C-10 restoration

[Chris LaFond]

My Cromemco C-10 that I have bought is having a problem powering up. When I turn the power on, The screen will raster and that is about all I am getting. I do not have a keyboard for it, but I would assume I should still see something happen. My first question would be is someone could explain the boot process of the C-10 with no keyboard or floppies connected, if i should see something on the screen or on the RS232 serial port.

On the power supply, I replaced the three RIFA caps (the big one has already been fried). Checking voltages do not seem correct. +12.4, -11.8, +4.84. The 5 volt rail being low is what I am curious about. So my second question is what someone thinks of the low 5 volt rail and if someone has a schematic for the power supply or knows how I could adjust the 5 volt output.

Lastly I would like to ask the community if anyone has a keyboard they would like to sell for the C-10 or of a good way to imitate the keyboard with someone else until I can acquire one.

Thanks to everyone and I think it is awesome there is a Cromemco group.

[Mike Stein]

Hi Chris, and welcome!

Here's most of the C-10 info out there; if you have trouble,use the wayback machine to access the amaus URL.

https://amaus.org/static/S100/cromemco/systems/C-10/

Check into the Cromemco github for instructions on how to get registered for access.

I may have some more documentation and the software bundle somewhere; I'll look when I get a chance.

Good luck!

mike

--
You received this message because you are subscribed to the Google Groups "Cromemco" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cromemco+u...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/cromemco/a3fcc9c1-b92c-4bee-afdb-213a82c7b624n%40googlegroups.com.

[Aron Hoekstra]

Welcome to the group. I'm following with great interest. I also have a non-working C10, sans keyboard & disk drive.

To view this discussion visit https://groups.google.com/d/msgid/cromemco/CAHHfo1vVzxtRf6cdW__zgXWBS44God%3DzX7dy%3Dj%2BGdMrpZq%3Dsnw%40mail.gmail.com.

[Mike Stein]

Sorry, looks like I don't have any extra documentation for the C-10 after all, just multiple copies of the technical manual. I've got their troubleshooting guide but it only covers the S100 systems.

As I mentioned to you before I do have a disk drive but it belongs with the system 3/300; if I do scrap it I'll let you know.

As you know I do have a C-5, which uses the same or similar keyboard; if I get the time one day I could probably scope out the protocol and character layout if you decide to build your own.

Have fun, guys!

To view this discussion visit https://groups.google.com/d/msgid/cromemco/CAD9iBDKpQM1gqh44hroZwyUGuCejM9%3DMsxvxt5FiaEBJ5GYa5A%40mail.gmail.com.

[geneb]

On 12/9/2024 9:04 PM, Mike Stein wrote:
> Hi Chris, and welcome!
>
> Here's most of the C-10 info out there; if you have trouble,use the
> wayback machine to access the amaus URL.
> https://amaus.org/static/S100/cromemco/systems/C-10/
>

There's a domain squatter there now.  IA has it:
https://web.archive.org/web/20170904045552/https://amaus.org/static/S100/cromemco/systems/C-10/

I've actually got one of those, but no boot media. :(

g.

[Mike Stein]

Yeah, the site was moved to github some time ago, which is why I suggested the archive. But to get the latest files you should really register.

You should find the files you need under code/disks, disks no. 382 to 398 and perhaps more for individual files and near the bottom images of the same disks in various formats.

Have fun!

--
You received this message because you are subscribed to the Google Groups "Cromemco" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cromemco+u...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/cromemco/808d5e7f-dd70-4b5b-8729-ddeec78f827a%40deltasoft.com.

[geneb]

Thanks, I'll make a note of that.


g.

