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Re: [midatlanticretro] makeshift IBM monitor

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  • Bill Degnan
    Joe, Do you have a copy of the technical reference manual? If not I can copy and scan the important pages. In the mean time can you take a picture of the
    Message 1 of 23 , Jun 1, 2009
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      Joe,
      Do you have a copy of the technical reference manual? If not I can copy
      and scan the important pages. In the mean time can you take a picture of
      the motherboard switches, and RAM? If not easy to do, can you just tell me
      whether there are open RAM slots and what the switches are set to? I am
      guessing it's a 64K + 512K with the QuadRAM card = 640K. With this you
      could do almost anything. Lastly, what are the markings on the ROM chips
      in U33? That will tell me if it has an upgraded ROM or the original. I am
      going to guess that it's been upgraded.

      I don't off hand know the voltages. The 8087 coprocessor is next to the
      processor near the power connector.

      Thanks
      Bill

      -------- Original Message --------
      > From: "Joe Giliberti" <Starbase89@...>
      > Sent: Monday, June 01, 2009 2:45 PM
      > To: midatlanticretro@yahoogroups.com
      > Subject: Re: [midatlanticretro] makeshift IBM monitor
      >
      > All I've done thus far is apply power to the power supply (which is
      > original). What are the voltages supposed to be going into the mainboard?
      I
      > want to check with a multimeter before hooking it to the motherboard.
      It
      > appears to have the co-processor installed. I do plan on doing a
      > methodological, slow restore on it.
      >
      > Aside from resocketing chips and removing dust, what is the procedure
      for
      > checking the motherboard?
      >
      > Joe
      >
      >
      > On Mon, Jun 1, 2009 at 9:38 AM, Bill Degnan <billdeg@...>
      wrote:
      >
      > >
      > >
      > > May I add that this is quite a lucky find, you may never get such a
      rare
      > > system in the trash ever again, you take this as an opportunity to
      perform
      > > a serious restoration/save. Learn about what you have and make the most
      of
      > > the experience. Don't try to hook this up to the Internet, try to
      return
      > > the computer to original condition. Don't power this up until you're
      > > confident you have tested the power, removed all cards and unhooked
      power
      > > to the motherboard, etc.
      > > Bill
      > >
      > >
      > > -------- Original Message --------
      > > > From: "Mr Ian Primus" <ian_primus@...
      <ian_primus%40yahoo.com>>
      > > > Sent: Monday, June 01, 2009 8:08 AM
      > > > To:
      midatlanticretro@yahoogroups.com<midatlanticretro%40yahoogroups.com>
      > > > Subject: Re: [midatlanticretro] makeshift IBM monitor
      > > >
      > > > --- On Sun, 5/31/09, Joe Giliberti
      <Starbase89@...<Starbase89%40gmail.com>>
      > > wrote:
      > > >
      > > > >there is a bit of rust on the cover, but not significant. I'm using
      a
      > > >random AT keyboard, as I do not have a model M
      > > >
      > > > An AT keyboard will not work on this machine. You need an XT
      keyboard.
      > > The plugs are the same, but the protocol is different. Some early AT
      > > keyboards also have a switch (sometimes hidden behind a little panel in
      th
      > > bottom) to switch between AT and XT modes.
      > > >
      > > > The original CGA card has RCA plugs on it, and if I remember
      correctly,
      > > it should be composite video. But, I do believe that the composite
      video
      > > output does not support all video modes that the CGA card can do. Your
      best
      > >
      > > bet is to find a real monitor...
      > > >
      > > > You can't connect the CGA card to a VGA monitor, but you CAN use
      (with
      > > limited color palette), an analog RGB monitor, such as the ones used on
      the
      > >
      > > Commodore Amiga. CGA is a digital RGB, and uses an intensity line. The
      > > analog monitors will display the digital signal, but can't use the
      > > intensity line - so all the "light" colors come out as the same color
      as
      > > their "bright" counterparts. It's usable though.
      > > >
      > > > -Ian
      > > >
      > > >
      > > > ------------------------------------
      > > >
      > > > Yahoo! Groups Links
      > > >
      > > >
      > > >
      > >
      > >
      > >
    • Joe Giliberti
      I downloaded a PDF copy of the technical manual last night. I m guessing the onboard RAM are the 27 or so small chips near the front visible corner of the
      Message 2 of 23 , Jun 1, 2009
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        I downloaded a PDF copy of the technical manual last night. I'm guessing the onboard RAM are the 27 or so small chips near the front visible corner of the board? I'll get all relevant information you asked for, including switch positions, and get back to you.
        Joe

