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Fixing a bad 32k card


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#1 Mad Hatter OFFLINE  

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Posted Tue Nov 30, 2010 9:29 AM

I have a couple bad TI 32k cards I'd like to fix. Never delved into this before.. any tips on where start? I haven't even opened the cases yet. Thanks

#2 Opry99er OFFLINE  

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Posted Tue Nov 30, 2010 9:33 AM

I know Gary from OPA was offering a few extra cards he had to people who needed them. They may be gone now, though.

Additionally, Matthew180 is doing a "console-swap" program.... send a bad console to Matthew, he'll send you a working one. Perhaps someone is equipped to do the same for the PBox cards. My own knowledge of hardware is pretty limited, so I wouldn't even be able to tell you where to start. =)

I'm assuming you re-seated the cards, tried a different P-Box card slot, etc?

One time I had a bad 32k card... re-seated, changed card slots, etc... Turned out the flex cable interface was screwed up and wasn't allowing access to my 32k card. Swapped the flex cable interface, and it all worked. I have no explanation for that, except it worked.

#3 matthew180 OFFLINE  

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Posted Tue Nov 30, 2010 11:27 AM

If you want to get into the electronics yourself, then I would suggest you head over the SparkFun and go through their tutorials first. Get yourself a decent soldering iron (ie. temperature controlled - NOT a RadioShack special), flux, cleaner, solder, some wire brushes, 99.9% alcohol, wire cutters, solder wick, solder sucker, hemostats, a good multimeter, etc. Doing this yourself means getting set up with a basic electronics workbench, IMO. You don't just do it with stuff around the house.

Assuming you are still with me, you will need to then head over to JameCo, Mouser, or Digikey and source all the chips on the 32K board. JameCo is more hobbyist-friendly and they carry the older ICs that you will probably find in the 32K board. Some of the ICs may be out of production, in which case JameCo usually has "new old stock", or pulls.

Without looking at the board, I'm going to assume there are some 74LS373, 245, or 244 buffers (can't remember which they liked to use), the SRAM chips themselves, and a 5V power regulator. There is probably some LS138 decoders and such. All this stuff is cheap, and unless you have a means to pull and test each part, your basic means of "fixing" is going to be some initial power testing with you multimeter, then pulling a chip, replace it with a socket, then put a known "good" part back in the socket, test the board. Basic isolation through swapping with known good parts.

If you don't have good soldering and desoldering skills (desoldering is harder than soldering), then I would suggest your practice (a lot) on some junk boards before trying to fix these.

I would start with testing the 5V and ground to all the power pins of all the ICs. If the power and ground is all good, I would swap the buffer ICs first. If that does not correct the problem, start swapping the SRAM ICs.

Matthew
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#4 marc.hull OFFLINE  

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Posted Tue Nov 30, 2010 1:29 PM

I have a couple bad TI 32k cards I'd like to fix. Never delved into this before.. any tips on where start? I haven't even opened the cases yet. Thanks


As an option.......

Mosey over to Mainbytes page and look at the 32K16 mod for the console. If you have an extra console I would suggest giving that a whirl. It may look intimidating at the start but it's pretty straight forward and likely a LOT easier and probably cheaper than trying to troubleshoot some old jankey TI MEMEX card plus it will get your feet wet with pictures and instructions. As a side benefit you have a console that can run faster (or in original mode) and you eliminate a card from the box. Total cost about 8 buck's in parts. As a side note..... my Radio Shack 12 dollar soldering iron works just fine ;-)

Marc.

#5 matthew180 OFFLINE  

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Posted Tue Nov 30, 2010 2:13 PM

Yeah, well, don't listen to Mr. Radio Shack soldering iron up there... ;)

If you don't want to fix the 32K card yourself, please let me know.

Matthew
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#6 marc.hull OFFLINE  

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Posted Tue Nov 30, 2010 3:48 PM

Yeah, well, don't listen to Mr. Radio Shack soldering iron up there... ;)

If you don't want to fix the 32K card yourself, please let me know.

Matthew


He just claims to dislike Radio Shack but in reality is a closet shack'r

Edited by marc.hull, Tue Nov 30, 2010 3:50 PM.


