S-100 Power supplies and Alternatives - CP/M

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  1. S-100 Power supplies and Alternatives

    A sad tale with a question ....

    Question: What do people use for replacement S100 S-100 power
    supplies ...?

    Having intergalactically freighted some Cromemco systems at vast
    expense imagine the sinking feeling I felt when I recently connected
    an IBM 40MB MFM drive. ....

    A small pop/bang later it became clear that something was dead.
    Cromemco PSU fuses however had not blown, something more fundamental
    has died :-(

    So having learnt from this mess I now connect all drives on separate
    IBM PC style power supplies. Here is plan

    a) Buy a 500W or greater ATX Power supply

    b) Connect pins 14 (green) and 15 (Black) together. See
    http://maben.homeip.net/static/S100/...20Supplies.pdf

    for more details

    Now the Power supply will operate.

    c) Connect any dodgy equipment to this indestructible 5V power rail.

    d) ATX supplies have circuitry that protects against even direct
    shorts (I've tested it frequently in the last weeks)

    ------

    Presumably the best thing to do would be to find a model Switch Mode
    PSU with equivalent outputs

    ------

    So that just leaves me the question ... Are "plug replacement" S100
    supplies available . I think the Cromemco unregulated outputs
    were. ...
    +8V 30A
    +18V 15A
    -18V 15A


  2. Re: S-100 Power supplies and Alternatives

    amouses@gmail.com wrote:

    > Question: What do people use for replacement S100 S-100 power
    > supplies ...?


    (snip)

    > a) Buy a 500W or greater ATX Power supply


    > b) Connect pins 14 (green) and 15 (Black) together. See
    > http://maben.homeip.net/static/S100/...20Supplies.pdf

    (snip)

    > d) ATX supplies have circuitry that protects against even direct
    > shorts (I've tested it frequently in the last weeks)


    It may put a lot of current through that short, but I believe, yes,
    that it does protect itself.

    > So that just leaves me the question ... Are "plug replacement" S100
    > supplies available . I think the Cromemco unregulated outputs
    > were. ...


    > +8V 30A
    > +18V 15A
    > -18V 15A


    Looking over the schematics for the SOL, basically an S100 system
    with onboard video, serial, and parallel port, it seems that it
    puts +5 and +12 on the S100 bus. That would seem to require bypassing
    the regulators on any S100 boards, but that seemed to be a fine
    solution in 1977 and it should be a fine solution today.

    -- glen


  3. Re: S-100 Power supplies and Alternatives

    On Mon, 01 Oct 2007 09:21:41 -0700, amouses@gmail.com wrote:

    >A sad tale with a question ....
    >
    >Question: What do people use for replacement S100 S-100 power
    >supplies ...?


    Assuming the transformer isn't fried (rare occurance) fix them.
    S100 power supplies are simple transformer rectifier capacitor
    systems, and thats it. They supply unregulated voltages to
    the bus with +8V(usually more like +10), +16V(more like 18-20V)
    and -16V(again more like 16-20V).

    Some system will also have regulators for powering things like
    floppy drives or hard disks. The regulators can eb simple linear
    regulators and easily repaired or the generic three terminal chip
    regulators. Nothing majick and easily fixed in most cases.

    Most common failure is random tantalum caps that tend to short
    and emit smoke.

    >Having intergalactically freighted some Cromemco systems at vast
    >expense imagine the sinking feeling I felt when I recently connected
    >an IBM 40MB MFM drive. ....
    >
    >A small pop/bang later it became clear that something was dead.
    >Cromemco PSU fuses however had not blown, something more fundamental
    >has died :-(


    You may have only fried a regulator that can be isolated and fixed.


    >So having learnt from this mess I now connect all drives on separate
    >IBM PC style power supplies. Here is plan
    >
    >a) Buy a 500W or greater ATX Power supply
    >
    >b) Connect pins 14 (green) and 15 (Black) together. See
    >http://maben.homeip.net/static/S100/...20Supplies.pdf
    >
    >for more details
    >
    >Now the Power supply will operate.
    >
    >c) Connect any dodgy equipment to this indestructible 5V power rail.
    >
    >d) ATX supplies have circuitry that protects against even direct
    >shorts (I've tested it frequently in the last weeks)


    ick poo. Laso every board installed will have to be modified for the
    5V rail rather than on board regulators. The problem is at those
    kinds of currents what starts as 5V at the PS often ends up as
    something less at the chips due to connectors and long PC traces.
    The less than 5V, more specifically less that about 4.75V is a bad
    thing as noise immunity goes to pot and some chips just done like
    running on low end voltages.

