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Osborne 1 Video Adapter.

cj7hawk

Veteran Member
Joined
Jan 25, 2022
Messages
1,266
Location
Perth, Western Australia.
Hi All,

It's not my schematic - just a repackaging of one of the original Osborne1A's video adapter, but modified to fit in the very tight slot of the Osborne1Bs video/reset/battery bay.

It's a low-profile design and comes out roughly flush with the top of the face, so will pack away nicely. I wil make up a nice case for it so it looks good, and can be easily installed and removed. Due to the design, it only fits properly one way, so should also avoid those incidents of people plugging them in upside down. All of the components sit below are are pretty much touching the O1's surface, so it's very tight in there, and components are either folded flat or fully seated. The potentiometer for the horizontal sync width is seated fully in slots so that the adjustment can be accessed from the PCB side also, keeping it all out of the way.

The main change I made was to switch the sides of the chip swapped the horizontal timer for the vertical timer, mainly to make it all fit nicely.

Happy to share files if anyone is looking to make their own. It's entirely single-sided as you might guess from looking at the copper. ( I love the simplicity of a good single-sided digital design... )

IMG_20230528_080915.jpg

IMG_20230528_081048.jpg


schematic.JPG
 
Just a simple 3060, with a 12000 rpm brushless, and using RNR ECO for the breakout. I run at a lower speed due to the poor quality opto's in the stepper controllers, but the hardware is quite repeatable.

I use FlatCAM 9.4 ( Waiting for Marius to put out 9.5 as an exe ) and autoleveller 0.9.5u2... Also, just figured out with this print I seem to be afflicted with the M31 bug, so set al M31's to -5.

The key to a good result though is the quality of the bits... Most are not really great, and I get mixed results from V tips. But then I found these Chinese bits that are fantastic and I can isolate to 0.0149, so with 50 thou pads, I can fit tracks up to 20 thou across between pads... Which works well.

I use FreePCB since it stores everything local and I don't really like cloud.

But, yeah, the bits are the key that everyone misses. Vtip would be my choice if these weren't available - but it's chalk and cheese between VTIP and these ones.

62 HRC, R0.2x4Dx50L-L2, 1 PCS


No one else sells anything like them that I've found, save one US company that charges 10 times as much per bit ( and I break a LOT, usually through mistakes... Plus they wear out pretty quickly ) They are a ballnose so put a much nicer angled finish on the edge, and I usually do three passes with 65% overlap, since I usually get a cut width of around 7 to 10 thou not fully going in, and mostly cutting with just the tip.

David.
 
Some pics, before polish, after polish ( just a hard wipe with a bunched up plain tissue to remove burrs etc ) and a close-up with side-lighting to show the grain of the cut, so you can see how clean the ball nose makes the PCB.

It may not look like much, but there's 5 years of experience, pain, trial and error, went into finally getting a good result, while some people get lucky with a mill.drill combo and get it the first time... Also I use the L2 Mill so I can do the entire PCB in one operation - it mills the tracks, then mills the holes, then cuts the PCB out. Which makes it easier to include things like the hole for setting the POT.

WIN_20230528_09_29_09_Pro.jpgWIN_20230528_09_31_15_Pro.jpgWIN_20230528_09_32_44_Pro.jpg
 
Wow! It's even more impresive looking at the close up shots.
Thanks for all the info on your tool flow. I'll be checking out FlatCAM and those bits.

Jesse.
 
Hi All,

It's not my schematic - just a repackaging of one of the original Osborne1A's video adapter, but modified to fit in the very tight slot of the Osborne1Bs video/reset/battery bay.

It's a low-profile design and comes out roughly flush with the top of the face, so will pack away nicely. I wil make up a nice case for it so it looks good, and can be easily installed and removed. Due to the design, it only fits properly one way, so should also avoid those incidents of people plugging them in upside down. All of the components sit below are are pretty much touching the O1's surface, so it's very tight in there, and components are either folded flat or fully seated. The potentiometer for the horizontal sync width is seated fully in slots so that the adjustment can be accessed from the PCB side also, keeping it all out of the way.

The main change I made was to switch the sides of the chip swapped the horizontal timer for the vertical timer, mainly to make it all fit nicely.

