Loading ...
Sorry, an error occurred while loading the content.
 

Solid State Music IO4 stopped working

Expand Messages
  • tkaragiris
    Unfortunately my SSMIO4 serial card has stopped working, It was working fine one day and then just dead the next. I ve been using this card successfully for
    Message 1 of 24 , Sep 5, 2014
      Unfortunately my SSMIO4 serial card has stopped working,  It was working fine one day and then just dead the next.  I've been using this card successfully for over a year and it's been very consistent and reliable.  I've had the card configured exactly like a MITS 88-2SIO with both ports fully functional for loading Basic and CP/M via the APE emulator, both worked well with this card.

      Something on the card has failed and I wanted to get some ideas on what I can test.  I've tested both ports and neither of them work, so it's something that affects both channels.  There's nothing visible on the card that I can spot.  This is a well built factory assembled card, and on the positive side all of the IC's on the board are socketed, and it has very few soldered components.  I suspect one of the IC's has failed so if I could detect which one it is, it can easily be replaced.

      One thing I've tried is to re-seat all the IC's on the board, this helped fix an issue with it in the past, but that hasn't made any difference this time round.

      Is there possibly some sort of test program I can run to determine if it's working internally?

      Luckily I also have a working MITS-882SIO which is now installed in my Altair so it's still working fine.  But I really liked the idea of having two working serial cards and to be honest I've found the SSMIO4 to work better than the MITS 882SIO.  Any suggestions would be appreciated.
    • deramp5113
      Theo, Based on problems I ve run into with serial I/O boards, I d try to narrow down the problem a bit: 1) Power problem? Verify power on the board is good -
      Message 2 of 24 , Sep 7, 2014
        Theo,

        Based on problems I've run into with serial I/O boards, I'd try to narrow down the problem a bit: 

        1) Power problem? Verify power on the board is good - look at the regulator outputs including the +/-12 volt supply for the RS-232 drivers.

        2) I/O address decode or data buffer (out to bus) problem? Write a simple program to read and display the status register of the UARTs. Do the values look like the UART is being properly addressed and that something is responding or are you getting all 1's (for example)?

        3) Look at the baud rate generator output to the UART. If the baud rate clock is not oscillating, the UART won't transmit/receive.

        Mike

      • Systems Glitch
        Another thing to test would be the parallel ports. If you can read/write with them, then that rules out a lot of the bus buffering/address decode logic on the
        Message 3 of 24 , Sep 7, 2014
          Another thing to test would be the parallel ports. If you can read/write with them, then that rules out a lot of the bus buffering/address decode logic on the board. If you can't, then it's probably not the baud rate generator!

          The SSM IO-4 is definitely worth saving, they are reliable boards with excellent documentation. I prefer most SSM products to MITS and IMSAI equivalents.

          Thanks,
          Jonathan

          On 07 Sep 2014 12:39:24 -0700
          "deramp5113@... [altaircomputerclub]" <altaircomputerclub@yahoogroups.com> wrote:

          > Theo,
          >
          > Based on problems I've run into with serial I/O boards, I'd try to narrow down the problem a bit:
          >
          >
          > 1) Power problem? Verify power on the board is good - look at the regulator outputs including the +/-12 volt supply for the RS-232 drivers.
          >
          >
          > 2) I/O address decode or data buffer (out to bus) problem? Write a simple program to read and display the status register of the UARTs. Do the values look like the UART is being properly addressed and that something is responding or are you getting all 1's (for example)?
          >
          >
          >
          > 3) Look at the baud rate generator output to the UART. If the baud rate clock is not oscillating, the UART won't transmit/receive.
          >
          >
          > Mike
          >
          >
        • Jack Rubin
          Couldn t agree more regarding SSM versus MITS/IMSAI. Has anyone ever contacted Malcolm Wright, designer of many of their boards? Jack
          Message 4 of 24 , Sep 7, 2014
            Couldn't agree more regarding SSM versus MITS/IMSAI. Has anyone ever contacted Malcolm Wright, designer of many of their boards?
            Jack

