Additional help buliding the Orton 3C

[James Harland]

Hello everyone,

Happy New Year!

I got myself a full Orton 3C kit for Christmas, and now I am starting to think about putting it together. I have had a look at the images on the z80 kits site, and the documentation on the rc2014 site, and searched this forum for Orton 3C references.

So looking at the pictures, I can see that the main board of the Orton 3C is double sided, with the LEDS and switches on one side and everything else on the back. 

I also got a useful piece of information from a discussion here that the main board is soldered into slot 5 of the backboard.

I couldn't find any YouTube videos of the build process. I wonder if anyone here has any more advice or information on putting together the Orton 3C? So far my total soldering experience is a few kits from AliExpress and then the RC 2014 Classic ][ which I put together and got working a few months ago.

Thanks everyone,

James

[Mark T]

I agree with Mike, don’t solder two boards together. If you look closely at the photos on z80kits you can see the backplane 5 has a right angled single row female header and the front panel board has a vertical pin header. An alternate method that might work would be a straight female header on the front panel and right angle pin header on the backplane, then the cpu card could also connect directly to the front panel, but at right angle to it. That might make it easier to debug if you need to start probing with a scope or logic probe.

On Friday, January 2, 2026 at 11:08:39 PM UTC-5 mike i wrote:

By the looks from all the pics at https://z80kits.com the cpu board has female headers and boards with switches has male headers i would recommend this because if something went wrong in future

you will have a he+2hockeysticks of a job to desolder all of those connections to get it apart. Desolder a couple of pins is ok but not many more than that. If there are copperplanes(lots of extra copper)

it is a pain you know where, groundplanes sucks the heat out of the solder iron. One can use a heat gun or a hot air soldering gun for such things but if not familiar with these tools these tools there is a

big chance of burning the pcb. A soldering iron of 50-60w will suffice if not big " planes are there, you can also warm pcb with a hairdryer to 50-60c this will help to solder flow easier. Flow of the "lead/tin"

will depend on how much oxides is on there, solder some caps/res to see how it flows, if there is issues use a rubber (lead pencil) that can help to clean oxides there is also a sort of pen with a glass fiber tip

but one has to go easy with those.

That was what i could come up with quickly

Use ic-sockets will make it easier to fix is an ic goes bad especially since some circuits are n/a anymore  

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[sunnyboy010101]

I took a bunch of photos when I built my Orton 3-C before Christmas. I think the best way to post them is to make a web page and put them there as they are large images. It will be about 1/2 hour and I'll post a link here. The secret is to build male headers on the main Orton 3-C board and then appropriately use the female headers on the extender (if you buy it) and the backplane-5. I used a blue box to hold it all.

-R

[sunnyboy010101]

I built a simple web site for my build of the Orton 3-C. 

https://huntrods.com/orton3c.html

at the moment it's just my photos of the build, but there are photos of the back of the main board (installed in the blue box) showing the connectors to the backplane-5 as well a two photos of the backplane-5 with the small I/O board. I did find in my blue box that I needed to use some threaded nylon standoffs to allow it to sit level with the main board connector and still be able to push down to install a board on the backplane. (as built it was kind of unsupported).

I used a finishing wax on the wood panel as I like the finish it provides, and was super easy to apply.

-R

[sunnyboy010101]

oh yea, happily answer any questions about my build, with all due respect to Spencer, recognizing that he is the real authority on his kits. I'm just a super happy builder of his kits in Canada.

-R

[Spencer Owen]

Thanks to those of you that have replied to this. I hope that helps James. 

The assembly guide on the RC2014 website is my best attempt at showing how it goes together and in which order - however, I am well aware that I am trying to describe things that I already know how to do, and that I am probably making assumptions or overlooking things that might seem obvious to me. So, for those of you that have built an Orton 3C already, please let me know how I can improve the documentations. 

(I will also reiterate that the front panel should not be soldered directly to the backplane or the CPU module. Header pins need to be fitted to the front panel. If it is being used with a backplane then a right angle socket needs to be used on the backplane, or if the CPU module is being connected directly to the front panel, then the CPU module needs sockets)

Cheers

Spencer 

To view this discussion, visit https://groups.google.com/d/msgid/rc2014-z80/c66756a5-19dc-4ec2-a9b4-23a99210ab7en%40googlegroups.com.