    >
    >Presumably the best thing to do would be to find a model Switch Mode
    >PSU with equivalent outputs


    None exist in common availbility.
    >
    >------
    >
    >So that just leaves me the question ... Are "plug replacement" S100
    >supplies available . I think the Cromemco unregulated outputs
    >were. ...
    >+8V 30A
    >+18V 15A
    >-18V 15A


    Those are not regulated so a simple PS is in order.

    Allison


  4. Re: S-100 Power supplies and Alternatives

    No, wrong. The SOL puts out +5 and +12 for it's own motherboard, but it
    puts out the standard, higher voltages for the S-100 bus.


    glen herrmannsfeldt wrote:

    >
    > Looking over the schematics for the SOL, basically an S100 system
    > with onboard video, serial, and parallel port, it seems that it
    > puts +5 and +12 on the S100 bus. That would seem to require bypassing
    > the regulators on any S100 boards, but that seemed to be a fine
    > solution in 1977 and it should be a fine solution today.
    >
    > -- glen
    >


  5. Re: S-100 Power supplies and Alternatives

    Barry Watzman wrote:

    > No, wrong. The SOL puts out +5 and +12 for it's own motherboard, but it
    > puts out the standard, higher voltages for the S-100 bus.


    It looks like the S-100 slot on the SOL board has +5 on its +8 connector
    through a jumper. In the usual case, though, a multislot backplane
    plugs in to that slot. As far as I can tell from the schematics,
    there is a connector from the power supply that supplies +8 and +16
    to that board.

    I was previously only looking at the SOL board S100 slot schematic.

    -- glen


  6. Re: S-100 Power supplies and Alternatives

    On Oct 1, 8:21 am, amou...@gmail.com wrote:
    > A sad tale with a question ....
    >
    > Question: What do people use for replacement S100 S-100 power
    > supplies ...?


    I have fully decked the Altair with 8k SEALS cards... With this route
    you could leave your cards alone. I banged my head into a wall trying
    to maintain the cards original design while still having switchers...

    Some people ask me if 100w/60w is enough. Power Factor has bigger
    supplies if it is a concern. The switchers will supply their output
    with a lot less voltage drop than a linear supply. I wonder if a lot
    of the linear supplies were over done because of that...

    They are trimmed up from 7.5v and +/-15v. Look at http://www.power-factor-1st.com/

    S-100F
    T-60

    Grant


  7. Re: S-100 Power supplies and Alternatives

    On Tue, 02 Oct 2007 06:51:17 -0000, Grant Stockly
    wrote:

    >On Oct 1, 8:21 am, amou...@gmail.com wrote:
    >> A sad tale with a question ....
    >>
    >> Question: What do people use for replacement S100 S-100 power
    >> supplies ...?

    >
    >I have fully decked the Altair with 8k SEALS cards... With this route
    >you could leave your cards alone. I banged my head into a wall trying
    >to maintain the cards original design while still having switchers...


    Not going to succeed unless you either mod a PC switcher (involved)
    or find something out there ($$$). The simple S100 PS is far too
    simple to not fix.

    Where a switcher is handy in the S100 world is for powering disks.
    Some systems, NS* Horizon come to mind have regulators
    for running the disk drives and they will not run a hard disk as
    they were intended for SA400 class floppies. There a seperate
    50W +5 and +12 switcher is a useful item for running hard disks
    especially those older 5.25 full height types that sucked up around
    30W.

    Generally if power was suppled for Drive is was off seperate
    regulation from the baords even though the raw DC may have
    come from the same source.

    A few of the fancier S100crates like the Compupro and Intergrand
    added a constant voltage transformer in place of the usual large
    iron and that tended to keep the +8/+16/-16 a more like 10%
    regulated and also helped with brownouts.

    >Some people ask me if 100w/60w is enough. Power Factor has bigger
    >supplies if it is a concern. The switchers will supply their output
    >with a lot less voltage drop than a linear supply. I wonder if a lot
    >of the linear supplies were over done because of that...