            > -----Original Message-----
            > From: altaircomputerclub@yahoogroups.com
            > [mailto:altaircomputerclub@yahoogroups.com]
            > Sent: Sunday, September 07, 2014 3:51 PM
            > To: altaircomputerclub@yahoogroups.com
            > Subject: Re: [Altair Computer Club] Re: Solid State Music IO4 stopped working
            >
            > Another thing to test would be the parallel ports. If you can read/write with
            > them, then that rules out a lot of the bus buffering/address decode logic on
            > the board. If you can't, then it's probably not the baud rate generator!
            >
            > The SSM IO-4 is definitely worth saving, they are reliable boards with excellent
            > documentation. I prefer most SSM products to MITS and IMSAI equivalents.
            >
            > Thanks,
            > Jonathan
            >
            > On 07 Sep 2014 12:39:24 -0700
            > "deramp5113@... [altaircomputerclub]"
            > <altaircomputerclub@yahoogroups.com> wrote:
            >
            > > Theo,
            > >
            > > Based on problems I've run into with serial I/O boards, I'd try to narrow
            > down the problem a bit:
            > >
            > >
            > > 1) Power problem? Verify power on the board is good - look at the regulator
            > outputs including the +/-12 volt supply for the RS-232 drivers.
            > >
            > >
            > > 2) I/O address decode or data buffer (out to bus) problem? Write a simple
            > program to read and display the status register of the UARTs. Do the values
            > look like the UART is being properly addressed and that something is
            > responding or are you getting all 1's (for example)?
            > >
            > >
            > >
            > > 3) Look at the baud rate generator output to the UART. If the baud rate
            > clock is not oscillating, the UART won't transmit/receive.
            > >
            > >
            > > Mike
            > >
            > >
            >
            >
            > ------------------------------------
            > Posted by: Systems Glitch <systems.glitch@...>
            > ------------------------------------
            >
            >
            > ------------------------------------
            >
            > Yahoo Groups Links
            >
            >
            >
          • tkaragiris
            Thanks very much, these were the sort of suggestions I was after. I ll give them a go.
            Message 5 of 24 , Sep 8, 2014
              Thanks very much, these were the sort of suggestions I was after.  I'll give them a go.
            • deramp5113
              Oh, and I forgot to mention the most simple and obvious S100 board fix (though you ve probably already done this one) - unplug and reinsert the board a
              Message 6 of 24 , Sep 8, 2014
                Oh, and I forgot to mention the most simple and obvious S100 board "fix" (though you've probably already done this one) - unplug and reinsert the board a couple of times. This fixes most of the "this damn thing was working fine yesterday" problems I encounter ;)

                Mike

              • john_crane_59
                DeOxit Gold and Qtips. Your friend and mine... Besides that, the Altiars are notorious for wobbly card guides. I ALWAYS check a reinserted card with a
                Message 7 of 24 , Sep 10, 2014
                  DeOxit Gold and Qtips.

                  Your friend and mine...

                  Besides that, the Altiars are notorious for 'wobbly' card guides.  I ALWAYS check a reinserted card with a flashlight to check that it was inserted exactly right.

                  But I never have to do that on an IMSAI.  Absolutely straight and solid 'thunk' sound when I insert a card.

                  -J
                • deramp5113
                  Theo, I ve recently acquired a SSM IO4 board and managed to get it up and running in my Altair. Theory of operation, schematics, etc., for this board are still
                  Message 8 of 24 , Oct 3, 2014
                    Theo,

                    I've recently acquired a SSM IO4 board and managed to get it up and running in my Altair. Theory of operation, schematics, etc., for this board are still fresh on my mind if you still need help working on your board.

