Ok...so after much messing about..I finally swapped out the 3.5 inch floppy drive for a 5.25 inch that could read High density disks (1.2mb) since this is what the compaq defaults to apparently..
The inserted an ms dos 3 boot disk..
It was recognised at boot/power up and allowed me to at least access the A: prompt..
Progress 😀
I then fired up one of my old windows desktops...which also had a HD 5.25" floppy drive....and inserted a new high capacity disk and formatted it /s
The took the 3.5" floppy I'd already made but wasn't recognised by the compaq and copied the contents onto the newly created bootable 5.25 inch disk...and inserted this into the compaq and yes it allowed me a A: dos prompt ..and access to the directory of A:where the setup .exe could be found.
So ..I now have a working 5 1/4 inch setup/configuration disk for this Compaq III.
Again..
Progress.
There is a hard drive in this unit ...a seagate ST3250A...
no idea if it works but is larger capacity than those supplied by compaq as standard..
There are 4 in the drive type list
Type 1 ...10.7mb
Type2 ... 21.4mb
Type 4 ... 71.3mb
Type 6 ...30.3mb

Obviously the seagate is non of these ...but a drive type could possibly be entered manually but what 'Type' would be correct ??
Sadly not much information available.
So it would be total guesswork on my part...unless Drive types are standard...and equate to specific geometries.
can anyone help me with this ?
I'm pleased to have got this far...but would like to go further and get the hard drive recognised.

The key was realising that having the battery go empty ...and the unit default to a 1.2mb 5 1/4 inch floppy meant the 3.5 inch floppy was no longer recognised.

rgds
VS

More progress..
The default hard drive setting appears to be type 14...which was obviously wrong ...this would indicate a 20mb drive or similar..
My hard drive is 214mb..
poking the keys in setup /fixed disk mode I found more drive types lited by switching the lists using page up/down.
I found the closest ...Type 51 and selected this..
hit enter and allowed a reboot without power down...and at the A: prompt tried c:
Yep ..the hard drive is recognised and still viable..
See photo.

I guess I need to replace the battery next..but have never seen one for a Compaq III ..
I'm guessing this is going to be 3.6v or thereabouts..
I'm sure I can come up with something.
wish me luck.

Looks like These are still available ..
AA size and PCB mount.
I may have to mount somewhere else in the case and run wires to a connector.
Over 2 AH and 3.6v...
A bit pricey at £8 each..but more available than the original.
SL360PT
3.6V Lithium Thionyl Chloride AA Battery

more progress..
finally got the seagate hard drive to boot..
after much messing around.
It would seem that Compaq has 2 hard drive controller interfaces..
One of which is proprietory (compaq) and if the hard drive was formatted and indentified using the compaq controller ..then access and drive recognition MUST use the same interface.
So..
Windows 3.XX had been installed on this unit on the seagate.
Once I power down this of course will be forgotten...so the cmos battery is now a priority.
regards
VS

Time to unveil the motherboard of my Compaq III
see pictures.
I have been working under the assumption it was a 286 ...turns out I'm totally wrong..
The unit is fitted with a 386DX which is nice.
All the ones I've seen on youtube are 286 so was unaware there were at least 2 versions.
There is a socket to fit a math co processor...but the ram although 2 free sockets uses a different form factor simm ..
42 pin ????
Something I dont have sadly.
...and I cannot see a cmos battery ...???
help ?
I need a manual for this now...
anyone ?

https://minuszerodegrees.net/manuals/Compaq/C … -%20options.htm

Murugan wrote on 2023-02-06, 09:16:

https://minuszerodegrees.net/manuals/Compaq/C … -%20options.htm

Thanks for the link buddy..

Just been doing some reading...and apparently this is what I have.

https://en.wikipedia.org/wiki/Compaq_Portable_386

Did you have a peek already on the other side of the board?
https://www.retropaq.com/booting-up-opening-up/

Murugan wrote on 2023-02-06, 09:16:

https://minuszerodegrees.net/manuals/Compaq/C … -%20options.htm

Thanks for the link buddy..
Sadly it doesnt seem to apply to this version...
ie no low profile flat battery on the mobo....nor a dallas RTC chip...
I'm really confused now...as to how the cmos can be maintained.

