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[Altair Computer Club] Re: 38 years late, but now I finally own a working 8800!

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  • steve
    Stuart- Gates signed the cassette, but did he sign the computer? Do you have any kind of evidence that Gates played with your computer, or even looked at it?
    Message 1 of 13 , Jan 15, 2013
      Stuart-

      Gates signed the cassette, but did he sign the computer? Do you have any kind of evidence that Gates played with your computer, or even looked at it? If the answers are "no", then I would say that most people would prefer to have an unmodified/original Altair rather than a "FrankenAltair". Put the 8800 back in original condition and put the 8800b in the homemade case. Let the cassette tape stand by itself.

      On the other hand, if there's an autograph or some other demonstrable connection between your upgraded computer and Bill Gates, then the collectors' value might be greatly increased.

      Steve
      ==========================

      --- In altaircomputerclub@yahoogroups.com, Stuart Wyatt wrote:
      >
      > To B or not to B is a quandary I've had for years.
      >
      > I have an 8800 that was upgraded to an 8800B. The upgrade was virtually everything but the case, so we built a new case for the 8800 that was left over after the upgrade and have a working 8800 (w/ homemade case) and 8800B (upgraded from original 8800).
      >
      > The 8800 is older and I have the original invoice. The 8800B was used at the Microsoft 20th annual meeting and I had the BASIC cassette autographed by Bill Gates at that time.
      >
      > So given that history, which is more collectible: 1) 8800 upgraded to 8800B and used at Microsoft meeting, 2) 8800 if it was restored to original (case) but the one that was at the Microsoft meeting no longer exists, or 3) both the 8800 and 8800B pair as their own intertwined history?
      >
      > -Stuart
      >
      >
      > From: altaircomputerclub@yahoogroups.com [mailto:altaircomputerclub@yahoogroups.com] On Behalf Of steve
      > Sent: Monday, January 14, 2013 2:57 PM
      > To: altaircomputerclub@yahoogroups.com
      > Subject: [Altair Computer Club] Re: 38 years late, but now I finally own a working 8800!
      >
      >
      >
      > Tom-
      > I'm certainly not going to say that the 8800b is perfect, but I think you have picked a couple of poor examples of "problems".
      >
      > I have seen yellowed 8800b faceplates, but only on those computers that were exposed to a lot of sunlight. Most were in darker office or home environments, and they are still fine. As for durability, how many painted 8800 and 8800a faceplates have we seen with worn off labels and graphics? That doesn't happen with the model B's mylar(?) surface. I have some other front panels from Data General and DEC that are considerably more aged looking than any 8800b I've seen.
      >
      > You can't really fault the 8800b because of its necessarily heavier supply. It has a very large and heavy transformer, so large currents can be applied to the power supplies. You can't have a beefy power supply and a light weight supply at the same time (remember that in the late 1970s, light weight switching PS's were not in use much, and they were very expensive). Yes, that weight makes shipping difficult, but MITS solved that problem with proper packaging. If later resellers/reshippers use non-factory shipping methods, it's not MITS' fault.
      >
      > The TIP regulator transistors will fail due to excessive heat, as will any semiconductor. In the 8800b's power supplies, they're also very susceptable to damage caused by having their outputs shorted. This is not an uncommon situation, and I would guess that it's the main reason for the failure of those transistors. It is amazingly easy to short the positive and negative 16 volt supplies to each other, as the previous 2 messages have indicated. Is this a design flaw? Yes, but killing the power before removing boards and other careful troubleshooting techniques will avoid most problems.
      >
      > If you want examples of real flaws, how about those surprisingly fragile card guides, to which Deramp will surely attest? How about lack of motherboard termination? How about poorly thought-out bus pinout arrangements (including the abovementioned 16 volt placements)? These flaws aren't specific to the model B, though- they apply to all of the Altairs and partially to all S100 systems.