                    Mike

                  • tkaragiris
                    Mike, Thanks, that s great to hear. I haven t had much time to spend on looking at my SSMIO4, I ll see if I can do some basic tests this weekend. I suspect
                    Message 9 of 24 , Oct 3, 2014
                      Mike,

                      Thanks, that's great to hear.  I haven't had much time to spend on looking at my SSMIO4, I'll see if I can do some basic tests this weekend.  I suspect though that it's not going to be simple fix.  If you recall my SSMIO4 was working perfectly and then just quit, so I suspect it's some sort of hardware failure.  Good to hear that you got yours working, I haven't known too many others that use them in the Altair.
                    • deramp5113
                      I wired it up to look like an 88-SIO board at 6/7 and connected a high speed tape reader/punch to it. Since the Altair cassette interface is also an 88-SIO
                      Message 10 of 24 , Oct 3, 2014
                        I wired it up to look like an 88-SIO board at 6/7 and connected a high speed tape reader/punch to it. Since the Altair cassette interface is also an 88-SIO board at 6/7, the Altair thinks the tape reader/punch is the cassette and no new software is required to use it. Even CLOAD and CSAVE in BASIC work as expected.

                        Mike


                      • tkaragiris
                        Very nice, I ve thought about doing something like that myself. I d like to get my hands on a paper tape reader/punch one day. In fact I was looking at the
                        Message 11 of 24 , Oct 4, 2014
                          Very nice, I've thought about doing something like that myself.  I'd like to get my hands on a paper tape reader/punch one day.  In fact I was looking at the GNT4604 after reading a post on the VCF.

                          I'd be interested to know how you configured your SSMIO4 board differently to mine, because mine is set up to mimic an 88-2SIO.  What settings did you use for status word and port reversal, and what chips did you use in U18 and U16?

                          I wrote up the 88-2SIO configuration here:
                          http://tkc8800.com/page/Configuring-SSMIO4-for-use-in-an-Altair-8800
                        • deramp5113
                          The board is configured as follows to make port B on the IO4 look like the ACR SIO board at 6/7: - Set only A2 on S3 to make the serial ports show up at 4-7.
                          Message 12 of 24 , Oct 4, 2014
                            The board is configured as follows to make port B on the IO4 look like the ACR SIO board at 6/7:

                            - Set only A2 on S3 to make the serial ports show up at 4-7. This puts serial port B at 6/7.
                            - Install a 74LS368 in U16 to invert status signals on port B.
                            - Wiring on W1: P4 to P9 (DAV in D0), P5 to P16 (TBMT in D7)

                            Mike



                          • tkaragiris
                            That s the Altair Rev. 1 configuration from the manual. It s great to have someone confirm that it works. I ll take note of this info thanks. When I get my
                            Message 13 of 24 , Oct 5, 2014
                              That's the Altair Rev. 1 configuration from the manual.  It's great to have someone confirm that it works.  I'll take note of this info thanks.  When I get my board working again, I'd like to try it out.

                              So I spent some time today and did some troubleshooting with the board.  First I removed all the chips and cleaned the pins.  About four chips had very oxidized pins, so I cleaned them and re-seated all chips.  I tested the board and no change, still didn't work.  Next I checked the voltages on the four regulators and this is what I found:

                              U1   +4.98
                              U14  +0.58
                              U27  +11.96
                              U37  +5.05

                              The manual says that:

                              U1 & U37 should be between +4.8 & +5.2, GOOD
                              U27 should be between +11.5 and +12.5, GOOD
                              U14 should be between -11.5 and -12.5, BAD

                              So it looks like there is a voltage problem on U14.

                              One other thing I took note of is that this board uses seven tantalum capacitors.  I recall from discussions about early Macs that use these capacitors that they quite often need replacing.  Could this be the problem?
                            • Robert Weatherford
                              I doubt it the tantalum caps. It sounds like an open 7912 regulator. If the middle pin (or the case) of U14 is in the vicinity of -18V, then the 7912 is bad,
                              Message 14 of 24 , Oct 5, 2014

                                I doubt it the tantalum caps. It sounds like an open 7912 regulator. If the middle pin (or the case) of U14 is in the vicinity of -18V, then the 7912 is bad, probably open. The slightly positive voltage you’re getting is from positive current flow from the circuits it’s driving. I used to do in-house board repairs for IMSAI back in ’77 ;-)

                                 

                                Robert

                                 

                                From: altaircomputerclub@yahoogroups.com [mailto:altaircomputerclub@yahoogroups.com]
                                Sent: Sunday, October 05, 2014 7:05 AM
                                To: altaircomputerclub@yahoogroups.com
                                Subject: [Altair Computer Club] Re: Solid State Music IO4 stopped working

                                 

                                 

                                Ok so that's the Altair rev. 1 configuration from the manual, it's good to know that it works.  I'll make note of it and try it out when I get my board working again.

