PDA

View Full Version : Early PC 6300 Help



marcoguy
January 8th, 2016, 09:47 AM
Hi all, it's been a while :)

I'm posting today because a friend of a friend was cleaning out his attic, one thing lead to another, and I'm now the proud owner of two working 6300s, plus a monochrome monitor, two keyboards, and the original docs and software :D

Cracking open the earlier of the two units was a little bittersweet, there was some damage to the frame in one corner that required me bending it back into place so I could slide the bottom cover off, and when I did I found that some spiders made a home in the underside of this system. After a little cleaning, however, I was overall pleased to find that the only component that had suffered damage was the internal speaker, which had detached from the motherboard. Not even any corrosion on the RTC battery. I was more pleased to find that the BIOS in this thing is 1.0, dated 5/84. That makes this a very early system, as according to Wikipedia AT&T didn't launch the 6300 until June of that year. This leads me to my first question: Is this BIOS revision particularly rare, or of value to anyone here? I can't seem to find any info about the 6300's BIOS online, other than the fact that many systems shipped with 1.21, and that the last revision was 1.43. Does the 6300's BIOS differ at all from that of the M24? Other than the BIOS, I can't find any indications that this machine is a particularly early one. The RAM was upgraded to 640k, and it was upgraded with a long dead ST-225 (which definitely wasn't original as the drive labels on the front are "A" and "B," suggesting this was originally a dual disk drive system). There are also three 16-bit connectors on the bus extender on this older system rather than two on the newer one, but I don't know if that is of any significance. Anyway, if someone has info on anything to look for in this system unit that would differentiate an early 6300 from a late one other than the BIOS revision, that would be much appreciated so I can get a better idea of the system I have.

The more recent of the two systems has a BIOS version 1.1 which, to my knowledge, is relatively early as well. This system is pretty standard, but it's causing me an issue. I built one of James Pearce's amazing ISA compact flash adapters a while back, and was able to successfully flash the 8k IDE_XT ROM and use this card in my Deskpro 286. However, when I insert this board into either 6300, they are able to detect an option ROM at C800:0000, which is correct, but the XT-IDE BIOS isn't loaded by the system. I just get "No fixed disk present" and it attempts to boot from the floppy drive. I've inspected the jumper settings and, using the manual fir reference, configured one of the systems to "use external hard drive code" (which I take to mean the system will assume there is an HDC installed with an on-board BIOS), but no dice. I won't be able to access either system for a day or two, but I could take a few pics of a boot up to show the issue when I get the chance. Until then, I'd appreciate if someone had some insight into how the 6300 handles option ROMs, and if it differs from that of a standard PC compatible.

One last bit of info, one of the keyboards isn't an original AT&T. Its a Key Tronic KB5151, and it appears to have been sold specifically for the 6300, as it's compatible both electrically and in protocol. I wasn't aware of any 3rd party keyboards for the 6300, and I found it interesting as this KB has a superior layout compared to the original AT&T keyboard IMO.

Well, there you have it. These are my two latest acquisitions, and some of my favorites. The PC 6300 is my favorite XT compatible, and I'm very fortunate to now have two in my possession. I haven't yet decided what the fate of these systems will be, I might keep one and sell one, or maybe set one up with the original AT&T peripherals, and the other with a VGA monitor/adapter and the 3rd party KB. Either way, I'm glad to finally have a 6300 in my collection. I look forward to running Windows 1.03 with the AT&T drivers. :) I appreciate any help that anyone has to offer, thank you.

Compgeke
January 8th, 2016, 10:06 AM
The more recent of the two systems has a BIOS version 1....I built one of James Pearce's amazing ISA compact flash adapters a while back, and was able to successfully flash the 8k IDE_XT ROM and use this card in my Deskpro 286. However, when I insert this board into either 6300, they are able to detect an option ROM at C800:0000, which is correct, but the XT-IDE BIOS isn't loaded by the system. I just get "No fixed disk present" and it attempts to boot from the floppy drive...Until then, I'd appreciate if someone had some insight into how the 6300 handles option ROMs, and if it differs from that of a standard PC compatible.

One of the first things you're going to want to do is find a copy of the PC-6300 BIOS 1.43. I had to do that in order to use a Future Domain TMC-850 in my PC-6300 and even then there were occasional issues of it wanting to boot from floppy first. If you have a programmer and a few spare ROMs the images are easy to find. If not, asking around here usually turns up someone willing to write 'em for a few bucks.

