Ohh dear. I forgot all about that connector. I ran a computer lab with a dozen Zenith Z-386/25 computers once . I feel like those computers may have had that power connector. That school loved computers with proprietary back planes . The other computers were AT&T 6386 WGS. Could never find the right power supply when something broke.

Help with Zenith Data System Expansion cards (Z-386/25)

I should have the service manual for the Z-386SX machines (which this board belongs to). It does include pinout for the power connector.

Note that the power conmector is 12 pin on SX, and 15 pin on DX (incase you use my scan in the thread Douglar linked to)

Thanks douglar & vetz! Digging into the shared link I did find the scans vetz posted for similar ZDS units. Posting in thread to hopefully help anyone looking for this.

I don't know why Zenith used this wacky connector as it's barely smaller than industry standard AT.

I guess I can come up with something using a pico-ATX power supply and Voltage Blaster to get the -5V.

vetz wrote on 2024-07-03, 20:39:

I should have the service manual for the Z-386SX machines (which this board belongs to). It does include pinout for the power connector.

Note that the power conmector is 12 pin on SX, and 15 pin on DX (incase you use my scan in the thread Douglar linked to)

Oh, yes, I see that now. Wow, a 12-pin and a 15-pin, that's mental. If you could find the Z-386SX manual that would be amazing. Thanks!

Found it! You have the newer model revision of the mainboard. Attached the most important pages, and pin-out of the power connector.

User manual just sold on Ebay. I hope the person who bought it will scan & upload it.
https://www.ebay.com/itm/326155497545

Pinout:

I'll do a proper scan at some point.

vetz wrote on 2024-07-03, 21:21:

Found it! You have the newer model revision of the mainboard. Attached the most important pages, and pin-out of the power connector.

Awesome, thank you so much! No -5V DC on the 12-pin connector version, even better.

The Ctrl-Alt-Ins MFM-300 Monitor program is super interesting, hope I can get this up and running to try it out.

Unfortunately I'm missing some pages for this model, which include the jumpers information, but I managed to find it on the Packard Bell archive (https://archive.org/details/packard-bell-ftp-zd.-7z).

Jumpers
Main Board
J101 On* Colour Video Card
Off Monochrome Video Card
J102 On Bypass Keylock
Off* Keylock Enabled
J103 On Asynchronous Coprocessor Clock
Off* Synchronous Coprocessor Clock
J104 1-2 Expansion Bus Clock is the System Clock
2-3* Expansion Bus Clock is 8MHz
J105 Off* Write precompensation 125 nanoseconds
On Write precompensation 187 nanoseconds
J106 On Floppy Drive Speed is 250 / 500 kb/s
Off* Floppy Drive Speed is 250 / 300 / 500 kb/s
J107 On Interrupt IRQ12
Off* No Auxiliary Interrupt
J108 1-2* Coprocessor Clock is 32MHz
2-3 Coprocessor Clock derived from J111
J109 On* Cache SNOOPRDY connected to IOCHRDY
Off Cache SNOOPRDY not connected to IOCHRDY
J110 1-2* Diagnostic LEDs show Boot diagnostics
2-3 Diagnostic LEDs show ROM checkpoints
J111 1-2 CPU Clock is 32MHz
2-3* CPU Clock is 40MHz
J112 Off* 1 Speed motor on Floppy Drive
On 2 speed motor on Floppy Drive
J113 Off Floppy Drive Disabled
On* Floppy Drive Enabled
J114 Off Hard Drive Disabled
On* Hard Drive Enabled

The following jumpers have been added to main board PN 240-7835-3x
(circuit board artwork #85-3797-01)

J301 On Lock Pin Connected
*Off Lock Pin Not Connected
J302 On Monitor Mode Disabled
*Off Monitor Mode Enabled
J303 1-2 I/O Channel Ready Extended
*2-3 I/O Channel Ready Normal

* = Factory Setting
NB: J104 and J111 interact.
When J104 is at position 1-2, J111 should remain in position 2-3.
When J104 is at position 2-3, set J111 to position 1-2.

