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Osborne 1 Video Adapter.

I don't have my CNC set up at the moment, but have to make some new PCBs in the next month for a customer, so when I do I'll CNC up some extra PCBs of this and let's see if we can work out how to ship these to the US as a letter so I can figure the cost of shipping a single PCB by itself.

Theoretically, I should be able to send it so you can just solder it up and pop it out of the holder... After all, that's how I made them. I'll print up the extra spacers for the edge connector also so you don't have to judge and solder carefully.

But give me a little while since I'm not sure when I'll get around to the PCB making part of the project.

It won't be tinned, but it should solder up OK. And IIRC, your soldering skills are pretty good.
 
PCB File in FreePCB format, and Gerbers.

Also, some notes I earlier communicated in a PM that may assist anyone.

Three things to be certain of during assembly.
1) Glue the 78L05 down to the PCB to help distribute heat. There's no room for a heatsink. though it is possible to include a thin piece of heatsink metal bent if necessary.
2) The Video Connector bridges both sides of the PCB and carries ground to the final output transistor section. So if you connect wires, don't forget to bridge the grounds with a piece of wire since there's no jumper there.
3) The edge connector is spaced from the PCB by about 2mm. I do have a 3D printer spacer, but this can also be done when soldering.

I used these connectors for the RCA connector: https://www.aliexpress.com/item/4001050402165.html
And these for the edge connector: https://www.aliexpress.com/item/1005003003362076.html - eg, 20 pin version.

Also, none of the components can be higher than the chip when soldered fully in. There is not much space under the PCB, so capacitors are on their side and all components are flat, including transistors. Flat face down. There is no room for sockets and capacitors and transistors should be on their flat side. Diodes are all 1N4148 or similar small signal diodes. They are used mostly to adjust the voltage levels of the output signal by the same amount as the bias voltage.

I used potentiometers like this;
https://www.aliexpress.com/item/1005002780073685.html

I didn't use that specific one, but it's probably the same size. It can be adjusted from the PCB side, to make tuning easier as each unit must be appropriately adjusted, though the values are relatively consistent to set them in advance.

Regards
David
 

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cj7hawk said:
PCB File in FreePCB format, and Gerbers.

Also, some notes I earlier communicated in a PM that may assist anyone.

Three things to be certain of during assembly.
1) Glue the 78L05 down to the PCB to help distribute heat. There's no room for a heatsink. though it is possible to include a thin piece of heatsink metal bent if necessary.
2) The Video Connector bridges both sides of the PCB and carries ground to the final output transistor section. So if you connect wires, don't forget to bridge the grounds with a piece of wire since there's no jumper there.
3) The edge connector is spaced from the PCB by about 2mm. I do have a 3D printer spacer, but this can also be done when soldering.

I used these connectors for the RCA connector: https://www.aliexpress.com/item/4001050402165.html
And these for the edge connector: https://www.aliexpress.com/item/1005003003362076.html - eg, 20 pin version.

Also, none of the components can be higher than the chip when soldered fully in. There is not much space under the PCB, so capacitors are on their side and all components are flat, including transistors. Flat face down. There is no room for sockets and capacitors and transistors should be on their flat side. Diodes are all 1N4148 or similar small signal diodes. They are used mostly to adjust the voltage levels of the output signal by the same amount as the bias voltage.

I used potentiometers like this;
https://www.aliexpress.com/item/1005002780073685.html

I didn't use that specific one, but it's probably the same size. It can be adjusted from the PCB side, to make tuning easier as each unit must be appropriately adjusted, though the values are relatively consistent to set them in advance.

Regards
David
Click to expand...
So I ordered those edge connectors, rca connectors, and potentiometers you linked. I thought I threw away all the bad pcbs but I guess the one I took a photo of I put aside and I found it. Even though my boards are wrong/backwards I tried to fit the parts. The edge connector fits fine. The rca connector would would if I could wrap the legs around the edges of the pcp to the solder side (if mine was correct) but the pots are way way too large.

IMG_20240521_150834.jpg
 
OK, Boards should be with you soon. Here's a diagram of where the components go. Both TO-92 cases are glued face down with CA glue to help with heat dissipation into the PCB.


Diode orientation is pretty obvious from the photo, with the cathode marking band clear on each. You can substitute parts, but nothing can be thicker than the IC, so some small capacitors are inportant. The types I used are common and cheap. Preset the resistance across the pot to be around 8.25K when measured in circuit, though because there's an access hole, you can adjust it from the other side of the PCB when it's installed as required.