On 12/10/2024 11:02 AM, Mike Stein wrote:
> Yeah, the site was moved to github some time ago, which is why I
> suggested the archive. But to get the latest files you should really
> register.
>
> You should find the files you need under code/disks, disks no. 382 to
> 398 and perhaps more for individual files and near the bottom images
> of the same disks in various formats.
>
> Have fun!
>
> On Tue, Dec 10, 2024 at 1:07 PM 'geneb' via Cromemco
> <crom...@googlegroups.com> wrote:
>
>
> On 12/9/2024 9:04 PM, Mike Stein wrote:
> > Hi Chris, and welcome!
> >
> > Here's most of the C-10 info out there; if you have trouble,use the
> > wayback machine to access the amaus URL.
> > https://amaus.org/static/S100/cromemco/systems/C-10/
> >
> There's a domain squatter there now.  IA has it:
> https://web.archive.org/web/20170904045552/https://amaus.org/static/S100/cromemco/systems/C-10/
>
> I've actually got one of those, but no boot media. :(
>
> g.
>
> --
> You received this message because you are subscribed to the Google
> Groups "Cromemco" group.
> To unsubscribe from this group and stop receiving emails from it,
> send an email to cromemco+u...@googlegroups.com

> <mailto:cromemco%2Bunsu...@googlegroups.com>.

> To view this discussion visit
> https://groups.google.com/d/msgid/cromemco/808d5e7f-dd70-4b5b-8729-ddeec78f827a%40deltasoft.com.
>
> --
> You received this message because you are subscribed to the Google
> Groups "Cromemco" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to cromemco+u...@googlegroups.com.
> To view this discussion visit

> https://groups.google.com/d/msgid/cromemco/CAHHfo1vu4nyjBeZaiH-%3DnQ2CCOUy%2BqUBWqhH-KZm%3DUP7nKKMXQ%40mail.gmail.com
> <https://groups.google.com/d/msgid/cromemco/CAHHfo1vu4nyjBeZaiH-%3DnQ2CCOUy%2BqUBWqhH-KZm%3DUP7nKKMXQ%40mail.gmail.com?utm_medium=email&utm_source=footer>.

[Mike Arnold]

Welcome to your Cromemco journey. 

I did not do much with the C10 in the later 1980s as we were moving away from Cromemco by that stage. However, I do remember that they were quite nice machines and great as 3102 terminals. If I recall correctly, the keyboards were serial interface (RJ11 connector?) and the disk drive was pretty vanilla being wired through a multi-pin connector. 

As you surmise, I am not sure how the C10 behaves if it cannot find a keyboard but I am sure it should do something sensible.

The low voltage on the +5V rail does not sound too serious. TTL is specified down to 4.75V and usually runs ok even lower than that. I would advise testing the voltages on chip legs in case there is a corroded connector. However, if you can tweak the voltage up a tad over 5V then you can eliminate any doubt around this. If you can supply a good picture of the PSU I might be able to guess where to adjust things. Of course, you may have a boot ROM problem if you have a UV type. They do not have infinite retention life.

If someone can find a circuit diagram of the motherboard things may become a little clearer.

Mike

[Mike Stein]

Schematics are in the Technical Reference Manual, although they could be clearer; some pages of the original aren't much better.

To view this discussion visit https://groups.google.com/d/msgid/cromemco/a50f128e-ea77-407d-9ae3-29c6183e7f0cn%40googlegroups.com.

[Chris LaFond]

I have been probing around the motherboard on this C-10 and signals don't look too bad.

clokc signal to Z80 looks nice and the machine does 'run'.

I have noticed that after a few seconds of booting the CAS signal to the ram will stop and most of the activity goes away. RAS still runs and it seems like it loads ROM into ram and then when it bank switches to un-enable the ROM is when things fall apart. Hooking a logic analyzer up to the data bus shows stuff moving around for a few seconds but the just repeats a FE and Bsomething (I think this is the Dram refresh but looks half-baked).

As of right now I am thinking it could be a bad ROM (doubtful), bad chip the runs the refresh or a bad bus transceiver. 

I will keep poking around and if I discover something else I will report.

[Chris LaFond]

I did some more probing and research and found the CAS line comes from IC24, a 40 pin DIP that is called 'C10 CPU & MEM support'. I don't know who makes the chip. Attached is a picture of the chip next to the z80 CPU. If this IC is bad I doubt there is a chance of replacing it which is too bad since this machine is in nice condition.

If someone could take a look at the schematics in the technical manual and give me some thought about what they think about the CAS line that stops working a few seconds into boot. I was reading some 'z80 CAS line problems' where if the addressing is getting messed up it could change the cas line.