#7 Mad Hatter OFFLINE  

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Posted Tue Nov 30, 2010 4:39 PM

Thanks for the replies guys. Fixing the card sounds like it would be fairly involved. I don't really need the cards, just bugs me having broken stuff sitting around. Matthew, if you would like I will send you one of the cards for the cost of shipping. I don't need it back. I'll hang on to the other one in the hopes that maybe someday in the very distant future I will attempt to tackle the chore of fixing it.

#8 matthew180 OFFLINE  

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Posted Tue Nov 30, 2010 4:43 PM

Yeah, send it over, I'll fix it. Then you can partake in the good-for-bad hardware program. :)

Think you can stuff it in a USPS priority mail, small flat rate box?

As for Mr. Hull, ask him who's wife was shopping at Radio Shack during the Faire!!

Matthew
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#9 Tursi OFFLINE  

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Posted Wed Dec 1, 2010 10:52 PM

Without looking at the board, I'm going to assume there are some 74LS373, 245, or 244 buffers (can't remember which they liked to use), the SRAM chips themselves, and a 5V power regulator.


It's worse than that, it's DRAM, and has refresh circuitry onboard.

If I had a dead 32k card and wanted to keep using it, I'd probably cut the board off just above the pins and solder in a '138 decoder and a 32k SRAM chip. :) Personally I prefer having it in the console.

I recently published a simple console 32k mod. It's not on the 16 bit bus, but as a result you need only two chips (the SRAM and a gate) and far fewer connections (and no cut traces). All parts are available at Digikey, total cost (excluding wire, solder) is under $2.50: http://harmlesslion..../TI 32k Mod.pdf

Edited by Tursi, Wed Dec 1, 2010 10:53 PM.


#10 matthew180 OFFLINE  

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Posted Thu Dec 2, 2010 7:50 AM

DRAM?! Ugh. Well, it seems like the problem will be obvious then. Seems like DRAM is starting to fail all over the place. I can't believe all that DRAM and refresh circuitry was cheaper than a few SRAMs back in the day...

Nice mod. A buffer and an SRAM is the way to go! But for people who can't solder, they need a pluggable solution.

Matthew

#11 Tursi OFFLINE  

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Posted Thu Dec 2, 2010 3:08 PM

DRAM?! Ugh. Well, it seems like the problem will be obvious then. Seems like DRAM is starting to fail all over the place. I can't believe all that DRAM and refresh circuitry was cheaper than a few SRAMs back in the day...


Yeah, I agree with you there... but if you look at it - that statement remains true today... 1 gigabyte of DRAM plus refresh circuitry is far cheaper than 1 gigabyte of SRAM. Of course today I suspect it's a case of market demand.

At least in the sizes we need SRAM is now nice and cheap. I remember paying $30 apiece for the SRAM chips when I did my first 32k mod.

Nice mod. A buffer and an SRAM is the way to go! But for people who can't solder, they need a pluggable solution.


Thanks! Not a buffer though, you don't need one there. It's a dual quad AND gate providing the address decode and chip select. My document includes a technical explanation of the mod, since I always was unhappy that the old document never explained why anything was hooked up where it was. :)

As for the pluggable solution, I barely have time to document things, let alone produce them for the masses. I still have a keyboard interface to get out there. ;)

#12 TheBF OFFLINE  

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Posted Fri Sep 7, 2018 7:27 AM

This is an old thread but I have unpacked my old hardware and I also have a bad 32K board.

I have a significant amount of electronics experience, but don't have any digital test gear at my disposal beyond a good bench meter.

 

After I check the three voltage regulators are there any common problems that this old board exhibits?  

(The PEB and disk drives work just like they did when I  last used them. Programs that can run with VDP RAM only work perfectly)

 

Last time I woke it up I was able to confirm that it worked at power up but memory contents slowly faded away.

?Refresh problem. (?)

 

I am thinking I like Tursi's solution. Replace  the card with a 32K static ram. But it would be nice to have the card working.

 

Any thoughts out there?



#13 Lee Stewart OFFLINE  

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Posted Fri Sep 7, 2018 8:44 AM

There are quite a few capacitors on board that might need replacing.  I counted 19 cans topside.

 

...lee



#14 TheBF OFFLINE  

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Posted Fri Sep 7, 2018 10:29 AM

There are quite a few capacitors on board that might need replacing.  I counted 19 cans topside.

 

...lee

 

My first guess too.  I pulled one end of each and they seemed ok. I found a capacitor meter in my junk so I guess I should check them again.

 

Might just buy one off E-BAY to get moving.