      >
      > That's my $0.02.
      >
      > steve
      > ===========================
      >
      > --- In altaircomputerclub@yahoogroups.com , "W Tom" wrote:
      > >
      > > My congratulations too. I'm an 8800b owner and fan, however there are
      > > problems.
      > >
      > > In my opinion the Altair 8800b was one of the best looking computers
      > > made. The problem is the the black on the faceplate fades and the white
      > > tends to yellow. The 8800/8800a face plate is plain, but the paint is
      > > durable. The flat switches look good, but are weak causing them to bend
      > > and break.
      > >
      > > The 8800b has a "much better" power supply, but there are still
      > > problems. The mass of the power supply is enough to cause shipping
      > > damage to the case. Extra packing care is required to protect the
      > > switches and power supply corner. Boards should be removed before
      > > shipment and the case top screwed down tight.
      > >
      > > The 8800b Regulator board is a weak point. The TIP147 failure is an
      > > example. After discussion with Tom Durston and Martin Eberhard, I think
      > > the TIP14x parts fail due to heat. The heat grease on Altair parts in
      > > getting pretty old and dry. MITS used a mica sheet and plastic screw to
      > > mount the TIP14x. Looking at the circuit board, it dose not look like
      > > insulation is necessary. The plastic screws stretch over time and the
      > > heat transfer connection gets loose. I think not using mica and using a
      > > metal screw might be more reliable.
      > >
      > > The TIP14x parts come in more than one package. MITS used the larger
      > > package. A smaller package might have more heat problems. A laser
      > > thermometer shows some larger working TIP14x parts get pretty hot.
      > >
      > >
      > > Tom S
      > >
      > >
      > > --- In altaircomputerclub@yahoogroups.com , "steve" wrote:
      > > >
      > > >
      > > >
      > > > Congrats, Deramp.
      > > >
      > > > The original 8800 *may* be more collectable, but the 8800b is, in my
      > > opinion, a machine that not only looks better, but is also more
      > > reliable, has a much better power supply, and has a much more useful and
      > > better designed front panel.
      > > >
      > > > steve
      > > > ==================================
      > > >
      > > > --- In altaircomputerclub@yahoogroups.com , "deramp5113" wrote:
      > > > >
      > > > > Nobody in my circle of friends or family cares about this, so I'll
      > > post here!
      > > > >
      > > > > I purchased a non-working 8800b off eBay recently. The computer and
      > > boards are in remarkably good physical condition, though 21 card guides
      > > were broken during transit and there was some minor damage to boards
      > > from flopping around.
      > > > >
      > > > > The negative supply had lost regulation and the excess negative
      > > voltage took out some tantalum caps on the display board. A new TIP147
      > > transistor fixed the negative supply. I replaced the burnt out tantalum
      > > caps on the display board and numerous disc caps that were falling apart
      > > on several boards. The negative regulator on the display board was still
      > > fine.
      > > > >
      > > > > A couple of front panel switches didn't function (single-step,
      > > examine). The switches themselves ended up being fine. The problem was
      > > due to pin surface corrosion on a couple of IC's (socketed) connected to
      > > the switches.
      > > > >
      > > > > Board by board, the rest of the computer came up without a hitch. It
      > > came with 64K of static RAM (two MITS 16K, one EconoRAM 16K, and one
      > > Digital Research 16K) a MITS 2SIO board with both ACIAs and the MITS
      > > vectored interrupt RTC card.
      > > > >
      > > > > My wife just doesn't understand, but I'm thrilled!
      > > > >
      > > >
      > >
      >
    • Stuart Wyatt
      Steve, Gates didn t sign the computer. I guess at the time I thought the cassette made sense with the connection to Gates/Micro-Soft, but not as much for the
      Message 2 of 13 , Jan 15, 2013

