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  1. #21
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    I have some teardown pics of the machine, these are pre "decontamination". The machine was covered in a greasy rubbery layer of smut, below that layer was MDF chips.
    20151017_154241.jpg20151017_154318.jpg

    Here's what the spindle motor looks like before and after new bearings and several hours of cleanup. I have probably 6 hours of work into this motor. I didn't clean it to spic and span because I suspect it will need a rewind in the nearish future.

    Before:
    20151017_154328s.jpg

    After:
    20151021_214412s.jpg

    I have all new metering units and a lube line for the saddle on their way to me. It'll get the attention needed to the lube system, then I can explore the machine a bit further.

    The motor pulley is Aluminum and is shrunk onto the shaft. I used a harmonic balancer puller to remove the pulley (once hot) and a hot plate (lab style) to heat the pulley for reinstallation. I took a measurement of the distance between the motor face and the largest step in the pulley before I removed it. During installation I used a set of adjustable parallels to set the height so all I had to do was heat the pulley and set it on the shaft, the parallels made certain the spacing was the same as before I tore it down.

    If there is one thing I can recommend to anyone working on a machine without complete documentation: carefully inspect everything, measure everything, write down any identifying info, because you may not realize that some parts are not interchangeable.

    This machine uses 4 different sizes of metering units and their order is important.

  2. #22
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    I got all my lube system parts from CNCPros on Thursday and got the manifolds reinstalled.

    The manifold on the head was reconnected and the system primed several times until oil was leaking down the ways. I then reconnected the Z servo and exercised the Z axis at slow speeds, then progressively faster until I got to 100% jog speed.

    These pictures show the newly oiled ways, but the machine still looks like a pig sty.



    One thing that was missing was the lube line that ran from the oiler to the saddle. I searched, but my machine is too old for anyone to have reliable information about the factory setup for that line. I decided the factory configuration was not very good and ordered a lube upgrade kit for a late 4020. This was just to get a grab bag of parts to roll my own lube line. I used one of the cable chains and made a bracket that mounts just above the chip pan. The lube line will run from the oiler through the chain and attach to the manifold. I will also make a sheet metal guard to cover the plastic line inside the chip pan area, so the whole lubrication system should be resilient against hot chips and sweeping out the chip pan.





    I'm considering just installing the chip guard that attaches to the table and running mist coolant for the time being. I know that once I get into stainless or titanium I will need flood coolant, but the flood system is not particularly well sorted on this machine. I need to make a coolant trough that sits under the chip pan and directs the return coolant back to the coolant tank. I may use some ABS DWV pipe to do this, now that I think of it.
    Attached Thumbnails Attached Thumbnails 20151022_222103s.jpg   20151022_222134s.jpg   20151023_205646s.jpg   20151023_205708s.jpg  

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  4. #23
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    Crap, drag n' drop doesn't work on Firefox for Linux when trying to upload pictures, post lost!

    Ok, so today I had a diversion while winterizing the trailer, the cold knob of the outside shower came off in my hand. The cheap plastic nut that holds the cartridge into the faucet just failed.

    I tried to get a new one at the RV place, but they neglected to note their parts dept closes at 3pm on their website where they list their hours!

    So I went to HD and milled around there for a bit, nothing of the sort was available.

    So, the nut is a 1"-20 thread, about 7/16" deep with a shoulder to a 51/64th through hole.

    Grabbed a piece of Al tube from the pile and spent a while turning up the part. Cut a blind ID thread single point, dead reckoning to dials because I didn't have a 1"-20 sample to test -- the faucet WAS the test.

    Finished it up, parted off, then tried it on the faucet, fit snugly but went on -- that's a win in my book!

    Now the faucet has a nut that's worth more than the whole faucet...