        On Mon, Jun 1, 2009 at 2:55 PM, Bill Degnan <billdeg@...> wrote:


        Joe,
        Do you have a copy of the technical reference manual? If not I can copy
        and scan the important pages. In the mean time can you take a picture of
        the motherboard switches, and RAM? If not easy to do, can you just tell me
        whether there are open RAM slots and what the switches are set to? I am
        guessing it's a 64K + 512K with the QuadRAM card = 640K. With this you
        could do almost anything. Lastly, what are the markings on the ROM chips
        in U33? That will tell me if it has an upgraded ROM or the original. I am
        going to guess that it's been upgraded.

        I don't off hand know the voltages. The 8087 coprocessor is next to the
        processor near the power connector.

        Thanks
        Bill



        -------- Original Message --------
        > From: "Joe Giliberti" <Starbase89@...>
        > Sent: Monday, June 01, 2009 2:45 PM
        > To: midatlanticretro@yahoogroups.com
        > Subject: Re: [midatlanticretro] makeshift IBM monitor
        >
        > All I've done thus far is apply power to the power supply (which is
        > original). What are the voltages supposed to be going into the mainboard?
        I
        > want to check with a multimeter before hooking it to the motherboard.
        It
        > appears to have the co-processor installed. I do plan on doing a
        > methodological, slow restore on it.
        >
        > Aside from resocketing chips and removing dust, what is the procedure
        for
        > checking the motherboard?
        >
        > Joe
        >
        >
        > On Mon, Jun 1, 2009 at 9:38 AM, Bill Degnan <billdeg@...>
        wrote:
        >
        > >
        > >
        > > May I add that this is quite a lucky find, you may never get such a
        rare
        > > system in the trash ever again, you take this as an opportunity to
        perform
        > > a serious restoration/save. Learn about what you have and make the most
        of
        > > the experience. Don't try to hook this up to the Internet, try to
        return
        > > the computer to original condition. Don't power this up until you're
        > > confident you have tested the power, removed all cards and unhooked
        power
        > > to the motherboard, etc.
        > > Bill
        > >
        > >
        > > -------- Original Message --------
        > > > From: "Mr Ian Primus" <ian_primus@...
        <ian_primus%40yahoo.com>>
        > > > Sent: Monday, June 01, 2009 8:08 AM
        > > > To:
        midatlanticretro@yahoogroups.com<midatlanticretro%40yahoogroups.com>
        > > > Subject: Re: [midatlanticretro] makeshift IBM monitor
        > > >
        > > > --- On Sun, 5/31/09, Joe Giliberti
        <Starbase89@...<Starbase89%40gmail.com>>
        > > wrote:
        > > >
        > > > >there is a bit of rust on the cover, but not significant. I'm using
        a
        > > >random AT keyboard, as I do not have a model M
        > > >
        > > > An AT keyboard will not work on this machine. You need an XT
        keyboard.
        > > The plugs are the same, but the protocol is different. Some early AT
        > > keyboards also have a switch (sometimes hidden behind a little panel in
        th
        > > bottom) to switch between AT and XT modes.
        > > >
        > > > The original CGA card has RCA plugs on it, and if I remember
        correctly,
        > > it should be composite video. But, I do believe that the composite
        video
        > > output does not support all video modes that the CGA card can do. Your
        best
        > >
        > > bet is to find a real monitor...
        > > >
        > > > You can't connect the CGA card to a VGA monitor, but you CAN use
        (with
        > > limited color palette), an analog RGB monitor, such as the ones used on
        the
        > >
        > > Commodore Amiga. CGA is a digital RGB, and uses an intensity line. The
        > > analog monitors will display the digital signal, but can't use the
        > > intensity line - so all the "light" colors come out as the same color
        as
        > > their "bright" counterparts. It's usable though.
        > > >
        > > > -Ian
        > > >
        > > >
        > > > ------------------------------------
        > > >
        > > > Yahoo! Groups Links
        > > >
        > > >
        > > >
        > >
        > >
        > >


      • Brian Cirulnick
        ... Sure, we can arrange that. Let me just test that it works (I have an old Epson PC clone that uses CGA), and then I ll leave it in my kitchen so it s
        Message 3 of 23 , Jun 1, 2009
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          --- In midatlanticretro@yahoogroups.com, Evan Koblentz <evan@...> wrote:
          >
          > >
          > > Not sure where you live, but I'm in Belleville NJ, if you're willing to take a drive to my place one evening, you can pick it up.
          > >
          > >
          > Brian, why don't I get the monitor from you, then I'll bring it to the
          > museum. Joe lives close the museum and often comes there on weekends.
          >
          -------------------

          Sure, we can arrange that. Let me just test that it works (I have an old Epson PC clone that uses CGA), and then I'll leave it in my kitchen so it's reminding me to call you to come get it...