    This is not true. I have linears that have less noise and droop than
    any switcher. Power One was a common source of those. However,
    _ most_ S100 system didn't use linear supplies for the bus DC, they
    put raw rectified and filtered DC and the cards handled regulation
    locally using 7805, LM309, LM323 type three terminal regulators.

    FYI: droop is not related to type of supply but the leads and traces
    from the PS to the load (boards) and the only way to nullify that is
    to use remote sensing that most better linear and switch mode PS
    offer. This is also referred to as a four wire power, where two heavy
    leads supply DC and the two fairly light leads connect the load at
    point of use back to the regulator circuits.

    However the average S100 +8 bus was rated for 25 Amps and that
    would be 200W output (for a 8V switcher). You also have the +16
    that was usually good for at least 3A (48W at 16V) and the -18 was
    often lightly loaded at under 1A (16W at 16V).

    >They are trimmed up from 7.5v and +/-15v. Look at http://www.power-factor-1st.com/


    Yes, some switchers will tweek up to those but watch as some also have
    over voltage fault sensing and shut down. Also 7.5V is marginal for
    most three terminal regulators. It will work but.. you have no
    margin. I'd use four wire hookup (remote sense) for the 7.5V
    if you do that to help matters.

    It's possible to mod a PC swicher for any voltage out but it's not for
    the novice. FYI: switchers have HV inside!


    Allison

    >
    >S-100F
    >T-60
    >
    >Grant



  8. Re: S-100 Power supplies and Alternatives

    On Oct 1, 12:21 pm, amou...@gmail.com wrote:

    > Question: What do people use for replacement S100 S-100 power
    > supplies ...?[ references to cost of shipping heavy supply, power supply failure, deleted]
    >
    > So having learnt from this mess I now connect all drives on separate
    > IBM PC style power supplies. Here is plan
    >
    > a) Buy a 500W or greater ATX Power supply
    > [snip[
    > Presumably the best thing to do would be to find a model Switch Mode
    > PSU with equivalent outputs


    > So that just leaves me the question ... Are "plug replacement" S100
    > supplies available . I think the Cromemco unregulated outputs
    > were. ...
    > +8V 30A
    > +18V 15A
    > -18V 15A


    My colleages have posted some details but did not describe the
    fundamental issues about S-100 power supplies. Since S-100 systems
    were not all standard, uniform, identical; I think it pays to know the
    fundamentals.

    The S--100 bus IN GENERAL used lightly regulated but high-current
    power supplies, typically with the voltages mentioned above, and
    roughly the same currents. Each S-100 card had a number of voltage
    requlators which will reduce the +8 to +5, +18 to -12, and -18 to -12.
    The on-card regulators provided filtering of the power BETWEEN cards
    as well as regulating from the power supply itself.

    Early S-100 cards used a lot of current, so that's why the power
    supplies were so large in order to supply that current. Heavy = more
    current, in the old days. Later cards and systems needed less current;
    also much later on, swiching power supplies became cheaper. A
    "switching" supply uses a small transformer, because it "switches" the
    60 cycle current to a much higher frequency which needs a smaller
    transformer than at 60 cycles".

    Later, some S-100 companies went to REGULATED voltages on the S-100
    bus - providing +5V, +12V, -12V directly to each card. Most often, the
    cards were MODIFIED to replace the voltage regulators with a simple
    jumper or wire. from bus voltage supply side to the board's power
    line. BEWARE! DANGER! if you put one of these modified cards in a
    UNREGULATED S-100 bus - you will FRY THE BOARD. So another choice is
    to use REGULATED power but at the higher voltage - say, by using a
    light-weight switching supply but adjusting the voltage "up" so the
    regulators can bring it back "down". Then the cards need no
    modification.

    If one understands the above, and has some idea of how to determine
    the current requirements of cards and drives in a specific system,
    then that person has a chance to replace the "original" power supply
    with something else. That could be a switching supply or an "open
    frame" non switching supply from some industrial source, could be a
    supply from a PC, and so forth. If the above discussion is cryptic,
    don't mess with it until you get more information. There is no one
    simple solution, so knowing what is going on is very VERY helpful, in
    my opinion.