        Steve,

         

        Gates didn’t sign the computer.  I guess at the time I thought the cassette made sense with the connection to Gates/Micro-Soft, but not as much for the Altair hardware.  At the 20th annual company meeting, they had a 20 year timeline of Microsoft stuff.  The timeline started with the Altair.  We had “kill the lit bit” running on it.  Gates visited the timeline and talked about the Altair in general, about the round switches and how they were hard on your fingers, and how they asked Monte Davidoff to join them in Seattle, but he declined.  That is when/where the cassette was signed.  I’m not sure if any pictures were taken.  It was very crowded.  I’ve talked with the Microsoft archives and they haven’t found any pictures from the event that have that part of the timeline.  The furthest to the “left” photo was the IBM PC.  The only “evidence” I have of the event are emails arranging it, and a crew pass for the meeting.  Would a photo of Gates/Altair change your opinion?  I’m still hopeful there might be one out there.

         

        In general, it sounds like you feel the 8800 is more collectible than the 8800B?  The comments from others about being fans of the 8800B made me wonder if the B might be more attractive.  The B was certainly far easier to keep running.

         

        -Stuart

         

        From: altaircomputerclub@yahoogroups.com [mailto:altaircomputerclub@yahoogroups.com] On Behalf Of steve
        Sent: Tuesday, January 15, 2013 10:36 AM
        To: altaircomputerclub@yahoogroups.com
        Subject: [Altair Computer Club] Re: 38 years late, but now I finally own a working 8800!

         

         

        Stuart-

        Gates signed the cassette, but did he sign the computer? Do you have any kind of evidence that Gates played with your computer, or even looked at it? If the answers are "no", then I would say that most people would prefer to have an unmodified/original Altair rather than a "FrankenAltair". Put the 8800 back in original condition and put the 8800b in the homemade case. Let the cassette tape stand by itself.

        On the other hand, if there's an autograph or some other demonstrable connection between your upgraded computer and Bill Gates, then the collectors' value might be greatly increased.