          Now if only I hadn't thrown out all those keyboards 7 years ago. (You guys would cry hearing about all I had to throw out when I closed my business in 2002)...

          Ah well.

          Anyhow; Evan, I'm available most evenings after 8pm. I think you have my cell phone #, if not, email my home e-mail and I'll send you that and my address..
        • Evan Koblentz
          ... Brian, can we meet at the mall (or some other central location) like we did when you retrieved Chris bag?
          Message 4 of 23 , Jun 1, 2009
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            >
            > Evan, I'm available most evenings after 8pm. I think you have my cell phone #, if not, email my home e-mail and I'll send you that and my address..
            >
            Brian, can we meet at the mall (or some other central location) like we
            did when you retrieved Chris' bag?
          • Bill Degnan
            Remember when you work with the manual not to confuse the directions and settings for the 16K-64K board and the 64K-640K board. They re both in the manual. I
            Message 5 of 23 , Jun 1, 2009
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              Remember when you work with the manual not to confuse the directions and
              settings for the 16K-64K board and the 64K-640K board. They're both in the
              manual. I have more info on my web site, vintagecomputer.net/ibm. Also
              search the blog for various notes and pictures about this model. I have
              restored three of these models in the past 12 months.

              Usually what kills them is the monitor card, usually if you replace the
              card the system comes back to life. The other likely thing to go wrong is
              RAM. I can teach you some tricks to locating the bad RAM and replacing.

