justacruzr2

Thanks for the backside photo. Very helpful and also a bit puzzling. Only one modification (or correction) is the same on both our cards. That being the wire jumpering pins 2 and 5 on the right side of the 74LS74 together. 2 other modifications on mine are not present on yours. Also mine has the first 4 pins of the MCM2114P jumpered together. I think this is OK though as my Rev A card does the same thing but it has a circuit trace doing the job instead of a wire. Probably one of the CC revisions made on that later card. You might want to consider doing that also. I think it's necessary. Before I undo those other 2 mods and see what happens just a question....did your card ever work to start with? Trying to determine if those were user mods that didn't pan out. My card does power up and present the CC menu screen but it doesn't recognize a floppy disk in the drive. Weird. Gotta be a reason for that.

Hi Ricky, Thanks for posting the photos but could you please take a photo of the backside (solder side) of your early version CC9900? This is the side I'm not sure about (for reasons mentioned above). One of the other things I found on my Rev A card was a broken trace. When I repaired that, the card worked. If you have an LED flashlight, shine it through the board from one side while looking at the other side. That was how I found it. It's not a bad idea to make this check due to the age of these boards and you might find something similar on yours. That's all it takes for the board not to work. All circuits must be complete. I also have a complete nearly unused set of the MG EPROMS that I bought from Bud Mills Services. By nearly unused I mean I plugged them in when I first bought them to see what they did for the card but didn't like the MG blurb at the top of the TI master screen and didn't like that I couldn't access the disk manager with one keypress. Also, I used them a couple of times while trying to figure out what was wrong with my cards to eliminate the possibility that the original EPROMS were bad (testing purposes). I would be willing to sell these and they come within the original packaging (blue plastic cube with foam pad) and the original instructions detailing the extra commands contained in those EPROMS. Let me know if your interested and we'll proceed from there. I'm still working on repairing my floppy drives so I'm not completely back up to speed yet. It's very tedious work to remove and replace the 45 pin 4 sided surface mount master floppy read/write IC. PS I also see that your EPROMS are missing the paper tags which identify which bank they are and the revision date. With those tags removed there is always the possibility that they were exposed to ultraviolet light and have been either erased or messed up.

His email address is: [email protected]

OK. Found the problem with the Rev A card. A bad solder joint making intermittent contact. It's back online now, with heatsink, and works perfect. Ran it for about an hour with no problems. So this one has good PALs too. It was good to be able to catalog disks again and see that everything is OK. All smiles here! Now this leaves the matter of the early card which does work also except it doesn't read the disk. The following are the things that I have identified which may be affecting it: 1) 2 unadjusted trim pots. 2) 3 mods (or corrections) on the solder side. Not sure how to proceed with #1 unless someone knows where on the board to take the readings and what value I should be getting for each one. As for the mods, does anyone have a clean early version CC9900 card that is working that you could take a nice picture of the solder side of the board and post it in a reply so I can compare it with what I have? By "clean" I mean a board that hasn't been modified by the end user. Any original CorComp mods or corrections it may have is OK. That's what I'm trying to determine. Mine has 3 mods which look like CorComp mods but I can't be sure without comparing it, or hearing from someone who knows what the official CorComp mods were. Frequently their cards did not work exactly right when they went out the door. The Triple Tech card I bought from them had to be sent back for repair because it wasn't working exactly right when I got it and they made some mods on the back to correct it, I guess it was some design flaw.

That's what the datasheet said also. It gave a ratio of better than 4:1. Or at least four chips could be eliminated with 1 PAL. The flipside of that though is if the PAL becomes bad you have a tough problem. Especially when factory support is no longer available. I would also add that I think CorComp never expected the TI crowd to still be going after all this time. Hats off to TI. Still haven't found why the Rev A card isn't working. But I did get a strange reaction when I replaced the new WD1773 with the original one. The LED came on when the PEB was turned on but the console off. It's not supposed to do that. No cards light should come on until the console is powered up....Hmmmm...... At least that would seem to confirm that the original WD1773 had a problem. Because there seems to be some other problem with the early card which is preventing it from reading a disk, I'm concentrating on the Rev A card since, when it was working, it was able to access a disk.. It's puzzling when the state of something changes for no apparent reason. Anyway, I'm going to take a break from it today to get some other things done. Sometimes you have to walk away from a frustrating problem and come back to it later fresh.