        Steve
        ==========================

        --- In altaircomputerclub@yahoogroups.com, Stuart Wyatt wrote:
        >
        > To B or not to B is a quandary I've had for years.
        >
        > I have an 8800 that was upgraded to an 8800B. The upgrade was virtually everything but the case, so we built a new case for the 8800 that was left over after the upgrade and have a working 8800 (w/ homemade case) and 8800B (upgraded from original 8800).
        >
        > The 8800 is older and I have the original invoice. The 8800B was used at the Microsoft 20th annual meeting and I had the BASIC cassette autographed by Bill Gates at that time.
        >
        > So given that history, which is more collectible: 1) 8800 upgraded to 8800B and used at Microsoft meeting, 2) 8800 if it was restored to original (case) but the one that was at the Microsoft meeting no longer exists, or 3) both the 8800 and 8800B pair as their own intertwined history?
        >
        > -Stuart
        >
        >
        > From: altaircomputerclub@yahoogroups.com [mailto:altaircomputerclub@yahoogroups.com] On Behalf Of steve
        > Sent: Monday, January 14, 2013 2:57 PM
        > To: altaircomputerclub@yahoogroups.com
        > Subject: [Altair Computer Club] Re: 38 years late, but now I finally own a working 8800!
        >
        >
        >
        > Tom-
        > I'm certainly not going to say that the 8800b is perfect, but I think you have picked a couple of poor examples of "problems".
        >
        > I have seen yellowed 8800b faceplates, but only on those computers that were exposed to a lot of sunlight. Most were in darker office or home environments, and they are still fine. As for durability, how many painted 8800 and 8800a faceplates have we seen with worn off labels and graphics? That doesn't happen with the model B's mylar(?) surface. I have some other front panels from Data General and DEC that are considerably more aged looking than any 8800b I've seen.
        >
        > You can't really fault the 8800b because of its necessarily heavier supply. It has a very large and heavy transformer, so large currents can be applied to the power supplies. You can't have a beefy power supply and a light weight supply at the same time (remember that in the late 1970s, light weight switching PS's were not in use much, and they were very expensive). Yes, that weight makes shipping difficult, but MITS solved that problem with proper packaging. If later resellers/reshippers use non-factory shipping methods, it's not MITS' fault.
        >
        > The TIP regulator transistors will fail due to excessive heat, as will any semiconductor. In the 8800b's power supplies, they're also very susceptable to damage caused by having their outputs shorted. This is not an uncommon situation, and I would guess that it's the main reason for the failure of those transistors. It is amazingly easy to short the positive and negative 16 volt supplies to each other, as the previous 2 messages have indicated. Is this a design flaw? Yes, but killing the power before removing boards and other careful troubleshooting techniques will avoid most problems.
        >
        > If you want examples of real flaws, how about those surprisingly fragile card guides, to which Deramp will surely attest? How about lack of motherboard termination? How about poorly thought-out bus pinout arrangements (including the abovementioned 16 volt placements)? These flaws aren't specific to the model B, though- they apply to all of the Altairs and partially to all S100 systems.
        >
        > That's my $0.02.
        >
        > steve
        > ===========================
        >
        > --- In altaircomputerclub@yahoogroups.com , "W Tom" wrote:
        > >
        > > My congratulations too. I'm an 8800b owner and fan, however there are
        > > problems.
        > >
        > > In my opinion the Altair 8800b was one of the best looking computers
        > > made. The problem is the the black on the faceplate fades and the white
        > > tends to yellow. The 8800/8800a face plate is plain, but the paint is
        > > durable. The flat switches look good, but are weak causing them to bend
        > > and break.
        > >
        > > The 8800b has a "much better" power supply, but there are still
        > > problems. The mass of the power supply is enough to cause shipping
        > > damage to the case. Extra packing care is required to protect the
        > > switches and power supply corner. Boards should be removed before
        > > shipment and the case top screwed down tight.
        > >
        > > The 8800b Regulator board is a weak point. The TIP147 failure is an
        > > example. After discussion with Tom Durston and Martin Eberhard, I think
        > > the TIP14x parts fail due to heat. The heat grease on Altair parts in
        > > getting pretty old and dry. MITS used a mica sheet and plastic screw to
        > > mount the TIP14x. Looking at the circuit board, it dose not look like
        > > insulation is necessary. The plastic screws stretch over time and the
        > > heat transfer connection gets loose. I think not using mica and using a
        > > metal screw might be more reliable.
        > >
        > > The TIP14x parts come in more than one package. MITS used the larger
        > > package. A smaller package might have more heat problems. A laser
        > > thermometer shows some larger working TIP14x parts get pretty hot.
        > >
        > >
        > > Tom S
        > >
        > >
        > > --- In altaircomputerclub@yahoogroups.com , "steve" wrote:
        > > >
        > > >
        > > >
        > > > Congrats, Deramp.
        > > >
        > > > The original 8800 *may* be more collectable, but the 8800b is, in my
        > > opinion, a machine that not only looks better, but is also more
        > > reliable, has a much better power supply, and has a much more useful and
        > > better designed front panel.
        > > >
        > > > steve
        > > > ==================================
        > > >
        > > > --- In altaircomputerclub@yahoogroups.com , "deramp5113" wrote:
        > > > >
        > > > > Nobody in my circle of friends or family cares about this, so I'll
        > > post here!
        > > > >
        > > > > I purchased a non-working 8800b off eBay recently. The computer and
        > > boards are in remarkably good physical condition, though 21 card guides
        > > were broken during transit and there was some minor damage to boards
        > > from flopping around.
        > > > >
        > > > > The negative supply had lost regulation and the excess negative
        > > voltage took out some tantalum caps on the display board. A new TIP147
        > > transistor fixed the negative supply. I replaced the burnt out tantalum
        > > caps on the display board and numerous disc caps that were falling apart
        > > on several boards. The negative regulator on the display board was still
        > > fine.
        > > > >
        > > > > A couple of front panel switches didn't function (single-step,
        > > examine). The switches themselves ended up being fine. The problem was
        > > due to pin surface corrosion on a couple of IC's (socketed) connected to
        > > the switches.
        > > > >
        > > > > Board by board, the rest of the computer came up without a hitch. It
        > > came with 64K of static RAM (two MITS 16K, one EconoRAM 16K, and one
        > > Digital Research 16K) a MITS 2SIO board with both ACIAs and the MITS
        > > vectored interrupt RTC card.
        > > > >
        > > > > My wife just doesn't understand, but I'm thrilled!
        > > > >
        > > >
        > >
        >

      • steve
        Stuart- As antique collectors are fond of saying, a photo or signature would add provenance to your 8800b, just as it will to the cassette. The value is
        Message 3 of 13 , Jan 15, 2013
          Stuart-

          As antique collectors are fond of saying, a photo or signature would add "provenance" to your 8800b, just as it will to the cassette. The value is all in the eye of the beholder, however.

          If you just want an investment to sit on the shelf and look at, the 8800 or 8800a (the rarest version) might be more desirable. If you're actually going to do something with it, the B is the way to go.