Just been doing some reading...and apparently this is what I have.

https://en.wikipedia.org/wiki/Compaq_Portable_386

Vipersan wrote on 2023-02-06, 09:23:

Thanks for the link buddy.. Sadly it doesnt seem to apply to this version... ie no low profile flat battery on the mobo....nor a […]
Show full quote

Murugan wrote on 2023-02-06, 09:16:

https://minuszerodegrees.net/manuals/Compaq/C … -%20options.htm

Thanks for the link buddy..
Sadly it doesnt seem to apply to this version...
ie no low profile flat battery on the mobo....nor a dallas RTC chip...
I'm really confused now...as to how the cmos can be maintained.

Just been doing some reading...and apparently this is what I have.

https://en.wikipedia.org/wiki/Compaq_Portable_386

Not as yet ...but I will soon..

According to the second link I sent you,the white connector under the FPU socket (P118) leads to the battery. On your pics, I see red/black wires there.

Murugan wrote on 2023-02-06, 09:20:

Did you have a peek already on the other side of the board?
https://www.retropaq.com/booting-up-opening-up/

On my to do list..
cheers

Certainly not designed for quick battery change/easy access..
The mobo has to be removed and the battery is on the underside of the metal mobo carrier plate..
🤣
buried well deep in its guts..
Looks like the £8 battery I have on order will be perfect for this.

I'm calling that a win..
Now remembering todays date and time....also remembers the hard drive type...following the replacement of the cmos battery ...
I managed to force open the plastic case and swap out the AA size lithium battery inside....
This made for a perfect fit..
rgds

New keyboard coiled cable constructed...
cut the ends off a ps2 extension cable ...which was a little thicker having 6 cores..
only 4 needed.
the coil loops were wider so wound it tight around a long drill bit....and popped in the oven for 20 minutes..
This fixed the coil loops a bit tighter.
Needed to physically fit into the cable groove under the screen.
Whilst the keyboard was fully stripped down to attach the new cable...I gave it a deep clean.
It came up pretty good...so was very pleased.
Final job was to cut off the PS2 plug and fit a large 5 pin din ...
standard AT keyboard connections.
A quick test running up win 3.0 /notepad proved the keyboard was working well.
A good days work I think.

I made a new ..shorter...IDC floppy cable this morning to fit a 1.44 3.5 inch floppy drive...
This lends itself to better cable management and of course means it can now read the 720k compaq image on a 3.5 floppy disk.
..after changing the drive type in bios of course.
This means I no longer have to use a 5.25 inch drive hanging outside the portable III.
it boots just fine as evidenced by the picture.

Now..I am considering the small form factor 486 shown in the other picture...
This is the same pinout as a 386 so should be a straight swap.
....but also ...would there be any advantage to adding a floating point 387 ?
I doubt it...but there would presumably be an advantage to adding a 387 if I decide to leave the 386 in the computer..
The base as shown is larger than the 387 chip....so I'm showing my ignorance here..
Do I just fit this in the centre of the 387 base with a row of pins exposed all around the 387 ?
I simply dont know..so any advice here would be welcome.
rgds
VS

Just got very lucky on fleabay...
Found a listing for these ...

2 MB RAM (4 x 512k) memory for Compaq Portable 386 SIMMs - Assy no. 000576-001
...and put in an offer which was accepted..
I only have 2 simm slots free ...but at least I can upgrade to 2mb now.

Took a chance and fitted my 80387 co pro in socket U69
Set jumper E20 unlinked 2-3 linked 1-2
...and applied power allowing to boot the setup floppy.
It did boot to the disk in A:
and the 387 was recognised.
I guess this at least verifies the chip as working....which up to now was an unknown quantity.
The 386DX is a 386DX-20 ...but my 387 is only a 387-16...
so I'm guessing a clock speed mismatch..
Will this be a problem ?
I simply dont know.
anyone ?