Microsoft multiuser Basic for the Altair 8800

Tue Jul 28 22:32:37 CDT 2015

Hi Jay,
I appreciate you explaining reforming in such detail and I will look it up as you suggest and I'll definitely keep this in mind when I start checking things out in my Altair.  Thank you very much.

Kip Koon
computerdoc at sc.rr.com
http://www.cocopedia.com/wiki/index.php/Kip_Koon

> -----Original Message-----
> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Jay jaeger
> Sent: Tuesday, July 28, 2015 11:01 PM
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: RE: Microsoft multiuser Basic for the Altair 8800
> 
> OK at the risk of restarting a long discussion about the value of reforming or lack thereof....
> 
> Reforming a cap means to apply power to the cap at or a little below its rated voltage but limiting the current with a resistor in series
> with the cap until the voltage drop across the resistor indicates acceptably low leakage current.  At the low voltages in use on an Altair
> I typically use something in the range of 4.7k ohms.  I have a dual 1-20v power supply to do this.
> 
> The idea is that this redeposits some of the aluminum that had migrated into the electrolyte while the cap was idle reducing the
> leakage current of the capacitor.
> 
> This procedure  done correctly with the correct polariy and voltage will never harm the cap, so it isn't unreasonable to reform all of
> the filter caps on a linear supply like that on an Altair 8800. The current list!meeting resistor prevents the cap frm drawing too much
> current and overheating or worse until the reforming is complete or too much time has elapsed without reaching an acceptably low
> leakage current.
> 
> Just google it and you will find articles on the procedures.
> 
> As others have pointed out, this will not help if the cap has unacceptably large effective series resistance (ESR).  On a linear supply,
> That will show up as unacceptably high ripple ac on top of the DC the supply is designed to provide.
> 
> I would test the supply with at least SOME test Load before using it to supply the machine.
> 
> When I did this to my Altair a few years back I think rather than disassembling the power supply to unsolder the caps I clipped one lead
> of each one so that one lead was free, but that then leaves one with the need to splice them back, but does avoid potential damage
> to the board.  I also recently did that with an ALTOS which has switching supplies.  Both would probably have done just fine without
> reforming.  I also did in on an IMSAI, same story.  I also did it to a pdp12, which had blown out rectifier before I did this.
> 
> Doing a good job of restoring a machine does often mean disassembling and reassembling.  It comes with the territory.
> 
> It sounds like you !might have pretty limited electronics experience, and if that is the case you might try and find Someone local to
> help you over the humps.
> 
> SAFETY FIRST.
> 
> 
> Kip Koon <computerdoc at sc.rr.com> wrote:
> 
> >Hi Jay,
> >Thank you so much for the advice.  What is reforming a capacitor?  Does that mention the electrolytic capacitors may have to be
> repolarized?  If so, how to you do that?  How do you know if a power cap needs to be reformed or not?  To get to the transformer, I'll
> have to take out just about everything including the card guides.  Labeling the wires will be paramount too.  I don't want to get those
> rascals mixed up!  If remember my linear power supplies correctly, I don't need to put a load on them when I test them, but I will need
> to test the caps disconnected, correct?  I doesn't sound too difficult, just tedious and much detail to consider.  I definitely want to
> baby this thing.  :)  Thanks again for the restoration advice.  I'll need it and more before I'm finished.  Take care my friend.
> >
> >Kip Koon
> >computerdoc at sc.rr.com
> >http://www.cocopedia.com/wiki/index.php/Kip_Koon
> >
> >
> >> -----Original Message-----
> >> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Jay
> >> Jaeger
> >> Sent: Thursday, July 16, 2015 9:39 AM
> >> To: cctalk at classiccmp.org
> >> Subject: Re: Microsoft multiuser Basic for the Altair 8800
> >>
> >> First of all, safety first when working around these power supplies.
> >> You have mains voltage exposed all over the place, including the front panel switch.
> >>
> >> What I typically do is take it all the boards out and disconnect the
> >> power supply, and pull it out.  I then re-form the capacitors by
> >> taking them off completely or, more often, unsoldering one lead.  In
> >> one case recently the power supply was regulated (an Altos computer),
> >> and the power transistors were inserted through the power supply case
> >> and into the board from the backside, making removal both a pain and
> >> a little risky, so I just clipped one lead of each larger in place to do the re-forming (it turned out that in that particular case, they
> really didn't need it).  I'd be pretty surprised if you actually had to replace your capacitors.  For reforming I have had pretty good luck
> with a 4.7K ohm resistor in serial with the capacitor, and in more than half the cases, the capacitors really didn't need it.