    Attached Thumbnails Attached Thumbnails 20151024_184026s.jpg  

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  6. #24
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    Here's a quick video of the first run.

    https://youtu.be/D2oOiMmWqww

    And here's the list of what I've done to get it to this point:

    • Replaced Bijur oiler intake filter
    • Cleaned old goo from oiler reservoir
    • Cleaned goo from lubrication manifolds
    • Replaced all Bijur metering units
    • Made/installed new saddle oiling feeder line
    • Disassembled spindle motor and cleaned tons of goo out of it
    • New bearings on spindle motor
    • File ridge off top of spindle pulley
    • Replace spindle oiler fuse
    • Clean and get HV cabinet fan working
    • Scrape and remove at least 10lbs of crusted goo and chips from machine


    On the plus side, the control works and the axis drives/motors work. It's not a case of "good iron, bad control" like was on my Hardinge CHNC1, it's a case of "good control, neglected iron".

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  8. #25
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    Well, the drama continues. Last night I discovered that one of the oiler channels on the saddle is not getting enough lube to the table. It seems this has been this way for a very long time and has caused damage to the ways.

    I'm going to have to remove the table and clean and stone the ways.

    The gibs are so tight that I cannot move the table with a pry bar or by pushing on it, it's just amazing to me the amount of thrust the ballscrew can generate.

    More pictures and video to come, this ought to be interesting.

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  10. #26
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    Well, I've got more pictures to share.

    Here is the table just as it came off the machine:


    This is what the ways look like on the saddle, covered in crud:


    This is the rear way, that oiling hole has about 5/8" of crud blocking the orifice, for quite some time. It just boggles my mind that people would not take care of a machine, putting crap way lube in it, not cleaning it, and not taking care of obvious lube issues. The gibs were filthy and corroded. The space between the gibs and the table was filled with rust and caused the gibs to be so tight that the table wouldn't budge, and they were only adjusted about 1/4" from the stops. Once I removed the gibs I could push the table quite easily.


    This is what the saddle looks like after I cleaned the oiling holes out with a drill:



    Here's what the gibs look like:
    Attached Thumbnails Attached Thumbnails 20151029_185933s.jpg   20151029_190039s.jpg   20151029_190047s.jpg   20151029_190847s.jpg   20151029_183847s.jpg  


  11. #27
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    Here's a tangentially related aside:



    That's the contents of the character generator ROM on the Fadal video card. I used a Parallax Propeller development board to make a breadboard EPROM reader.

    I'm interested in making a video card that will plug in place of the Fadal card and output a video format of my choosing.

    Specifically I'm talking about using a Parallax Propeller microcontroller to generate a VGA signal. The picture is actually the Propeller outputting the ROM data to a VGA monitor.

    With the Propeller I can add pseudo color when the coordinates are displayed in the upper left corner of the screen. I could also add a clock to the upper right to display the current time.

    With access to the video RAM data I can add more visual capabilities to the machine without the machine even knowing what's going on.

    This would enable me to upgrade the screen to an LCD without spending the ridiculous sums that people charge for Fadal LCD upgrades.

    The Fadal chargen ROM only implements 64 of the 128 glyphs in the character set, the other 64 are filled with blocks. I suspect the other blocks may be pseudo graphics that are part of some easter egg in the control.

    The characters are 16 lines tall, and the screen is 40x25. I suspect the blank 8 lines below the characters are for the second field, the video card only outputs 1 field worth of data, because NTSC is interlaced you have 2 fields and I bet they just do a blank line on the second field. The graphic characters don't have blanks in the second 8 lines, so they would implement a double high character in the even and odd fields.

    lol, looking at the data again, I think I'm overthinking it. They put a 4KB ROM on the board, but only used the upper 2KB, and only half of that was used for actual glyphs. I see that the unimplemented glyphs actually repeat every 16 characters, so I suspect it's just random stuff that was left over from whatever program they used to generate the character glyphs.

    I've figured out the basics of how the video card works, based on this card and later cards. Later cards used a dual port 1KB RAM so the CPU could talk to the video card while the video data was rendering to the CRT. The older cards required the CPU to share time with the video rendering circuitry, I believe this may cause a waitstate in the main CPU, reducing the block execution rate. By going to dual ported RAM they can eliminate that waitstate and execute faster.