I do. I kept all the chips I replaced just in case they weren't bad after all. Even though they were replaced with new ones along with everything else I'm going to check it again anyway along with the DSRs and the WD1773. The WD1773 and 9901 came from China. Maybe they weren't so good after all although I bought 2 9901s from them for both cards. They were the only place that had them. Getting tough to find the specialized chips these days. Believe I will need an eprommer to do that though and I don't have one. Maybe I can find someone who will lend it just for this purpose. Getting a read on the ones from the early card would be a nice thing to accomplish since the early card is more rare (I think) and the PALs are not interchangeable between the 2 versions of the cards. The chip used (PAL12L6) is the same but the PCB traces are different. Both PALs do the same thing on both cards but the traces come to different pins so I think just the order is different.

@ Ksarul It seems you were right. When I put the heatsink back on the early model card it works without shutting down and locking up. I had it going for about 10 minutes to be sure. But it's not reading the disk. When I press 1 for Disk Manager it goes out drive by drive looking for it but doesn't find it even though the disk is in the drive and I know the disk (and file) are good because I've loaded it before during these tests. However, I did that using the Rev A card not the early model card. The early model card uses 2 trim pots which I replaced but didn't adjust because I have no idea what voltage they are supposed to be delivering and no idea where to take that reading. There are pins in several locations on the board that look like they are for hooking up a meter but which one and what should I be getting for a reading is unknown. The datasheet on them states their voltage adjustability as being +- 0.01%. On a 5V input that would be 0.0005 volts. Didn't think that was significant enough to be a problem but maybe something on the board is that sensitive. This may have something to do with not being able to see the disk but I don't know. Or it could have something to do with the mods on the back side. As for the Rev A card it didn't even come on at all...no LED...no CC menu screen. And why it did that I don't know since it was fine just a couple days ago when I tried it last. I'll have to investigate that. But for now it would seem that I will get the same result as the early model card when I use the heatsink for that one too. Anyway, it looks like I'm making some progress and at least on the early card the PALs are not bad. BTW, do the volt regs have something like a bi-metal strip in them that breaks the connection if they get too hot? Will keep you posted as things progress. @ marc.hull Yes and after reading the above we may have solved the overheating issue which prevented any extensive testing more than a minute. I'm not totally out of the woods yet but getting closer. Thanks for your help.

Yes. I asked him about that and he confirmed your identity. Thanks for taking the time to help. Anyway......... At first I did not. In a previous post I mentioned that I had mistakenly replaced the WD2793 with a WD2793A that, when I first turned the system back on to test the card, it blew several support chips and both my floppy drives and the floppy I was using in the drive (hope a disk utility program will get that back). That was the early model card. At the time I did not yet have the Rev A card done. So my next tests were without the drives connected. My thinking at the time was that maybe signals from the floppy drives boards might be causing the problem. OK. Just checked my PEB and it has the 1/2 height dividers. But I'm going to check for interference with the card anyway. It has the spring loaded tangs that do touch the card but from what I can see these cards have the fat ground trace running along the outer edge of the card and I figured that was just an extra safety measure by giving them a secondary ground source to the PEB. I have been testing it in slot 7 since I'm putting it in and out so frequently it made it easier to attach the ribbon cable and to also put my finger down the side to feel the volt reg. I actually was going to ask you if using slot 7 instead of 8 could be the problem. Thought maybe there was a reason slot 8 is supposed to be used for the FDC other than because of the ribbon cable. Like maybe there were slightly different lines that run to that connector than slots 2 thru 7. But your suggestion answers that. As for the volt reg output, I did a simple test where I temporarily soldered 2 wires (30ga strapping wires), one to pos one to neg to see what the voltage was during actual use. I put my volt/ohm meter on them and got a reading of 5 volts. It was steady.. My Rev A card came with the metal clamshell but the early model that I bought from a guy at the Yahoo TI group site came bare. Getting a clamshell for it was one of the things I wanted to do for it after I got it working again. And my Rev A card/clamshell uses the metal screws with the nylon washers. The nylon washers are only used on the 3 screws that are not the volt reg. Actually the washers are used to keep the card even in the clamshell. Only the volt reg screw shoulder is taller. The other 3 are shorter and need the washers to keep the card from bending at the corners when put all back together. Hope you're not going to kill me for this one but so far I've been doing this without the heatsinks attached since the screw that goes thru them attaches to the clamshell and has no nut. Didn't think that would make much difference over the short haul but now with what you and marc.hull have said I'm going to go out to the garage and find a small screw with a nut and put them back on for these next tests. I do have heat sink compound. So my next tests will be with the heatsink attached. First I will just see if THAT is the problem (am I bad?). If the problem still persists I will then do as you say above starting with the 74 series chips and no DSRs, PALs or 9901 installed. I will be doing this right after I get offline so I'll let you know later what happened.