          I agree that the original bat handle front panel switches weren't easy to use. The later flattened handles on the B made switch flipping much easier. I never liked IMSAI's wide paddle switches, though- I couldn't easily feel the separation between them and often flipped the wrong switch. I guess their switches were modeled after those of DEC and DG panels, but not well enough.

          steve
          ===============

          --- In altaircomputerclub@yahoogroups.com, Stuart Wyatt wrote:
          >
          > Steve,
          >
          > Gates didn't sign the computer. I guess at the time I thought the cassette made sense with the connection to Gates/Micro-Soft, but not as much for the Altair hardware. At the 20th annual company meeting, they had a 20 year timeline of Microsoft stuff. The timeline started with the Altair. We had "kill the lit bit" running on it. Gates visited the timeline and talked about the Altair in general, about the round switches and how they were hard on your fingers, and how they asked Monte Davidoff to join them in Seattle, but he declined. That is when/where the cassette was signed. I'm not sure if any pictures were taken. It was very crowded. I've talked with the Microsoft archives and they haven't found any pictures from the event that have that part of the timeline. The furthest to the "left" photo was the IBM PC. The only "evidence" I have of the event are emails arranging it, and a crew pass for the meeting. Would a photo of Gates/Altair change your opinion? I'm still hopeful there might be one out there.
          >
          > In general, it sounds like you feel the 8800 is more collectible than the 8800B? The comments from others about being fans of the 8800B made me wonder if the B might be more attractive. The B was certainly far easier to keep running.
          >
          > -Stuart
          >
          > From: altaircomputerclub@yahoogroups.com [mailto:altaircomputerclub@yahoogroups.com] On Behalf Of steve
          > Sent: Tuesday, January 15, 2013 10:36 AM
          > To: altaircomputerclub@yahoogroups.com
          > Subject: [Altair Computer Club] Re: 38 years late, but now I finally own a working 8800!
          >
          >
          >
          > Stuart-
          >
          > Gates signed the cassette, but did he sign the computer? Do you have any kind of evidence that Gates played with your computer, or even looked at it? If the answers are "no", then I would say that most people would prefer to have an unmodified/original Altair rather than a "FrankenAltair". Put the 8800 back in original condition and put the 8800b in the homemade case. Let the cassette tape stand by itself.
          >
          > On the other hand, if there's an autograph or some other demonstrable connection between your upgraded computer and Bill Gates, then the collectors' value might be greatly increased.
          >
          > Steve
          > ==========================
          >
          > --- In altaircomputerclub@yahoogroups.com , Stuart Wyatt wrote:
          > >
          > > To B or not to B is a quandary I've had for years.
          > >
          > > I have an 8800 that was upgraded to an 8800B. The upgrade was virtually everything but the case, so we built a new case for the 8800 that was left over after the upgrade and have a working 8800 (w/ homemade case) and 8800B (upgraded from original 8800).
          > >
          > > The 8800 is older and I have the original invoice. The 8800B was used at the Microsoft 20th annual meeting and I had the BASIC cassette autographed by Bill Gates at that time.
          > >
          > > So given that history, which is more collectible: 1) 8800 upgraded to 8800B and used at Microsoft meeting, 2) 8800 if it was restored to original (case) but the one that was at the Microsoft meeting no longer exists, or 3) both the 8800 and 8800B pair as their own intertwined history?
          > >
          > > -Stuart
          > >
          > >
          > > From: altaircomputerclub@yahoogroups.com [mailto:altaircomputerclub@yahoogroups.com ] On Behalf Of steve
          > > Sent: Monday, January 14, 2013 2:57 PM
          > > To: altaircomputerclub@yahoogroups.com
          > > Subject: [Altair Computer Club] Re: 38 years late, but now I finally own a working 8800!
          > >
          > >
          > >
          > > Tom-
          > > I'm certainly not going to say that the 8800b is perfect, but I think you have picked a couple of poor examples of "problems".
          > >
          > > I have seen yellowed 8800b faceplates, but only on those computers that were exposed to a lot of sunlight. Most were in darker office or home environments, and they are still fine. As for durability, how many painted 8800 and 8800a faceplates have we seen with worn off labels and graphics? That doesn't happen with the model B's mylar(?) surface. I have some other front panels from Data General and DEC that are considerably more aged looking than any 8800b I've seen.
          > >
          > > You can't really fault the 8800b because of its necessarily heavier supply. It has a very large and heavy transformer, so large currents can be applied to the power supplies. You can't have a beefy power supply and a light weight supply at the same time (remember that in the late 1970s, light weight switching PS's were not in use much, and they were very expensive). Yes, that weight makes shipping difficult, but MITS solved that problem with proper packaging. If later resellers/reshippers use non-factory shipping methods, it's not MITS' fault.
          > >