> >>
> >> The transformer is either good or not - and it is probably just fine.
> >> Just measure its output voltages.  Do make sure that the transformer
> >> is wired for your voltage depending upon where you live.  One could
> >> disconnect it first, but the odds of it putting out too high a voltage are very very slim, so long as it is wired for the mains voltage
> wherever you happen to live.  Bad ones either put out nothing for one of the voltages (open winding) or get hot (shorted winding).
> >> Neither is dangerous to the rest of the power supply.
> >>
> >> Then, check all the voltages to make sure they are not way too high,
> >> and throw and oscilloscope on it to make sure that there isn't a whole lot
> >> of ripple (typically caused by a bad rectifier).   Remember that on the
> >> original Altair and most S100 machines each board had its own
> >> regulator, so this isn't an exact thing.  (On my machine, I actually
> >> had to add a second 8V supply in order to provide power for a
> >> backplane completely full of boards.)
> >>
> >> For bootstraps, perhaps look for a ROM board on eBay (a Bytesaver or the like), and burn yourself a ROM.
> >>
> >> For a serial card, you can find T-UART or IMSAI MIO and the like show up
> >> on eBay pretty frequently.  Be patient so you don't overpay. ;)   Real
> >> MITS Altair cards come up far less frequently.  Make sure you
> >> research (say, on bitsavers.org/pdf) which ones support current loop if you really want to hook up a real teletype.
> >>
> >> Not sure where you'd find your multi-user basic, but there is quite a
> >> lot of Altair/S100 software available as part of the SimH
> >> environment, and a separate web site at http://schorn.ch/altair_6.php
> >>
> >> JRJ
> >>
> >> On 7/15/2015 1:56 PM, Kip Koon wrote:
> >> > Hi Drlegendre,
> >> > How did you go about checking things out before you applied power
> >> > for the first time (again)?  :)  I think I need to check out the
> >> electrolytic capacitors and the transformer at least.
> >> > In my system, the front panel is wired to the backplane along with
> >> > the power supply wires so when I do power up, how do I protect
> >> everything?
> >> > There are screws the power wires come from, but they are difficult to get to.  Do I need to consider replacing any other caps?
> >> > Do you have a write up about your experience?  Any help you can
> >> > give in the hardware department is most appreciated.  Thanks in
> >> advance.  Take care my friend.
> >> >
> >> > Kip Koon
> >> > computerdoc at sc.rr.com
> >> > http://www.cocopedia.com/wiki/index.php/Kip_Koon
> >> >
> >> >
> >> >
> >> >> -----Original Message-----
> >> >> From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of drlegendre .
> >> >> Sent: Wednesday, July 15, 2015 1:15 AM
> >> >> To: General Discussion: On-Topic and Off-Topic Posts
> >> >> Subject: Re: Microsoft multiuser Basic for the Altair 8800
> >> >>
> >> >> Hey Kip
> >> >>
> >> >> I can't help you with the software, but I just finished an Altair
> >> >> restoration (my first) a few months ago, and am still interested
> >> >> in getting the machine connected and actually doing something
> >> >> interesting. The Altair was almost totally below the radar by the
> >> >> time I really started getting up to speed on micros, which would
> >> have been around 1983-1984 or so. This one was sort-of given to me by
> >> a former colleague of mine, around eight years ago. It was a total basket case, a real pile.. but it seems to be sorted at this point.
> >> >>
> >> >> It would be great if you'd let me follow along, keep in touch and
> >> >> let me know how you're working to get the Altair linked up to the
> >> >> term, getting the system bootstrapped, loading software, etc..
> >> >> that's been a problem here, figuring out the serial I card (or
> >> >> finding one to
> >> replace it, that does have docs).
> >> >>
> >> >> Best,
> >> >> Bill
> >> >>
> >> >> On Tue, Jul 14, 2015 at 11:56 PM, Kip Koon <computerdoc at sc.rr.com> wrote:
> >> >>
> >> >>> Hi Guys,
> >> >>>
> >> >>> I have finally decided to restore my original Altair 8800 which
> >> >>> has been in storage for over 30 years.  Does anyone have a copy
> >> >>> of Microsoft's Multiuser Disk Extended Basic for the Altair 8800?
> >> >>> When I was in college in '79 to '81, in the computer room was an
> >> >>> ASR-33 Teletype and 3 Learseigler terminals connected to an Altair 8800B.
> >> >>> An IMSAI was also there connected to one
> >> >>> ASR-33 Teletype.  I'd like to resurrect this multiuser Basic
> >> >>> software environment on my Altair someday once the restoration is complete.
> >> >>> Any help in securing a copy of all the necessary software would
> >> >>> be most appreciated.
> >> >>> Thanks a bunch in advance.  Take care my friends.
> >> >>>
> >> >>>
> >> >>>
> >> >>> Kip Koon
> >> >>>
> >> >>>  <mailto:computerdoc at sc.rr.com> computerdoc at sc.rr.com
> >> >>>
> >> >>>  <http://www.cocopedia.com/wiki/index.php/Kip_Koon>
> >> >>> http://www.cocopedia.com/wiki/index.php/Kip_Koon
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> >>>
> >> >
> >> >
> >