SSlmixed.com Forum
Tech discussion => 4K,6K,8K Series => Topic started by: marcmozart on February 14, 2014, 10:20:54 PM
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Starting this new thread as I'm currently troubleshooting the Mix Computer.
Check the "Rebirth of the Mix Computer" for details of cleaning/refurbishing the beast!
http://forum.sslmixed.com/index.php?topic=499.0
(http://i895.photobucket.com/albums/ac155/mozartandfriends/2014-02-14210044_zps0bc1b1f8.jpg) (http://s895.photobucket.com/user/mozartandfriends/media/2014-02-14210044_zps0bc1b1f8.jpg.html)
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I got a 490 card (E-Series) in this computer with the earlier (standard) memory.
There's a CA Floppy Controller Card to connect the computer to the 8" Floppy Drives.
All the other components + the rack case are from a 1991 G-Computer.
When I switch the power supply on, I get the (totally normal) scrambled screen on the Consoles VDU.
Upon switching the "Solid State Logic"-logo on the the Dual Floppy Drive, nothing happens though. The Floppy drive with the program disc (with a red "P" on the front panel of the Floppy Drive) shows the red activity LED, but the system does not boot.
There is of course a working 8" Floppy (with E-Series System Software) in the drive.
Any ideas?
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OK, here we go - the actual troubleshooting begins. I am trying 3 different CPUs (2x 4/30 E-Series, 1x 4/90 E-Series) with the standard memory module to see if anything changes.
These are the 2x 4/30 CPUs:
(http://i895.photobucket.com/albums/ac155/mozartandfriends/2014-03-11123633_zps498152ea.jpg) (http://s895.photobucket.com/user/mozartandfriends/media/2014-03-11123633_zps498152ea.jpg.html)
When I switch the computer on, I am getting the following pictures on the VDU - here's one picture for each installed CPU:
(http://i895.photobucket.com/albums/ac155/mozartandfriends/2014-03-11125010_zps41e8333c.jpg) (http://s895.photobucket.com/user/mozartandfriends/media/2014-03-11125010_zps41e8333c.jpg.html)
(http://i895.photobucket.com/albums/ac155/mozartandfriends/2014-03-11124124_zps04a8ae98.jpg) (http://s895.photobucket.com/user/mozartandfriends/media/2014-03-11124124_zps04a8ae98.jpg.html)
(http://i895.photobucket.com/albums/ac155/mozartandfriends/2014-03-11124442-1_zps8e7dc922.jpg) (http://s895.photobucket.com/user/mozartandfriends/media/2014-03-11124442-1_zps8e7dc922.jpg.html)
Fairly consistent result, I would say. The letters on the screen are almost the same on all three CPUs, with a few different ones.
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I hope anybody with knowledge of the mix computer can chime in at one point. My problem is, I'm getting the "scrambled screen" upon switching the computer on, but the connected 8" Floppy Drive does not boot (after pressing the "Solid State Logic-Logo"-button on the 8" Drive. The drives are spinning, but the heads never try to access anything, I can never hear the heads of the Floppy Drive.
Here are the next steps I'm going to try - these are suggestings from other forum members that I've spoken to in the last couple of days:
- Lower row of cards have to be installed in the right order.
- Lower row of cards should all be connected to the computer interface card (the card in the back door of the computer).
- Tape Machine Interface needs to have fresh batteries.
- Measure voltages of power supply.
- Check LEDs on Bus Driver Card (anybody knows what these mean?).
- Test all involved ribbon cables.
- Try a different Floppy Disc Controller Card (could be defective and not sending anything to the Floppy Drive).
Since I've tested 3 different CPU/Memory-Combinations, and getting consistent results, I am ruling out the CPU/Memory as the problem for now.
I'd be grateful for any input and/or help!!!
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This is the boot sequence of my machine, 4100/A CPU, My "Solid State Logic-Logo" button is broken.. so it starts without activating this, need to investigate if this contact has been jumpered.
https://www.youtube.com/watch?v=9y220c59Jhs&list=UU4h-bJXCVct3T-WrPx4NwXw
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Hi chaps
I remember those old large computer cards and I'm surprised they are still just about working today.
I guess cleaning the edge connectors (Marc is probably an expert in this) and inspecting the cards for dry joints has been done (30 years is a long time). Both cards seem to produce the same scrambled results on the screen so it has to be another problem.
Also, Marc has cleaned his computer rack but, I must say that, a lot of the problems with SSL's these days (apart from changing components) seem to be related to the connectors from what I have read on here. So often, I read that, taking out a card or connector, giving it a clean and putting it back, seems to work.
It's a bit like your modern day computer, tablet or phone when it doesn't connect to anything else for some reason. Apart from component failure, it just could be a case of cleaning the connection and putting it back.