              Bill

              -------- Original Message --------
              > From: "Joe Giliberti" <Starbase89@...>
              > Sent: Monday, June 01, 2009 3:03 PM
              > To: midatlanticretro@yahoogroups.com
              > Subject: Re: [midatlanticretro] makeshift IBM monitor
              >
              > I downloaded a PDF copy of the technical manual last night. I'm guessing
              the
              > onboard RAM are the 27 or so small chips near the front visible corner
              of
              > the board? I'll get all relevant information you asked for, including
              switch
              > positions, and get back to you.
              > Joe
              >
              > On Mon, Jun 1, 2009 at 2:55 PM, Bill Degnan <billdeg@...>
              wrote:
              >
              > >
              > >
              > > Joe,
              > > Do you have a copy of the technical reference manual? If not I can
              copy
              > > and scan the important pages. In the mean time can you take a picture
              of
              > > the motherboard switches, and RAM? If not easy to do, can you just tell
              me
              > > whether there are open RAM slots and what the switches are set to? I
              am
              > > guessing it's a 64K + 512K with the QuadRAM card = 640K. With this you
              > > could do almost anything. Lastly, what are the markings on the ROM
              chips
              > > in U33? That will tell me if it has an upgraded ROM or the original. I
              am
              > > going to guess that it's been upgraded.
              > >
              > > I don't off hand know the voltages. The 8087 coprocessor is next to
              the
              > > processor near the power connector.
              > >
              > > Thanks
              > > Bill
              > >
              > >
              > > -------- Original Message --------
              > > > From: "Joe Giliberti" <Starbase89@...
              <Starbase89%40gmail.com>>
              > > > Sent: Monday, June 01, 2009 2:45 PM
              > > > To:
              midatlanticretro@yahoogroups.com<midatlanticretro%40yahoogroups.com>
              > > > Subject: Re: [midatlanticretro] makeshift IBM monitor
              > > >
              > > > All I've done thus far is apply power to the power supply (which is
              > > > original). What are the voltages supposed to be going into the
              mainboard?
              > >
              > > I
              > > > want to check with a multimeter before hooking it to the
              motherboard.
              > > It
              > > > appears to have the co-processor installed. I do plan on doing a
              > > > methodological, slow restore on it.
              > > >
              > > > Aside from resocketing chips and removing dust, what is the
              procedure
              > > for
              > > > checking the motherboard?
              > > >
              > > > Joe
              > > >
              > > >
              > > > On Mon, Jun 1, 2009 at 9:38 AM, Bill Degnan
              <billdeg@...<billdeg%40degnanco.com>>
              > >
              > > wrote:
              > > >
              > > > >
              > > > >
              > > > > May I add that this is quite a lucky find, you may never get such
              a
              > > rare
              > > > > system in the trash ever again, you take this as an opportunity to
              > > perform
              > > > > a serious restoration/save. Learn about what you have and make the
              most
              > >
              > > of
              > > > > the experience. Don't try to hook this up to the Internet, try to
              > > return
              > > > > the computer to original condition. Don't power this up until
              you're
              > > > > confident you have tested the power, removed all cards and
              unhooked
              > > power
              > > > > to the motherboard, etc.
              > > > > Bill
              > > > >
              > > > >
              > > > > -------- Original Message --------
              > > > > > From: "Mr Ian Primus" <ian_primus@...
              <ian_primus%40yahoo.com>
              > > <ian_primus%40yahoo.com>>
              > > > > > Sent: Monday, June 01, 2009 8:08 AM
              > > > > > To:
              > > midatlanticretro@yahoogroups.com <midatlanticretro%40yahoogroups.com>
              > > <midatlanticretro%40yahoogroups.com>
              > > > > > Subject: Re: [midatlanticretro] makeshift IBM monitor
              > > > > >
              > > > > > --- On Sun, 5/31/09, Joe Giliberti
              > > <Starbase89@...
              <Starbase89%40gmail.com><Starbase89%40gmail.com>>
              > > > > wrote:
              > > > > >
              > > > > > >there is a bit of rust on the cover, but not significant. I'm
              using
              > > a
              > > > > >random AT keyboard, as I do not have a model M
              > > > > >
              > > > > > An AT keyboard will not work on this machine. You need an XT
              > > keyboard.
              > > > > The plugs are the same, but the protocol is different. Some early
              AT
              > > > > keyboards also have a switch (sometimes hidden behind a little
              panel in
              > >
              > > th
              > > > > bottom) to switch between AT and XT modes.
              > > > > >
              > > > > > The original CGA card has RCA plugs on it, and if I remember
              > > correctly,
              > > > > it should be composite video. But, I do believe that the composite
              > > video
              > > > > output does not support all video modes that the CGA card can do.
              Your
              > > best
              > > > >
              > > > > bet is to find a real monitor...
              > > > > >
              > > > > > You can't connect the CGA card to a VGA monitor, but you CAN use
              > > (with
              > > > > limited color palette), an analog RGB monitor, such as the ones
              used on
              > >
              > > the
              > > > >
              > > > > Commodore Amiga. CGA is a digital RGB, and uses an intensity line.
              The
              > > > > analog monitors will display the digital signal, but can't use the
              > > > > intensity line - so all the "light" colors come out as the same
              color
              > > as
              > > > > their "bright" counterparts. It's usable though.
              > > > > >
              > > > > > -Ian
              > > > > >
              > > > > >
              > > > > > ------------------------------------
              > > > > >
              > > > > > Yahoo! Groups Links
              > > > > >
              > > > > >
              > > > > >
              > > > >
              > > > >
              > > > >
              > >
              > >
              > >
            • Evan Koblentz
              ... Sorry to bog down the list in details. I meant to reply to Brian off-list.
              Message 6 of 23 , Jun 1, 2009
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                Evan, I'm available most evenings after 8pm. I think you have my cell phone #, if not, email my home e-mail and I'll send you that and my address..   
                    
                Brian, can we meet at the mall (or some other central location) like we 
                did when you retrieved Chris' bag?
                  