                                So I spent some time today doing some troubleshooting.  I removed all chips from the board, several chips had  very oxidized pins, so I cleaned them and re-seated all chips.  I'd hoped that this was the problem but after testing no change.  So then I tested the voltages from the four regulators and I got these results:

                                U1   +4.98
                                U37  +5.05
                                U14  +0.58    (BAD)
                                U27  +11.96

                                I checked the manual and all voltages check out except for U14.  The manual says it should be between -11.5 and -12.5, so it seems way off.  I also noticed that this board uses seven tantalum capacitors.  I know from reading about old Macs that these quite often need replacing in old hardware, could these capacitors be the problem?

                              • tkaragiris
                                Robert, Yes, U14 says 7912C on it. I checked the voltage on the middle pin and I get -14.8. So pretty clearly this regulator is bad. I checked my local
                                Message 15 of 24 , Oct 5, 2014
                                  Robert,

                                  Yes, U14 says 7912C on it.  I checked the voltage on the middle pin and I get -14.8.  So pretty clearly this regulator is bad.  I checked my local parts store and they have them, so I'll get one tomorrow and replace it.  Hopefully that will fix it.

                                  -14.8 sound low, this is the voltage that comes directly from pin 52 on the motherboard, from looking at the circuit diagram for the original Altair this should be -16v.  Is this also a problem?  The machine is fully functional so it doesn't seem to affect it's operation.
                                • Robert Weatherford
                                  As long as you have at least two volts differential across the regulator, it will function properly. -14.8 is a little low. If all of the unregulated voltages
                                  Message 16 of 24 , Oct 5, 2014

                                    As long as you have at least two volts differential across the regulator, it will function properly. -14.8 is a little low. If all of the unregulated voltages out of the power supply are likewise low, some (IMSAIs at least) power supplies had multiple primary taps to bump everything up or down a little bit depending on the line voltage coming in to the Altair. Certainly the +16V and the -16V rails should be similar. If not, pull out all of the cards and check the voltages again. Normally, there is very little current demand on the -16 rail.

                                     

                                    Robert

                                     

                                    From: altaircomputerclub@yahoogroups.com [mailto:altaircomputerclub@yahoogroups.com]
                                    Sent: Sunday, October 05, 2014 9:01 PM
                                    To: altaircomputerclub@yahoogroups.com
                                    Subject: RE: [Altair Computer Club] Re: Solid State Music IO4 stopped working

                                     

                                     

                                    Robert,

                                    Yes, U14 says 7912C on it.  I checked the voltage on the middle pin and I get -14.8.  So pretty clearly this regulator is bad.  I checked my local parts store and they have them, so I'll get one tomorrow and replace it.  Hopefully that will fix it.

                                    -14.8 sound low, this is the voltage that comes directly from pin 52 on the motherboard, from looking at the circuit diagram for the original Altair this should be -16v.  Is this also a problem?  The machine is fully functional so it doesn't seem to affect it's operation.

                                  • deramp5113
                                    I agree with Robert, -14.8v is still sufficient input differential for the 7912, but it might be worth digging into as to why it s a bit low while you have the
                                    Message 17 of 24 , Oct 6, 2014
                                      I agree with Robert, -14.8v is still sufficient input differential for the 7912, but it might be worth digging into as to why it's a bit low while you have the computer open.

