SEB-3

[billdrom]

Yes, I can make a real floppy.
I am currently using eight inch drives but I probably can setup a five inch drive system if necessary.
Am using greaseweazle F7 plus to create floppies.

[billdrom]

Yes, I can make a real floppy.
I am currently using eight inch drives but I probably can setup a five inch drive system if necessary.
Am using greaseweazle F7 plus to create floppies.

Will this be a bootable disk?

I don't know why there are jumpers. It is the way I got it.
Don't have the manual or schematic.

[bxdanny]

Here is an image to make a bootable 8" floppy with the SEB-3 driver.

The monitor display will be a total mess until the disk boots, but then it should stabilize if the board is good.
Let me know if it works.

[billdrom]

Thank you.
It will probably be about a week until I get to try it.
But I'll try to do it sooner.

Bill

[billdrom]

I booted the C8p up to the D/W/M screen just to make sure it still worked.
I don't have the floppy drive connected right now.
Pulled the 540 card and replaced it with the SEB-3 card and rebooted the system.
Absolutely nothing on the screen I guess the 6845 needs to be initialized first.
Did not connect the keyboard because I don't know what jack to use.
There are three empty sockets on the SEB-3 card.Could be missing some chips.
I have no manual or schematic.
Scoped the larger crystal, it is running at 3.99 MHz the small Crystal is running at 12.6 MHz.
Nothing at the RCA output jack.
I did make the disk and tried it on a serial system but of course it did not boot.
I'll have to move the cards from the C8p to a test system near my other disk drive set up and try again.
Would the disk boot in a 540 based system? Maybe just enough to know the disk is basically OK?
I could use some suggestions. I know the guy I got the board from had the manual but haven't heard from him in years.
I'll try reaching out.

[bxdanny]

The disk should boot on a serial system or one using a 540. The program tests for those conditions and doesn't load the SEB-3 driver or initialize the 6845 if it finds either.

Are all three empty sockets 16 pins? If they are, I really don't know which is the keyboard socket. Are all four RAM chips present?

Anyway, if the board was working, what you should see before the 6845 is initialized is a picture that is tearing horizontally, since there is no stream of sync pulses in the right frequency range, but there should be both black and white (or green, whatever) areas visible. If the screen is completely blank, I guess the board isn't working. Thanks for trying, though.

[billdrom]

I am not done trying yet.
I'll keep at it for a while.All four ram chips are present.
Three empty sockets are all 16 pins.
I'll try the disk in a 540 system with 48 K of memory.
The serial system I tried was a 510 board with added memory from D000 to EFFF.
I remade the disk and will try again.
Still looking for the schematic. Did you say you might have it somewhere?

[billdrom]

Apparently the first disk I made was bad.
I forgot to tell the program it was single sided. I didn't think it would matter because it was a single sided disk drive.
I re-copied the disk with the correct parameters and was able to boot it on a serial system.
It signs on as follows.
OS-65D V3.2 BASIC
System Open
OK

So I know the disk is good. That is the starting point.
I reached out to the person I got the board from for a copy of the manual.
Now I will wait for his response.

[bxdanny]

I found the parts-placement guide and one page of the schematic, which are attached. It looks like they are pages 15 and 17 of a manual, but I don't recall ever having it, and I don't have any other pages of it. The notes on the schematic do look like my handwriting (they are in blue pen); everything on the parts-placement guide is part of the printed document. There are holes visible (in the upper-right corner of the landscape pages) showing where the pages were once stapled together.

Bill, at least you can now see which socket is the keyboard jack. Hopefully, you will be able to get the full manual from your source. If you do, I'd like to see it.

-Danny

[billdrom]

Thanks for the pages from the manual. They were a big help getting started.
First I found that the two missing IC chips were 8T26s used for reading the keyboard. And of course the actual keyboard socket.
I was able to boot your program using the keyboard and new 8T26s even though there is no actual display on the monitor,
I just typed "D" and listened to the drive go through its paces. Before booting there was no sync or video at the IC 37 outputs but as soon as booted all the pulses seem to be there. The screen went from "No Signal" message on screen to a raster display and no video. The horizontal frequency is 15809 on my scope.Video is 4.7MHz. I replaced the 2n3904 transistor just in case because I had some available. Didn't help any. Next I looked at IC-35 outputs and there may be a timing issue with display enable and the video. All the jumpers and cut traces seem to be involving IC-37. The extra chip is a Cmos type dual flipflop. I am thinking that I should remove all the jumpers and fix all the cut traces back to the original board and retrace my steps.
I think someone was using a chip location meant for the floppy interface for their experiment.
It seems to be pretty close to operating correctly. The computer can read the keyboard and the board responds to your initialization commands by outputing sync pulses from the 6845 chip that are not there until after boot.

Even if the display was correct, how would you see the D/W/M message on reset when first starting if it needs initializing first?

Any way, progress is being made. I won't be able to do any more until next week, about Tuesday or so.

Bill

Trouble shooting SEB-3 Grafix card.jpg (811.23 KiB) Viewed 5503 times