                Sorry to bog down the list in details.  I meant to reply to Brian off-list.
              • Joe Giliberti
                Here s as much info as I can pull off the mainboard Machine Serial: 0177038 On the planar: SW1 on on on on off on on off SW2 on off on on off off off off U28
                Message 7 of 23 , Jun 1, 2009
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                  Here's as much info as I can pull off the mainboard

                  Machine Serial:
                  0177038

                  On the planar:

                  SW1
                  on on on on off on on off

                  SW2
                  on off on on off off off off

                  U28
                  Empty Socket

                  U29
                  MK35748 J
                  5700019
                  ZA
                  (copyright) IBM 1981
                  D Malaysia
                  8135 Q

                  U30
                  5700027
                  (copyright) IBM 1981
                  XE
                  (motorola symbol) 8201BNM

                  U31
                  (motorola symbol) 5700035
                  (copyright) IBM 1981
                  XE8135ANM

                  U32
                  MK36728 P
                  5700043
                  ZA
                  (copyright) IBM 1981
                  D Malaysia
                  8142 D

                  U33
                  MK36C35N-4
                  1501476
                  ZA
                  (copyright) IBM CORP
                  1981, 1983
                  D Malaysia

                  U34
                  (not socketed)
                  NEC
                  PIY229-147
                  D8253C-5

                  Has a total of 36 of what I believe to be memory chips. Nine are soldered direct to the board, the remaining 27 are socketed
                  The chips are marked:

                  (AMD symbol) AM9016DPC
                  8144WPP

                  All 36 are the same chips


                • B Degnan
                  U33 MK36C35N-4 1501476 ZA (copyright) IBM CORP 1981, 1983 D Malaysia Tells you it s a 2nd REV16K-64K (upgraded) ROM set. The first rev did not have a routine
                  Message 8 of 23 , Jun 1, 2009
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                    U33
                    MK36C35N-4
                    1501476
                    ZA
                    (copyright) IBM CORP
                    1981, 1983
                    D Malaysia

                    Tells you it's a 2nd REV16K-64K (upgraded) ROM set.  The first rev did not have a routine for using hard drives, and some other things so most people upgraded the ROMS so they could use newer parts and memory.



                    Here's as much info as I can pull off the mainboard

                    Machine Serial:
                    0177038
                    this year I worked on the following other 16-64K boards, so yours is right in there among them, definitely an original, probably from late 1981 early 1983.:

                    0159618
                    0239462
                    0192592 (MARCH's with original ROMS)

                    On the planar:

                    SW1
                    on on on on off on on off

                    SW2
                    on off on on off off off off


                    you have a full complement of RAM (64K) on the motherboard. 

                    I assume you have SW1 reversed.  Up means "on" if facing from the front looking down. 
                    If you have a co-processor, two drives, CGA monitor then SW1 should be: [off on -- -- on off off on] (where pertains to RAM).

                    If SW1's 5 is up and 6 down  - that means CGA display.  Monochrome 5 and 6 are down.  Never mix and match without first changing the switches before powering on.  Otherwise you will fry the board and short the system.

                    Math co-processor 2 = up/on.

                    In a nutshell it looks like you have a standard configuration, no changes needed assuming you use a CGA monitor.  Don't try to use monochrome with these settings.  Someone did that to MARCH's 5150, and we had to replace the display card as a result. 

                    Hope this helps.

                    Bill

                  • Joe Giliberti
                    Thanks for the info, Bill Some more questions Does it matter whether I take video from the CGA port or the composite? So I could, if I wished, install an MFM
                    Message 9 of 23 , Jun 1, 2009
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                      Thanks for the info, Bill
                      Some more questions

                      Does it matter whether I take video from the CGA port or the composite?
                      So I could, if I wished, install an MFM hard drive/controller, or perhaps a hardcard. Correct?
                      Also, due to the different ROM, will it support a full 640k, or the 544k from the first gen?

                      Joe

                      On Mon, Jun 1, 2009 at 10:45 PM, B Degnan <billdeg@...> wrote:


                      U33
                      MK36C35N-4
                      1501476
                      ZA
                      (copyright) IBM CORP
                      1981, 1983
                      D Malaysia

                      Tells you it's a 2nd REV16K-64K (upgraded) ROM set.  The first rev did not have a routine for using hard drives, and some other things so most people upgraded the ROMS so they could use newer parts and memory.




                      Here's as much info as I can pull off the mainboard

                      Machine Serial:
                      0177038
                      this year I worked on the following other 16-64K boards, so yours is right in there among them, definitely an original, probably from late 1981 early 1983.:

                      0159618
                      0239462
                      0192592 (MARCH's with original ROMS)


                      On the planar:

                      SW1
                      on on on on off on on off

                      SW2
                      on off on on off off off off


                      you have a full complement of RAM (64K) on the motherboard. 

                      I assume you have SW1 reversed.  Up means "on" if facing from the front looking down. 
                      If you have a co-processor, two drives, CGA monitor then SW1 should be: [off on -- -- on off off on] (where pertains to RAM).