    The video card works by generating an asynchronous clock on the board, which drives a set of counters. The RAM data lines are directly connected to the A4 through A10 address lines of the chargen ROM, using the ASCII code for the character to lookup the block of 16 bytes for each character. An external counter iterates through the 16 lines to generate the scan lines on the CRT. The signal is turned into a Black and White composite video signal which is sent to the video monitor. The video data is generated by a shift register that takes the bit pattern output of the chargen ROM and shifts it out as black or white dots to the video monitor.

    I'm working up a schematic right now to help understand exactly how the memory arbitration scheme works, I assume the video card asserts asserts a wait signal while it's addressing and reading the memory, then during the vertical sync interval the CPU has access to the RAM.

    This means the CPU can only update the display about 30 times per second. It's curious that the maximum block rate on the old controls was 27 blocks per second, pretty close to that waitstate interval.
    Attached Thumbnails Attached Thumbnails 20151031_120911s.jpg  

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  13. #28
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    I sure like your work very nice . One thing I learned you may probably all ready know is if you save or buy old good screwdriver handles grind them down to fit carbide inserts for scraping off crud on castings or any parts .Many sizes to chose from all different edge configuration to chose from , with a green wheel you can sharpen or change them .They work very good .Thanks Mike

  14. #29
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    I finished my reverse engineered schematic of the Fadal 1420-1 video board. I'd estimate I have 20-25 hours into the schematic at this point.

    The schematic, and observation of the control display, lead to some interesting observations about the original design.

    It's widely told that Adrian de Caussin is the one who designed the control hardware, unfortunately he passed away some time ago (a reference from 1996 indicates he'd passed by then), so this public accounting may be the only hardware level details known outside of the de Caussin family.

    I did reach out to David de Caussin the younger to try and learn details about the original control development, because at this point they are considered vintage computer systems. Unfortunately I didn't receive a reply from him, so I had to go at it myself.

    Up to this point I had dumped the character generator ROM, as seen in a previous post. This lead to some curious questions which I believe are answered by the schematic diagram, namely why each character is represented by 16 lines, but the latter 8 lines are blank?

    Well, let's start with some simple things we can observe about the video display. First, the display is 64 columns by 16 rows. My research indicates this was a common format for S100 computers around the time the Fadal control was created. It makes sense then that the Fadal control would leverage some existing standards, but why roll their own video card instead of buying one or copying an existing design?

    Well the second observation may give that answer. When the control goes into a mode where the axes are moving and the DRO display is active, it switches the top 6 lines of the screen into a doublewide mode. The top 6 lines become 32 columns wide and the characters become square. This is to aid in viewing the DRO output during operation. I presume the top 6 lines were chosen because the control is 5 axis capable, so 1 line per axis and then a blank line to separate the DRO from the scrolling portion of the display.

    The third observation we can make is that the screen seems to flicker at times when the cursor is blinking, or the display is scrolling. This is answered too by the schematic.

    So, let's discuss some of the components of the video card and why it's unique. I'll just get the unique part out first: the video card is implemented entirely in discrete logic. This is like using a bunch of small PLCs or relay logic to implement something complex instead of an integrated control. Many video cards of the era were built around CRTC (CRT Controllers), such as the Motorola 6845, which was common in the IBM PC video cards.

    Fadal generated the video with a bunch of 4 bit counters, a standalone 3.4992Mhz dot clock, and a shift register that is fed by the output of the character ROM.

    The 64x16 display area is stored in a pair 2114 1Kx4 static RAMs, giving a total of 1KB of video RAM. This hints at why the screen has noise artifacts. The video generator circuitry is constantly running, generating a video display while the machine is turned on. The main CPU of the control needs to write characters to the video memory and copy the contents when the screen scrolls. The cursor is implemented by a routine that blinks the < on and off by updating video memory.

    When you have a CPU that needs to read/write to memory and a video generator that needs to read the memory, there becomes a conflict. You could eliminate the conflict by signalling the CPU that the video display is during the vertical retrace (vertical sync) and only write to the RAM then, however this is not how Fadal did it. Video cards based on the 6845 can signal this vertical sync to the CPU, but the Fadal card simply allows the CPU to step on the video generator. That is, the CPU asserts control of the video memory, does its read/write, then deasserts control, allowing the video generator to read the video memory and render the screen. It's this heavy handed control of the video memory that results in the visual artifacts when the cursor blinks or the screen is updated.

