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Compaq Portable Plus memory check question, and another question, and one more...

J

Juror22

Experienced Member
Joined
Jul 26, 2011
Messages
211
Originally, when powered on, my Compaq Portable Plus yielded this error code on the display:
1000 201

According to the Maintenance and Service manual, that indicated an error with U38

1000 201 Bank 1, Parity Bit U38 Replace System Board

So, I replaced U38 (an OKI M3764A-15), repaired a questionable trace and confirmed continuity. On startup, it now proceeds to this error code:
7020 201

Removing the extended memory board (a Persyst Time spectrum 384L) or replacing it with a different (working) memory card allows the system to proceed and reach a fixed disk error 1701 prompt. I would like to replace the faulty memory in the Persyst card, so checking out the extended memory codes from the manual

xx Code Beginning Address
70yy 201 448 Kbytes
yy Code Failed Bit
xx20 Data Bit 5

Which chip is bad? The same card was recently listed on eBay https://www.ebay.com/itm/NOS-Vintage-Persyst-Time-Spectrum-384L-Circuit-Board-Card-/273201341598?

My board is fully populated with (TI TMS4164-20NL), so I think the top chip in bank 3 is faulty, if I'm counting correctly.

1) Can someone confirm this should be the faulty chip and also can I replace it with one of my spare OKI memory chips? They should be equivalent and the OKI is a faster chip, so it should work?
2) Does anyone have documentation for this card? (I know that a manual was included in the eBay auction and if I had seen that while it was up, I would have tried to get it) I found where someone asked about the dip switch settings, but I was hoping for a bit more than that.
3) My computer uses standard drive hex top screws to secure the access panels and the expansion cards, but the pictures that I have seen of other CPP's online use torx screws - have mine been replaced or were both types of screws used by Compaq?
 
Juror22 said:
1) Can someone confirm this should be the faulty chip ...
Click to expand...
The eBay photo shows that the RAM chips are in sockets. So you can prove your hypothesis by swapping the suspect RAM chip with one from within the same bank. If the bit error code changes, you were right.

Juror22 said:
... and also can I replace it with one of my spare OKI memory chips? They should be equivalent and the OKI is a faster chip, so it should work?
Click to expand...
If it is equivalent and faster, yes.
 
Holy round-robin Batman, that's a great idea! I swapped out boards, but forgot about doing the same thing on a more granular level to sort the issue. Thanks for the suggestion.

I re-examined the board and from the markings, I concluded that I should count from the bottom, left of the card and exclude the chips in the parity slots and came up with 4th row from the bottom, in bank 3 as the faulty chip. However, when I swapped that one out for another, there was no change, so I'm back to investigating which chip is bad. There is a separate code for parity chips, so I know that is not the issue.
 
Juror22 said:
I re-examined the board and from the markings, I concluded that I should count from the bottom, left of the card and exclude the chips in the parity slots and came up with 4th row from the bottom, in bank 3 as the faulty chip. However, when I swapped that one out for another, there was no change, so I'm back to investigating which chip is bad. There is a separate code for parity chips, so I know that is not the issue.
Click to expand...
If:

* 256 KB on the motherboard, addressed from 0 to 256 KB; and
* Time Spectrum is providing 384 KB (6 banks of 64 KB) addressed from 256 to 640 KB

Then:

Time Spectrum bank 0 = 256 KB to 320-1
Time Spectrum bank 1 = 320 KB to 384-1
Time Spectrum bank 2 = 384 KB to 448-1
Time Spectrum bank 3 = 448 KB to 512-1 <------- '448 Kbytes' in this bank
Time Spectrum bank 4 = 512 KB to 576-1
Time Spectrum bank 5 = 576 KB to 640-1

So yes, I agree that it is bank 3.

Bit 5 in bank 3 should be per the photo at [here].
 
After spending the day popping out chips , I found that the chips in bank 3 always gave the same error whether they were there or not. I checked on the card info that I had (Dip switch settings) and changed one to reflect the correct amount of memory on the card (I had assumed that it was correct) and it booted to the HD error. I am checking the HD next.

Thanks for your help M7.
 
So, I made a 5-1/4 boot floppy and it boots fine after complaining about the HD error (Rodime HD is dead and looks like someone opened it up at some point and failed to revive it). After booting to a prompt, I tried typing and the only key that worked (about 4 times then it stopped) was the '5', so I know that I need to restore the keyboard and it looks like there is already a current thread, where someone is working through that, so I will join in there.
 
Yes, Compaq loved Torx screws. The bastiches. If you have some hex heads in there someone probably replaced them for Torx.
 
Originally, this CPP presented with a memory error and after I replaced the bad chip, it would boot to a hard disk error and the keyboard would not work. I finally replaced the dead keyboard foam disks with ones that were purchased online. When I startup, I get the following...
46 301
FIXED DISK ERROR 1701
Non-System disk or disk error
Replace and strike any key when ready
Starting MS-DOS…


Microsoft(R) MS-DOS(R) Version 6.20
(C) Copyright Microsft Corp 1981-1993.
A:\)>ax-+89451

I am not able to type anything in at this point.
I have swapped out another keyboard cable that I have, with no changes
unplugging the keyboard entirely yields a 301 startup code, I'm not sure what the "46 301" is about, I couldn't find it in the fixit manual.
 
if I remove the keys from the board, I don't get the error and I can 'type' with my fingers where the disks make contact. So I'm guessing there is a problem with how I installed them (they go shiny[mylar] side down, right?
 
The silver mylar side is supposed to make contact with the metal on the circuit board when you push the key. Just remember the mylar is supposed to be non-conductive. It is capacitive. Where did you get the replacement pads?

Try popping out one of the pads and trying it against the circuit board to see if that works. Of course, it is easy for one pad to stick out too far and create a key that is stuck as if it were pressed down.
 
Juror22 said:
... I'm not sure what the "46 301" is about, I couldn't find it in the fixit manual.
Click to expand...
In the IBM PC family, the number before the 301 indicates a 'stuck on' key. Per [here], one uses a number-to-key diagram to discover which key it is on the IBM keyboard.

Compaq have done the same. In table 5-2 of the Maintenance and Service Guide (at [here]) is "3XX or dd 3XX Keyboard assembly or 'stuck' key". But, I do not see a number-to-key diagram in the guide.
 
Thanks for the assistance in finding the error entry in the manual. I tried using one of the extra disks to type with and it worked fine, so there is at least one or more keys that are not installed correctly. I'll report back when I've worked through testing the keyboard a bit more.
 
The issue was the replacement keypad thickness - I have re-replaced the keys with ones of the proper thickness and the keyboard now functions perfectly.

Now on to the next problem in getting this puppy up and running.
FIXED DISK ERROR 1701 (the Rodime HD that never worked, since I had the machine and looks like someone previously disassembled it in a failed attempt at repair)

I was thinking of using some kind of SD replacement card to take the place of the failed hard drive. Thoughts?
 
I had an XT-IDE laying about and stuck it into the Compaq. I had a spare slot, the additional weight is negligible and now the Compaq is up and running.
Thanks for all the help along the way.
 
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