@ Ksarul OK. Wasn't sure what you already knew. It helps if we're both on the same page. When I de-populated the board and started re-populating it one at a time the voltage regulator did start getting hot. I did not have to get every chip back in place before this happened. I replaced starting from the left side of the card to the right and from the top to the bottom on both. I wasn't really paying attention to how many chips I had replaced when the volt reg started getting hot again but I believe it was about 5 or 6 and I believe the PALs had already been put back. I'm going to do this again and pay close attention. Does it matter the order in which I do this? Should I put the PALs back last or first? Also have a new set of the MG ROM chips which I could temporarily swap to confirm that the original CC ROMs aren't the problem. I didn't do this up to this point since the cards do work for a short time and I can load the Disk Manager and catalog a disk or load a file into the Gramulator with no problems. That's about the time the cards shut down. Both behave exactly the same way. One thing that crossed my mind was the PEB power supply. Was it possible that the voltage supply to the card slots also absorbed some of the static charge and fouled something up there too. Unsure if the PEB supplies more than one voltage line to the slots and if there are a couple of different voltages (ie. 12V, 5V) supplied to the slots for cards to use. Because none of the other cards in my box have volt regs that are overheating I discounted this but maybe I'm wrong. Maybe the CC card uses more than one voltage? One other thing I mentioned before in a previous post was that the early model FDC has some modifications on the solder side of the board that look like CC mods but I have no way to confirm this. But since both cards are acting the same way (and the Rev A card has no mods) I'm thinking they probably aren't the problem. I agree with everything you have said. There is a piece of this puzzle missing yet and in my enthusiasm to get these working again I'm rushing thru things. So as I said above I will do it again and pay attention to how many chips are back on the board (and which ones) when the volt reg starts getting hot again. Also agree that this is a good place to sort this out. I'm aware that there are also a few other people out there with CC9900 cards that aren't working who could benefit from this discussion. I also have a Rave99 512K card and yea I saw that it had a PAL too. But it does function correctly. But I think Rave provided buffering on this card. One last thing. One of the chips on both boards is the SN7438. At the time, DigiKey didn't have them and a Google search revealed that the SN74S38 can be substituted for it. I had wondered whether or not this might have something to do with it so I downloaded the TI datasheet for the SN7438 family of chips which includes the SN74S38 and SN74LS38. According to the datasheet there is a difference in the low level output current. The SN7438 puts out 48ma whereas the 74S38 puts out 60ma. My local electronics guy said this shouldn't make a difference but I still wonder. However those chips were among the last ones I put back and the volt regs were already overheating.