NeXT
January 8th, 2016, 10:23 AM
Not even any corrosion on the RTC battery.
Remove it. I don't care if it even checks good you MUST remove it.
Myself included, we've been discovering that if the battery leaks, no matter how clean the board looks after the machine seemingly drops dead. We still can't figure out what causes it.

marcoguy
January 8th, 2016, 10:32 AM
One of the first things you're going to want to do is find a copy of the PC-6300 BIOS 1.43. I had to do that in order to use a Future Domain TMC-850 in my PC-6300 and even then there were occasional issues of it wanting to boot from floppy first. If you have a programmer and a few spare ROMs the images are easy to find. If not, asking around here usually turns up someone willing to write 'em for a few bucks.

Well, its a good thing I've already got a copy of the 1.43 BIOS coming in the mail ;) I'm hoping the BIOS upgrade will fix the way it handles expansion cards with on-board ROMs, and based on your experience with the TMC-850 it seems that's true to some degree.

EDIT: Don't worry NeXT, that was the first thing I did after opening the case

Stone
January 8th, 2016, 10:49 AM
Remove it. I don't care if it even checks good you MUST remove it.
Myself included, we've been discovering that if the battery leaks, no matter how clean the board looks after the machine seemingly drops dead. We still can't figure out what causes it.Probably the same scenario that many boards appear to succumb to after battery leakage. The leakage gets to the inner layers (that are not visible) of the board and destroys some traces there. I have several different boards with battery leakage where all the visible surface traces are continuous or have been successfully repaired to become continuous but still will not function. Apparently there is internal damage that is neither visible nor accessible.

Chuck(G)
January 8th, 2016, 11:08 AM
I replaced the leaking 6300 NiCd battery with a plain old coin cell in series with a Schottky diode. Works fine. One thing works to your advantage--if the battery leaks in a 6300 that's been stored in a "working" orientation (i.e. not on its side), the goop from the battery will tend to drip away from the inverted motherboard. As documented in other threads, there are modifications to the bus converter board that can make for better operation.

IIRC, there were some issues with the XTIDE board and the 6300. Check your data by using DEBUG to dump the area starting at C800:0.

marcoguy
January 10th, 2016, 03:11 AM
I've always loved the 6300's downward-facing motherboard for that among other reasons. A nice piece of Italian engineering :)

Chuck, is this (http://www.vintage-computer.com/vcforum/showthread.php?11712-Wanted-bus-correction-kit-for-AT-amp-T-6300-(Olivetti-M24)&highlight=6300+bus+converter)the bus converter mod you're talking about? If so, I might have to see about implementing that in one of my systems. It seems like it would be pretty handy to have.

I'll be home later today, and can dump the XTIDE BIOS with debug then to see if the data is intact/being read properly. However, from the research I've done it seems the 6300 BIOS 1.43 should help with the issue.

1ST1
January 10th, 2016, 08:17 AM
Please note that with BIOS 1.43 the meanings of the dip switches will change. You have to resetup your harddisk dip switches.

Seagate ST225 is not the original harddisk when Olivetti shipped out M24 with HDU kit. Usually it was Olivetti Lexikon 5520 harddisk, which has the same CHS parameters as ST225.

Chuck(G)
January 10th, 2016, 08:58 AM
My own 6300 has an 80MB "hard card" drive, and, although I've reported on using the XTIDE and issues, I've largely forgotten about it. Something about using the "Chuck Mod" on the XTIDE requiring special code because 16-bit I/O instructions on the 6300 fetch the high order byte first, then the low order, instead of what the 8088 BIU does.

Sorry that I can't be of more help, but memory of the events is suffering from wetware bit-rot.

Krille
January 11th, 2016, 06:58 AM
My own 6300 has an 80MB "hard card" drive, and, although I've reported on using the XTIDE and issues, I've largely forgotten about it. Something about using the "Chuck Mod" on the XTIDE requiring special code because 16-bit I/O instructions on the 6300 fetch the high order byte first, then the low order, instead of what the 8088 BIU does.

Sorry that I can't be of more help, but memory of the events is suffering from wetware bit-rot.

I think this (http://www.vintage-computer.com/vcforum/showthread.php?19591-XTIDE-tech-support-thread&p=242162#post242162) is what you are referring to.

AFAIK, there shouldn't be any problems as long as you're using the "XT-CF 8-bit PIO mode". It's the default (and also the slowest) transfer mode on all XT builds with XT-CF support and compatibility with these machines is the very reason for that.