          > > The TIP regulator transistors will fail due to excessive heat, as will any semiconductor. In the 8800b's power supplies, they're also very susceptable to damage caused by having their outputs shorted. This is not an uncommon situation, and I would guess that it's the main reason for the failure of those transistors. It is amazingly easy to short the positive and negative 16 volt supplies to each other, as the previous 2 messages have indicated. Is this a design flaw? Yes, but killing the power before removing boards and other careful troubleshooting techniques will avoid most problems.
          > >
          > > If you want examples of real flaws, how about those surprisingly fragile card guides, to which Deramp will surely attest? How about lack of motherboard termination? How about poorly thought-out bus pinout arrangements (including the abovementioned 16 volt placements)? These flaws aren't specific to the model B, though- they apply to all of the Altairs and partially to all S100 systems.
          > >
          > > That's my $0.02.
          > >
          > > steve
          > > ===========================
          > >
          > > --- In altaircomputerclub@yahoogroups.com , "W Tom" wrote:
          > > >
          > > > My congratulations too. I'm an 8800b owner and fan, however there are
          > > > problems.
          > > >
          > > > In my opinion the Altair 8800b was one of the best looking computers
          > > > made. The problem is the the black on the faceplate fades and the white
          > > > tends to yellow. The 8800/8800a face plate is plain, but the paint is
          > > > durable. The flat switches look good, but are weak causing them to bend
          > > > and break.
          > > >
          > > > The 8800b has a "much better" power supply, but there are still
          > > > problems. The mass of the power supply is enough to cause shipping
          > > > damage to the case. Extra packing care is required to protect the
          > > > switches and power supply corner. Boards should be removed before
          > > > shipment and the case top screwed down tight.
          > > >
          > > > The 8800b Regulator board is a weak point. The TIP147 failure is an
          > > > example. After discussion with Tom Durston and Martin Eberhard, I think
          > > > the TIP14x parts fail due to heat. The heat grease on Altair parts in
          > > > getting pretty old and dry. MITS used a mica sheet and plastic screw to
          > > > mount the TIP14x. Looking at the circuit board, it dose not look like
          > > > insulation is necessary. The plastic screws stretch over time and the
          > > > heat transfer connection gets loose. I think not using mica and using a
          > > > metal screw might be more reliable.
          > > >
          > > > The TIP14x parts come in more than one package. MITS used the larger
          > > > package. A smaller package might have more heat problems. A laser
          > > > thermometer shows some larger working TIP14x parts get pretty hot.
          > > >
          > > >
          > > > Tom S
          > > >
          > > >
          > > > --- In altaircomputerclub@yahoogroups.com , "steve" wrote:
          > > > >
          > > > >
          > > > >
          > > > > Congrats, Deramp.
          > > > >
          > > > > The original 8800 *may* be more collectable, but the 8800b is, in my
          > > > opinion, a machine that not only looks better, but is also more
          > > > reliable, has a much better power supply, and has a much more useful and
          > > > better designed front panel.
          > > > >
          > > > > steve
          > > > > ==================================
          > > > >
          > > > > --- In altaircomputerclub@yahoogroups.com , "deramp5113" wrote:
          > > > > >
          > > > > > Nobody in my circle of friends or family cares about this, so I'll
          > > > post here!
          > > > > >
          > > > > > I purchased a non-working 8800b off eBay recently. The computer and
          > > > boards are in remarkably good physical condition, though 21 card guides
          > > > were broken during transit and there was some minor damage to boards
          > > > from flopping around.
          > > > > >
          > > > > > The negative supply had lost regulation and the excess negative
          > > > voltage took out some tantalum caps on the display board. A new TIP147
          > > > transistor fixed the negative supply. I replaced the burnt out tantalum
          > > > caps on the display board and numerous disc caps that were falling apart
          > > > on several boards. The negative regulator on the display board was still
          > > > fine.
          > > > > >
          > > > > > A couple of front panel switches didn't function (single-step,
          > > > examine). The switches themselves ended up being fine. The problem was
          > > > due to pin surface corrosion on a couple of IC's (socketed) connected to
          > > > the switches.
          > > > > >
          > > > > > Board by board, the rest of the computer came up without a hitch. It
          > > > came with 64K of static RAM (two MITS 16K, one EconoRAM 16K, and one
          > > > Digital Research 16K) a MITS 2SIO board with both ACIAs and the MITS
          > > > vectored interrupt RTC card.
          > > > > >
          > > > > > My wife just doesn't understand, but I'm thrilled!
          > > > > >
          > > > >
          > > >
          > >
          >
        • W Tom
          Steve- My poor examples come from the mainframes I am repairing. I have four 8800b regulator boards to repair. I don t know if heat or shorts caused the
          Message 4 of 13 , Jan 16, 2013
            Steve-