Already did that and already checked over all the solder joints with a 30x magnifier and already checked all the circuit board traces for breaks. The only thing that overheats is the voltage regulator. No other chip on these boards gets hot. All the IC's have been replaced along with every other electronic component. Essentially these are now new boards except for the PALs. Don't know how much you know about the PALs but I located the datasheet for them and learned quite a bit. These chips are all fusible links. They are not programmed in the conventional sense (ie. assembly or "C" code which is then burned onto them like a ROM or PROM). They are programmed by burning out or leaving intact the fusible link. Each pin has one and 2 are reserved for the programmer to protect the chip from being duplicated (this can be overcome though and not everyone does that anyway). So by programming the fusible links you permanently set the pins either to an active high ("1" - intact) or active low ("0" - burned out) state. Since these cards took a static surge hit it's very likely that whatever fusible links weren't originally burned out are burned out now. It takes only 400ma to program (burn out) a fusible link according to the datasheet. A static surge would have delivered much more than that. CorComps cards (all of them) were notorious for this since they did not provide any buffering on the cards to stop such an event dead in its tracks. One thing I plan to do when I get the extra time is to make a schematic of where every trace from the PAL pins goes to. If one of the 5 people I've already contacted can't come up with good sets of the PALs this may provide some insight into how it was originally programmed and maybe it can get done that way. Oh...BTW...with no chips installed the voltage regulator does not overheat.

I have just finished replacing everything on my 2 CC9900 cards except the PALs and they still overheat and shut down within about 1-2 minutes. But they do work before they shut down. So it would seem that the PALs are bad. I have just purchased a lot of 10 12L6CN PALs but now need either what was burned on them or someone who has a good set to temporarily donate them for copying. They would be returned to you unharmed. I realize that trust doesn't come easy. This is a mission of mercy for the TI community. Several of us have CC9900 cards that need these to put these cards back to use. I have tried to find a way to contact both W R Moseid and Craig Miller but no luck. I will make the extra sets available at a very reasonable price. Would appreciate hearing from anyone who can help. Thanks.

Googled for W R Moseid but found nothing of use. However, I was looking at the CorComp manual for the CC9900 card and saw that Craig Miller was involved with this project. It may be that he was privvy to some of the details of the PALs. It might be worth contacting him to see what he knows about them...if anything. Other than that, we just have to hope that we can come across a good set that can be copied. It's frustrating that this is holding up putting these cards back to use.

I just did a Google search too but couldn't find exactly what I was looking for. Part of what I remember reading was that the "buffer tank" (whatever that is) operates in a different manner than the standard WD2793. Maybe the voltage is different or is applied to the wrong pin of a chip on the receiving end. Wish I could find that again or remember more. It was about 2 - 3 years ago that I read that. That's about the same time I came across them too.

Ahhh. A fellow Hawkwinder. That's one of the best album covers I've seen and I frequently use it as my avatar. I don't think I have as much as you though. Only have the first 6 Hawkwind albums and RC's Captain Lockheed and the Starfighters. As for the 2793A....just don't want to see more people make this same mistake. Usually the suffix part on a chip doesn't mean that much but in this case it does.

I think that's a pretty good guess and makes sense from what I understand about caps. Thanks for the enlightenment. I may consider making that mod once the cards are working right again.

If this picture of the early CC9900 you posted is yours I can tell you right now that one of the problems is that WD2793A on it. Made the same mistake myself. Didn't realize that the "A" suffix does mean something with this chip. Specifically, this is a variation of the WD2793 for Apple computers and there is something very different about it. Forgot where on the web I found that info but get rid of it and get a WD2793. The WD2793A I mistakenly put on my board blew several ICs and messed up my floppy drives so that they don't read/write at all (but they do spin) and blew one of my floppies. A costly mistake. After I get my cards working right I'll have to figure out what went bad on the floppy drives and fix that too. Fortunately I have another floppy drive that wasn't connected at the time and I'm using that for testing purposes. Also noticed the 2 tantalum caps on the voltage regulator and wondering why they are there? Also, unless you have some unusual floppy drives that require faster seek times, the switches on the 8 position DIP are set incorrectly. They should be : 1 - ON 2 - OFF 3 - ON 4 - OFF 5 - ON 6 - OFF 7 - ON 8 - OFF This is the factory setting for nearly all drives (as per the CorComp manual that comes with the card).