Oscar
January 11th, 2016, 10:26 AM
Originally Posted by NeXT

Remove it. I don't care if it even checks good you MUST remove it.
Myself included, we've been discovering that if the battery leaks, no matter how clean the board looks after the machine seemingly drops dead. We still can't figure out what causes it.
Probably the same scenario that many boards appear to succumb to after battery leakage. The leakage gets to the inner layers (that are not visible) of the board and destroys some traces there. I have several different boards with battery leakage where all the visible surface traces are continuous or have been successfully repaired to become continuous but still will not function. Apparently there is internal damage that is neither visible nor accessible.

I have a battery goop damaged 6300 as well. Actually, the Olivetti M24 version of it. It has the classical symptoms of this problem.
There's no visible damage, it must be a matter of eating away the inner layers.

Very unlikely, but does anyone have the PCB layout sheet showing what traces pass by the battery area?

Getting the M24/6300 going is one of my to-do projects.
Assuming the battery goop does not travel very far inside the board, it must be one or two bad traces at most.

Regards,

Oscar.

marcoguy
February 9th, 2016, 08:38 AM
Alright, time for an update. I've finally got one of the 6300s up and running with BIOS 1.43. However, I'm still having some issues with the XT-IDE BIOS. I've since built another one of James' boards, this time his Lo-Tech 8-bit IDE adapter. I've tested it on a 486 computer of mine and it works fine with the BIOS provided on James' site. However, when plugged into the 6300 with the same hard drive, the BIOS now loads thanks to the AT&T BIOS 1.43, but no drive is detected. I've tried flashing the XT-IDE BIOS with the controller setting set to PIO mode, but no luck. Has anyone else had this issue with the 6300 and an XT-IDE card?

NeXT
February 9th, 2016, 08:48 AM
I have a battery goop damaged 6300 as well. Actually, the Olivetti M24 version of it. It has the classical symptoms of this problem.
There's no visible damage, it must be a matter of eating away the inner layers.

Very unlikely, but does anyone have the PCB layout sheet showing what traces pass by the battery area?

Getting the M24/6300 going is one of my to-do projects.
Assuming the battery goop does not travel very far inside the board, it must be one or two bad traces at most.

Regards,

Oscar.

Whatever it is, it's not something super critical or major. When I hung a logic analyzer off the EPROMs and CPU I was finding the Data bus was pushing 1's and 0's around and it would go silent when the RESET was asserted but beyond I could not tell exactly why there was data flying around or what it was coming from. It's not like the systems go 100% brain dead. Even if it's pure garbage it's trying to do something.

Krille
February 9th, 2016, 09:29 AM
Alright, time for an update. I've finally got one of the 6300s up and running with BIOS 1.43. However, I'm still having some issues with the XT-IDE BIOS. I've since built another one of James' boards, this time his Lo-Tech 8-bit IDE adapter. I've tested it on a 486 computer of mine and it works fine with the BIOS provided on James' site. However, when plugged into the 6300 with the same hard drive, the BIOS now loads thanks to the AT&T BIOS 1.43, but no drive is detected. I've tried flashing the XT-IDE BIOS with the controller setting set to PIO mode, but no luck. Has anyone else had this issue with the 6300 and an XT-IDE card?

Regular 16-bit I/O doesn't work on these machines. That's why you need to use the XT-CF 8-bit PIO mode. That mode in turn is only supported by ATA-2 compliant drives, ie Compact Flash cards and Microdrives. There are also "real" harddrives that support this transfer mode but they are rare.

marcoguy
February 9th, 2016, 10:16 AM
Ah, thanks for the info. I wasn't educated as to the nature of 8-bit PIO, and didn't realize it would restrict me to 8-bit ATA compliant devices. Time to get a CF adapter :)

Trixter
February 9th, 2016, 12:44 PM
I was more pleased to find that the BIOS in this thing is 1.0, dated 5/84. That makes this a very early system, as according to Wikipedia AT&T didn't launch the 6300 until June of that year. This leads me to my first question: Is this BIOS revision particularly rare, or of value to anyone here?

I'm not sure if it is of any value to anyone, but that is indeed exceedingly rare. They switched to the 1.21 BIOS fairly early on, although the 1.43 BIOS is what you want because it enhances compatibility (later versions of Microsoft Word for DOS require the 1.43 BIOS) and allows for add-in video cards. I've never seen the 1.0 BIOS; if you can dump it before replacing it, that might be nice to archive somewhere.