    Herb Johnson

    Herbert R. Johnson, New Jersey USA
    http://www.retrotechnology.com/herbs_stuff/ web site
    http://www.retrotechnology.net/herbs_stuff/ domain mirror
    my email address: hjohnson AAT retrotechnology DOTT com
    if no reply, try in a few days: herbjohnson ATT comcast DOTT net
    "Herb's Stuff": old Mac, SGI, 8-inch floppy drives
    S-100 IMSAI Altair computers, docs, by "Dr. S-100"





  9. Re: S-100 Power supplies and Alternatives

    no.spam@no.uce.bellatlantic.net wrote:

    (snip)

    > It's possible to mod a PC swicher for any voltage out but it's not for
    > the novice. FYI: switchers have HV inside!


    The usual design takes the incoming line through a bridge rectifier
    (with 230V input) or a voltage doubler (115V input) to about 300VDC.
    Then through a switch transistor to the primary of a ferrite core
    transformer at around 20kHz. About half the circuit is directly
    connected to the power line, which complicates testing.
    (Don't use a scope or meter with a ground wire.)

    There is some feedback from the secondary to the switching circuit,
    usually through a transformer but sometimes an opto-isolator.
    I don't know how many have an actual adjustment for the output
    voltage, though.

    -- glen


  10. Re: S-100 Power supplies and Alternatives

    On Tue, 02 Oct 2007 12:15:49 -0800, glen herrmannsfeldt
    wrote:

    >no.spam@no.uce.bellatlantic.net wrote:
    >
    >(snip)
    >
    >> It's possible to mod a PC swicher for any voltage out but it's not for
    >> the novice. FYI: switchers have HV inside!

    >
    >The usual design takes the incoming line through a bridge rectifier
    >(with 230V input) or a voltage doubler (115V input) to about 300VDC.
    >Then through a switch transistor to the primary of a ferrite core
    >transformer at around 20kHz. About half the circuit is directly
    >connected to the power line, which complicates testing.
    >(Don't use a scope or meter with a ground wire.)
    >
    >There is some feedback from the secondary to the switching circuit,
    >usually through a transformer but sometimes an opto-isolator.
    >I don't know how many have an actual adjustment for the output
    >voltage, though.


    Yes, lethal voltages and currents lie there.

    Most do not have any adjustment. If you need to move the output up
    say to 8V you rewind the transformer with a few more turns as running
    the high side up to get more voltage tends to beat up the switching
    devices and heat up the transformer ferrtie. SMPS systems are not for
    the faint of heart.

    Allison


  11. Re: S-100 Power supplies and Alternatives

    On Oct 2, 7:05 am, no.s...@no.uce.bellatlantic.net wrote:
    > On Tue, 02 Oct 2007 06:51:17 -0000, Grant Stockly
    > wrote:
    >
    > >On Oct 1, 8:21 am, amou...@gmail.com wrote:
    > >> A sad tale with a question ....

    >
    > >> Question: What do people use for replacement S100 S-100 power
    > >> supplies ...?

    >
    > >I have fully decked the Altair with 8k SEALS cards... With this route
    > >you could leave your cards alone. I banged my head into a wall trying
    > >to maintain the cards original design while still having switchers...

    >
    > Not going to succeed unless you either mod a PC switcher (involved)
    > or find something out there ($$$). The simple S100 PS is far too
    > simple to not fix.


    The two supplies I listed are $80 total, not too bad. 150-300W
    versions are available, but are larger. Trimming up to 8v is
    supported by the manufacture, and with all that load I still get a
    good hard 7.9-8v to the cards. The model of supply I have does not
    support remote monitoring, but I think the 150W and up models do.

    I have a Altair replica with 6 SEALS 8k ram cards, 2-SIO, tarbell disk
    card, and 1k rom card. The 8v line is right at about 8v. Never had a
    problem. It runs cool with no fan.


  12. Re: S-100 Power supplies and Alternatives

    On Tue, 02 Oct 2007 22:03:04 -0000, Grant Stockly
    wrote:

    >On Oct 2, 7:05 am, no.s...@no.uce.bellatlantic.net wrote:
    >> On Tue, 02 Oct 2007 06:51:17 -0000, Grant Stockly
    >> wrote:
    >>
    >> >On Oct 1, 8:21 am, amou...@gmail.com wrote:
    >> >> A sad tale with a question ....

    >>
    >> >> Question: What do people use for replacement S100 S-100 power
    >> >> supplies ...?