Any advice or suggestions would be appreciated. I am assuming that this IC is bad and the computer is useless without it.

[Peter Higgins]

If the computer is just "idling" and is doing no reading or writing to system RAM, the only activity you will see within the RAM chips are the DRAM chip refresh cycles. During refresh, CAS is inactive (high) and only RAS is strobed as each of address lines A0-A7 is incremented. In other words, it may be the computer is hanging for other reasons, and because it has "hung" the only output you see from the IC24 DRAM controller is the RAS signal indicating that only DRAM refresh is happening in the absence of read/write requests to system RAM.

[David Roberts]

I was just going to say the same thing.

If the CPU has halted, or is stuck in (say) a loop in ROM (say waiting for a disk to be loaded or the user pressing a key) then the DRAM will not be accessed.

In thus state, you should be observing /RAS cycles (for the refresh) but no /CAS cycles.

Dave

To view this discussion visit https://groups.google.com/d/msgid/cromemco/8dd1abe8-25a5-4603-b760-9f42a09fad20n%40googlegroups.com.

[Chris LaFond]

I think this means what I found is a good thing in that the IC is working properly. I am going to read through the technical manual and try to learn its boot procedure. Maybe it could be hanging on no keyboard but I would assume it would display a no keyboard error. I am also going to hook a speaker up to the keyboard port and see if it makes any tones. After that it would be hooking a logic analyzer up to the address lines and also dumping the ROM to see if it is getting loaded into the CPU correctly. Thank for the help. I will keep you posted. Any suggestions or insight is always appreciated!

[Chris LaFond]

An update on the C-10 restoration:

I have acquired a keyboard and have had a few days to test some things. After plugging in the keyboard, the C-10 boots to CROS 1.05. looks and feels just like RDOS.

The computer passes it's memory and floppy read tests. The prompt and commands seem to work. (I could not get the RD command to work. I may have been using it wrong).

My next attempt was to boot a C-10 image from a floppy disk. this is where I am stuck. I have tried all 7 image files listed in the repository. Using IMD and a controller that I write other Cromemco disks with, I wrote these images to disk but the machine refuses to boot. If I leave the disk in before power on or trying to boot from the prompt gives me little result. I do get something on the screen. Most of the disks display some unrecognizable symbols in the top left corner, or maybe a few lines or graphics with an inverse blinking background. 

This lead me to believe something is happening, but not in the right way. I think data is being loaded into memory and executed but I don't think it is valid data. The glyphs and garbage on the screen look like graphics mode and not normally characters from a set. which means enough of the code is executable to send stuff to the screen. 

Now I have to figure out where the data is going bad. I think the floppy drive and disk are good. each pin on the cable connecting the floppy to the computer was probed and checks out ok so I don't think it is the cable. This makes me think it could be the floppy controller. Booting different disks I would get the error 'disk controller not ok'. This error *I think* is from a bad load from the floppy disk and not fatal.

Any suggestions on what the group may think. Disk controller IC bad? The computer seems completely sane, it just can't get a good load from the floppy disk.

Thanks.

[Chris LaFond]

I forgot to add this picture:

[Roger Hanscom]

Hi Chris,

Picture looks like your hardware is OK.  What sort of disk drives are you using?  What's your FDC?  I'd be happy to send you some bootable diskettes, but they would have to be 5.25" HD generated on a System One.  Would they be compatible with a C-10?

Roger

[Aron Hoekstra]

Can you tell me what happens when you try to boot the computer with the keyboard? does it not boot at all?  I see that keyboard come up on eBay, got a notice from a saved search and by the time I clicked on it, it was gone ;) glad it went to a good home

To view this discussion visit https://groups.google.com/d/msgid/cromemco/7ef2516b-3150-48dc-ac5e-4b0572104a72n%40googlegroups.com.

[Chris LaFond]

Aaron and Roger:

The computer does not boot without a keyboard. It's a blank screen without it. 