There are also three 16-bit connectors on the bus extender on this older system rather than two on the newer one, but I don't know if that is of any significance. Anyway, if someone has info on anything to look for in this system unit that would differentiate an early 6300 from a late one other than the BIOS revision, that would be much appreciated so I can get a better idea of the system I have.

I don't think I've ever seen that before -- cool. You may want to leave that one alone as stock or something.


I look forward to running Windows 1.03 with the AT&T drivers.

Geoworks Ensemble using the AT&T drivers is also wickedly fast and impressive. However, it locks up if you swap your 8086 for an NEC V30, so you have to keep the 8086 if you want to run it.

Krille
February 9th, 2016, 01:22 PM
I guess it should be possible to add a transfer mode specifically for Olivetti machines. Something like this;


; Reading from drive
in ax, dx
xchg ah, al
stosw

; Writing to drive
lodsw
xchg ah, al
out dx, ax


It would be slow but would allow use of normal harddrives.

Am I correct in this line of thinking? What do you Olivetti experts say?

Trixter
February 9th, 2016, 01:56 PM
Seems ok to me, but someone should rope Chuck(G) in to verify. Are all communications (not just sector transfers) with the hardware performed in 16-bit words? If not, my concern would be reading the final single byte reliably.

I question the usefulness of doing this though. CF cards are such an improvement over period hard drives (10x or more IOPS, capacity, small size, silent) that I can't imagine anyone preferring anything else...

Krille
February 23rd, 2016, 12:51 AM
Time for an update.

I went ahead and added a new device type/transfer mode to XTIDE Universal BIOS based on the idea I wrote about in the above post. It's the same code as used in the "XT-CF PIO16" mode except for the xchg instructions added as above. Marcoguy then kindly tested the new build on his machine and the results are very strange.

This image is with the regular "XT-CF PIO16" mode;
29758
This image is with the "XT-CF PIO16RO" mode (RO as in Reversed Order);
29759
As you can see (hopefully, unless the forum destroys these images), the problem is not (only) that the byte order is swapped. It appears that there's a single odd byte inserted somewhere which cause the bytes to be swapped across word boundaries.

If someone could determine exactly what happens when doing 16-bit I/O on these machines (and provided there's no data loss in transfers) then I'm sure we could add a compatible transfer mode to the XTIDE Universal BIOS.

Bottom line is; I need help with this.

Trixter
February 23rd, 2016, 06:09 PM
I'd love to help but I'm not knowledgeable at that low a level. Would a link to the hardware/tech schematics help? Try this: ftp://ftp.oldskool.org/pub/drivers/ATT6300/Documentation/Olivetti_M21_M24_Theory_of_Operation_Nov84.pdf
Specifically pages 3-2 and 3-3 describe how 16-bit transfers work.

I have the actual 6300 tech ref somewhere; it's the only thing I haven't scanned and put online because it's a beast. But I'll give it my best effort if the above document doesn't help, just let me know.

Chuck(G)
February 23rd, 2016, 08:44 PM
I keep telling myself that I shouldn't get roped in again.

For what it's worth, I already have a hard disk on my 6300 and it works fine. But if this was my system and I had to use the XTIDE CF board, I'd just set the configuration to do 8-bit transfers. CF cards can do this very easily, but not so much with PATA drives.

Trixter
February 23rd, 2016, 09:02 PM
But 16-bit transfers in an 8086-based system are SEXY, Chuck! Where's your sense of adventure? Where's your desire for MAXIMUM SPEED?

;-)

1ST1
February 23rd, 2016, 10:36 PM
I would love to have a 16 Bit XT IDE BIOS which runs fine on the M24!!! Please implement it! (as boot device and as 2nd device controller)

marcoguy
February 25th, 2016, 08:00 AM
I agree, while not necessary, 16-bit transfers on the 6300 would be pretty sweet :)

I can't offer much in terms of low-level coding, but as I did with Krille, I can always help with testing should someone choose to work on this. I'd love to see it implemented.

Krille
March 1st, 2016, 05:52 AM
I'd love to help but I'm not knowledgeable at that low a level. Would a link to the hardware/tech schematics help? Try this: ftp://ftp.oldskool.org/pub/drivers/ATT6300/Documentation/Olivetti_M21_M24_Theory_of_Operation_Nov84.pdf
Specifically pages 3-2 and 3-3 describe how 16-bit transfers work.
Thanks for the link! Unfortunately, it didn't help. It was an interesting read though. Just imagine what it would be like if modern computers would come with documentation with that level of detail. :)

I have the actual 6300 tech ref somewhere; it's the only thing I haven't scanned and put online because it's a beast. But I'll give it my best effort if the above document doesn't help, just let me know.
I wouldn't want to put you through all that work of scanning everything. However, parts relating to the Bus Converter Board and other relevant stuff such as source listings that does I/O (if such is available) would be nice.