                                      On the original Altair, the -16v supply comes from its own dedicated transformer, so it doesn't necessarily mirror and track the +16v supply. The negative supply comes from an 11v RMS transformer, so with its full bridge rectifier in line, I'd expect the -16v supply to be about where you're seeing it, if not even a bit lower!

                                      Now I'm curious. I'll measure mine when I get home tonight.

                                      Is your Altair using the original US transformers? If so, I assume you have an external 240/120 transformer? If so, measure the 120v input to the Altair as reference point.

                                      Mike

                                    • deramp5113
                                      I just checked the negative supply on my original Altair 8800. It has the 133-P-5 transformer shown in the parts list, but clearly this is not an 11 VRMS
                                      Message 18 of 24 , Oct 6, 2014
                                        I just checked the negative supply on my original Altair 8800. It has the 133-P-5 transformer shown in the parts list, but clearly this is not an 11 VRMS transformer as shown on the schematic I have. Under load of several boards in my system that draw on that supply, the transformer reads 14 VRMS. The rectified and filtered supply meausres -16.2 volts across the power supply filter cap. Again, this is under load of several boards that use the -16v supply.

                                        Mike

                                      • tkaragiris
                                        Mike, Yes, my machine is using the original US transformers. I plug the Altair into a step-down transformer to convert the local 240v to 120v. I ll see if I
                                        Message 19 of 24 , Oct 6, 2014
                                          Mike,

                                          Yes, my machine is using the original US transformers.  I plug the Altair into a step-down transformer to convert the local 240v to 120v.  I'll see if I can measure the input voltage and let you know.
                                        • tkaragiris
                                          So I went down to my local parts store today and got a replacement 7912 regulator. I just finished installing it onto the SSMIO4. Once the board was back in
                                          Message 20 of 24 , Oct 7, 2014
                                            So I went down to my local parts store today and got a replacement 7912 regulator.  I just finished installing it onto the SSMIO4.  Once the board was back in the machine I tested the output voltage of the new regulator at U14 and was greeted with a wonderful -11.97v.  I then switched on the terminal and ran the rom monitor and was greeted with an even better monitor prompt!  I'm glad to say that the SSMIO4 lives again!  Thanks very much to everyone for their help. 

                                            Mike - I didn't have time to check the output voltage of the step down transformer, but I did find one thing wrong with my power supply, I noticed one of the wires on the big gray capacitors was broken where it goes into the circuit board.  This is the first one of the six large gray capacitors on the rectangular circuit board in the power supply.  I suspect the wire is still making contact because I can insert it firmly back into the hole, but it will need to be fixed.  Could this be causing the low voltage on the -16 line?
                                          • deramp5113
                                            Is it the capacitor closest to the transformers? If so, that is the -16v filter cap and yes, that could definitely be related to the -16v problem. I d fix that
                                            Message 21 of 24 , Oct 7, 2014
                                              Is it the capacitor closest to the transformers? If so, that is the -16v filter cap and yes, that could definitely be related to the -16v problem. I'd fix that sooner rather than later.

                                              Mike

                                            • tkaragiris
                                              Mike, No, it s the one closes to the fuse, it s the wire facing the card connectors.
                                              Message 22 of 24 , Oct 7, 2014
                                                Mike,

                                                No, it's the one closes to the fuse, it's the wire facing the card connectors.
                                              • deramp5113
                                                That cap is just one of several in parallel for the 8v supply, so it s not as critical as if it were the single cap for the -16v supply. Mike
                                                Message 23 of 24 , Oct 8, 2014
                                                  That cap is just one of several in parallel for the 8v supply, so it's not as critical as if it were the single cap for the -16v supply.

                                                  Mike

                                                • tkaragiris
                                                  Great, thanks Mike, that s probably why it hasn t affected the operation of the machine (surprisingly). It must have been broken when it was shipped to me
                                                  Message 24 of 24 , Oct 8, 2014
                                                    Great, thanks Mike, that's probably why it hasn't affected the operation of the machine (surprisingly).  It must have been broken when it was shipped to me from Canada in 2011!
                                                  Your message has been successfully submitted and would be delivered to recipients shortly.