[Jamesbloke]

James,

I could kiss you. 

Child 1 and I have been trying to work out why his Orton isn't working and it is because we put the front panel on slot 1 of the backpane, not slot 5. We (I) didn't look at the pin numbers on the backpane, just the slot numbers, and had everything back to front.

Now I have 80 pins to unsolder and re-solder as penance.....

Nice photos sunnyboy010101!

Thanks,

James

[Mark T]

If you plug the front panel into vertical connector on slot 5, the other connectors on the backplane will be blocked by the front panel, but you could plug the processor into right angle slot 1. Check the pin numbers in case I got this wrong but I think you could test your front panel and processor board like this before reworking the connectors.

[Jamesbloke]

Thanks Mark T, that's what we did, which is why I was so excited.

[James Harland]

Thank you everyone for your advice and comments. I think I understand now about how to connect the front panel to the backplane :-) Your pictures are really useful 
sunnyboy010101 and so are your instructions Spencer, it's just that I hadn't found them until you mentioned they exisited :-D

I'm glad me mentioning slot 5 helped you and your child to figure things out, James!

I'm a bit overwhelmed by the quantity of parts to solder, but I suppose I just need to break things down and take it slowly. In this connection I have one overall and a couple of more specific questions.

Overall question

Am I right that the minimal working build is the Front Panel (PCB & Passive, and LEDs & Switches), and the Z80 CPU and RAM Module? 

(As I am intending to extend this later with the Front Panel Module and the 16K ROM, I take it I should also assemble and connect the Backplane 5, which is where I will connect the CPU and RAM module.)

With the backplane I got the following components in the bag;

• One 40 pin RA female connector (I use this in slot 5 to connect to the front panel)
• One 40 pin RA male connector (not sure what this is for)
• Five regular 40 pin connectors (I suppose I only need four of these)
• Five ceramic capacitors (I can see where these go)
• One barrel jack port
• Two resistors (1k and 2k)
• One small green LED
• One push button

My questions for the backplane:

1. Should I be worried about the things marked on the silk screen for which I appear to have no components? Two circles marked 100uF and 10uf.
2. Should I use the power here to power everything once I have everything set up, or should I use something on the front panel (see below), and if there are two potential sources of power, how can I switch between them?

I've looked carefully at the front panel, and again at different images of it.

My questions for the front panel

1. What is the purpose of the 1 pin RA header, which on both the Z80 Kits and on sunnyboy010101's images is soldered where it says "HALT" on the silk screen?
2. I take it the nylon spacers etc. are for the build where the RAM and CPU are attached directly to the front panel, and are so not necessary for me?
3. What are the four metal screws which I can't see in the bill of materials for? (Maybe these were in with the backplane and got mixed up with the other parts?)
4.  Can I power the computer from the FDTI connector using the adapter I have on my RC 2014? I can see this adapter is attached on sunnyboy010101's build. Again, as above, what do I do to make sure the power is only coming from one place? 

Thanks all, I'm getting closer to starting with this project!

James

[Spencer]

On Thursday, 15 January 2026 at 15:46, James Harland <harla...@gmail.com> wrote:

Overall question

Am I right that the minimal working build is the Front Panel (PCB & Passive, and LEDs & Switches), and the Z80 CPU and RAM Module?

Yes, that is correct, although see the note below...

(As I am intending to extend this later with the Front Panel Module and the 16K ROM, I take it I should also assemble and connect the Backplane 5, which is where I will connect the CPU and RAM module.)

... The pin headers you solder on to the CPU/RAM module will be different depending if it is to plug in to the Front Panel directly or to the backplane.  You're probably best off soldering the right angle pins to the CPU/RAM module and building the backplane. [If you're confident with header pin removal, solder straight pins in to the CPU/RAM module for minimal operation, then remove them and replace with RA pins when your backplane is built. If you're that confident though, just build the backplane as well :-) ]

With the backplane I got the following components in the bag;

• One 40 pin RA female connector (I use this in slot 5 to connect to the front panel)
• One 40 pin RA male connector (not sure what this is for)
• Five regular 40 pin connectors (I suppose I only need four of these)
• Five ceramic capacitors (I can see where these go)
• One barrel jack port
• Two resistors (1k and 2k)
• One small green LED
• One push button

My questions for the backplane:

1. Should I be worried about the things marked on the silk screen for which I appear to have no components? Two circles marked 100uF and 10uf.

