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Problems after replacing CMOS battery DS12887 in Compaq Deskpro 286e

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Booch

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Oct 22, 2010
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This is a detailed story, and I need your help…

I have a Compaq Deskpro 286e purchased in 1989. The box is in mint condition and has been dedicated to communication with a Honeywell W7505 Building Management System of same vintage using communication software written by Honeywell (ZM7505 v3.01). I have a Cardinal 2450 modem installed, and have been receiving status and history data from the control site. I noticed the time and date were incorrect – tried to reset using the SETUP program on the Compaq User Diagnostic disk, which resulted in the inability to save any setup configuration, rendering the box useless.... This is a critical application, and I thought I would now have to consider upgrading the entire Building Management system at significant cost… :(

I searched for a replacement CMOS battery, and purchased a Dallas DS12887+ chip. From what I have read, this is a direct replacement for the original Dallas DS1287 chip which was installed. I installed the chip, entered the SETUP application once again, made the appropriate date and time entries, and rebooted to find a message indicating “missing operating system”. Using the MS Startup disk, I confirmed the content on the 40GB HD appeared to still be in tact. I ran FDISK, and the HD looked fine. I updated the OS (DOS 3.31) and Master Boot Record (MBR), and still no fix. In an effort to avoid reformatting the HD, I finally tried an old version of Norton Desktop v 1.0 to attempt an “emergency fix”, and I was now able to boot from the HD. Thought all was well! :)

I launched the Honeywell ZM7505 application, attempted my connection and successfully connected with the Building Control, however, I lost communications to the Control after a short period. I tried repeatedly to connect, with the same result. In one instance I also received a quirky security code mismatch message (a security code is sent and matched against the code in the Control prior to exchange of data).

I reinstalled the communication software and retried with the same result. This is now about 10-hours later… I ran the “TEST” program from the User Diagnostic disk, which indicated “1 Modem(s) – 2400 baud COM2 at IRQ?”. This obviously raised a question – IRQ should be “3”. I continued to test system hardware with this same diagnostic tool. All was fine until the modem test. The loopback test failed indicating an “Interrupt circuit failure”. This is when I had to stop… Don’t know where to go so I came here… :(

Can anyone help? Could it be a Y2K issue? Could I have a bug in my OS and require a reformat and new install? Is the new DS12887+ chip incompatible (I noticed Interrupt capabilities on the datasheet that might be problematic)? Could the modem have failed? Did a circuit on the Motherboard fail? Would appreciate any assistance or recommendations anyone could provide.
 
I use the DS 12887 to replace the DS1287, never used the DS12887+.

Not sure how you get a 40GB HD working in a 286 system without some kind of software overlay hack (did you mean 40MB?)? I would think the compaq would have a BIOS section where you picked the HD disk type and not input the Cyclinder/heads/sectors like you would in newer machines. Without the correct type it will not boot and that information is lost when the battery died (you can look up the HD information online and pick the closest type asuming you mean 40MB and not 40GB).
 
Unknown_K is correct. When you removed the old battery you effectively "reset" your BIOS and lost everything. The BIOS should be your starting point.
 
Thank you for your response - My error - certainly 40MB on the HD. Difficult working in two worlds... Any other thughts?
 
Thank you Agent Orange. After replaceing the battery I did complete set-up entries (limited). Reset Date and Time; confirmed HD Type (Type 43 - 40MB - Non-Compaq); Num Lock power off on start. That's about it...
 
Make sure you set up the floppies correctly, I assume you can boot from a floppy drive?

Now when you updated the OS did you use MS-DOS 3.31 or Compaq DOS 3.31? MSDOS 3.31 had partition limits of 32MB while the Compaq OEM version of the same number had the 32MB limit for partitions (fixed in DOS 4.0). IS there one partition on that 40MB HD and if so what is the size?
 
I assume this is an internal modem? Did you by any chance disturb it, accidentally drop a jumper, let something fall into the slot, etc., when you replaced the RTC chip? Is it properly and firmly seated (and not tilted a bit)? Try removing it and polishing the connector fingers with a soft eraser.
 