    >>
    >> >I have fully decked the Altair with 8k SEALS cards... With this route
    >> >you could leave your cards alone. I banged my head into a wall trying
    >> >to maintain the cards original design while still having switchers...

    >>
    >> Not going to succeed unless you either mod a PC switcher (involved)
    >> or find something out there ($$$). The simple S100 PS is far too
    >> simple to not fix.

    >
    >The two supplies I listed are $80 total, not too bad. 150-300W
    >versions are available, but are larger. Trimming up to 8v is
    >supported by the manufacture, and with all that load I still get a
    >good hard 7.9-8v to the cards. The model of supply I have does not
    >support remote monitoring, but I think the 150W and up models do.


    Yes, 8V is where you want to be. An earlier posting had 7.5V which is
    marginal.

    >I have a Altair replica with 6 SEALS 8k ram cards, 2-SIO, tarbell disk
    >card, and 1k rom card. The 8v line is right at about 8v. Never had a
    >problem. It runs cool with no fan.


    I would expect that. Glad to hear you didn't replicate the the
    Altair PS exactly. The early ones were way undersized and
    the later ones tended to run the 8V near 12V leading to a lot of
    hot regulators that were hard to get air to.

    Those Seals 8k boards even with the regulators running cool still
    do some heat due to the large numbers of 2102s.

    Have one system that is only four boards in a 6slot backplane
    and to reduce the fan to a minimal (25CFM very quiet) noise
    I built a supply based on a LVSMPS to put 8V on the bus.
    The low voltage switch mode regulator is a varient of a design
    from National Semi from a 555 timer apnote. The efficientcy is
    good and 11V in for 8V out is a good match.


    Allison



  13. Re: S-100 Power supplies and Alternatives

    On Oct 1, 1:21 pm, amou...@gmail.com wrote:
    > A sad tale with a question ....
    >
    > Question: What do people use for replacement S100 S-100 power
    > supplies ...?
    >
    > Having intergalactically freighted some Cromemco systems at vast
    > expense imagine the sinking feeling I felt when I recently connected
    > an IBM 40MB MFM drive. ....
    >
    > A small pop/bang later it became clear that something was dead.
    > Cromemco PSU fuses however had not blown, something more fundamental
    > has died :-(
    >
    > So having learnt from this mess I now connect all drives on separate
    > IBM PC style power supplies. Here is plan
    >
    > a) Buy a 500W or greater ATX Power supply
    >
    > b) Connect pins 14 (green) and 15 (Black) together. Seehttp://maben.homeip.net/static/S100/POWER%20SUPPLY/ATX%20and%20P4%20P...
    >
    > for more details
    >
    > Now the Power supply will operate.
    >
    > c) Connect any dodgy equipment to this indestructible 5V power rail.
    >
    > d) ATX supplies have circuitry that protects against even direct
    > shorts (I've tested it frequently in the last weeks)
    >
    > ------
    >
    > Presumably the best thing to do would be to find a model Switch Mode
    > PSU with equivalent outputs
    >
    > ------
    >
    > So that just leaves me the question ... Are "plug replacement" S100
    > supplies available . I think the Cromemco unregulated outputs
    > were. ...
    > +8V 30A
    > +18V 15A
    > -18V 15A


    I'd think that repairing the Cromemco supply would be a much simpler
    task than trying to find an appropriate SMPS; which model are we
    talking about? Schematics are around for pretty well all models,
    although most are so simple that you don't really need one. The 5&12V
    for the drives were supplied by separate regulator boards on most of
    the early models (Z2, S-3 &c); later models (S-1, 1xx to 4xx) had
    5 & 12 (or 24) V available on the main PSU.

    Since the main voltages seem OK, sounds like you've just blown
    a regulator chip; should be a breeze.

    mike


  14. Re: S-100 Power supplies and Alternatives

    On Oct 2, 6:57 pm, no.s...@no.uce.bellatlantic.net wrote:
    > On Tue, 02 Oct 2007 22:03:04 -0000, Grant Stockly
    > wrote:
    >
    >
    >
    > >On Oct 2, 7:05 am, no.s...@no.uce.bellatlantic.net wrote:
    > >> On Tue, 02 Oct 2007 06:51:17 -0000, Grant Stockly
    > >> wrote:

    >
    > >> >On Oct 1, 8:21 am, amou...@gmail.com wrote:
    > >> >> A sad tale with a question ....