                      If SW1's 5 is up and 6 down  - that means CGA display.  Monochrome 5 and 6 are down.  Never mix and match without first changing the switches before powering on.  Otherwise you will fry the board and short the system.

                      Math co-processor 2 = up/on.

                      In a nutshell it looks like you have a standard configuration, no changes needed assuming you use a CGA monitor.  Don't try to use monochrome with these settings.  Someone did that to MARCH's 5150, and we had to replace the display card as a result. 

                      Hope this helps.

                      Bill


                    • B Degnan
                      ... only use a real cga monitor in the CGA port. do not use the composite. ... yes but this system did not come with a hard drive and would not be in the
                      Message 10 of 23 , Jun 2, 2009
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                        Joe Giliberti wrote:
                        Thanks for the info, Bill
                        Some more questions

                        Does it matter whether I take video from the CGA port or the composite?
                        only use a real cga monitor in the CGA port.  do not use the composite.

                        So I could, if I wished, install an MFM hard drive/controller, or perhaps a hardcard. Correct?
                        yes but this system did not come with a hard drive and would not be in the spirit of what it was originally.

                        Also, due to the different ROM, will it support a full 640k, or the 544k from the first gen?

                        full 640.  Should be at 640K now.
                        Joe


                        P.S. - Evan - the disk you gave me for the IBM at MARCH has some bare spots, the drive needs to be cleaned or replaced.    Do we have any replacement Tandon 100-2a drives at MARCH?

                        Bill
                      • Evan Koblentz
                        ... I don t know.
                        Message 11 of 23 , Jun 2, 2009
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                          > Evan - the disk you gave me for the IBM at MARCH has some bare spots,
                          > the drive needs to be cleaned or replaced. Do we have any
                          > replacement Tandon 100-2a drives at MARCH?
                          I don't know.
                        • Mr Ian Primus
                          ... The drive probably just needs a good cleaning. I ve never seen a Tandon in an IBM fail so badly as to scrape up disks. The heads are probably just really
                          Message 12 of 23 , Jun 2, 2009
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                            --- On Tue, 6/2/09, Evan Koblentz <evan@...> wrote:

                            > > Evan - the disk you gave me for
                            > the IBM at MARCH has some bare spots,
                            > > the drive needs to be cleaned or replaced. 
                            >   Do we have any
                            > > replacement Tandon 100-2a drives at MARCH?
                            > I don't know.

                            The drive probably just needs a good cleaning. I've never seen a Tandon in an IBM fail so badly as to scrape up disks. The heads are probably just really dirty. Also, the disk itself could have been compromised - some brands are more apt to start shedding oxide with age.

                            -Ian
                          • Bill Degnan
                            ... in an IBM fail so badly as to scrape up disks. The heads are probably just really dirty. Also, the disk itself could have been compromised - some brands
                            Message 13 of 23 , Jun 2, 2009
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                              -------- Original Message --------
                              > From: "Mr Ian Primus" <ian_primus@...>
                              > Sent: Tuesday, June 02, 2009 8:56 PM
                              > To: midatlanticretro@yahoogroups.com
                              > Subject: Re: [midatlanticretro] Re: makeshift IBM monitor
                              >
                              > --- On Tue, 6/2/09, Evan Koblentz <evan@...> wrote:
                              >
                              > > > Evan - the disk you gave me for
                              > > the IBM at MARCH has some bare spots,
                              > > > the drive needs to be cleaned or replaced.
                              > > Do we have any
                              > > > replacement Tandon 100-2a drives at MARCH?
                              > > I don't know.
                              >
                              > The drive probably just needs a good cleaning. I've never seen a Tandon
                              in an IBM fail so badly as to scrape up disks. The heads are probably just
                              really dirty. Also, the disk itself could have been compromised - some
                              brands are more apt to start shedding oxide with age.
                              >

                              True on all counts. I was just curious about whether we had another drive
                              if next time I come up and I can't fix the problem, I can bring a spare
                              drive if I have one. Hopefully you're right and a good cleaning will
                              suffice, or a new disk. The disk in question is a copy of DOS 2.11 with a
                              few scratched tracks, but not completely bare. I never had issues with
                              these drives when I was working with the system myself, but I was mostly
                              focused on the hardware and did not do much disk exercising other than
                              format a disk in both drives.

                              bd
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