 

B



#15 arcadeshopper OFFLINE  

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Posted Fri Sep 7, 2018 12:22 PM

1- don't get another 32kcard get a sams card, they are 80$ new assembled or $20 for the bare pcb (new from Jim here and pcb from arcadeshopper.com)  they give you 1mb instead of 32k, and include the TI 32k ram in there.. 

2- I have a bunch here that need repair too.. lmk if you get anywhere

 

Greg



#16 Ksarul OFFLINE  

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Posted Fri Sep 7, 2018 3:16 PM

I do have a couple of the assembled SAMS boards on hand too--although the price for this batch is $85, as I had to pay somewhat more for a couple of the chips this time.



#17 Stuart OFFLINE  

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Posted Fri Sep 7, 2018 3:31 PM

Any of the chips getting particularly hot? Can you use MiniMem EasyBug to examine a couple of memory locations - is it just a small number of bits failing in each byte, or failing completely?



#18 TheBF OFFLINE  

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Posted Fri Sep 7, 2018 8:27 PM

Any of the chips getting particularly hot? Can you use MiniMem EasyBug to examine a couple of memory locations - is it just a small number of bits failing in each byte, or failing completely?

 

Have not noticed any chips getting hot.  But I seem to have another problem now. :-)

 

The disk drives are not spinning.  Light comes on, but no motor.  Got to open up this thing up I guess.

 

B



#19 TheBF OFFLINE  

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Posted Fri Sep 7, 2018 8:27 PM

I do have a couple of the assembled SAMS boards on hand too--although the price for this batch is $85, as I had to pay somewhat more for a couple of the chips this time.

 

Sounds good to me.  PM me for details.

 

Thanks!



#20 TheBF OFFLINE  

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Posted Sat Sep 8, 2018 10:22 PM

 

Have not noticed any chips getting hot.  But I seem to have another problem now. :-)

 

The disk drives are not spinning.  Light comes on, but no motor.  Got to open up this thing up I guess.

 

B

 

The good news is that the PEB power supplies are all working fine. 

The bad news is one of my 1/2 height Shugart drives is dead. Motor not spinning.  #2 is now jumpered as #1 and working fine.

 

I am wondering about putting a 31/2" drive in this thing.  Hmm... that would give me 720K per disk with single density setup on the card.

Has anybody done this before?



#21 Ksarul OFFLINE  

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Posted Sat Sep 8, 2018 10:48 PM

Actually, the controller will only do single density and 40 tracks per side without modification (180K). There is a modification to the DSR that will allow 80 tracks per side (360K in single density), but that is it. This mod is an ideal use for 3.5 inch drives or 80 track 5.25 drives designed for DD use (normally described as 720K drives--and avoid any 5.25 drives certified for HD use). Note that to make the DSR change, you have to desolder the existing DSR ROM and replace it. Most folks doing this socket it at this point. . .



#22 TheBF OFFLINE  

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Posted Sun Sep 9, 2018 5:55 AM

Actually, the controller will only do single density and 40 tracks per side without modification (180K). There is a modification to the DSR that will allow 80 tracks per side (360K in single density), but that is it. This mod is an ideal use for 3.5 inch drives or 80 track 5.25 drives designed for DD use (normally described as 720K drives--and avoid any 5.25 drives certified for HD use). Note that to make the DSR change, you have to desolder the existing DSR ROM and replace it. Most folks doing this socket it at this point. . .

 

 

Good to know. Thanks.

 

The knowledge on this sight never ceases to amaze me.



#23 arcadeshopper OFFLINE  

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Posted Mon Sep 10, 2018 7:30 AM

 
 
Good to know. Thanks.
 
The knowledge on this sight never ceases to amaze me.

I sell modified disk controllers with the 80 track ROMs installed at arcadeshopper.com BTW

Sent from my LG-H872 using Tapatalk

#24 TheBF OFFLINE  

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Posted Mon Sep 10, 2018 7:13 PM

I sell modified disk controllers with the 80 track ROMs installed at arcadeshopper.com BTW

Sent from my LG-H872 using Tapatalk

 

Hey Mr. Arcadeshopper.  That is a pretty cool store you have there!  Nice work by you.

 

I think my order for the Magic FM program will get me going with transferring CAMEL99 to my real iron.

 

Thanks for being there for the ninety-niner community.

 

B






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