The composite plug is soldered partway down, with the center signal tab soldered directly ONTO the PCB, to give the lowest possible profile when installed. The solder tabs are just cut off. The side flaps are soldered to the side of the PCB on BOTH SIDES, as they also carry electrical ground across the PCB so I did't need to use any jumpers in the circuit.


Capture2.JPG


Capture.JPG
 
kc4bqk said:
Is there a schematic for this?
Click to expand...

Loosely drawn by hand earlier in the thread. But it is accurate.
(Original Post) - Though I didn't copy the filter caps quite the same.

Also, it's not my circuit - I copied it from one that came with an Osborne 1 I bought... It was small and black and a bit bulky, and was from a Version1 and didn't fit a Version1A, so I made mine a bit flatter... There are gerbers in the thread also. And some that got made backwards. :(
 
cj7hawk said:
Ohhh. You got a Vixen too! .... Nice... I don't have one of them :(
Click to expand...
Actually I have 2. I have one working and one that needs repair. I am looking for the O3 to complete my collection. I will be set up at VCF Midwest with my Osborne's. Have you joined the Osborne Facebook Group?
 
cj7hawk said:
Loosely drawn by hand earlier in the thread. But it is accurate.
(Original Post) - Though I didn't copy the filter caps quite the same.

Also, it's not my circuit - I copied it from one that came with an Osborne 1 I bought... It was small and black and a bit bulky, and was from a Version1 and didn't fit a Version1A, so I made mine a bit flatter... There are gerbers in the thread also. And some that got made backwards. :(
Click to expand...
I was working with that one and got confused, I will have to try again.
 
kc4bqk said:
Actually I have 2. I have one working and one that needs repair. I am looking for the O3 to complete my collection. I will be set up at VCF Midwest with my Osborne's. Have you joined the Osborne Facebook Group?
Click to expand...
Yes, I did see the group as I looked more closely so joined it yesterday.

I also have a very nice full height Gotek face for the Osborne that looks like the original drive,


It hides the controls when it's down, and flips up to reveal them, though the display is always visible... It keeps the same look and feel even when a gotek is installed, and recesses the USB so it doesn't stick out.

I am currently reviewing the STL files to improve the design and also making a Kaypro version with the different form factor to the Osborne drives, and a shorter latch.

I'm in Australia, so don't get to visit the fairs - I'd love an O3, but I haven't even seen one appear over here. I was lucky enough to find an executive, as I had previously bought a full set of manuals for one that came with a spare O1/2 keyboard.
 
cj7hawk said:
Yes, I did see the group as I looked more closely so joined it yesterday.

I also have a very nice full height Gotek face for the Osborne that looks like the original drive,


It hides the controls when it's down, and flips up to reveal them, though the display is always visible... It keeps the same look and feel even when a gotek is installed, and recesses the USB so it doesn't stick out.

I am currently reviewing the STL files to improve the design and also making a Kaypro version with the different form factor to the Osborne drives, and a shorter latch.

I'm in Australia, so don't get to visit the fairs - I'd love an O3, but I haven't even seen one appear over here. I was lucky enough to find an executive, as I had previously bought a full set of manuals for one that came with a spare O1/2 keyboard.
Click to expand...
That is a nice drive caddy!
 
So I received some of these boards from @cj7hawk Thank you again sir!

I boneheadedly forgot to order a couple of the components so I am waiting on that to test them out. Once I successfully build one, Ill make a few more so if anyone with an Osborne 1 wants a composite video out adapter here in the States send me a PM.
 
IIRC, the sync for horizontal or vertical ( Horizontal I think ) coming out of the osborne is a 50% square wave or similar, rather than the typical sync timing, hence why they used the timer IC to generate the correct sync on the edge.

There's two elements to consider - one is the voltage levels, and the other is the pulse widths. Though whether you pay a lot of attention to them depends on whether a lesser circuit works. The once I posted works, but isn't ideal. I used the same circuit as an encoder in my video PCB I recently made, but got the voltage levels and timing a lot closer to what is expected.

How well does the one you've tried work?
 
The PCB has a pair of blue resistors on it, between ground and the two syncs, so they might be there to adjust the voltage levels going into the device.

In this video I fiddle around with the adaptor, so you can maybe get a better look at it.

And then here I've captured the output ... composite-to-HDMI then HDMI-to-USB. Output is pretty good.

I didn't take a clear photo of the other side of that main component earlier - you can see some parts sticking out, like surface mount passives or transistors.

I should hook it up to my oscilloscope and capture the waveforms perhaps.

EXMON_8.jpg
 
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