Last edited:
Unknown_K, Agent Orange and Mike S:

Thanks for your comments - here's the scoop...

1) OS
The OS is "MS-DOS" (VER 3.31 - 082489 - REV 5) issued and labeled by Compaq ("The COMPAQ Personal Commuter OPERATING System")

2) Hard Disk Data:
In Compaq User Diagnostic SETUP: I designated this HD as "Type 43" (Non-Compaq 40MB Drive)
From FDISK: Partition - C:1; Status - A; Type - PRI DOS; Start - 0; End - 978; Size - 979; Total disk space is 804 Cylinders.
From Norton Disk Dr: Media Descriptor - F8; Large Partition - YES; FAT Type - 16-BIT; Total Sectors - 83,197; Total Clusters - 20,750; Bytes/Sector - 512; Sectors/Cluster - 4; Bytes/Cluster - 2,048; # of FATS - 2
1st Sector of FAT - 1; # Sectors/FAT - 32; 1st Sector of Root Dir - 165; # Sectors in Root Dir - 32; Max Root Dir File Entries - 512; 1st Sector of Data Area - 197.


3) Modem:
Yes - The modem is a Cardinal MB2450 Internal Modem. I did not configure the modem in any way (should I have?). It came with an application called "Bitcom" however, this is not used. As indicated earlier, when I ran the "Test" from the Compaq User Diagnostic Disk-1, the results indicated "1 Asynchronous Communications Interface(s) COM1 at IRQ4". and "1 Modem(s) - 2400 baud COM2 at IRQ?". I ran the hardware diagnostics from the same test and all components passed except the modem. I received the following message:
"Error Testing Modem at COM2, IRQ?
18:08:05
Error 1201-09
Modem Failed Internal Loopback Test
Interrupt Circuit Failure"

With respect to contacting the card or dropping anything on it, I was very careful when replacing the RTC. I pulled the card and cleaned the contacts with an eraser; and gently pushed down any chips that were in sockets.

There are two Switches on the Motherboard - SW-1 with 6-DIPS and SW-2 with 8-DIPS. Today I played with alternating Dips 4&5 of SW-2, which the Systems Overview Manual indicates - "Selects the primary (COM1) and secondary (COM2) address for the serial interface, When to change - To change the integrated serial interface to COM2 when adding an additional serial device addressed as COM1. For example a modem”. Unfortunately I went through each permutation of the two switches and continued to get the error message...

I hope this helps. Any guidance you could provide would be greatly appreciated…

Booch
 
Hmm... well, it's starting to look as though the modem's got a problem, but that'd be a real coincidence; I can't see how this would be affected by replacing the RTC and restoring the setup.

Do you have enough information to swap COM1 and COM2 on BOTH the MB and the modem, i.e. change the MoBo to com 2 (or disable altogether) and switch the modem to com1 (in case there's a problem with the MoBo handling IRQ3)?

If you remove the modem and set the MoBo to COM2, does it pass the diagnostic?

I'm sure I don't have to mention it but jic, make sure you write down all switch and jumper settings so you can put them back if necessary.

Do you think this software would not run on a more modern computer?

And what part of the world are you in, BTW?
 
I think COMM 1 defaults to IRQ4 and COMM 2 to IRQ 3. If your modem is on IRQ 3 then you have a conflict with the COMM 2 port. Either change the modem IRQ to something not used (5 or 7 maybe) or just disable COMM 2 via jumpers. Not sure why the settings would have changed since it was in storage unless it was put away with issues.

Most 40MB IDE HDs seem to be type 17, why did you pick type 43? Get the make and model so we know what it is.
 
Unknown_K said:
I think COMM 1 defaults to IRQ4 and COMM 2 to IRQ 3. If your modem is on IRQ 3 then you have a conflict with the COMM 2 port. Either change the modem IRQ to something not used (5 or 7 maybe) or just disable COMM 2 via jumpers. Not sure why the settings would have changed since it was in storage unless it was put away with issues.