The ebay sale for the keyboard wasn't cheap but I figured I wouldn't see one again for awhile. The keyboard looks in really good condition and works fine. the keys feel dry. The switches are attached to a metal plate. The switches have plastic pins that go through holes  in the metal plate and then melted to make it kind of like a rivet. I think this makes it extremely difficult if a switch had to be replaced. There are two plastic membranes between the switches and the metal plate. Horrible design for a keyboard.

I have tried multiple floppy drives with the unit. Most have been Tandon TM-100. The strange thing is the cable was changed to run 2 disk drives off one cable. The cable is a GPIB type connector to the computer and then  directly into the floppy drive housing where it turns into a 34 pin connector and power. The previous owner had soldered (daisy chained) wires from the first floppy to the second. looks like they used lamp/appliance electrical cord to do the job. I think they moved the DS1 pin to the the Motor on A signal, and used the motor signal wire as DS2 for the other drive. It took awhile to figure this out. I unsoldered the 2nd drive from the first and added an additional wire to create the motor on signal for drive a. The other wire they had used for DS2 is missing its connector pin and is too short to use.

Anyway the drive (or all that I have tested) will seek and change heads using the CROS commands (S)eek and (SS)side select.

The FDC controller IC is a WD FD1793B-02. black square window type. Directly soldered to the main board.

The C-10 is essential a SBC with a crt monitor built into it.

I don't think I need disks made for it. One of the images from the cromemco repo is readable with my CDOS machine. I think I have a good bootable image but the c-10 will not display a good screen when trying from disk. It is odd I am not getting any CRC errors.

More I think about it it seems like it would be the FDC IC. It's hard to probe anything while running the way the main board is tucked under the screen in the chassis.

Thanks for the replies.

To view this discussion visit https://groups.google.com/d/msgid/cromemco/CAD9iBDLW7vW54exCADSe3TwE2Mnwfb%3DfN72Hoqgh5V6ihBEtZg%40mail.gmail.com.

--

[Aron Hoekstra]

I have no idea if my C-10 motherboard works or not, but if it helps you narrow down your issue by chip swapping I wouldn't mind sending it your way. Then you can at least let me know if my motherboard works and if I should invest in a keyboard next time one comes up :)

To view this discussion visit https://groups.google.com/d/msgid/cromemco/769b16af-885b-4d11-a0f5-7e92b2584960%40gmail.com.

[jos]

Do I understand correctly that the C10 had 2, and now only  1 floppydrive ?
Did you put back  the termination resistors on the drive ?

Jos

[KDK KDK]

Yes termination chip is installed in the single drive. I have not looked at the schematics but I think it's the fd1793 chip. I feel like the way they soldered the two drives together I plugged it in and it instantly ruined the FDC.

--
You received this message because you are subscribed to the Google Groups "Cromemco" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cromemco+u...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/cromemco/1284df8a-2647-4cb7-9752-ea6903ccccc1%40greenmail.ch.

[Peter Higgins]

On Friday, January 31, 2025 at 5:38:16 AM UTC-8 Chris LaFond wrote:

Yes termination chip is installed in the single drive. I have not looked at the schematics but I think it's the fd1793 chip. I feel like the way they soldered the two drives together I plugged it in and it instantly ruined the FDC

It is very unlikely you damaged the 1793 FDC chip. All connections between it and the drives are buffered, therefore it is more likely one of the two 8T98 buffer/driver chips would be damaged.

Are you certain the C-10 will boot from a "standard" Cromemco CDOS boot disk, rather than a CDOS boot disk specific to the C-10?

[Mike Arnold]

If I remember correctly the C10 will only boot from a C10 disk. It will not boot from a normal CDOS disk.

To unsubscribe from this group and stop receiving emails from it, send an email to unsub...@googlegroups.com">cromemco+unsub...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/cromemco/389c923f-1972-430d-aab3-83a8d6a446a0n%40googlegroups.com.

[KDK KDK]

I don't think it will boot off normal CDOS. The images I have been using are the different release versions for the c-10. I was able to read the c-10 image using CDOS which tells me the image is ok.
I will check the buffers. I hope that is the problem. They are easier to replace

To view this discussion visit https://groups.google.com/d/msgid/cromemco/5a5ab62a.19250.194bd3f5626.Webtop.11%40talk21.com.