AAAHHHHHH! Too late for today. But then I guess it's the first Saturday of the month. Anyone know where they are meeting these days?

Thanks for posting those pictures, especially the early model CC9900 card. The picture I have is low-res and when you zoom in, it just gets pixelated and you can't read the chip numbers. I see on that card there are jumpers on the two 3-pin blocks in the upper left hand corner next to the ROMs. Mine only has one jumper on the lower pin block and it is connecting the middle and lower pins...that one is connecting the middle and upper pins. Wonder if that is just for testing or is mine missing a jumper and also connected wrong? Testing will only tell. Would need to find another jumper. The way mine is jumpered is like the picture I found so I assumed it was right. Maybe not. The early card also has several single pin jumper blocks which I am assuming are for testing, diagnosing and adjustment (of the trim pots) purposes. I'm going to recheck my card by comparing it with the picture you supplied to see if there is anything else amiss. Anyway a bit of good news. Both my cards (early and Rev A) now display the CC menu screen at power up and do work for about 1 minute before both LEDs get dimmer, go out and the system locks up with the voltage regulator getting very hot. I'm thinking that the problem is the same on both and that it's the PALs. I suppose that even though both PALs are electrically active (if they were burned out the menu screen wouldn't even come up at all) what happened could have scrambled what is burned on them and they might be working incorrectly. Unfortunately the only way to confirm this is with known good ones and right now I have no idea where they might come from. Here's another interesting thing. There's someone on eBay right now selling a loaded PEB for $500. It has the 32K card and the CC9900 controller card and 2 1/2 height floppies. They say it has been tested (for 2 hours) and is working perfectly. That's a little too much just to get the CC9900 but isn't that bad if you need everything. Here's the link if your interested: http://www.ebay.com/itm/TI-99-4A-TI99-Peripheral-Expansion-Box-System-DUAL-DS-DD-Disk-Drives-CORCOMP-/371644793321?hash=item5687c181e9:g:~3MAAOSwnNBXT5es Still trying to find out when the Chicago TI Users Group (CTIUG) has its monthly meetings. I've been told that they give away something at every meeting (donated equipment). I live in the Chicago area so it wouldn't be a problem attending. I used to be a member anyway. Would be great to be at the meeting that they gave away a CC9900. Or at least maybe I could find out a way to get good PALs for mine. One last thing. That picture of the CC9900 you have posted. Is it yours? If it is could you please take a picture of the reverse side (solder side of the board) and post it in a message? I would like to compare it with mine. There are some mods on the back of mine that look like they are CC mods but I would like to confirm this. Appreciate it if you can and Thanks.

Although I haven't, as yet, tried to contact him, I was going to start with a Google search. He might have a Facebook account or something like that. Agree that we need to do something with CorComp products. As for the PALs, 12L6's are not the only thing that will work. Take a look at the picture of the Rev A card I found on the internet. It has PAL's with a different number on them. So I guess there's more than one choice for an IC. If someone would be kind enough to allow someone to copy their PALs that would be a good start.

Aahh. Didn't know that what you were working with was the Micro Expansion System. And yes. That system was designed to be added to. You could start out with just the 32K and add more functionality later. I believe it all daisy-chained if I remember correctly.. On my Rev A card the PALs are definitely part of the problem. When I power up it just makes a racket (loud buzzing and the screen goes berserk). When I put the PALs from the early version card on it (those ones are good) no buzzing or berserk screen but I still don't get any display on the screen so there is more wrong than just the PALs. The only thing I don't know is whether the early version card PALs have the same thing burned on them as the Rev a card PALs.