Another idea; I'm sure we're not the first ones to try this. Were there software or hardware back in the day that claimed to be compatible with these machines? If so, a peek at the disassembly of such software might provide some hints?

1ST1
March 1st, 2016, 08:51 AM
However, parts relating to the Bus Converter Board and other relevant stuff such as source listings that does I/O (if such is available) would be nice.

I have the same level detailed description "Theory of Operations" for Olivetti LSX 5010/5020 CP486 M486 PCs (BA867, BA886, BA894,BA887, BA892 mainboards) it includes all logics, GAL listings and so on, same style like the M21/M24 document. But as that are 486/EISA boards with optional Weitek 4167 and i860 "coprocessor", 64 bit memory interface and some onboard interfaces, and a very special EISA VGA card (EVC-1) and EISA SCSI (ESC-1) controllers which have some acelleration by the i860 (if it's available), onboard diagnostics with own LCD, that book is much thicker, it's in A4 format and about 8 cm thick... Scanning would be possible as I have access to a scanner with automatic sheet feeder... (I also have two of these machines)

Trixter
March 5th, 2016, 10:09 AM
I wouldn't want to put you through all that work of scanning everything. However, parts relating to the Bus Converter Board and other relevant stuff such as source listings that does I/O (if such is available) would be nice.

Another idea; I'm sure we're not the first ones to try this. Were there software or hardware back in the day that claimed to be compatible with these machines? If so, a peek at the disassembly of such software might provide some hints?

They likely just do 8-bit transfers. Chuck had this to say in another thread: "On the 6300, the problem was the hardware 16-bit-to-8 bit BIU implemented in external hardware that was the problem. It wasn't so much the MOVSW (which works okay), but the IN AX,DX instruction. The Olivetti engineers didn't quite get it right." To me, that sounds like there is no way to fix this, if it's a bug in the hardware?

6885P5H
March 5th, 2016, 11:46 AM
I have the same level detailed description "Theory of Operations" for Olivetti LSX 5010/5020 CP486 M486 PCs (BA867, BA886, BA894,BA887, BA892 mainboards) it includes all logics, GAL listings and so on, same style like the M21/M24 document. But as that are 486/EISA boards with optional Weitek 4167 and i860 "coprocessor", 64 bit memory interface and some onboard interfaces, and a very special EISA VGA card (EVC-1) and EISA SCSI (ESC-1) controllers which have some acelleration by the i860 (if it's available), onboard diagnostics with own LCD, that book is much thicker, it's in A4 format and about 8 cm thick... Scanning would be possible as I have access to a scanner with automatic sheet feeder... (I also have two of these machines)

Wow, scans of this would be very nice indeed. Do you own an M486? That one has a simple front panel unlike the towers you mentioned. I myself have managed to gather a bunch of the Pocket Service Guides that were once available on Olivetti's support site. I have all of the guides related to the SNX and NetStrada systems in English (and I have Italian versions of two of them), and a lot of the ones from the M24 up to the early M6 supremas. I have almost none of the guides for the late 486 and Pentium systems though but I do have a few including M6 520/540/560 suprema and Envision. I could send them to you in a zip package if you want...

marcoguy
March 24th, 2016, 03:40 PM
Alright, I've made some progress.

I ended up biting the bullet and acquiring a few CF cards and adapters for use with the 6300 as well as a couple other vintage PCs of mine. In the AT&T box, it worked like a charm with my ISA CF adapter. I've now got it booting to AT&T's OEM of MS-DOS 3.3 and talking to an NE2000 in 8-bit mode. Man, Windows 1.03 is sweet with the AT&T drivers :)

However, I've run into my next hiccup in this project. I've got a GSI Model 12 4-floppy controller that fits in an 8-bit ISA slot and can handle just about every PC format 360K-2.88M. Obviously, to get this functionality in an 8-bit compatible, the card uses its own BIOS. The card has the option to be used as either the primary or secondary FDC. Given the fact that the 6300 has an on-board FDC and doesn't seem to have a DIP switch option for no diskette drives (unless I'm missing something), I configured the original Olivetti 360k drive as drive A: on the 6300 controller, and I set up the Model 12 to function as a secondary controller with a 1.44M drive connected.