Just a thought and hope it helps. Meanwhile, roll on the replacement computer system chaps as I'm sure everyone will have far less hassle in future if it happened.
Regards from Jim Lassen
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Bruce Millett knows everything.
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You are in a very bad place for troubleshooting. None of this system can be said to be known working as it has been disassembled, reworked and reassembled recently.
You need a working computer to start making headway. Substitution into a known working system of the cards one by one is the best way to begin proceeding. Then you can have a smaller number of problems to pursue. Do you really even know if the disc you are attempting to use is in good shape? I have seen similar results from a bad disc.
Without reducing the number of potential problems, you could be chasing your tail for a while.
Alan
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Hi Marc,
We've been talking a lot about this and going through several hypothesis and procedures. At this stage I would go through the following steps:
My 5cents would go to the floppy controller or the floppy drive. With this said, and to rule out all stuff before sourcing these parts, I would also try the following things:
- Do a continuity test all important ribbon cables with a multimeter. Many times plugin and unplugging these cables some bus lines can be broken. Also it's often that the plugs on these cables get bad connections. So I would go through these 1st...
- Since the Tape card should be connected to boot the computer, I would also replace all the dried batteries, just to make sure this card is working correctly.
- Make sure all the ribbon cables for the lower cards are connected to the Computer I/F card. I'm not sure of this, but this can actually make some interconnections between the cards and the computer that can be important to properly boot:
(http://i1362.photobucket.com/albums/r686/adassumpcao1/Capture_zps5ab136b8.png)
- If the drive's not spinning but it's lighting, sometimes this happens because the drive is missing one voltage to the motors. This often is a problem with bad connections. I would check with a multimeter if all voltages are present.
- Is the drive trying to read the disk and making the noise, like the one in Sintech's video? If so, the reading head of the drive could also be dirty and needs to be cleaned.
Cheers,
Artur
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I'm not sure the Tape card needs to be in there.
I took mine out for a while.
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Try to boot by pushing and holding both switches on the bus driver. From ancient memory, you hold both until the LED's change state then release and check that the yellow (i think) is flashing indicating data from the floppy. It should flash while booting and then the green goes solid. A solid red light is not a good thing. Again, totally from memory have not done this in over 12 years.
I would do this with the I/O cards, TR, Tape, etc unplugged and only the CPU, bus, floppy, keyboard cards plugged. It should boot partially and then indicate that hardware is missing.
Have you verified all voltages from the supply? You can do that from the solder side of the motherboard.
Mike
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I'm not sure the Tape card needs to be in there.
I took mine out for a while.
I'm just recalling from documentation. If someone can test this out on a working computer and checks out then Marc can totally remove this card for troubleshooting purposes. When troubleshooting less variables is better! :D
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Try to boot by pushing and holding both switches on the bus driver. From ancient memory, you hold both until the LED's change state then release and check that the yellow (i think) is flashing indicating data from the floppy. It should flash while booting and then the green goes solid. A solid red light is not a good thing. Again, totally from memory have not done this in over 12 years.
I would do this with the I/O cards, TR, Tape, etc unplugged and only the CPU, bus, floppy, keyboard cards plugged. It should boot partially and then indicate that hardware is missing.
Have you verified all voltages from the supply? You can do that from the solder side of the motherboard.
Mike
This is very good info! One of the things I've learned is that the leds on the bus driver card (i think) actually give you some troubleshooting info, but I've found hard to get any info on how to decode/troubleshoot these. Do you have any info on this?
Cheers,
Artur
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Tying to understand more of the computer side of things, as my last computer worked flawlessly for seven years it was with me.. great reliability, but not so great for the learning curve.
Regarding Computer PSU rails, could anyone explain the principles of the 5v Hang Regulator?
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OK I got some news.
I've exchanged a few e-mails with Werner (the designer of the "The Konnektor" Sync Box), who is probably one of the most knowledgable people about this computer.
Here's what he says:
1. The "scrambled screen" is produced by the VDU & Keyboard Card. The screens I'm getting at start are not related to the CPU at all. In fact, I've took the CPU out, and I'm getting the same exact "scrambled screen". It could be that the computer hangs at this graphic, so trying to reseat the graphics card and the ICs helps sometimes. (Tried that, no luck!)
2. Tape Machine Interface is not needed to boot the computer. So I'm taking it out until we got the computer to boot.
3. The CPU needs to have a working Autoload-ROM. It's a chip on the CPU that tells the CPU what device to boot from. Back in the day, you could boot it from a paper card or Tape or Floppy.