    >
    > >> >> Question: What do people use for replacement S100 S-100 power
    > >> >> supplies ...?

    >
    > >> >I have fully decked the Altair with 8k SEALS cards... With this route
    > >> >you could leave your cards alone. I banged my head into a wall trying
    > >> >to maintain the cards original design while still having switchers...

    >
    > >> Not going to succeed unless you either mod a PC switcher (involved)
    > >> or find something out there ($$$). The simple S100 PS is far too
    > >> simple to not fix.

    >
    > >The two supplies I listed are $80 total, not too bad. 150-300W
    > >versions are available, but are larger. Trimming up to 8v is
    > >supported by the manufacture, and with all that load I still get a
    > >good hard 7.9-8v to the cards. The model of supply I have does not
    > >support remote monitoring, but I think the 150W and up models do.

    >
    > Yes, 8V is where you want to be. An earlier posting had 7.5V which is
    > marginal.
    >
    > >I have a Altair replica with 6 SEALS 8k ram cards, 2-SIO, tarbell disk
    > >card, and 1k rom card. The 8v line is right at about 8v. Never had a
    > >problem. It runs cool with no fan.

    >
    > I would expect that. Glad to hear you didn't replicate the the
    > Altair PS exactly. The early ones were way undersized and
    > the later ones tended to run the 8V near 12V leading to a lot of
    > hot regulators that were hard to get air to.
    >
    > Those Seals 8k boards even with the regulators running cool still
    > do some heat due to the large numbers of 2102s.
    >
    > Have one system that is only four boards in a 6slot backplane
    > and to reduce the fan to a minimal (25CFM very quiet) noise
    > I built a supply based on a LVSMPS to put 8V on the bus.
    > The low voltage switch mode regulator is a varient of a design
    > from National Semi from a 555 timer apnote. The efficientcy is
    > good and 11V in for 8V out is a good match.
    >
    > Allison


    I was going to qualify "cool". ; ) About as cool as it should be in
    an Altair. : ) The fan/card/vent positioning never really did seem
    to do much for me... In fact one the the vintage Altairs requires a
    little heat to get going. ; )


  15. Re: S-100 Power supplies and Alternatives

    > Yes, 8V is where you want to be. An earlier posting had 7.5V which is
    > marginal.


    7.5v is what the supplies were trimmed up from.

    9v supplies are also available which can be trimmed down.


  16. Re: S-100 Power supplies and Alternatives

    On Wed, 03 Oct 2007 07:33:28 -0000, Grant Stockly
    wrote:

    >On Oct 2, 6:57 pm, no.s...@no.uce.bellatlantic.net wrote:
    >> On Tue, 02 Oct 2007 22:03:04 -0000, Grant Stockly
    >> wrote:
    >>
    >>
    >>
    >> >On Oct 2, 7:05 am, no.s...@no.uce.bellatlantic.net wrote:
    >> >> On Tue, 02 Oct 2007 06:51:17 -0000, Grant Stockly
    >> >> wrote:

    >>
    >> >> >On Oct 1, 8:21 am, amou...@gmail.com wrote:
    >> >> >> A sad tale with a question ....

    >>
    >> >> >> Question: What do people use for replacement S100 S-100 power
    >> >> >> supplies ...?

    >>
    >> >> >I have fully decked the Altair with 8k SEALS cards... With this route
    >> >> >you could leave your cards alone. I banged my head into a wall trying
    >> >> >to maintain the cards original design while still having switchers...

    >>
    >> >> Not going to succeed unless you either mod a PC switcher (involved)
    >> >> or find something out there ($$$). The simple S100 PS is far too
    >> >> simple to not fix.

    >>
    >> >The two supplies I listed are $80 total, not too bad. 150-300W
    >> >versions are available, but are larger. Trimming up to 8v is
    >> >supported by the manufacture, and with all that load I still get a
    >> >good hard 7.9-8v to the cards. The model of supply I have does not
    >> >support remote monitoring, but I think the 150W and up models do.

    >>
    >> Yes, 8V is where you want to be. An earlier posting had 7.5V which is
    >> marginal.
    >>
    >> >I have a Altair replica with 6 SEALS 8k ram cards, 2-SIO, tarbell disk
    >> >card, and 1k rom card. The 8v line is right at about 8v. Never had a
    >> >problem. It runs cool with no fan.

