Identifying IBM PC XT model and year

[Stone]

The ProPrinter received a new ribbon and has been tested for communication with the PC: slow, noisy and grainy character output, just as I remember. Lots of pin-feed paper, though.

I have some NOS black ribbons for the Proprinter.

 

[clh333]

Modem connected successfully to another (I have a WinModem in this PC and a second phone line attached to it; can walk between the two to see either terminal).

The terminal software I was using, Com-It, uses a lot of reverse video. It revealed a lot of flicker (guess that's why IBM used high-persistence phosphor) and also variations in intensity (not software driven). Does this suggest power supply, i.e. capacitor, problems in the monitor? What else might it be?

Thanks again for your suggestions.

-CH-

 

[modem7]

I have the NEC V20 chip but have not installed it as yet, partly because I want to ask about the AST SixPack Plus. I read the thread from several years ago with comments by Modem7 about his experiences.

You will be writing of [this].

The compatibility issue might be a consideration, though apparently solvable, but the real questions are about the abilities of the AST SixPack Plus itself:

Can the RTC (clock) handle dates after Y2K?

Yes. See [here].

And can the AST board be used as expanded (i.e. up to 1 Mb) memory?

The SixPack Plus cannot provide expanded memory.

I already have a functioning board that takes system memory from 256 to 640K. If the AST clock is useless and the memory can't be used in conjuntion with my existing board then it won't be worth the trouble it might cause with the NEC processor.

According to [here], there are 4 models of SixPakPlus. Maybe the model that you have does not suffer from the problem.

Or should I upgrade the BIOS anyway?

There is a possible negative ramification of using the third (final) BIOS revision for the IBM 5160. It was reported in the thread at [here]. I have yet to do my own investigation.

 

[clh333]

The SixPack Plus cannot provide expanded memory.

According to [here], there are 4 models of SixPakPlus. Maybe the model that you have does not suffer from the problem.

Thank you for your reply.

I don't have a SixPackPlus (any more); I was considering acquiring one. Your reply has saved me from yet another error. It seems that what I want is a SixPack Premium. Is there any other card with similar abilities; i.e. expanded memory and RTC?

I had a SixPack, probably a Plus, in an AT&T PC6300 I owned back in the mid-'80s. As I recall I thought it was going to give me expanded memory but only could use it as a ram disk and printer buffer because the AT&T was already populate with 640K RAM.

Is there a repository for IBM BIOS versions' code? The ROMs are socketed... looks like 28 pins. Could a new version be burned to a 2764 or 27C64 and substituted? Or is there a better solution?

Thanks again for all your help.

-CH-

 

[clh333]

" Is there a repository for IBM BIOS versions' code? The ROMs are socketed... looks like 28 pins. Could a new version be burned to a 2764 or 27C64 and substituted?"

Sorry, stupid question. Found it here: http://www.minuszerodegrees.net/5160/motherboard/5160_u18_u19_sockets.htm. Who are these geniuses at minuszerodegrees.net, anyway?

I'm sure I have the early version of IBM's 5160 ROMs. I'm also sure I can find the ST M27C256B and burn it with v2 or v3 BIOS. I'm not sure about the wiring issue described here. My traces at U18 and U19 are uncut. Will it be necessary to cut them?

Thanks, and again, sorry to ask needlessly.

-CH-

 

[Malc]

Who are these geniuses at minuszerodegrees.net, anyway?

Modem7 is the Genius, It's his Website.

... I'm not sure about the wiring issue described here. My traces at U18 and U19 are uncut. Will it be necessary to cut them?

No, If you use the M27C256 or the AM27C256 as per the web page you should be fine, Also the TMS27C256 works too. Some older Eproms are incompatible with the way the U18 - U19 sockets are wired hence the mod.

 

[clh333]

Thanks for the clarification. I'll have to acquire the specific EPROM but I have a burner now...

I noted in an earlier post about the 5151 monochrome display. The flickering didn't bother me but I thought the variations in brightness might indicate a problem.

After thinking about it I decided it might be something as simple as dirty wipers on the pots so I decided to "exercise" them. When I turned up the brightness I was surprised at what I saw (picture attached).

The scanned area is considerable smaller than the glass tube face; the scan area is not quite rectangular and there are brighter lines among the field that are curved traces. I found a discussion of 5151 power supply repair here and from it I'm wondering if my 5151's power supply may be under-performing, perhaps due to aging, weakened caps.

No pops, no smoke, but maybe leaky? Or are we in spec?

Thanks again for all your help.

-CH-

P.S.: Fahrenheit or Celsius? Last winter we had minustwentytwodegrees... Fahrenheit.

View attachment 29370

 

[clh333]

Modem7 is the Genius, It's his Website.

.

I did not intend any insult by the term "genius" and I apologize if any offense was taken. Clearly an admirable work displaying exceptional knowledge and dedication, from which I have benefited greatly.

-CH-

 

[retrogear]

Can't open your picture, says invalid attachment

Larry G

 

[clh333]

Can't open your picture, says invalid attachment

Larry G

I'll try again...