    Looking at pictures of the later board revisions, they implemented a dual ported 1KB video RAM. This allowed the CPU to write to addresses arbitrarily and the video generator to read from the memory without any contention. The end result is that Fadal 1420-2 video card does not have the visual artifacts because the video generator can read the video memory while the CPU is writing and reading it. This point may seem rather minor to some, but for customers that paid the price of a small house in the 80's, it was a subtle, but welcomed improvement.

    The video generator circuitry is really rather simple. The 3.4992Mhz clock is piped into a latch that selects between the original frequency, or half that frequency (more on that later). Then the clock goes to an 8 bit shift register, which is loaded with each line of the character bitmap from the char EPROM. The shift register shuffles bits via an invertor directly to the output driver chip, which then controls a 2N3904 transistor and some resistors make an NTSC compatible video output. There is other logic to generate the sync signals, but the basic pixel pipeline is short and simple.
    The main clock also drives several counters which control the address lines of the video ram, stepping through all of the character locations. This gets somewhat complicated because of the next feature.

    The doublewide DRO feature of the video card is actually what is novel and uses up a significant portion of the logic on the board. If all you had to do was step through 1KB of ram and generate video lines, it could be probably half the chip count. The doublewide feature is enable by writing to the I/O port allocated to the video card. That I/O port is shared between the option bits (J2 where you specify baud rates and line voltage) and the double wide mode. In conjunction with a write to I/O port 32, the data line DO1 determines if doublewide mode is on or off. When a read from I/O port 32 is done, you get all the option bits. The Fadal control has the ability to set many of the critical hard power-on options in dip switches or jumpers. Specifically the backlash is settable in dip switches on the axis drive boards and the basic option bits are set on the video card. These settings are all adjustable via BL or SETP commands anyway, overriding the settings in the hardware.

    The doublewide mode is generated by keeping each pixel on for twice the time, by using a video clock that runs at half speed. This results in overscanning the characters from the first 32 columns of the display, creating a more legible font.

    So, to summarize, the Fadal 1420-1 video card was a clever piece of engineering, the primary complexity was driven by the need for a doublewide mode on the first 6 lines of the display and this is why Fadal didn't use an off-the-shelf card or copy and existing card.

    The 6845 CRTC doesn't offer a double-wide mode either, but it offers other capabilities. I think that since the roots of the Fadal control were based on hardware they were already familiar with, the Altair 8080 S100 bus computer, they decided to stick to the late 70's tech instead of embracing the early 80's tech that existed at the time.

    The IBM MDA Monochrome Display Adaptor used the 6845 CRTC, had 4KB of 2114 based static ram, and about 30% higher chip count, not to mention it was more expensive, by BOM standards. I think Fadal made the choices they did based on cost, owning the design, simplicity, and ease of manufacture. The board is a mix and match of 74 series TTL logic, with only a small number of costly components (RAM, EPROM, and Intel specific S100 bus interface chips).

  15. #30
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    Wow those gibs needed a shot of oil or two, about 15yrs ago... Good luck thanks for sharing.

    Charles

  16. #31
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    Quote Originally Posted by CBlair View Post
    Wow those gibs needed a shot of oil or two, about 15yrs ago... Good luck thanks for sharing.

    Charles
    Yeah, they are aluminum and it looks like electrolysis has taken its toll. The material is flakey and coming apart like it was sintered. Very pecular patterns in the material -- they are shot.

    Because of the corrosion, the original dimensions are not trustworthy, so I'll have to build a stack of gage blocks to determine what thickness of gib I need to order. But to do that I have to get everything cleaned up first and the table back on the machine

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    Here's the schematic for the Fadal 1420-1 video card. I'm sure there are some errors, I can almost guarantee there are a couple, buyer beware, YMMV, always wear your seatbelt, etc...

    https://drive.google.com/file/d/0Bza...ew?usp=sharing

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  19. #33
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    Quick update:

    Ordered new gibs, hopefully they show tomorrow.