Unfortunately, when I boot the system and the Model 12 BIOS loads, it seems to hang on the following screen:
http://i.imgur.com/qlVDf2xl.jpg (http://i.imgur.com/qlVDf2x.jpg)

However, I've found that if I keep my finger on the INSERT key for long enough (maybe 30 seconds) I'll get this:
http://i.imgur.com/yYggnM5l.jpg (http://i.imgur.com/yYggnM5.jpg)

Which is odd because, to my knowledge, BIOS shadowing did not exist on the 6300 :p

This one's got me stumped. I was thinking it could be some sort of interrupt conflict, but I've tried the card with IRQ 3, 5, and 6, and DMA 1, 2, and 3. I've also tried changing the option ROM starting address, c800h through e000h. However, all my efforts have been met with the same results. Is it possible that the 6300 is messing with the BIOS data itself, or is it that the third party FDC is just conflicting with the on-board controller and I should give up hope of high-density media on this thing? As always, any help would be much appreciated.

Trixter
March 24th, 2016, 03:50 PM
Remember that IN AX,DX does not work on the M24/6300. If the floppy BIOS has that instruction anywhere, all bets are off. Considering that your floppy controller was made 4 years after AT&T and Olivetti thought the system would be functional (the RTC only goes to 1992), I think it is likely that it does, and that you cannot use that controller with the 6300.

If you *must* have 3.5" in some capacity, you can use "drivparm=/d:1 /f:2 /t:80" in config.sys to connect a DSDD 720K drive to the second floppy header.

marcoguy
March 24th, 2016, 05:41 PM
Ah, alright. Thanks for the info, Trixter. I feared there was some incompatibility of this nature with the BIOS on my FDC, especially considering the later manufacturing date. I also have a ~1992 generic HD 8-bit FDC that I've tried in the system but experienced similar results with. I'm sure you're right, the developers of cards such as these definitely didn't have the 6300 in mind so it's likely that IN AX,DX would have been used. I'd like to have 3.5" access on this system for compatibility reasons if nothing else, so I'll probably end up using that drivparm line you mentioned. Again, thanks for the tip.

Also, I'd just like to add that the information you've published online over the years about your experiences with the 6300 are a big part of what got me interested in the machine and in vintage computing as a whole. I just want to thank you for that. You do great work, man :)

Trixter
March 24th, 2016, 08:45 PM
I'd like to have 3.5" access on this system for compatibility reasons if nothing else, so I'll probably end up using that drivparm line you mentioned.

Just be sure to test it -- I had some odd issues with data getting silently read or written incorrectly and I never tracked it down. I had to resort to using pkzip just so I could be 100% sure my transfers weren't corrupted (pkzip calcs a CRC).


You do great work, man :)

The 6300 was the first system our family owned, and I used it daily for hours for a period of 5 years. It has a special place in my heart.

marcoguy
March 25th, 2016, 07:57 AM
Alright, I fired up the system with drivparm parameters you described, and although it was originally having issues writing disks, I swapped out the ALPS 3.5" drive I was using for an older Teac model and now everything seems to be running smoothly. I even used pkzip for a few transfers and CRC checks to ensure everything was working as it should, and I haven't seen any problems yet.

Where I eventually hope to go from here with this system is to track down an AT&T or Olivetti Display Enhancement Board, EMS board, and color monitor so I can get something out of those proprietary 16-bit expansion slots that help make this system unique. On that note, I know the DEB and EMS boards are a long shot, but if anyone has any of the aforementioned equipment, feel free to drop me a PM. :)

Also, I currently have a ROM programmer headed my way, so I'll be able to dump the ROMs in the earlier 6300 with the REV 1.0 BIOS. I'll have that uploaded somewhere hopefully some time next week.

1ST1
March 25th, 2016, 12:38 PM
Somewhere (was it 6300 shrine?) an adapter was described, for how to use color mode of M24 with a VGA multisync monitor. Quite difficult to get the original color monitor...

marcoguy
March 25th, 2016, 12:54 PM
I've seen that document, it's on this (http://www.olivettim24.hadesnet.org/doc.html) site. I certainly wouldn't mind building an adapter for my Multisync, but ideally I would like to source an original. I can't imagine it being any harder to find than the other two items I'd like to upgrade this system with, which are both pretty much unobtanium.

