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Western Digital WD1002-WX2 MFM controller repair (Turbo XT)

VeryVon

VeryVon

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Hello, I’m working on a Turbo XT with a WD1002-WX2 controller / ST-251 drive combination and the card hangs up any machine I put it in. Once by some miracle I was able to boot on a floppy and low-level format the drive using g=c800:5 at the debug prompt, but fdisk locked up on the next boot and now I’m back to hanging up at boot no matter what I try.

I’ve noticed there’s a ton of good info on this card out there in various threads, and I’ve already read the bios chip and it looks clean compared to the other ROMS floating around there. If I can somehow get past the post screen with the card intact I’m sure I can find more out.

Has anyone successfully repaired a board like this, or have any other tips / tricks to get past post? I noticed a few of the chips are extremely hot on the board (see screenshot below.) Guess I’ll work out a way to get it on the bench and start poking around with a logic probe / scope with the schematics handy.

Hot IC’s / Components on the board (in red):

WD1002-WX2.jpg

Maybe I should just replace that LS74` on the right but I'd be shooting in the dark.

Motherboard for Reference:

TurboXTMobo.JPG
 
I have a similar controller , but with no floppy drives. I'll dig it out later today for ya and dump the bios.

Edit scratch that, I dont see floppy on yours either. I'll go look for it when I get home. I believe mines almost same card. Cant remember if its a 1002-wx2 or 1003-wah that I kept. Kept one traded the other, as I went to CF early 2010s, and now going back to spinning rust in some machines, go figure! :)

Seems when you are younger you want to hot rod everything, as you get older you prefer it the way it was... Kinda humerous what was common and uncommon always become vice versa with time.
 
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modem7 said:
The listing at [here] suggests 2732.
Click to expand...
Thanks for that, I assumed 2532 because my reader read the existing ROM using that device type. I have to go back and scrutinize the pin-outs because if you notice on my board the ROM is mounted "to the right" in the socket leaving the two highest and lowest pins empty. At one point it did work though, loading the format program. So it can read it. Maybe once I get this straightened out everything will start working again. I'll look into those 2732's.

WD0003.JPG
 
Progress! I wrote back to a 2732 what I read off the original ROM (attached, see below), and now I see "System Error 20" reported at post which corresponds to "Bad expansion ROM checksum" as documented on the pcxtbios GitHub (I've been tinkering a bit, and replaced the stock system ROM with pcxtbios.)

Does anyone have a known good image of the WD1002-WX2 bios compatible with the ST-251 drive?

TruboXTBios.JPG

btw, the ROM is reading from debug, but cannot format the drive (Error completion code 01)

Debug.JPG

Thanks for your help with this
 

Attachments

  • wd1002-wx2 - wd 0003 sw rom dump.zip
    1.6 KB · Views: 2
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Well I dug out my MFM controller, and isnt much help for you. Its a WD1003-WAH. Sadly the eprom is soldered in, Guess I can try desoldering it , and throwing in a socket to dump it. Wont have time today though.

IMG_20220601_171754123_HDR.jpg
 
Update: I found a free hex editor that will compute the 8-bit checksum of the rom file. Using that I'm able to fix the checksum problem (by tweaking the last byte in the file) but now it's hanging again. I'm going to try a few more ROM images.
 
Did you try that link modem7 posted? There are various WD BIOS there. None seem to be the exact model, except one that says it’s custom for some special computer. But maybe one would work for you.

I've got a couple of WD1002S-WX2, but I'm not sure how much of a difference the S makes... maybe a lot?
 
jafir said:
Did you try that link modem7 posted? There are various WD BIOS there. None seem to be the exact model, except one that says it’s custom for some special computer. But maybe one would work for you.

I've got a couple of WD1002S-WX2, but I'm not sure how much of a difference the S makes... maybe a lot?
Click to expand...
same here, have 2 of the 'S' designated ones and have a couple different ROM revisions for those
 
I've got a 2732-fit Western Digital BIOS, but for the life of me, I don't recall the controller that used it. But here 'tis.
 

Attachments

  • wdbios.zip
    2.3 KB · Views: 2
RESOLVED!

I burned and tried half a dozen ROMS last night and came to the conclusion that a "working" ROM with good checksum would lock the computer at Post. So that's when I made the decision to start operating on the board.

I started by replacing the LS74 that I noticed was overheating badly. I usually never get lucky with these kind of blind fixes, but I put the card back in the machine and behold everything started working! Post, low-level format, fdisk, etc. Couldn't believe it. Guess I got off easy.

Thanks for everyone's contributions to keep this going. I'm going to (re)attach my bios here on this post in case someone comes across this with the exact same setup (WD1002-WX2 controller / ST-251)

(Update! Keep reading if you have an ST-251, the ROM I posted here will only format it to 20MB as it is coded for ST-225 geometry. ST-251 should have twice the capacity available...)

Socketing and replacing this guy was the key:

74LS74-2.jpg

WX2 Format
1654169172216.png

fdisk
1654169223458.png

format
1654169309151.png

Thanks!
 

Attachments

  • wd1002-wx2 - wd 0003 sw rom dump.zip
    1.6 KB · Views: 4
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That's great you got the card working, but the ST-251 should be twice that size. You're only getting half the capcaity because it appears your ROM is coded for ST-225 geometry
 
maxtherabbit said:
That's great you got the card working, but the ST-251 should be twice that size. You're only getting half the capcaity because it appears your ROM is coded for ST-225 geometry
Click to expand...
Oh wow, I guess the journey continues! I'll try to tweak the settings as mentioned here in this thread / post and burn it to a new ROM. Now that the card is fixed and I know how to get the checksum correct it should be a no-brainer (famous last words :p)
 
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