-CH-

 

[retrogear]

That raster is ok. You need to do vertical linearity and vertical height adjustments. Your raster is compressed at the top and stretched at the bottom which linearity corrects. Also will straighten the curved lines which are supposed to be diagonal. The width is ok. It's not supposed to fill the screen horizontally. A quick and dirty way to adjust the vert ht and lin is to put on a screen full of text like all capital X. Then move the vertical hold control so the screen slowly rolls and the text should be equal heighth as it rolls. You could also turn the brightness up and just watch the black blanking bar scroll up and it will be easy to see if the height of that bar changes. It should be same thickness up through the entire screen. If your brightness range is too high there is also a sub-brightness control. Your brightness is cranked up too high which is why you have retrace diagonal lines now. Those controls are all on the back. Can't remember at the moment if there are holes in the back cover for a screwdriver or how it is but SAMS shows the locations.

Larry G

 

[Stone]

Your brightness is cranked up too high which is why you have retrace diagonal lines now. Those controls are all on the back. Can't remember at the moment if there are holes in the back cover for a screwdriver or how it is but SAMS shows the locations.

Actually, all those controls are *inside* the case which needs to be opened and removed to gain access.

 

[clh333]

Thank you for your reply.

Found the Sams document here.

Illustration of main board (annotated, attached) shows V-HOLD at position B, V-SIZE at C, V-LIN at D, SUB-BRIGHTNESS at A. These would be disk variable resistors, actuated with a small screwdriver blade (with one hand in a pocket)?

I assume E and F, CONTRAST and BRIGHTNESS, are pots for front panel controls.

Sams document says to turn up the brightness and contrast (E, F) fully and adjust sub-brightness (A) to an acceptable level where characters don't bloom. Would you do that last, after the other adjustments? How about focus? Before or after sub-brightness?

Never been inside one of these things and don't want to screw it up...

Thanks again for your help.

-CH-

 

[retrogear]

I didn't realize this was a part of a monster thread. I just jumped in when you started talking about distortion on the display. I looked back at some of your previous screenshots and the linearity looks just fine. Did something change? Are you using a different video card now? If the adjustments are all internal then nobody obviously tweaked them which is what I thought. It's possible that turning the brightness up too high to show retrace lines can shift the power load and cause linearity to shift, etc. If the text all looks uniform and with adjusting brightness / contrast you can achieve good text and focus then I wouldn't worry about adjustments. If something external changed to cause this then it does no good to adjust the display internally. I'm lost as to what happened ...

 

[modem7]

Who are these geniuses at minuszerodegrees.net, anyway?

Modem7 is the Genius, It's his Website.

I did not intend any insult by the term "genius" and I apologize if any offense was taken. Clearly an admirable work displaying exceptional knowledge and dedication, from which I have benefited greatly.

Genius? I'm not even 'smarter than the average bear'.

The web site is simply me creating a repository of information, primarily about the IBM 51xx series of computers.
Information has come from many sources, including many members of these forums.
It is a collective work, helping many, just like these forums.

 

[clh333]

Update:

Replaced Intel 8088 with NEC V20.
Replaced marginal B: drive Tandon TM-100 2A with 20 Mb Seagate ST225 HD. Loading config files, applications and utilities. Still running IBM PC DOS 3.3.

Identified problem with ProPrinter due to replacement ribbon cartridges: Case height (thickness) out of spec, causing ribbon advance not to mesh with printer advance gear. No advance = faded printing. Looking into re-inking OEM ribbons.

TBD:

Configure, install and test Everex multi I/O card as COM2: and LPT2:
Waiting for shipment of '256 EPROMs to update BIOS from V.1 to V.3.
Waiting for shipment of DTK clock card

-CH-

 

[Stone]

Identified problem with ProPrinter due to replacement ribbon cartridges: Case height (thickness) out of spec, causing ribbon advance not to mesh with printer advance gear. No advance = faded printing. Looking into re-inking OEM ribbons.

Can you post a pic of the ribbon? I have some sealed, NOS, black ribbons for an IBM PC Color Printer 5182. They are ¾" wide. That's the width of the actual ribbon material, itself.

Also, if your ribbons are dried out from age rather than used-up, a little squirt of WD-40 will rejuvenate them.

 

[clh333]

Can you post a pic of the ribbon?

Pics attached: shows the "IBM" OEM ribbon and one of the new replacements side-by-side. Physically they are identical in size; about 12.25 X 3.25 inches for the case, less than 1/2 inch for the ribbon.

I think the difference is in the mounting tabs at either side. Apart from a slightly different construction I also notice the tabs won't allow the replacement ribbon to "snap" into place. The drive wheel doesn't sit on the printer drive gear and so the ribbon never advances.

-CH-

 

[Stone]

I know it's messy but you could transfer the new ribbon(s) into the IBM cartridge(s). But if you wear surgical gloves...

 

[clh333]

I know it's messy but you could transfer the new ribbon(s) into the IBM cartridge(s). But if you wear surgical gloves...

Took one apart: I was amazed anyone ever put one together in the first place. No thanks!

But I did come up with a Rube Goldberg way to re-ink the IBM ribbon. It worked quite well: 1/2 inch variable-speed drill chucked to the advance knob, looped the ribbon over a stick with a pad on the end; saturated the pad with ink and let 'er rip - a lot faster than my old MacInker!

Not sure my ink was the best "solution", pun intended, but might try stamp pad ink next time.

Pics attached.

-CH-