    I have pictures of the restoration work on the ways, unfortunately the ways aren't spectacular.

    I pulled the CPU card and made a reader to download all of the ROM data from the CPU card, so I've got a copy of the system software that runs the control.

    I've begun disassembling the system software and learned that the video memory resides at address 0xfbc00, which matches up with my reverse engineering of the schematic.

    I also learned that Fadal did not adhere to the S100 standard as such, they seemed to use various address and DMA lines as card selects, to choose which bus card to talk to. I'm still unravelling this.

    Once I have gotten a bit further, I'll share why I pulled the ROMs and started disassembling them, I assure you it's a cool idea.

    Some trivia:

    There are 5 ROMs on the board, U1 is a lookup table, perhaps log or trig functions, there is only 2KB of table in this ROM (8KB ROM)

    The system software resides in U2, another 8KB ROM, of which only 6.5KB is used.

    The NC executive resides on U3, U4, U5, they are 32KB ROMs, no wasted space here.

    In total, the CNC control runs on 96KB of ROM for the control proper, 6.5KB for system functions, and 2KB for arithmetic lookup tables (that's what I'm supposing they are, I'll have to do more analysis).

    Your cellphone uses more than 96KB to bloop and flash when you turn it on.

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    G'day Perry,

    Thanks for an informative explanation of the process of restoration.

    Did I miss reading somewhere that you are an electronics engineer?
    I am not, but your explanations reminded me of an electronic engineer friend whom I helped in the early 1980 to build his first computer and his explanations of what was happening.
    I am glad you have this ability as it is this aspect of old CNC machines that makes most of us run a mile when offered a machine at a good price.

    Again thanks for your thorough explanations.

    Regards

    Quentin

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    Oh, I'm not an electrical engineer by a longshot, just someone who has tinkered with electronics since I was 12. I have picked up quite a bit over the years and designed a few boards (that worked), but engineer is a stretch.

    I'm like one of those country boys that has self taught themselves everything they know, some people just pick stuff up and understand it.

    Oh, I should add that the "country" I grew up in was the Santa Cruz Mountains, 20mi south of Silicon Valley. I was exposed to all manner of surplus electronics growing up, the valley was absolutely one of the neatest places to be in the 80's and early 90's because of all the innovation. Boom and bust, every bust resulted in lots of surplus parts ending up at one or more of the famous surplus joints. Back in the day it was Halted's, Weird Stuff, A-Z computers, Action computer, and a few other outfits that came and went. At one time Weird stuff was the biggest surplus place in the valley, just tons and tons of as-is stuff. The as-is stuff bore this saying on a sticker "Guaranteed not to work, if it does you can bring it back and exchange it for one that doesn't". Both Halted and Weird Stuff are still around, but they are much less vibrant and all that old nostalgia is now really expensive stuff that's sold to ageing geeks with large disposable incomes.

    My first several computers that I actually had a hand in, came from surplus, a MAD-1, a short lived DTK 286, and my first long term, a 386sx overclocked to 20Mhz, which had a 40MB hard disk and EGA graphics.

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    Update:

    Gibs did not arrive on Friday due to shipping snafu, gotta wait till Monday to hear the whirr of motors again.

    What does one do with the time? Well other than helping cut some firewood and doing some grocery shopping, I started on the schematic for the 1400-1 CPU card

    I figure I'm about half way done, I learned a lot about the architecture by reverse engineering the video card, and the CPU card is going faster because I can apply some assumptions.

    I built a ROM downloader a few days back and figured out the ROM addressing scheme in the process. I have some some reverse engineering of the software with the idea that I could potentially run the Fadal software in a virtual machine on top of a modern processor. I expect a modern processor to execute the old code much faster, even with emulation.

    My idea is to use the Intel Edison module to emulate the Fadal CPU card and potentially build a card that replaces the CPU, RAM, Video, and Serial interface cards.