The 3 CPUs I have here, have the number 682-38 handwritten or printed on the Autoload-ROM. Werner says that he never got his computer to boot from Floppy when using the Autoload-ROM with this exact number. He is using an Autoload-ROM with the number 683-38. Plan is to clone the Autoload-ROM that works on Werner's computer.
Will try some things and keep you updated.
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Marc,
That's weird, because those computers (provided by SSL) never were meant to boot on paper, so that ROM should work out of the box, unless it was faulty. Also having 3 CPUs with the same ROM, they all must have worked at some point.
I agree that the scrambled screen is produced by the VDU/Graphics, but that's because it must be dumping the memory contents or something similar, and since it's not booting it finds garbage on the video buffer.
From the troubleshooting so far I would still pursuit something related with the floppy controller or drive, or the connection between them. Anyway replacing with a more recent ROM it's always another issue to clear.
Good luck! :D
Cheers,
Artur
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Yes, we cleared that up now. All those CPUs allegedly bootet from 8"-Floppy Drives before.
Still in complete darkness, but working on it. Will keep you guys updated.
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Keep us updated! :D
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Just checked another CPU here.. and it has the same Boot Rom as the other three Processors you have Marc.
CPU wise, the 430, the 490 and the 4100/A all booted from 8” floppy… no tape! no paper punch cards!
The 490 is the best option in terms of upgradeability, even over the 4100/A, which is imprisoned in the technology of it's fleeting 20 meg moment!
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Could be just too simple ..... but if I recall correctly from memory, I had the same problem which I overcame by changing the power-on sequence.
Can't remember which one was first - the computer itself or the desk.
I have the 3.5" floppy though.
Maybe worth a try if you didn't do it already.
Matt
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Hi guys,
I'm just posting a section of the Automation manual, just to keep things in perspective and accordingly to the SSL Manual:
(http://i1362.photobucket.com/albums/r686/adassumpcao1/startup_zps33883fea.png)
Cheers,
Artur
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Ok - yesterday I restarted my desk after about a 1 year break ........ the computer came up fine .... the first time.
When I switched off the computer again, it didn't access the drives at all - got the scrambled screen that marc posted.
Then, I shut down the computer leaving the desk up and waited about 5 min restart with the same result : scrambled screen, no drive access.
I then decided that there are other things to care about as well and left the computer switched-off for about 1 - 2 hours or so.
Switching on the unit again made the computer boot fine without any problems.
I am just guessing here - but probably there's some kind of logic inside the computer, that keeps it from accessing the drives in case of fast on/off cycles ?
Matt
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I have never worked with the big 8" drives, I pop the desks out before I turn off,
Turn the computer on, disk led flashes, then I put the disks in. As far as I have
seen, it does not matter if the computer or desk is on first.
I agree with above you should check all the voltages in the computer not its
power supply, also those things are full of tantalum caps which are famous
for shorting they are worth checking. reseating the chips can't hurt, but
make sure you work on anti-static mat. May the force be with you. N
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What kind of ROM IC is it? I suggest verifying the ROM first before trying to source another one if you have the tools available.
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Old information maybe, but I just found my (very) sketchy notes from my 6K training course.
" G Series 4/100 processor card has a 10-12 second delay before reset can be pressed. Processor has an
Autoload line which is held off to let discs (8" that would be) get up to speed. Reset line is in Floppy power lead"
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With Andy / sintech's help I have confirmed that my BUS DRIVER + KEYBOARD/VDU-Cards are working fine in other systems, but not the FLOPPY CONTROLLER-Card for the 8"-Drives that I bought, so next step is to return that and get another one.
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Occam's razor (also written as Ockham's razor from William of Ockham (c. 1287 – 1347), and in Latin lex parsimoniae) is a principle of parsimony, economy, or succinctness used in problem-solving. It states that among competing hypotheses, the one with the fewest assumptions should be selected. Other, more complicated solutions may ultimately prove correct, but—in the absence of certainty—the fewer assumptions that are made, the better.
;)
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The moment my SSL Mix Computer is working, will be similar to the moon landing for the United States! 8)
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Has anyone brought the 3 sandwich Total Recall Computer back from the dead? Is so let me, I would like to talk to you.
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The computer that came with my console didn't have Total Recall. It's on the list of things to do, but not a priority.
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When my TR computer went south I sent it to Bruce Millet who did a rebuild and test for a reasonable price though I don't remember what the price actually was. He is a great guy and very very helpful!!
I had a really hard to track down problem .. no booting or operating of the computer that was caused by this. If you have replaced screws in the rack side, you can install one that is slightly too long and it will connect to the buss and/ or crush an unused connector. Mine was on the upper left top connector. This pulled a couple buss lines down with out either frying anything of screwing up power rails. I can't even tell ya how much fun it was figuring that out!
