Challenger 3 OEM Restoration

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CrawfordG
Posts: 3
Joined: Sat Jun 22, 2019 7:38 pm

Challenger 3 OEM Restoration

Post by CrawfordG » Mon Jul 08, 2019 11:10 am

Hello All,

My name is Crawford, I’m returning to OSI world having had a C2-4P back in the late ‘70’s.

I have. Challenger III bought off eBay, sat in my daughter’s basement for a while and now in my hands. I’ve been working on it for the last few months trying to get the disks to boot. Glitch and TangentDelta have helped me along, since I brought it with me to VCFEast in May.

Here’s where I am on this. I blew an electrolytic cap while runnng it for the first extended warmup. Fixed that, and have since been trying to get the 8 inch diskettes to work. At VCFE we found a blown driver on the disk board, glitch took it home, fixed and tested it. Still did not work in my system.

Next I discovered a dead small 5v power supply that powers the disk logic cards, and the last 2 motherboard slots (for some reason). I just replaced that supply.

So now the floppy steps to track 0 when I select D for disk at the H/D/M? Prompt. But I get no further than that. I guess I have to start troubleshooting the disk drives.

Any ideas where to start with the disk drive? It spins and steps. Power is good (now) for AC, 24v and 5v.

- Crawford

Mark
Posts: 41
Joined: Tue Sep 16, 2008 6:04 am
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Re: Challenger 3 OEM Restoration

Post by Mark » Mon Jul 08, 2019 4:55 pm

It might be informative to see what the C3 disk controller is reading.
After pressing D, if the data is being read, it should load at $2200 to $2EFF or so depending on OS.
You can view the data using the 65A ROM monitor. Try 'D', afterwards <RESET> press 'M', then 'P2200' (any keypress to exit).

I have a program on the tools section of my web page that can dump diskettes ( http://osi.marks-lab.com/software/files ... C3dump.zip ). You load it from the serial console on the C3, and control it from the serial port. It can provide the same information with a bit more friendly interface.

My 8" floppy drives have failed to read disks when the disk read head was not pressed close enough to the disk surface due to the foam rubber used to provide head-load pressure having decayed.

F.Y.I.
65A monitor commands as used by serial OSI systems
R - Reset
L - (load) <2 Byte Address in hex><data as hex> R to exit
P - (print) <2 Byte Address in hex> dump data at address, Any key to exit
G - (go) $0129=Y, $012A=X, $012B=A, $012C=P, $012D=K, ($012F,$012E) = RTI (GO) address

Good Luck!
-Mark

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glitch
Posts: 127
Joined: Mon Nov 28, 2011 12:43 am

Re: Challenger 3 OEM Restoration

Post by glitch » Tue Jul 09, 2019 2:24 am

Good to see both of you here!

Crawford, make sure you've got good RAM throughout low memory. I chased bad SEMI4200s basically every time I set up my Challenger 3 until I got all of the bad ones weeded out.
Check out The Glitch Works
OSI Challenger 3, 510 CPU, 8" floppies, 74 MB hard disk system in need of restore
Parts bin Challenger 3 board set, never had a chassis in its time

CrawfordG
Posts: 3
Joined: Sat Jun 22, 2019 7:38 pm

Re: Challenger 3 OEM Restoration

Post by CrawfordG » Sun Jul 14, 2019 8:46 pm

Folks,

Mark, Jonathan - thanks for the info.

Well here is the status so far...

I filled in memory with values in a couple of places, then dumped it back out again. Granted this isn't a complete ram test, but seemed to be consistently giving back correct results. I filled in the area 2200 and above with zeros, then reset and tried disk boot. No change happened to the RAM at 2200-2eFF, so it looks like reading disks does not work. I will try Mark's disk dump routine next.

I took out the 2 disk drives and looked for differences. I was hoping to quickly swap the bottom disk to act as the top one for boot. No luck - there are a number of cuts and jumpers that need to soldered in, at the board edge connector area. I have tech manuals for the Siemens 100-8 drives, but the info doesn't seem to match my drives.

Other suggestions welcome.

-Crawford

Mark
Posts: 41
Joined: Tue Sep 16, 2008 6:04 am
Contact:

Re: Challenger 3 OEM Restoration

Post by Mark » Mon Jul 15, 2019 1:16 pm

I have two versions of Siemens FDD100-8 manuals at http://osi.marks-lab.com/reference/reference.html
I'll see what else I can come up with.
-Mark

CrawfordG
Posts: 3
Joined: Sat Jun 22, 2019 7:38 pm

Re: Challenger 3 OEM Restoration

Post by CrawfordG » Tue Jul 16, 2019 10:00 am

Folks,

So I did get Mark’s C3dump utility loaded, and found out the following:

Drive A erroerd out with the message that it could not detect index. So I guess there is something wrong with the photodiode, led, or related circuit.

Drive B seemed to start dumping out the disk. I’m not sure how far it got with that, as the disk is on the bottom, so I couldn’t see if it stepped all the way across the surface.

I tried to run it several times, but the system started freezing up. Maybe I should have heeded Jonathan’s advice about memory more closely! I’m only running one of the 16k boards. I built out one of the OSI-RAM boards, so will try that.

-Crawford

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