    It's not going to be as straightforward as I hoped, while there are several emulators to choose from, none of them are nicely modular in a way that I can very quickly spin up a virtual Fadal control. The upshot is that the Fadal control is very simple from an architecture standpoint, probably half as complex as the original IBM PC -- no interrupt controller, DMA, floppy, timer chip, keyboard, etc. While it *does* have many of those capabilities, they are implemented as separate subsystems that talk to the main CPU as peripherals.

    To be honest, I'm just curious about how the original design was put together, there were 2 more major revisions, the -4/5 cards and the -6 card. My understanding is that the -6 card was probably rare, since it isn't listed on the repair sites, but there is one on ebay.

    The -4/5 cards are more complex, as the memory limit went from 422K to 16MB because they changed from an 8088 (IBM XT) processor to a 286/386sx (IBM AT) processor. There are considerable software changes that are required to address the full 16MB of memory on the 286/386.

    It so happens that Intel still sells the 386sx and 386dx, for about $8 apiece.

    In contrast, the Intel Edison is $50, has a 500Mhz dual core processor that supports virtualization, a 100MHz Pentium processor for ancillary tasks, builtin WiFi, USB, and 2 real serial ports. It also happens to run Linux, which I've been running for the last 21 years and I very proficient in Unix/Linux programming.

    Now you might ask "what gives, this dude is confusing me?".

    Ok, so in 2004 I decided to start a Machine/Fabrication/Electronic Fuel Injection shop. I was still working for a company at the time (home based job), so I setup my office in the mezzanine of the shop and worked from there. When I wasn't working I was tinkering.

    I purchased a 1540 lathe, Rong-fu mill drill, bandsaw, a lift, several welders, and a Shizuoka AN-S CNC mill with Bandit control.

    I retrofitted the Shizuoka with an Ajax CNC control, a DIY brand from Centroid. I built the computer and did all the wiring, etc myself.

    Fast forward 2 years and I bought a Hardinge CHNC-1 because I was making round parts for a customer and the manual lathe was getting tiresome. That machine was a basket case, I paid $1500 for a 'guaranteed not to work' machine. I bought a spare control for $300, swapped monitors, fixed some broken wires in the turret control, replaced some parts in the turret, replaced the X motor with an Ajax CNC retrofit motor, and fixed the original X drive amplifier. After that I had a semi-reliable lathe that made accurate parts. The drives started to fail, so I retrofitted AC motors and drives to the machine, I got them tuned really well, but they had a startup hiccup that caused problems.

    Anyway, the point is that I've always hacked on my machines and fixed whatever problems they had. The Fadal is really no different, the control seems to be robust and works, the mechanics not so much.

    But, this Fadal, the Hardinge, and many of the machines I've owned, they all have one thing in common: The controls are based on old tech that is hard to find now, not to mention expensive. Sure, you can retrofit, but I've never seen a retrofit that ended up being equal to and better than the original in every way, usually there is a compromise.

    I'm just looking at ways to address the ageing tech problem in a novel approach, using the skills I have. Right now my day job is a Principal Support Engineer for Oracle, supporting the MySQL product. When I wasn't supporting myself with machining (which was hard in 2008/2009/2010), I've been some mix of a software developer, system administrator, and support engineer.

    I got my professional start at 17 just out of high school, but during high school I was into computers and electronics and even played system administrator to the high school computer system for my Junior and Senior years -- nobody else wanted the (non-paying) job, and I got school credit for it. During the first half of my Senior year I had a real IRS after-school job fixing computers, before that I just did it casually for money since I was 15.

    What I've learned is that the people who knew much about a lot of these older machines, they've retired. There isn't anyone at Hardinge that can tell you how the CHNC collet closer comes apart anymore, he retired close to 5 years ago. Fadal is out of business, and while there are good folks selling parts, the true inner workings of the machines are a closely held secret by any who know.

    I have a friend locally who has a CHNC, and he sure likes to keep me on my toes, he's running production on one and has had the gamut of problems. I even swapped out all the RAM chips on his control CPU card because one of them was causing a drain on the backup battery circuit, leading to alarms and control errors. Those old Siemens 810 controls are based on the 80186 processor, it came after the 8086/8088 (IBM PC/XT) and before the 80286 (IBM AT). My first IBM compatible had an 80186, but it was buggy as hell because the 80186 isn't 100% compatible with the PC hardware chips.