Memory

2Mb SIMM supplied as standard, expandable to 8Mb on the system board. The 7Mb of main RAM can be configured as either EMS or extended memory, in 1Mb blocks, upto a maximum of 7Mb's. The 224K of memory left in high memory can also be configured as either EMS or extended. SIMMs must be fitted in pairs, each pair of sockets making a Bank. Main Board Memory options are:-
Main Board Bank Bank Bank Bank
Memory 0 1 2 3
1Mb 256K 256K
2Mb 256K 256K 256K 256K
2Mb 1M
3Mb 256K 256K 1M
4Mb 1M 1M
5Mb 256K 256K 1M 1M
6Mb 1M 1M 1M
8Mb 1M 1M 1M 1M

Quick update on this project... I was able to identify and procure the correct 12-pin power plug connector for these ZDS 386SX systems. (Thanks again vetz and douglar!)

It is a Molex PN : 03061122, https://www.molex.com/en-us/products/part-detail/03061122

Seems like use of this connector style may have come from the Heathkit side of things as it shows up on many of their earlier devices.

I picked up a 5-pack of them and they fit perfectly. Once the ATX-AT adapter cables come in I'll pin them up and see if it boots with this ATX-to-ZDS-SX cable.

Also, the 15-pin version for the Z386DX models should be Molex PN:39033157, in case anyone finds a motherboard sans original case/power supply.

Good news, the ATX-AT adapter finally came in. I hacked away at it and wired up the pictured ATX-ZDS12 power adapter. Not my best work, but it's just a prototype.

In my Zenith research I ran across VWestlife's Z-148 repair video which seems to show a 6-pin variant of this connector for PC/XT class systems - https://youtu.be/H02Jo7D15MQ at about 11:57 in.

This little Zenith board is alive!

I found the matching ISA riser board and HT208 VGA card and replaced the Dallas chip. The riser is impressive with its own set of diagnostic LEDs.

Here are some screenshots of the MFM-300 (ctl-alt-ins) of the board. This provides BIOS setup as well as diagnostic options.

This is all new to me, so I'm finding it really interesting. Only complication I see is that the HDD table does not allow custom entries, so my CF cards are not usable. (XuB coming soon.)

That is awesome! Would you mind doing a dump of the MFM-300 program/BIOS? I'd like to compare and see the versions are interchangeable with my DX machine.

vetz wrote on 2024-07-23, 17:39:

That is awesome! Would you mind doing a dump of the MFM-300 program/BIOS? I'd like to compare and see the versions are interchangeable with my DX machine.

Thanks, this project was a fun distraction. Now I need to find, modify or fab a case for it.

vetz, do you have any info on the P106 connector pinout? I think it's the status lights and reset button. All the multimeter tells me is pin 5 is ground.

Will dump the MFM chip it as soon as I can figure out how... The Retro Web has v2.9b and v3.2c posted but not v3.6d this board has.

On a related note, if there's anyone in the US NJ/NYC/PA area who has a chip reader, spare blank roms and can write out an at_large XTIDE Universal BIOS for a 3c509 please PM me.

Many Bothans wrote on 2024-07-23, 20:29:

vetz, do you have any info on the P106 connector pinout? I think it's the status lights and reset button. All the multimeter tells me is pin 5 is ground

I believe I do. Also I just got myself a double-sided document scanner, so hopefully I'll be scanning the manuals in no time later this week.

Many Bothans wrote on 2024-07-23, 20:29:

Will dump the MFM chip it as soon as I can figure out how... The Retro Web has v2.9b and v3.2c posted but not v3.6d this board has.

The MFM program is shadowed in the upper memory, so many programs should be able to do a dump. NSSI is probably the easiest. I'm curious if your version have more harddrive options? I can only select up to type 62, and there is no option for custom config of the CHS settings (on version 3.2).

Not sure if you are aware but Q=OFF is the slowest setting. Set it to 16 for maximum performance.

Many Bothans wrote on 2024-07-23, 20:29:

On a related note, if there's anyone in the US NJ/NYC/PA area who has a chip reader, spare blank roms and can write out an at_large XTIDE Universal BIOS for a 3c509 please PM me.

On the note of XTIDE, I've noticed some strange behavior when it's active. It works, and you can boot, but any CTRL-ALT-DEL soft reset takes way longer and gives an error message saying "DISK NOT READY". I do not know if this is only happening on the Z386 DX, but the IDE autodetection in the MFM program seems that it cannot be disabled, so you'll get an incorrect mismatched drive in the settings. I'm running SCSI in the system at the moment which does not cause this issue.