    >>
    >> I would expect that. Glad to hear you didn't replicate the the
    >> Altair PS exactly. The early ones were way undersized and
    >> the later ones tended to run the 8V near 12V leading to a lot of
    >> hot regulators that were hard to get air to.
    >>
    >> Those Seals 8k boards even with the regulators running cool still
    >> do some heat due to the large numbers of 2102s.
    >>
    >> Have one system that is only four boards in a 6slot backplane
    >> and to reduce the fan to a minimal (25CFM very quiet) noise
    >> I built a supply based on a LVSMPS to put 8V on the bus.
    >> The low voltage switch mode regulator is a varient of a design
    >> from National Semi from a 555 timer apnote. The efficientcy is
    >> good and 11V in for 8V out is a good match.
    >>
    >> Allison

    >
    >I was going to qualify "cool". ; ) About as cool as it should be in
    >an Altair. : ) The fan/card/vent positioning never really did seem
    >to do much for me... In fact one the the vintage Altairs requires a
    >little heat to get going. ; )


    Oh the joys of all the oneshots.

    Yes, my two are a bear to cool.

    Allison


  17. Re: S-100 Power supplies and Alternatives

    On Wed, 03 Oct 2007 07:34:43 -0000, Grant Stockly
    wrote:

    >> Yes, 8V is where you want to be. An earlier posting had 7.5V which is
    >> marginal.

    >
    >7.5v is what the supplies were trimmed up from.
    >
    >9v supplies are also available which can be trimmed down.


    They would work well enough stock. Most I've seen however are not
    good for more than a few amps. I'm sure there are 20A or larger
    versions out there.

    Allison


  18. Re: S-100 Power supplies and Alternatives

    On Oct 3, 4:14 am, no.s...@no.uce.bellatlantic.net wrote:
    > On Wed, 03 Oct 2007 07:34:43 -0000, Grant Stockly
    > wrote:
    >
    > >> Yes, 8V is where you want to be. An earlier posting had 7.5V which is
    > >> marginal.

    >
    > >7.5v is what the supplies were trimmed up from.

    >
    > >9v supplies are also available which can be trimmed down.

    >
    > They would work well enough stock. Most I've seen however are not
    > good for more than a few amps. I'm sure there are 20A or larger
    > versions out there.
    >
    > Allison


    Power Factor's prices are very reasonable. They have 7.5v supplies
    from 100-320W.

    Their 40A 7.5v supply with power factor correction is $117.

    For $1595 they have a 266A 9v supply. Might be too big even for the
    biggest S-100 machine. More Power!


  19. Re: S-100 Power supplies and Alternatives

    On Wed, 03 Oct 2007 16:40:19 -0000, Grant Stockly
    wrote:

    >On Oct 3, 4:14 am, no.s...@no.uce.bellatlantic.net wrote:
    >> On Wed, 03 Oct 2007 07:34:43 -0000, Grant Stockly
    >> wrote:
    >>
    >> >> Yes, 8V is where you want to be. An earlier posting had 7.5V which is
    >> >> marginal.

    >>
    >> >7.5v is what the supplies were trimmed up from.

    >>
    >> >9v supplies are also available which can be trimmed down.

    >>
    >> They would work well enough stock. Most I've seen however are not
    >> good for more than a few amps. I'm sure there are 20A or larger
    >> versions out there.
    >>
    >> Allison

    >
    >Power Factor's prices are very reasonable. They have 7.5v supplies
    >from 100-320W.
    >
    >Their 40A 7.5v supply with power factor correction is $117.
    >
    >For $1595 they have a 266A 9v supply. Might be too big even for the
    >biggest S-100 machine. More Power!


    At $1595.00 I'd expect custom three voltage.

    Allison

  20. Re: S-100 Power supplies and Alternatives

    no.spam@no.uce.bellatlantic.net wrote:

    > On Wed, 03 Oct 2007 16:40:19 -0000, Grant Stockly wrote:


    >>For $1595 they have a 266A 9v supply. Might be too big even for the
    >>biggest S-100 machine. More Power!


    > At $1595.00 I'd expect custom three voltage.


    At 266 amps it should be enough to start a car.
    I believe the starter voltage is closer to 9V than 12V,
    considering the voltage drop.

    $6/amp doesn't sound too far off.

    -- glen


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