No, unless you're adding your own LM7805 voltage regulator and feeding it with 9v or more, then you don't need those capacitors

2. Should I use the power here to power everything once I have everything set up, or should I use something on the front panel (see below), and if there are two potential sources of power, how can I switch between them?

It's up to you :-) The two main options are powering it from the barrel jack on the backplane or the FTDI connector. The FTDI connector has a 5v jumper next to it, so if you are using the barrel jack then remove this jumper.  Note that unfortunately the orientation of the backplane means that if it is fitted in a Blue Box enclosure the barrel jack socket will be right up against the metal case, so you'll need to cut a hole in it if you want to power from there.

I've looked carefully at the front panel, and again at different images of it.

My questions for the front panel

1. What is the purpose of the 1 pin RA header, which on both the Z80 Kits and on sunnyboy010101's images is soldered where it says "HALT" on the silk screen?

The Orton 3C will ideally have a 41 pin header between the Front Panel and the CPU/RAM module. This isn't a problem if connecting them directly as there's a 40 + 10 pin connection. But via the backplane 5, the HALT LED signal is missing. So the 1 pin RA header and the jumper cable between them will fix that. (if you don't fit it, you only miss out on the HALT LED. No biggie)

2. I take it the nylon spacers etc. are for the build where the RAM and CPU are attached directly to the front panel, and are so not necessary for me?

No, these are for the Backplane 5 to act as feet if fitted in the Blue Box Enclosure. The backplane is supported at the front by the Front Panel, but the screws/spacers help support the rear.

3. What are the four metal screws which I can't see in the bill of materials for? (Maybe these were in with the backplane and got mixed up with the other parts?)

The screws in the front plate of a Blue Box Enclosure are pretty short as they only need to hold thin metal in place. They aren't quite long enough to grip through the thicker wooden panel, so that's what these longer screws are for.

4. Can I power the computer from the FDTI connector using the adapter I have on my RC 2014? I can see this adapter is attached on sunnyboy010101's build. Again, as above, what do I do to make sure the power is only coming from one place?

Yes, that is probably the best option. (see note above about fitting the 5v jumper).

Thanks all, I'm getting closer to starting with this project!

Excellent. Take your time, enjoy the build, and good luck!

Spencer

[James Harland]

Thanks Spencer, that was really helpful!

I've now soldered the parts onto the back of the front panel, but I am a bit confused by the switches and LEDs, or more precisely by all the metal and plastic washers, nuts and standoffs.

As far as I can see from the pictures, the metal nuts will be used on the very front of the machine, to secure the switches to the wood panel? Not sure about the metal washers, or several of the plastic parts though. There seem to be two kinds of metal washer - serrated and non-serrated.

Sorry if this is really obvious. Maybe it will all make more sense in the morning!

Thanks again, all the best,

James

[James Harland]

Also what's the purple wire I see in some of the images? I suppose it is the 10cm Dupont cable mentioned in the bill of sale, though I haven't found that yet in what I've received (though I also haven't opened everything yet). What does it connect?

[James Harland]

OK I've figured out the above questions, and completed the build.

The instructions are really clear,  Spencer, but my careful reading skills need work :-D In particular I skipped the sentences "

"Remove the switches from the front panel and fit the LED bezels. These push through from the front and tighten up with a nut on the back.

At this point you should fit the spring washer and the round washers to every switch."

which caused me some delays going back and doing it afterwards.

Anyway, the good news is my minimal build (Front panel + backplate + CPU & RAM) is working, and I just ran the first program from Leventhal's book, with the desired effect (one's complement).

Next step is to make the input-output unit, which looks to be an easier version of the build so far.

Thanks again everyone for your support and advice,

James

[Spencer]

Excellent work James. Glad to hear that it's up and running, and you're toggling in your first Hello World!

Spencer

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[James Harland]

Thanks! Having done some additional toggling, I've decided the next step is actually the ROM board. I toggled PUTCH in only to make a mistake in my own code and garble everything I'd entered along with it :-p

Something did come through on the serial connection, just not what I'd intended :-D

Would be much easier to call PUTCH from ROM and then only have to enter my own code again if I mess it up again. 

All part of the fun!

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