[Mike Arnold]

I have some original C10 disks if you cannot get hold of one but I'm in the UK so will be a bit slow to post.

To unsubscribe from this group and stop receiving emails from it, send an email to unsub...@googlegroups.com" target="_blank">cromemco+unsub...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/cromemco/5a5ab62a.19250.194bd3f5626.Webtop.11%40talk21.com.

--
You received this message because you are subscribed to the Google Groups "Cromemco" group.
To unsubscribe from this group and stop receiving emails from it, send an email to unsub...@googlegroups.com">cromemco+unsub...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/cromemco/CANV55OvDhiZts_oL5RhT_57CJaAKThCF3Ro%3DqZcYwQTdr4prZg%40mail.gmail.com.

[Brett Hunter]

Hi,

 The C-10 will boot to CDOS if the upgrade was done (a new ROM that was increased to 32KB to hold the CDOS 3.0 itself).  As you boot into RDOS the upgrade was not done so you must use CDOS 2.X disks for the C-10 (NOT other CDOS variations for other systems - only the C-10 version will work).  The maximum number of disk drives was 2 - but in fact you can attached up to 4 no problem - just not real drives as the limitation of 2 was mainly due to the power consumption (a distinctive wobble on the monitor when accessing the drive even when 2 attached) .  The low power floppy emulators like the HxC work fine and so you can have more than the 2.  There was no terminating GPIB - you could just attach to the previous one plug.  I only ever had up 3 for routine use due to the stress of having hanging so many plugs off the one port as the GPIB connectors are not small. 

Hope that helps

Brett

To view this discussion visit https://groups.google.com/d/msgid/cromemco/16dd2a98.19374.194bd4e9cda.Webtop.11%40talk21.com.

[Chris LaFond]

I receive the 8T98 Buffers and have them installed. It did not make a difference. I have been probing around the board and there is a raw signal from the floppy drive into the FDC and the data lines dance as it is loading whatever is on the disk into memory.

This makes me think there is nothing wrong with the computer but the disk images I am using don't work.

Can anyone verify the images in the cromemco repository for the C-10 work? I have been using a gotek currently to boot

[Chris LaFond]

Hello,

I have an idea but I have a few questions:

The CROS monitor has a command RD that lets you read sectors off a disk into memory. I would like to copy the boot code from the floppy into memory and then verify if what was copied is what the sector actual contains.

I have messed with the RD command and it grabs data but crashes that C-10. maybe I am loading the data into the wrong spot in memory. The command I have been using is RD 0 100 1

RD - Read from disk

RD beginning-addr ending-addr sector

RD beginnning-addr S swath-width sector

My first question is what do I need off the boot disk to make the c-10 run? Do I copy Side 0, track 0, sector 1. Do I need more than one sector?

The next question is where in memory do I read the data into? The C-10 techinal manual page 75 shows a memory map. CDOS low memory is 0h - 100h, CROS ROM 8000h - BFFFh, high memory FFFFh - 12k to 16K from the top. Where does CDOS/Cromemco stick the data it has read before it executes?

Thanks for all the help!

To view this discussion visit https://groups.google.com/d/msgid/cromemco/874bde5e-76ca-4219-8997-6248d771d857n%40googlegroups.com.

--

[Chris LaFond]

I am convinced that there is nothing wrong with the C-10. I can load sectors off the disk into memory and everything looks fine.

I need images for booting this. Everything I have tried from the repository for the C-10 won't boot. If someone has an image I could try, that would be awesome. I have the hardware to make cromemco disks so there should be no reason to have to mail a hard copy.

Thanks for all of the help. I hope I can find something to boot with.

On 2/12/25 13:58, Chris LaFond wrote:

To view this discussion visit https://groups.google.com/d/msgid/cromemco/874bde5e-76ca-4219-8997-6248d771d857n%40googlegroups.com.

--

[Brett Hunter]

Hi,

  I have lots of C-10 disk images as well as the 2 ROM type images.  I will need to dig around to find, but will attach in another reply.