Are you sure they're 9902's? Those IC's are UART's and are generally used on the RS232 board. More likely the PALs are at fault. They're very sensitive to any spikes or surges since the card has no electrical buffering. I would also like to find someone who can burn new PALs. My REV A 9900 will need them. Last week someone on eBay was selling a new lot of 5 PAL12L6's for $22.00. Before I could get back to them someone snagged them. The PAL's aren't much good unless you can find someone who can read the code from a good one and then burn it onto a new one. Trying to get in touch with the CTIUG 'cause I'll bet someone in the group still has an eprommer. Problem with CorComp was they were never very forthcoming about details of their card. They could have released that info to the TI community when they went out of business. Would love to see a schematic of the 9900 card and/or the equations that were burned onto the PALs. It also might be possible to contact W.R. Moseid for some info. He was one of the CorComp team. Only other way I can think of is to borrow a couple from a good 9900 and copy them. Also hope some more come up on eBay

Hi Stuart. Socketing the few remaining chips that weren't originally was part of what I did while working on this card. So I can do that and that's a good suggestion. Something on this card is making the volt reg work harder than it should (at least that's my theory). Also occurred to me that whatever happened to this card may have damaged the crystal so that instead of not working at all...it's clocking faster than it should. I'm no electronics expert but I have read about people who overclock CPU's (non-TI) to increase the processing speed and one of their cautions is to install a better (larger) cooling fan. Makes me wonder if something similar is happening here? Anyway I'm going to try your suggestion and see what happens. Thanks.

Hi everyone. I'm going to jump in on this topic since I have a related problem. I recognize some of your handles from when I was last on the Yahoo TI 99/4A users group site. It's been 2 years since then and though I was distracted with other pressing things, I'm now back to trying to repair a CorComp 9900 disk controller card I bought from a fellow member. This one is an early model that is marked "Cor Comp Inc - PEB-DCC - 200002 H" and it's previous history is unknown. The seller had told me that it had an overheating problem at the voltage regulator and after a minute or 2 the card would lock up. I have confirmed the overheating problem simply by touching the voltage regulator when powered on. It gets hot like the steering wheel of a car that's been sitting in the summer sun for hours. That seems excessive. Anyway, I have replaced everything on that card with new parts with the exception of the floppy drive cable connector (seems unnecessary), the trim cap (my local electronics expert highly doubts that would cause the problem), the 8 postion DIP selector (for changing drive seek times) and the crystal. Also have not changed the diodes yet. I have them off the board but need to find a strong magnifying glass to be able to read the part numbers. So far nothing I've done has corrected the problem so I'm hoping this does the trick. I did compare the card to a picture of one sent me by another member and all the IC numbers check out as do all the other components. Did this in case someone had tampered with it before and installed incorrect parts. Seems like the solder side of the board has many variations though from pictures I've seen so it's hard to confirm if what's on mine is correct. There are about 3 mods that I see but they all look like CorComp mods. I have also confirmed the voltage at the PEB card connector (pin 2) at 8 volts and the output voltage at the regulator at 4.75 volts. That seems within tolerance. The CorComp menu screen does come up at power-up and I can go back and forth between menu selections a few times before the LED gets dimmer and finally goes out and it locks up. Assuming this is a built in protection of the voltage regulator when it exceeds heat tolerance. I have also checked the card using a different slot in the PEB but no change. The other cards in the PEB work fine and their regulators are not getting HOT....just normal warmth. Anyway, if the new diodes don't take care of this I guess I can undo the mods one at a time and see if that makes any difference. They look like CorComp mods but maybe they're not? I remember all sorts of mods for things in Micropendium and maybe there were some for the CorComp 9900? Would appreciate any suggestions from other users who have had this type of experience with the early CorComp 9900 and what they found. I also have a revision A CorComp 9900 that I'm trying to repair. This one I bought originally and know it's full history. Problem with this one is it took a static charge hit. I have replaced all the IC's on it too except for the PAL12L6's which I know were trashed by the static. I substituted the PAL's from the early version and it does respond a little better but still no menu screen. Does anyone know if the algorythms burned onto these PALs were different between the early version card and the revision A card? I also have not replaced the other various electronic components on this board yet but do have the parts to do so. Just taking it one step at a time. Any thought on this appreciated as well. Really need to get these cards working as all my floppies are DSDD and a TI DCC will not be able to read them. And if Hal Shanafeld is reading this, could you please contact me? I would like to know the meeting schedule of the CTIUG. Thanks.