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Re: [TI-99/4A] MYARC FDC Regulator

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  • Dan O'Quinn
    It s probably not heat alone, your original regulator(s) may have failed (or be failing) try replacing them with heavy duty ones (I did) or better yet low
    Message 1 of 4 , Dec 3, 2006
      It's probably not heat alone, your original regulator(s) may have failed (or
      be failing) try replacing them with heavy duty ones (I did) or better yet
      low voltage dropout regulators.
      for some good tips on cooling your FDC see this web page. (this info applies
      to any card you want to keep cool)
      http://web.infoave.net/~compdr/tidrive/HFDC-COOL.htm
      main page
      http://web.infoave.net/~compdr/

      Dan O'Quinn

      ----- Original Message -----
      From: "Bob Kaspar" <harleystroker2@...>
      To: <ti99-4a@yahoogroups.com>
      Sent: Sunday, December 03, 2006 10:20 AM
      Subject: [TI-99/4A] MYARC FDC Regulator


      MYARC FDC W/80 track upgrade

      I wrote about his problem awhile back, the regulator on the board is
      getting pretty hot and causing the controller to do some very strange
      things,
    • Insane Multitasker
      I use the 1.5A 5v regulators from National. Adding a heat sink and thermal compound is important, too. A metal clamshell is nice so long as you remove or tape
      Message 2 of 4 , Dec 3, 2006
        I use the 1.5A 5v regulators from National.

        Adding a heat sink and thermal compound is important, too. A metal
        clamshell is nice so long as you remove or tape all offending "tabs" which
        could short out the card. I've seen my share of cards shorted with 16V
        across the CRU and input lines.

        The Myarc "plastic" shells are generally OK. I would not advise running a
        card without some sort of shell, as you run the risk of it rocking in the
        PEB and shorting out the card.

        If you test the output voltage during a card lockup, and it registers 5V,
        your problem is either a CAP or a heat sensitive logic chip. If the
        regulator is bad, all drives will fail, not just one or two.

        Tim


        >From: swim4home@...
        >Reply-To: ti99-4a@yahoogroups.com
        >To: ti99-4a@yahoogroups.com
        >Subject: Re: [TI-99/4A] MYARC FDC Regulator
        >Date: Sun, 3 Dec 2006 10:59:23 EST
        >
        >All the HFDC/FDC/Geneve boards I have worked on in the past year or two I
        >have automatically replaced all regulators and caps (Including the bypass
        >caps
        >with better quality 35v rated parts.) on the power supply circuit. Tim
        >knows the
        >number of the higher current reg available from national. (I don't have any
        >here at the moment.) A standard reg with heatsink held tight with screw and
        >nut
        >and new 35v cap will work very well for years.
        >
        >The boards are old and as Michael Becker has pointed out in the past here
        >on
        >the OLUG the caps are drying out.
        >
        >
        >[Non-text portions of this message have been removed]
        >
        >
        >
        >For users/owners of TI-99/4A Geneve 9640 computers everywhere!
        > Visit the TI99'ers Hall of Fame at http://www.ti99hof.org
        > Check out the TI99ers On-Line User Group at http://www.ti99ers.org/home/.
        > Send abuse reports to abuse@...
        >Yahoo! Groups Links
        >
        >
        >

        _________________________________________________________________
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      • mark wills
        Presumably, drive 3 is the drive that is NOT in the PEB yes? In other words, it is controlled by the FDC, but *powered* elsewhere. It sounds to me like the PEB
        Message 3 of 4 , Dec 6, 2006
          Presumably, drive 3 is the drive that is NOT in the PEB yes? In other words, it is controlled by the FDC, but *powered* elsewhere.

          It sounds to me like the PEB doesnt have the grunt to power the two disk drives in the box. Drive 3 doesnt suffer, because it is powered externally...

          At least, thats what I pick up on from reading your thread...!

          Mark



          ----- Original Message ----
          From: ti99_forever <ti99_forever@...>
          To: ti99-4a@yahoogroups.com
          Sent: Tuesday, 5 December, 2006 11:22:32 PM
          Subject: Re: [TI-99/4A] MYARC FDC Regulator













          I think you are doing the right thing - process of

          elimination.



          I _do_ seem to remember the original issue was with

          the original cable you had. Cables can be problematic.

          They have a tendency to go out for no apparent reason.



          Sometimes a perfectly good cable can all of a sudden

          get a crimp and expose wires, like it was pinched

          between sharp sheet metal - go figure with the PEB. ;)



          Power supplies can go out for no apparent reason, too.

          If your power supply is under-powered, you can have

          access problems. Meaning trouble reading, data

          corruption during writes, etc.



          --- Bob Kaspar <harleystroker2@ yahoo.com> wrote:



          > Alright, I appreciate all your answers about this

          > problem but I am

          > going to throw a little curve here.

          >

          > I borrowed a MYARC FDC and the sysytem seems to be

          > doing the same things

          > If I do a CAll DIR(1) or DIR(2) I either get

          > "Syntax Error" or I start

          > to get a directory listing then after perhaps it

          > lists 5-6 programs I

          > get "Syntax Error" (That is the message). If I use

          > Call Dir(3) I have

          > no problem, I can run disk programs, Call DIR, write

          > to, read from,

          > etc . from drive #3, I am thinking that perhaps

          > there is a problem with

          > the floppy cable, drives or perhaps the power

          > quality from the PE Box,

          > the drive #3 power is suppled by a self contained

          > external supply,

          > separate

          > cable etc. Also sometimes if I am using a program

          > such a automatic

          > directory loader from drive #3 and I catalog drive

          > #2 I can then use

          > drive #1 for a few accesses before the problem re-

          > occurs.

          >

          > I am in the process of checking the floppy cable now

          > and if I can find

          > one in the mess of my storage I will try changing

          > the cable later

          > tonight otherwise I am have to go hunting to find

          > new connectors and

          > ribbon cable to make a new one.

          >

          > I also have a spare PE Box that I will put all my

          > cards in and test for

          > power supply problems.

          >

          > I await any opinions offered.

          > Thanx,

          > Bob K.

          >

          >

          >



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