Most 40MB IDE HDs seem to be type 17, why did you pick type 43? Get the make and model so we know what it is.
Click to expand...
I think the modem IS (and is supposed to be) on com 2 and there's only one on-board com port, set to com1/IRQ4 as it should be; the problem seems to be that IRQ3 from the modem is not being recognized.

Have I got that right?
 
Mike S. - Thank you for your response.

Well… I’m probably giving you much more than you asked for, but let’s start with the easy questions. I’m located in the Albany, NY area and use this box to communicate with a Building management System installed in a facility about 120 miles away in Northeastern CT. The facility is an old Mill building built in 1860, that has been in my family for nearly 50 years. My father started his Tool and Die business there in 1962, sold the business in the early 1980’s, and has leased out space to small businesses. It has been his life... Due to parent health problems, I am now getting back involved with this facility to assist in managing facility issues and attracting tenants to this “creative work space”. It is quite a unique environment, however, it is roughly 90% vacant at this time. As a result, I am in a very tight cost control mode…

The Building Control is a Honeywell W7505 also purchased in 1989 – same year as the Compaq Deskpro. As you are aware, both devices are well beyond obsolete. Honeywell has no resources, parts, nor documentation for this system. With all that said, I installed the system 20-years ago and it continues to work and do its job. I realize that I am pushing the envelope, and will need to bite the bullet at some point. Estimated cost to replace the Honeywell system is likely to be over $6k. My objective is to keep things going for as long as I am able.

To run properly, the DOS based application for the building control requires a box that runs very slow by today’s standards. The Deskpro 286e includes a 12Mhz processor. I had a Gateway box with a Pentium-1 processor in the mid 90’s that I was able to use to communicate to the control – but I had to reduce the processor speed in the BIOS Setup to be able to do so. After installing BIOS upgrades for this box, newer versions no longer allowed me to reduce processor speed, and as a result I could not use this box to communicate with the control. The control application defaults to a 300 baud rate for remote communications.

I could consider a new “old” box if I could find one that was reliable at a low cost – That is a possibility… However, If I could get this unit up and running, that would be best – it’s in mint condition, and with exception of a HD replacement in 1996, it has been a workhorse.

Back to the technical stuff:
As previously indicated, there are no switches on the modem card and two Switches on the Motherboard - SW-1 with 6-DIPS and SW-2 with 8-DIPS. Dips 4&5 of SW-2 appear to control COM1 and COM2 based on the Systems Overview Manual. Both originally were in the “ON” position (i.e., 1-1). I alternated each (i.e., 1-0, 0-0, and 0-1) and tested after each change. The test report consistently indicated the Modem IRQ as “?”. I did not remove the Modem and run the diagnostic. I will try this as you suggest.

This problem occurred after changing the CMOS Battery. My replacement is the DS12887+. I am wondering if this replacement battery is compatible. In the original response from “Unknown_K” it was noted that they replaced the DS1287 chip with the DS12887 – not the DS12887+. The Dallas data sheet for these chips identifies several versions…

As we get into “muck” in trying to diagnose and resolve this problem, I’d like to share some additional details in my process that may or may not be relevant… and would be very thankful for your input.

Here’s what I did from the start:
I opened the case and first blew out any dust on the board. There wasn’t much, however, I always start with housekeeping. The compressed air can had a little moisture in it (as normal) and at the time, I didn’t think much about it. Could this have potentially caused a short – or moved a particle across a circuit to result in this condition?

I carefully removed the old RTC chip and installed the new, entered the SETUP application, made the appropriate date and time entries, identified the HD as “Type 43” (Non-Compaq 40MB) and rebooted the box. I received the message “missing operating system”. Is this typical? Why would I get this message after updating the SETUP and why wouldn’t the HD be recognized?