Trixter
March 25th, 2016, 01:13 PM
Not to discourage you, but just so you know what you're getting into:



I've had only one color monitor, purchased with the system
It took me 28 years to find an EMS board
It took me 31 years to find a DEB (which I am still negotiating a price/trade for)
An AT&T Mouse shows up on ebay about once a decade (the logitech-branded equivalent, about once every 3 years)


Because the keyboard is also proprietary, I have sometimes considered buying a complete nonworking system just to get a spare keyboard.

The 6300/M24 line is a very difficult clone to collect and care for!

marcoguy
March 25th, 2016, 01:31 PM
You're absolutely right, most of this stuff is virtually impossible to source. This is a very hard PC to find parts for, but I'm currently pretty optimistic. I saw 2MB EMS board go for about $30 on Ebay last year before I realized what it was, and I just recently scored an AT&T mouse for that price. That said, I'm not being unrealistic. I don't expect to find everything I'm looking for tomorrow, and am willing to wait however many years it might take. I've grown a sort of soft spot for this system as I've worked on it, and despite its limitations, it's been extremely rewarding. I hope to one day have a system as complete as yours, but until then, I'm more than happy with mine as-is.

By the way, I assume you're the one getting the DEB card here (http://www.vcfed.org/forum/showthread.php?51405-Working-AT-amp-T-PC6300).
I can't say I'm not jealous :p I PMed the guy on the 26th but never got a response. That said, you certainly deserve it more than I do :)

marcoguy
April 4th, 2016, 01:44 PM
Well, I had a bit of good fortune recently!

I noticed a mislabeled "AT&T Terminal" that had been sitting on Ebay for a few weeks and looked suspiciously like a 6300 Color Monitor based on a few pics I've seen and the lack of a keyboard connector. Well, it arrived at my doorstep today and after a quick visual inspection and a test, it seems my hunch proved correct:

http://i.imgur.com/KGVPGPvm.jpg (http://imgur.com/KGVPGPv)

However, as can be seen from the image above, there seems to be an issue with the height of the picture. At the top of the viewable screen area, graphics and test appear just fine, but the lower portion of the screen is distorted and brighter than the rest of the screen, as if the pixels are being compressed vertically. Here are a few more pics to showcase the problem:

http://i.imgur.com/WO5figpm.jpg (http://imgur.com/WO5figp)

http://i.imgur.com/tUUyXDxm.jpg (http://imgur.com/tUUyXDx)

http://i.imgur.com/NeSWEbnm.jpg (http://imgur.com/NeSWEbn)

And here's the display without anything connected:

http://i.imgur.com/SepmTJVm.jpg (http://imgur.com/SepmTJV)

I'm inclined to believe that this is a capacitor issue, as so many older monitors have them. However, before I open the thing up and go digging around, I'd love to hear any input on what might be the root of this issue and how I could resolve it. At any rate, I sure am glad to have come across this gem.

Trixter
April 4th, 2016, 03:21 PM
Damn, I'd found an AT&T monitor listing that turned out to be an AT&T terminal! Guess I need to widen my search parameters.

My color 6300 monitor doesn't have the issue you're describing, but the intensity gun isn't firing so I only get the first 8 colors. I hope someday to know enough about electronics to repair it.

This document may help: http://www.repairfaq.org/sam/montest.htm

marcoguy
April 4th, 2016, 03:58 PM
Yeah, it took me a while to find this one because it was listed in some category I wasn't searching - I only found it because, on a hunch, I searched "AT&T Terminal" in all categories. Sometimes you just get lucky :p

Anyway, thanks for the link. There's tons of info in there that I look forward to going through and using for some troubleshooting.

marcoguy
April 5th, 2016, 12:59 PM
Alright, the research I've done today has led me to believe this is a vertical deflection issue, most likely one of the electrolytic caps. I cracked open the monitor and made a list (https://docs.google.com/spreadsheets/d/1OjM-y64T1qyGLZNUA5lE5wUY1DQzm8KdacVqjky6ZVA/edit?usp=sharing) of every tin can I could find. I think I'm just going to recap the whole thing, which will hopefully solve this issue and prevent similar problems in the future. If anyone notices anything obviously wrong with that parts list or has any advice on tackling this project it'd be much appreciated.

retrogear
April 5th, 2016, 01:24 PM
Any manufacturer name or model internally? Any internal adjustments you can see? Maybe take some good pictures of the circuit board component side. You definitely have a vertical linearity distortion. If all sides are compressed or distorted it could be what's called a low B+ voltage which is usually like 100-120 VDC. Sometimes there is an adjustment for that too. Yes, it could be caps but a schematic could sure narrow the possibilities. See any horizontal bars or wave moving up or down the screen?