    Well, that's enough rambling for tonight, good night all...

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    I only worked on the CPU board schematic a few minutes today, but I finished all the address decoding logic.

    The 8088 only has 20 address lines, of that, 16 of them are used for addressing segments of 64KB each. The address lines A16 through A19 are used as card selects to talk to the peripheral cards. There is a 4 to 16 line decoder that takes the upper nibble of the CPU address, then converts that to a selector that is 1 of 16 lines on the bus. Fadal repurposed a bunch of address and logic lines to make these card selects.

    A 20bit address is represented as 5 hex nibbles, like 0xFBC00, that's segment 15, address BC00. That happens to correspond to the video memory on the video card. The first F selects card 15, which is the video card (we are talking base 0 numbers here, so 0-15), the BC00 selects the base address within the F segment. The F segment also contains the system ROM, which is located at FE000-FFFFF, an 8KB chunk. The video ram is only 1KB, so it occupies addresses FBC00-FBFFF.

    It would seem that the memory expansion cards occupy a card select range, though I'm not certain exactly where the memory and NC executive ROMs are mapped yet.

    Once I have the schematic completed and the system ROM reverse engineered, I could design my own memory expansion card.

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    I'd be going for running the rom contents on MAME just like it was a video game, though the I/O issue probably brings its own complexity. I sure don't miss those 64k segments. Cool thread though

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    Jesus H Christ Perry !!!

    Looks like you really know your stuff inside and out. I can fix anything mechanical but know just enough to be real dangerous when it comes to computers. I can swap out an axis drive card like a real pro but it ends right there.

    I don't understand most of what you have written but enjoy reading it. I'm looking forward to seeing this machine make chips and can tell you won't be stopped from getting there. Today there are so many good used machines around but they lack support or people who know anything or enough about them to get them running again. Hardinge is a great example of this. I owned two CHNC's back in the 80's and 90's those are great machines and I know them inside and out mechanically. It's the things that could go wrong under the hood that keep me from buying a nice used one. I loved those machines they ran seven days a week and I built quite a shop around them.

    Good luck though I don't think you need it. keep us posted.

    Make Chips Boys !!

    Ron

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    I've finished the reverse engineering of the CPU board schematic, all except the little bit that does the battery backup of the memory (trivial).

    Here's what I learned:

    The system ROM, which boots up the CNC control and tests things, is located at 0xFE000, the lookup table ROM is located at 0xFA000, but only the last 2K is used, so the table starts at 0xFB800.

    The U3 user ROM, which contains 1/3rd of the NC executive, is at 0x00000, U4 is at 0x08000, and U5 is at 0x6000, with the onboard 32K of RAM at 0x68000.

    A little peeve/note about Fadal CPU boards. They DO NOT HAVE 38K, this is just a confusing doublespeak by sales/support people.

    The CPU has 32K of RAM, the video card has 1K of RAM, and each of the axis cards have 1K of RAM, that adds up to...you guessed it, 38K!

    I have to look at the code to figure out where the rest of the memory expansion address space is, but this is what I know:

    Segments 0x10000 through 0x5FFFF are open, that's 5 segments of 64K, or 320KB. I've read that the early boards are limited to 422K of RAM, so if we break that down from marketing speak:

    32K on board
    320K expansion
    6KB on the peripheral boards

    That leaves 1 more 64K chunk somewhere in the address space that isn't contiguous to the 64KB of ROM down low and the 32K ROM+32K RAM at 0x60000.

    I'll have to dig into the code to figure out when it senses the memory add-on cards and where they are located.

    The 8088 processor can address 1MB of memory, given the way they laid out the memory now, they've got a couple of holes in the address space, however due to the goofy addressing scheme where each segment is tied to a board select on the bus, they probably allocate 5 segments to the axis drives and maybe some more.

    Nothing really surprising or enlightening with the CPU card, all very straightforward, the most confusing part is the power on reset circuit, lots of annoying analog stuff to initiate the CPU reset.

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