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Got Marc’s CA floppy card to boot in the test computer.. which is just a load of spares that have never worked together, so hard to know what's good or not…
(http://i44.photobucket.com/albums/f23/sin-tech/IMG_5427_zpsa38f2931.jpg) (http://s44.photobucket.com/user/sin-tech/media/IMG_5427_zpsa38f2931.jpg.html)
Whatever the order of the cards, can never got the keyboard to work, yet.. could hear it beep back to warn me that a Reel Disc wasn’t inserted.
The bus driver is kind of doing this!!.. https://www.youtube.com/watch?v=3-JVOvR7LZM&feature=youtu.be
When tested in the studio computer, get the red light also.. and it seems fine, but I didn't have the console on for that test. Normal operation is just the yellow LED.
CA Floppy card tested in the known working Studio machine.. gives the same result, as the test computer.. boots, but keyboard doesn’t react, so this is definitely bad :(
(http://i44.photobucket.com/albums/f23/sin-tech/IMG_5566_zpsd9da1c6c.jpg) (http://s44.photobucket.com/user/sin-tech/media/IMG_5566_zpsd9da1c6c.jpg.html)
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Thanks mate! We're getting there Andy!!
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Andy,
Thanks so much for the troubleshooting! This is been the computer troubleshoot from hell! I feel for Marc... :D
And I promise I will cry when Marc gets his computer back to life! :)
You know what I say? Lets get the SSLMixed Computer running and you'll shed no tears anymore! ;)
Cheers,
Artur
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I'm having a similar issue with our G Computer -- The garbled screen, no disc access. We actually have two computers-- just received one from a guy in Germany. It was supposed to be totally working, but it didn't even come with the original floppy drives.
Our main mix computer has these aftermarket cards by the Desk Doctor. They're for G+ SCSI floppies, presumably to mate with a G computer. I'm kind of confused by these two computers which are externally ostensibly the same. Their cards are quite different. The BUS driver in the computer we just received doesn't have pushbutton switches like the other one.
Anyway-- no disc access occurs. The drives power up fine, but no action. Screen hangs on the garbled mess for a second, then clears and goes blank. Any tips would be appreciated.
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Actually, upon further inspection it appears the primary differences are in the total recall outfitting. Our original motherboard seems to have been modified to go along with the new cards provided by Desk Doctor for connection to G+ Floppy Drive systems. It contains a different Autoload Rom chip .
If I had the original G floppy drives, it might boot up correctly.
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You need to workout what processors are in the two computers. If you have aftermarket cards to run G+ 3.5" then the CPU is most likely to be a 490.
The G from Germany, maybe a standard 4100/A
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You need to workout what processors are in the two computers. If you have aftermarket cards to run G+ 3.5" then the CPU is most likely to be a 490.
The G from Germany, maybe a standard 4100/A
This is true. I don't really have any information pertaining to the main computer card. I purchased a G Service Manual from a link here in the forum, but it contains very "light" functional descriptions of the independent subboards and literally no information about the motherboard.
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One of the cards reads 'LSI 4/95 BASIC' -- this is the one modified by Desk Doctor.
The other has no marking that I can find (this is the one from Germany)
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If you can take some pics.
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If you can take some pics.
I'm pretty sure these two boards are 4/90 boards. I dug out a 4/100 board from our supplies and compared all 3. They appear to be almost completely 74 Series logic. From what I've extrapolated, one of the processors has a special AutoLoad ROM chip and mates with two other cards designed to trick it into working with the G+ 3.5" Floppy drives.
Swapping the ROM chip to the other motherboard, swapping out motherboards, etc has done nothing to change the fact that the screen loads up gibberish and appears to wait for data to load into memory from some medium. It's a shame the guy we bought this spare computer from didn't include the drives.
I don't have my Logic Analyzer on me, otherwise I could take a peek at what's happening on the busses. Looks like I need to call Desk Doctor...
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As Andy said, pics would be appreciated. Andy and I have most of the CPU-cards that were made around, so we can quickly compare.
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Sorry to dig up this old thread but I have a question related to all the 4/30, 4/90 and 4/100 processor and memory talk:
In the "SSL Setup page" (see G computer service manual section 1 page 11) there is a setting called "Processor/Memory Type". The manual says this setting should always be set to "1" and states "don't ask why". But I just came across setting up a computer where this setting needs to be "2" to make it read from the reel disk. It will boot and function in the "1"-setting but without any access to the reel floppy which of cause is of no use. Is it because the cpu board in this computer isn't the G type 4/100 but maybe an 4/30 or 4/90? I havn't checked on the physical pcb yet.
This is the g4.01 software connected to a 4000e vca console.
What does this setting do?
Cheers,
Uffe