Also remember you can boot XTIDE from floppy. Could be a temporary solution while you get your chip.

vetz wrote on 2024-07-23, 22:06:

I believe I do. Also I just got myself a double-sided document scanner, so hopefully I'll be scanning the manuals in no time later this week.

Thank you!

vetz wrote on 2024-07-23, 22:06:

The MFM program is shadowed in the upper memory, so many programs should be able to do a dump. NSSI is probably the easiest. I'm curious if your version have more harddrive options? I can only select up to type 62, and there is no option for custom config of the CHS settings (on version 3.2).

I think I got it, but probably the hardest way possible by using the DOS DEBUG commands to write f000~ffff to a file. The output appears to be correct at least in my hex viewer.

MFM-300 v3.6d goes up to HDD Type 64. The oldest working spinner I have is a WD Caviar 2120 and it doesn't match any of the parameters available.

vetz wrote on 2024-07-23, 22:06:

Not sure if you are aware but Q=OFF is the slowest setting. Set it to 16 for maximum performance.

Nice, thank you again. The setting was not obvious to what it does; I really have to go through those MFM-300 manual pages to better understand the system better.

vetz wrote on 2024-07-23, 22:06:

On the note of XTIDE, I've noticed some strange behavior when it's active. It works, and you can boot, but any CTRL-ALT-DEL soft reset takes way longer and gives an error message saying "DISK NOT READY". I do not know if this is only happening on the Z386 DX, but the IDE autodetection in the MFM program seems that it cannot be disabled, so you'll get an incorrect mismatched drive in the settings. I'm running SCSI in the system at the moment which does not cause this issue.

Oh, interesting, I guess I have some experimenting to do.

vetz wrote on 2024-07-23, 22:06:

Also remember you can boot XTIDE from floppy. Could be a temporary solution while you get your chip.

This is brilliant, I had no idea!

Thanks! I'll burn your ROM file to a chip and see if it works in my Z386/20. There are some more settings available in the version 3.6 compared to 3.2.

The visual changes in the Configuration screen are as follows (based on your screenshot):

- Serial and Parallel Port settings
- Copy Video BIOS to RAM setting
- Floppy and Hard Drive controller setting
- Atleast 2 more drive types

I also had a look through the manuals I have of Zenith machines, and unfortunately I do not have the pinout for P106 as the last couple of pages are missing for the Z386 SX machine you have. I do still believe it is possible that the pinout used on other machines might match. They did not use a 10 pin connector, but two connectors, one with 6 pins and one with 4 for the LEDs/speaker/etc. Hopefully the 10 pin connector is just the two combined with no further changes. I got the scanner in the mail now, so I'll test it later tonight.

When you get it booting I'd love to see some benchmarks to compare it to my DX machine. Your machine have 16kb more cache and is of a newer design.

I scanned almost 800 pages last night.

Here is all the service manuals I own for Zenith machines, as well as Zenith's internal parts and configuration list from October 91. I also did OCR on them so they are searchable.

https://www.mediafire.com/folder/knvgxqqpjh8h … Service_Manuals

Includes:

• Zenith Basic Personal Workstation Computer 386SX 16mhz Service Manual
• Zenith Z-286 LP Plus & Z-316 SX/LP Service Manual
• Zenith Z-386/20/25/33 Series Service Manual
• Zenith Z-386/33E Service Manual
• Zenith Z-386 SX 16/20 Service Manual
• Zenith Z-486/25E Service Manual
• Zenith Z-2300 Series Service Manual
• Zenith Internal Parts & Configuration list Oct 1991

I will also post these to archive.org and The Retro Web.

vetz, thank you! This is certainly most helpful.

Boy, you were not kidding about Zenith MFM-300 and XT Universal BIOS interaction! As you described I was able to boot any drive off of XUBDisk (thank you BurnedPinguin!) but it doubled boot time and maybe quadrupled soft reboot duration. Even a few hard lockups that needed the power switch. Very, very strange behavior indeed as it is completely solid and stable without XUB.

I should have a mid-90s Promise EIDE Max 16-bit ISA card in storage, will see if I can find it. This was a single IDE port card with an option ROM and jumpers to set it as only BIOS or 1st~4th IDE controller. Worth a shot I suppose.

Will try to benchmark the board this weekend and share results.

I cleaned up the prototype and here's the final version of the ATX-ZDS12 power adapter -