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Compaq Deskpro 386/20e, getting it running

Bill-kun

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Compaq Deskpro 386, getting it running

Compaq Deskpro 386/20e. Comes with a dealer-option 3.5-inch 1.44 MB. floppy drive, 5.25-inch 360 kB. floppy drive, and DC2120 tape drive.

I finally was able to source a hard drive bracket. The case and bracket require the HDD to be upside down. I know that I have seen that orientation forbidden on the sticker of many HDDs. If an HDD does not have that sticker, should I assume it is okay to be upside down?

I have created diagnostic/BIOS/setup disks from modern downloads.
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I started it up and it asked for the Diagnostic disk. I was able to get through the diagnostic and save it, then the computer reboots and it starts all over again, asking for the Diagnostic disk.

The motherboard says it is assembly number 001625001, revision not specified.

During one boot it said that switch #6 or jumper 17 was set so that certain things would not be able to be read or written to the ROM. My guess is that that is the reason the bootup always asks for the Diagnostic disk. I don't see any switches or jumpers for that in the diagram. Next to the blue SW1 in the photographs you can see a brown pin header connector, but that is for the speaker.

The other item is the BIOS battery. According to Stason.org, there should be a CMOS battery header on the motherboard, but there is not. There is space for one, but I don't even see the PCB pads for the header to be soldered on. (Was this another strange dealer option?) I don't see a header or a CMOS battery anywhere else on the motherboard. Do you?

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It looks like I can either modify the module to mount a button battery on its top (or solder extension wires to put the battery itself elsewhere inside the computer case), or I can buy a modern replacement module.

index.php

"More work?!" :sneaky:

What about the BIOS issue? Or are they one in the same because of the module? The videos above say that the computer often won't boot at all if the battery in the module is dead.
 
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It was common for Compaq desktops to mount the hard drive upside down. I've never had an issue with IDE drives upside down. Maybe that was a problem for older hard drives.

It keeps asking for the diagnostic disk because it can't save the settings. Once you get a new battery/module that should be fixed.
 
Yes sound like it is a cmos/rtc battery issue. It can cause a lot of problems/issue like the system not booting as mentioned.

It's great the you have done the resaerch and found repair/replacement options.

I need to mod a few myself. One rtc is soldered on so I'll get a suitable socket to solder to the mobo for easy fitment/replacement.
 
I did the modification on the Dallas module, using the one leg for the negative. The computer now seems to keep the BIOS settings, but looses the clock time at every boot.

When it prompts me to insert the diagnostic disk and press F1, I can insert a normal boot floppy and press F1 and it will boot from it. I also got a hard drive working in it.

Is the added battery modification working or not? Can I use a multimeter to find out?
 
Problems still not completely solved, but significantly stepped forward.

I drilled through the whole wall of the Dallas DS1287 module above pin 16 to break the negative connection to the original internal battery. Now the unit keeps time and all settings overnight. That is solved.

I also attached a hard drive and got that working. (Thankfully, this HDD is one of the types the BIOS is programmed for; it doesn't allow custom HDD geometry.)

Interesting thing about the BIOS of this Compaq Deskpro 386/20e: I kept setting the 5.25-inch floppy drive as 1.2 MB., but every boot up after that the BIOS gave an error that the settings had not been set. I went into the BIOS with the diagnostic disk and it said it had automatically corrected that drive to 360 kB. If I changed it back to 1.2 MB., I can go through that same error cycle again. I thought this was a 1.2 MB. drive.

Sadly, since that floppy drive doesn't give anything except a not ready error so far, I can't verify much. But I do have 2 other nonfunctional akin units that I can use as part sources. I will try the other two 5.25-inch drives.

Also, these 5.25-inch drives use a push-button toggle mechanism to lower the spindle instead of a lever. Innovative, but when ejecting, the mechanism often sticks and doesn't eject the disk, and then the only option to get the floppy out is to disassemble. I've cleaned as much of the old grease out with alcohol as I can and regreased it, but it still keeps happening.

Also, this unit came with a native DC-2120 tape drive, which I'm told was a dealer option. (The floppy cable has connectors for the 2 floppy drives plus the 1 tape drive.) How do I get the tape drive working? Do I just load the same software I used on one of my other computers with a DC-2120 tape drive, and it will automatically sense the right thing?
 
A couple of things you can do if you want a larger HD: drive overlay or newer OS. I've used drive overlays to good effect on my Compaq 286 and Portable 386. For my 386/20e, I used a large IDE drive that I partitioned into a 560 MB boot partition to match the CHS of one of the BIOS drives, 1 GB NTFS partition of NT 4 (I have a Cyrix DRx2 CPU) and the rest for Linux. NT4 boots off the main partition, but will load its own drivers for further disk access and luckily ignores the BIOS settings for HD access. Linux also boots from the 1st partition and then it ignores the BIOS and consults the partition map for HD access.

The floppy drives often show up on ePay as Canon floppy drives. I found my 1.2 MB and 1.44 MB drives that way.

As for the tape drives, they didn't work particularly good when new. I treat mine as a conversation piece. I believe there are some utilities that came with the Compaq branded MS-DOS release to backup/restore.
 
The 5.25-inch floppy drive keeps giving a not ready error, no matter which of the 3 ones I put in.

I installed Conner Backup Exec 2 for DOS. The tape drive seems to be giving some mechanical sound, then gives an error. If I try to identify the tape it gives internal driver error: unexpected tape change. If I tell it to retension the tape it gives internal driver error: command transmission unsuccessful.

I’ve got lots of other DC2120 tape drives loose, but I don’t know if I’ll be able to simply swap one into here or not.
 
Any advice on the floppy drive? How should I try to fix it before going to eBay?

Any advice on the tape drive? Should I try to repair this one? If so, how? If not, are they easily exchangeable between this Compaq and the various loose ones I have in storage?
 
Since the floppy drives and presumably the tape drive are all sharing the same onboard floppy controller/cabling I'd verify there's nothing weird going on there for it to either identify drives incorrectly or send commands to the wrong drive.
I'd say also do preventative maintenance on the drives but if you can at least boot to diagnostics from a floppy your 3.5" is at least working well enough.
 
Is your 3.5 “ drive able to read and write 1.44 Mb floppies? You should be able to disable the onboa d floppy controller and swap in an ISA card to see if there is any difference
 
Since the floppy drives and presumably the tape drive are all sharing the same onboard floppy controller/cabling I'd verify there's nothing weird going on there for it to either identify drives incorrectly or send commands to the wrong drive.
I'd say also do preventative maintenance on the drives but if you can at least boot to diagnostics from a floppy your 3.5" is at least working well enough.
I am totally unsure how to verify that with a multimeter or whatever. But I can say that the proper floppy/tape drive lights always light up when expected.
Is your 3.5 “ drive able to read and write 1.44 Mb floppies? You should be able to disable the onboa d floppy controller and swap in an ISA card to see if there is any difference
The 3.5-inch floppy drive works fine.
 
The 3.5-inch floppy drive works fine.
If you don’t want to swap in an ISA card then create 5 1/4 floppies for the setup program (360k images). Then swap the position of the floppy drives so the 5 1/4 is drive A. Will setup recognize drive A as 1.2 Mb? If not, are you *sure* they’re high density floppy drives?
 
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