Larry G

NeXT
April 5th, 2016, 02:10 PM
Ignoring retrogear above, DO NOT TOUCH ANY OF THE INTERNAL MONITOR ADJUSTMENTS UNTIL AFTER THE RECAP. If all it needs is the recap then everything should snap back to normal once you're done without any adjustments, if you fiddle with the controls before the recap you will have to go over them again after the recap and while monochrome displays are WAY easier to adjust it's still a total pain to get everything nice and perfect again.

Chuck(G)
April 5th, 2016, 02:45 PM
Because the keyboard is also proprietary, I have sometimes considered buying a complete nonworking system just to get a spare keyboard.

Do you think there would be an interest in a PS/2 to 6300 adapter? It probably wouldn't support the mouse, as I don't have one with which to test.

retrogear
April 5th, 2016, 03:39 PM
Replacing all caps just seems like a lot of unnecessary work to me. Vertical height and linearity adjustments are very easy on monochrome. Besides, who else might have tweaked the adjustments before selling it?
Agreed, adjusting a power supply voltage is not a good idea but then again, if it has an adjustment, who's to say it wasn't already moved? Adjustment controls go bad too. Yes, caps opening with
age are the most likely culprit.

marcoguy
April 5th, 2016, 05:57 PM
Well, just to clarify, this is a color monitor. The images I was displaying on it were in black and white because Windows 1.03 uses the AT&T 2-color hi-res driver. The picture is stable, there are no bars or waves moving up and down.
There are 15-20+ POTs spread out on the driver board, controlling various aspects of the vertical and horizontal geometry and the color intensity etc. I'd rather not play around with them without knowing what I'm doing, especially if they aren't the problem. At any rate, I don't think this is an adjustment issue, because if it were then I would imagine the picture would be uniformly compressed rather than the uneven distortion that it's exhibiting.

I just pulled apart the monitor again and took a closer look. I couldn't find any branding other than the CRT being made by Hitachi. I replaced a questionable looking 100V/100uF capacitor with a known good one that I pulled from another ailing CRT monitor, and had everything reassembled for testing before it occurred to me to take pictures. Unfortunately, the results were the same. All the other electrolytics passed a visual inspection, but still could very well be dried up.

It looks like the next step in this project is going to involve some more recapping. It would certainly be helpful to have a schematic so I could see which components are directly involved in handling the vertical deflection, but without any real branding inside the monitor, I doubt I'd be able to find one unless someone happens to have a service manual from AT&T.

Chuck, I would certainly be interested in such a project, but I don't know how many others would share that interest :p
That said, I would be more than happy to lend you my 6300 mouse for a couple months if you did want to work on an adapter with mouse support.

Chuck(G)
April 5th, 2016, 06:03 PM
I'll think about the project--the problem is, like so many other vintage things, is the low interest level.

NeXT
April 5th, 2016, 06:45 PM
Well, just to clarify, this is a color monitor. The images I was displaying on it were in black and white because Windows 1.03 uses the AT&T 2-color hi-res driver.
Right my bad. I misread earlier and remembered my own monochrome screen is green phosphor.
But yeah, color is even worse to fiddle with. convergence, geometry and purity can be a nightmare.

Trixter
April 6th, 2016, 11:05 AM
Do you think there would be an interest in a PS/2 to 6300 adapter? It probably wouldn't support the mouse, as I don't have one with which to test.

The mouse appears to be an OEM'd Logitech P7 series. I have a Logitech P7 with the same connector and it looks and works identically; only the branding is different.


Vertical height and linearity adjustments are very easy on monochrome.

While the monitor has a user-serviceable vertical height adjustment, it does not have linearity adjustments. The monitor definitely needs servicing.

1ST1
April 8th, 2016, 01:34 PM
I have checked my 1992 Olivetti Pocket Guide for Video Units. Unfortunately the M19/M24/M28 monitors are not in there. For all monitors in there it describes every setting. But I have little experience as I already fixed a M24 monochrome monitor with similar error. This was quite easy, it was not a capacitor, but the potentiometer for vertical height which had contact problem between the middle pin and ther rest. For a first test contact spray did the job, then after finding out it's value I replaced it. The point was that these potentiometer which were used inside this monitor are very open one, that means the resistor and the variable contact were not encapsulated in a chassis and I think the whole thing oxidized.

Chuck(G)
April 8th, 2016, 01:47 PM
Isn't the 6300 monitor line made by Hantarex? If so, there may be information on the monitor kicking around as such.