            My poor examples come from the mainframes I am repairing. I have four 8800b regulator boards to repair. I don't know if heat or shorts caused the problem.

            I have multiple bent and broken cases and chassis parts. I'm sure they result from the mass of the 8800b transformer. I've shipped enough 8800b mainframes to know what corner hits the ground first.

            MITS had good packing, but I don't think many original boxes survived. I think it is important to remind 8800b owners to pack carefully. I highly recommend screwing the Altair top on tight and removing boards.

            I patched one Regulator Board with the smaller package transistor and new plastic screws. I have three more to fix. I'm thinking of using a metal screw and no mylar. I'll double check but don't think this causes any short. There is also a small part made that insulates a metal screw.

            I've found loose heat sinks on regulator boards, so I don't thing ensuring a good thermal connection will hurt. Some transistors measure around 100 degrees. I don't know how much role heat plays in failure, but I have one working Regulator Board that measures 180 degrees at the cap next to the heatsink.

            I have to be careful not to break a card guide when replacing a Regulator board. The terminal block on the 8800b transformer makes it hard to connect the board to the bridge on the back panel.

            I'm looking at Tom Durston's upgraded 8800a. It has an 8800b Regulator Board and a sample transformer from the same manufacturer as the 8800b. The transformer is smaller that an 8800b transformer and bigger than an Attache. The terminal block is mounted on the backplate.

            I think the 8800b transformer was a bit overkill and the result is sometimes case damage. The 8000b can power 4K or 16K statics. Competitors of the 8800b had lighter weight dynamic RAM on a single 48-64K board. Four MITS 16K static boards have a lot of mass. The brittle card guides flex before they break and the boards come loose. That's like a loose brick in the mainframe during shipment. The card guides need a frame or card cage for mechanical support. Some competitors used a bar to lock boards in place.

            One thing that makes an 8800b better than the competition is the modified Turnkey Board. Having a full 64K is a big speed advantage for BASIC. An Attache transformer will run a 64K Altair board set.

            I'm fixing my Altair power supplies because the repairs are inexpensive. I would like to have a some switching supplies like Grant's reproduction 8800. It looks to me like an upgrade could done without damaging any original parts. I would keep the original parts for a the next owner.

            My newest working Altair is an 8800b-dm. This model has the unterminated Attache 10-slot motherboard. This shorter board will run Vector Graphic boards that come from a mainframe with passive termination. The 8000b transformer has enough power for 5.25" floppies. An Attache transformer would be enough. The good think about a Turnkey machine is there are only two flat switches to break.