Brett

To view this discussion visit https://groups.google.com/d/msgid/cromemco/0c192a7f-0f65-41ed-bf59-60d54a597593%40gmail.com.

[Chris LaFond]

I purchased another CFD floppy drive for the C-10. This one is on perfect shape. Same problems with not booting. I can read some of the disks. Some say it can't read the label. most try to boot, show random graphics characters at the top of the screen and the a long beep from the keyboard (like it is sending bad escape codes to screen).

I am still thinking I need good floppy images.

[Chris LaFond]

Hello,

I am still looking for a verified working image to boot this C-10 computer.  If anyone has images to try I would appreciate it. I know someone offered to mail a disk. That might need to be an option in which I can send money or figure out would you would like in exchange for a working floppy disk.

Thanks!

To view this discussion visit https://groups.google.com/d/msgid/cromemco/59c760b5-69eb-408b-b136-f3f39fbefb44n%40googlegroups.com.

--

[Chris LaFond]

I was able to get the Cromemco C-10 to boot. From the repository, not all images have cdos.com. If that file does not exist the machine will not boot (duh). I use the files from 386C10-Release5B. I formatted a DS/DD disk with CDOS, and used wrtsys to copy c10boot.sys to the boot sector of the floppy. And then I copied cdos.com and copied files from most likely to be used to least likely. (if you copy cdos.com on last the floppy has to seek all the way to the end tracks to find it.)
After this process The machine booted to the C10 menu. Everything else works.

To anyone that needs technical knowledge from this machine please let me know. A main reason for having a machine like this is to share my discoveries and hopefully it can be used as a tools for someone else to get things working.

To the person that has a C-10 main board: If you want to send it to me I can stick it in this machine and let know know if it works.

If anyone else has tests or questions for/about this machine please feel free to ask.

Thank you to everyone.

On 2/24/25 13:02, Chris LaFond wrote:

To view this discussion visit https://groups.google.com/d/msgid/cromemco/59c760b5-69eb-408b-b136-f3f39fbefb44n%40googlegroups.com.

--

[Aron Hoekstra]

Awesome! Glad to see you got that figured out. What a journey, I can't believe there wasn't already a bootable image archived. Would you mind sharing the boot disk image with the group? 

BTW that was me with the incomplete C10. I'll email you directly to set up shipment. Thanks!

To view this discussion visit https://groups.google.com/d/msgid/cromemco/d48d7e71-5f1e-4a3a-b366-2f401531e3f0%40gmail.com.

[Bill Mahoney]

Hey Chris;

All this talk about sharing floppy images… Personally, I’d like to see some actual images! Post a picture or three of the system - love to see it and the glowing terminal. 

Bill Mahoney

--
<EmailLogo.png>

--
You received this message because you are subscribed to the Google Groups "Cromemco" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cromemco+u...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/cromemco/d48d7e71-5f1e-4a3a-b366-2f401531e3f0%40gmail.com.

--
You received this message because you are subscribed to the Google Groups "Cromemco" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cromemco+u...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/cromemco/CAD9iBDKScrs0g7ycZ8phthmNHHOfba2D%3DmVq%3D%2BNgXz3ie4npnw%40mail.gmail.com.

[Chris LaFond]

I will post the image this evening with more pictures.

To view this discussion visit https://groups.google.com/d/msgid/cromemco/E4BE5876-BD10-455E-AFC2-E00D7DDCA4F5%40cox.net.

--

[Chris LaFond]

Here are some more picture and a bootable IMD image

On 3/21/25 15:34, Bill Mahoney wrote:

To view this discussion visit https://groups.google.com/d/msgid/cromemco/E4BE5876-BD10-455E-AFC2-E00D7DDCA4F5%40cox.net.

--

[Bill Mahoney]

Love it! Nice job, Chris.

On Mar 22, 2025, at 10:23 AM, Chris LaFond <kdkconstr...@gmail.com> wrote:

Here are some more picture and a bootable IMD image

<chess.jpg><chess_1.jpg>

To view this discussion visit https://groups.google.com/d/msgid/cromemco/5f673cd3-dc55-432c-9a40-90ef50dab8d1%40gmail.com.
<C10R5B.IMD>