disappointing end to the project, but I did learn a lot.

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Re: Starting an Apple I replica - already in over my head

I wouldn't give up yet...

Sure you may have fried something, but maybe you didn't maybe it's a minor problem. Do you own an Oscilloscope?

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Re: Starting an Apple I replica - already in over my head

Wow. Kudos to you for doing this. But why not use wire wrap? I'm hopeless with a solder pencil but have successfully built a few fairly large boards with a wrap gun. It's MUCH faster and easier.

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Re: Starting an Apple I replica - already in over my head

Hello CWJ_Wilko,

at the moment it´s normal to feel frustrated .....
but if you really acknowledge the truth - it is normal in such a project -
if you make attempt with only few experience - that some kind of mistake was to be expected at some stage....

It´s part of life that nobody is perfect.....

the point is - after disappointment settles down,
to raise again and to drink a cup of coffee and get some conclusions.....
first point to save as experience:
the cheapest path is not every time the really cheapest attempt....
that´s the reason why PCB´s had such a success: wire soldering bears too much risks of mistakes....
you have made that choice expecting to learn.... the mistake bears more chances to learn a lot more...
within the debugging process to discover the mistake and solve that problem bears
the chance to learn a lot more.... wasn´t that the true aim ?

And think about all stuff explained in this thread....
So just take a rest and then think over that task if you really want to surrender...
up to my private thought - i´d guess it´s to early to surrender....
It´s just another delay befor you may pick the champagne out from the cooler...

just my 5 cents
speedyG

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Re: Starting an Apple I replica - already in over my head

Thanks all, the initial disappointment has faded and I'll probably pick it up again in a few weeks and thoroughly test everything. I don't own a scope but this might be the perfect opportunity to buy one!

On the other hand, I may just call this like it is - a really great experience.

If I have learnt anything from several weeks of this, it's that the computing pioneers (Woz et al) are true geniuses, period. Not that I underrated the task ahead of me, but to me it's unbelievable that these machines ever existed at all. What an incredible amount of talent it must have taken to make these machines come to life - and look at what we have today! All I did was follow instructions, like a recipe. At one point or another these machines were invented out of thin air, and to me that just seems so incredible.

It also gave me a great chance to learn a little more about these machines that I enjoy very much - telling the difference between a data bus and an address bus (or even knowing they existed!) is something worthwhile that I can take away from this. I brushed up on my soldering skills, and I was getting quite good by the end of the project.

Practically I see a few things I can try in the coming weeks. I can try swap out some chips with the other computers I own, namely the //e, //c and the Commodore 128D to see if any have burnt out. I think a scope is out of my budget for the time being though. I could also just bite the bullet and buy the kit from Mr Briel, and at least produce something that works. Maybe with the latter, I can then compare chips between the two computers to see what works and what doesn't?

I'm also looking closely at the Mimeo - while it's well out of my budget, perhaps I can make an argument to put other projects on hold for a few weeks and save up the dollars to buy a kit.

As for wirewrapping or point to point, I honestly didn't know there was a difference when I started this. If I ever try and create something like this again from scratch, I'll try wire wrapping, but more likely I'll just be buying a larger breadboard to work on. The one I had was just too small and cramped. I think I could do much better with a bigger board.

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Re: Starting an Apple I replica - already in over my head

Hello CWJ_Wilko,

you just mentioned a point: size
When in the early days of computing PCBs have been made ( mid 70´s to end 70´s ) you will recognize
that between the chips there has been a lot space left.... processors havn´t been running faster than 1 Mhz....
when processor speed raised up to 10 MHz CPU´s started to need a cooling sink and PCB´s started to get compacted...
when in the third quater of the 80´s CPU raised speed to 40 or 50 MHz they demanded cooler with a fan to remove heat
from the CPU and mainboards started squeezing to compacted formats.....
and so on....

it´s a law given by the electricity:
the higher the frequency, the more heat by reistance of the trace or wire, the shorter that traces must get....

( besides of the problem that with raising speed of processors also radiotransmissionwaves getting more disturbed.... )

result up to this project:
at 1 MHz the size of that board may grow up by 50% of size without much pain or trouble....

another point:
i don´t know if you mounted stndoffs - but if you did not:
plan at next board placing some small stand-off´s in the corners and the middle to reduce stress to the soldered connections...

when you turn back to debugging don´t be shame to publish some links to precise high reolution pics of the
top and the bottom of the board.... ( preferably at least 4 to 5 meg pixel )with good lighting
that would permit to load the pics in photoshop and zoom in for examining details searching for possible trouble....

sincerely
speedyG

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In early days I had a lot of money but no time - now I have no money but a lot of time....
the second part includes less friends but a lot more joy on life....