            Tom S


            --- In altaircomputerclub@yahoogroups.com, "steve" wrote:
            >
            > Tom-
            > I'm certainly not going to say that the 8800b is perfect, but I think you have picked a couple of poor examples of "problems".
            >
            > I have seen yellowed 8800b faceplates, but only on those computers that were exposed to a lot of sunlight. Most were in darker office or home environments, and they are still fine. As for durability, how many painted 8800 and 8800a faceplates have we seen with worn off labels and graphics? That doesn't happen with the model B's mylar(?) surface. I have some other front panels from Data General and DEC that are considerably more aged looking than any 8800b I've seen.
            >
            > You can't really fault the 8800b because of its necessarily heavier supply. It has a very large and heavy transformer, so large currents can be applied to the power supplies. You can't have a beefy power supply and a light weight supply at the same time (remember that in the late 1970s, light weight switching PS's were not in use much, and they were very expensive). Yes, that weight makes shipping difficult, but MITS solved that problem with proper packaging. If later resellers/reshippers use non-factory shipping methods, it's not MITS' fault.
            >
            > The TIP regulator transistors will fail due to excessive heat, as will any semiconductor. In the 8800b's power supplies, they're also very susceptable to damage caused by having their outputs shorted. This is not an uncommon situation, and I would guess that it's the main reason for the failure of those transistors. It is amazingly easy to short the positive and negative 16 volt supplies to each other, as the previous 2 messages have indicated. Is this a design flaw? Yes, but killing the power before removing boards and other careful troubleshooting techniques will avoid most problems.
            >
            > If you want examples of real flaws, how about those surprisingly fragile card guides, to which Deramp will surely attest? How about lack of motherboard termination? How about poorly thought-out bus pinout arrangements (including the abovementioned 16 volt placements)? These flaws aren't specific to the model B, though- they apply to all of the Altairs and partially to all S100 systems.
            >
            > That's my $0.02.
            >
            > steve
            > ===========================
            >
            >
            > --- In altaircomputerclub@yahoogroups.com, "W Tom" wrote:
            > >
            > > My congratulations too. I'm an 8800b owner and fan, however there are
            > > problems.
            > >
            > > In my opinion the Altair 8800b was one of the best looking computers
            > > made. The problem is the the black on the faceplate fades and the white
            > > tends to yellow. The 8800/8800a face plate is plain, but the paint is
            > > durable. The flat switches look good, but are weak causing them to bend
            > > and break.
            > >
            > > The 8800b has a "much better" power supply, but there are still
            > > problems. The mass of the power supply is enough to cause shipping
            > > damage to the case. Extra packing care is required to protect the
            > > switches and power supply corner. Boards should be removed before
            > > shipment and the case top screwed down tight.
            > >
            > > The 8800b Regulator board is a weak point. The TIP147 failure is an
            > > example. After discussion with Tom Durston and Martin Eberhard, I think
            > > the TIP14x parts fail due to heat. The heat grease on Altair parts in
            > > getting pretty old and dry. MITS used a mica sheet and plastic screw to
            > > mount the TIP14x. Looking at the circuit board, it dose not look like
            > > insulation is necessary. The plastic screws stretch over time and the
            > > heat transfer connection gets loose. I think not using mica and using a
            > > metal screw might be more reliable.
            > >
            > > The TIP14x parts come in more than one package. MITS used the larger
            > > package. A smaller package might have more heat problems. A laser
            > > thermometer shows some larger working TIP14x parts get pretty hot.
            > >
            > >
            > > Tom S
            > >
            > >
            > > --- In altaircomputerclub@yahoogroups.com, "steve" wrote:
            > > >
            > > >
            > > >
            > > > Congrats, Deramp.
            > > >
            > > > The original 8800 *may* be more collectable, but the 8800b is, in my
            > > opinion, a machine that not only looks better, but is also more
            > > reliable, has a much better power supply, and has a much more useful and
            > > better designed front panel.
            > > >
            > > > steve
            > > > ==================================
            > > >
            > > > --- In altaircomputerclub@yahoogroups.com, "deramp5113" wrote:
            > > > >
            > > > > Nobody in my circle of friends or family cares about this, so I'll
            > > post here!
            > > > >
            > > > > I purchased a non-working 8800b off eBay recently. The computer and
            > > boards are in remarkably good physical condition, though 21 card guides
            > > were broken during transit and there was some minor damage to boards
            > > from flopping around.
            > > > >
            > > > > The negative supply had lost regulation and the excess negative
            > > voltage took out some tantalum caps on the display board. A new TIP147
            > > transistor fixed the negative supply. I replaced the burnt out tantalum
            > > caps on the display board and numerous disc caps that were falling apart
            > > on several boards. The negative regulator on the display board was still
            > > fine.
            > > > >
            > > > > A couple of front panel switches didn't function (single-step,
            > > examine). The switches themselves ended up being fine. The problem was
            > > due to pin surface corrosion on a couple of IC's (socketed) connected to
            > > the switches.
            > > > >
            > > > > Board by board, the rest of the computer came up without a hitch. It
            > > came with 64K of static RAM (two MITS 16K, one EconoRAM 16K, and one
            > > Digital Research 16K) a MITS 2SIO board with both ACIAs and the MITS
            > > vectored interrupt RTC card.
            > > > >
            > > > > My wife just doesn't understand, but I'm thrilled!
            > > > >
            > > >
            > >
            >
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