Using the Compaq MS Startup disk, I confirmed the content on the 40MB HD appeared to still be in tact. I ran FDISK, as mentioned and the HD looked fine.

I updated the OS (DOS 3.31) and Master Boot Record (MBR), with the original Compaq OS Disks (MS-DOS" VER 3.31 - 082489 - REV 5) and still no fix. In an effort to avoid reformatting the HD, I finally tried an old version of Norton Desktop v 1.0 to attempt an “emergency fix”, and I was now able to boot from the HD. I’m not sure what the Norton product did to get the HD to be recognized, but it seemed to work… I have experienced a couple of other intermittent quirky things, and though the tests don’t indicate an OS problem (other than the Interrupt circuit failure), I’m not sure I have full confidence in the system…

I want to say that I greatly appreciate your assistance and that of others in helping resolve this issue…
 
Unknown_K - I just saw your post - Thank you.

I would like to confirm that prior to the replacement of the RTC - all systems were working fine... Stupid me - I saw the time and date were off, and tried to correct in the SETUP - that's when I learned of the battery failure and lost my SETUP... Then it as too late... I am assuming when I replaced the HD in 1996, I selected "Type 43" - however, I can't find these records...

I will identify the HD best I can, and provide these details. In the SETUP I interpreted HD "Type 17" to designate a "Compaq 40MB Drive" Should this be changed to 17?

I would also like to provide you with the descriptions of the DIPswitches to insure I am addressing the correct switches. Is there any way I can forward an attachment?

Finally, I bring up your original question – is the DS12887+ compatible with the DS1287 chip?

Regards,

Booch
 
MikeS and Unknown-K:

I may have made a big mistake… After removing and checking the label on the back side of the HD, here is the data:

IBM
Model: DALA-3540
Capacity: 540 MB (527 MB)
(1049 CYL, 16 HEADS, 63SEC/T)
P/N: 85G3847
FRU P/N: 82G5928 JLY-95
MLC: D61625

Another label reads:
85G3855 JASMINE 45-S/N
53X524 08859 EC D61614

JP1: MASTER
JP2 SLAVE
JP7: 540MB/W
524MB/WO

Based on the capacity – the HD “Type” is in fact incorrect… Please confirm and I will re-run SETUP to find the closest capacity to 540 / 527 MB

My apologies…
 
While you are poking around inside what is the brand and model of the modem, does it have any jumpers or pins? In the setup do you have the option of type 47 for the HD (where you can enter the parameters for the HD iteself)?
 
MikeS and Unknown_K:

The Modem is a Cardinal MB2400 - No jumpers that I can see.

I ran SETUP to confirm HD alternatives. The following includes all options. I have made no changes and am including this info for your guidance, as I do not know the consequences of changing HD Type at this time…

“Disk Types supplied by COMPAQ are:
Type-1: 10 MB
Type-2: 20 MB
Type-4: 70 MB
Type-6: 30 MB
Type-12: 70 MB
Type-14: 30 MB
Type-17: 40 MB
Type-22: 40 MB
Type-25: 130 MB
Type-27: 84 MB
Type-28: 320 MB
Type-33: 110 MB
Type-35: 130 MB
Type-38: 300 MB
Type-41: 650 MB
XENIX USE
Type-42: 528 MB
NON-COMPAQ OS2
Type-43: 40 MB
Type-45: 100 MB
Type-47: 60 MB
Type-49: 650 MB
COMPAQ DOS, OS2
Type-54: 20 MB

Other fixed disk drive suppliers may supply types not listed above”

Booch
 
When you boot from floppy how much space is there on the HD? How many drive letters are there?

Type 42 seems close enough. The reason your drive hase 542/527 settings is because most older machines cannot deal with drivers over 527MB so they do not use all cylinders.

Either there is software for that modem to change serial ports or it is hard wired to comm x. Since you don't have two comm ports on that machine try running the modem software and see if it sees the modem.

If the system retains the date/time when unplugged from the wall for more then 5 minutes then don't worry about the battery backup it is working well enough.
 
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