Happy to share files if anyone is looking to make their own. It's entirely single-sided as you might guess from looking at the copper. ( I love the simplicity of a good single-sided digital design... )

View attachment 1258147

View attachment 1258148


View attachment 1258149
Im repairing an osborne 1 soon and would love to have these files!!
 
Hi Verault, Happy to share the files... I can provide Gerbers or raw FreePCB original files if that's preferred. Also have CNC milling files but generally the last bit may be more customised to my use than others would want to reuse.

David.
 

Attachments

  • Osborne 1 Video Adapter.zip
    3.3 KB · Views: 13
Note: When assembling, I swapped the one-shots on the IC for a better PCB layout single-sided to avoid needing wire links and keep the size small. So the pin numbers, resistors etc are all swapped from one side to the other of the chip.

Use the photographs to identify the correct component placement.

David
 
Hi Verault, Happy to share the files... I can provide Gerbers or raw FreePCB original files if that's preferred. Also have CNC milling files but generally the last bit may be more customised to my use than others would want to reuse.

David.
Gerbers is what I need.
Ok thanks for the heads up. Ill check the photo.
 
I had some difficulty reading what parts were used in the schematic, I would really like something like this for my Osborne 1. So got Kicad going to make a proper one. But I can't quite figure out what the diodes and the transistor have to be (It's not just the handwriting, mine is easily as bad... I just have little experience with the different part numbers here and in the US).

This is as far as I got so far.
 

Attachments

  • Schematic.jpg
    Schematic.jpg
    274.8 KB · Views: 13
Yes, I'll regenerate the files with a solder mask.

This particular circuit was designed for single sided production, so isn't optimised for double-sided or production methods, but should still be OK. I'll post up my design files tonight in case anyone wants to modify or change also.

The schematic was, as I noted, not mine, but was me jotting down what the original circuit did. I swapped the side of the chip on mine, so the schematic reflects the original (copied) circuit, not the layout I provided.

I'll try to locate it and get some better photographs later and note all the part location.
 

Attachments

  • CAM4.zip
    4.5 KB · Views: 5
Yes, I'll regenerate the files with a solder mask.

This particular circuit was designed for single sided production, so isn't optimised for double-sided or production methods, but should still be OK. I'll post up my design files tonight in case anyone wants to modify or change also.

The schematic was, as I noted, not mine, but was me jotting down what the original circuit did. I swapped the side of the chip on mine, so the schematic reflects the original (copied) circuit, not the layout I provided.

I'll try to locate it and get some better photographs later and note all the part location.
Im just trying to use pcb way and they keep kicking it back. First because of no solder mask. Now because the solder mask isnt right.
2212445086373t.png
 
I think it's because I've got that huge hole to remind me where the reset button is.... I'll pull it out and resend the files.

Also I'll add the component details to the silk screen to make assemby easier.
 
Yes, They've treated the copper side as the component side. Not the first time I've seen that happen. I used to put text on the PCBs to assist in determining the correct side.

I wrote an article for a magazine a few years back, and they didn't realize when they made the PCBs ( something they insisted on, and they hand made them too! ) that the text was all backwards, so they let me make the next round of PCBs.

I don't know why some manufacturers assume that if you only go single sided, you have flipped the gerber, because they don't assume that with 2 sided, and it's not like CAD systems assume that either. :(

It could still be populated, since you need to space the edge connector out about 2mm, so it would be possible to solder entirely from the top if you place the components carefully.

The difficult part would be the pot, but you can solder that to the top side through hole normally. Also, you'll need to manually bridge the ground where the connector goes since it may not fit in soldered in, in the normal way.

It's probably better to remake the PCBs. They might cover the error unless they made it clear that they were going to flip the PCB for single sided board.

BTW, when you come to soldering them, the best way to space the edge connector is to install the edge connector into the Osborne, then put the PCB on top so it's seated correctly, then solder the pins.

David
 
It would be a royal pain to put on some of those components and have to solder from the top. Ill reach out to pcbway. This is the first mistake that has ever happened to an order of mine. Lets see what they say.
 
Well PCBway is not going to help me. Big surprise there, China incapable of customer service. What a joke.

Anyway if someone else had boards made, and properly please sell me two of these pcbs so I can build the video adapter.
 
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