ITT Xtra

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ITT Xtra

Postby SpidersWeb on Sun Dec 09, 2012 2:00 pm

So I'm currently in the process of restoring this lovely donated machine (thanks Jon, and thanks Terry for passing on his message), and wanted to make a thread on my progress. There will be video footage coming, because as I work on it, I'm leaving my camera recording continuously.

The machine was originally a 128KB RAM unit with twin floppy drives and a monochrome CGA display.
Later in life it's had a couple of upgrades, namely a 512KB RAM card and a 30Mb 3.5" Miniscribe hard drive unit.
It is complete including monitor and keyboard and in much better condition than I expected (visually).
Had not had power applied for approximately ten years.

Some interesting things about the machine I discovered:
- very very easy to work on, the engineers did a great job of making this machine servicable, screws are easily accessible, easy to find, and there isn't a huge number of them.
- real time clock standard as part of the display adaptor
- no power supply cables to the motherboard, it's done using a block of pins which slide in to the PCB of the power supply when installed.
- you can access the inside of the PSU without removing it from the case, two screws then slide the cover off
- PSU and floppy drive are both from Qume
- BIOS dated 1983, display adaptor dated 1985
- Intel 8088 with AMD support chips
- video card has a COM1/2 jumper, and a UART but no COM port attachment
- PSU has an output on the back which I beleive is to tell the monitor to turn on
- PSU is 200W and has a 24V fan
- motherboard takes up the entire base of the case but is very well spaced and easily laid out

Power Supply
I removed the power supply from the machine and removed large amounts of rust dust with a toothbrush, quite a few diodes with corrosion but still appeared connected - all capacitors visually appeared healthy.
Using a hard drive as a dummy load I applied power and nothing happened. Since many of these power supplies need a motherboard attached to turn on, and the connectors were non-standard, I tried it on the original motherboard. Nothing happened again. I checked the fuse and it was fine. I tested the +12V rail and found off I had 0V but on I had 0.04V (peak of 0.07 for a second).

With these voltages, I made a quick standalone video of the multimeter readings, when the 2 amp fuse went bang and I jumped like a little girl. A peak of around 1V (from memory) showed up on the multimeter.

No components were damaged. I'm going to do some investigating, and possibly send the power supply by itself to an electronics repair guy who has done work for me before. I think the fault is actually in the transformer units, the plastic covering which holds them together seems to have perished allowing the coils to move away.

Hard Drive
A 30Mb Miniscribe 3.5" in a 5.25" bracket. Would not spin up.

You'd apply power and after ten seconds just get error codes flashing at you. The error codes said to me the logic board was likely OK. I put my ear to it and could hear a hum before the light flashes - I suspected this was the motor engaging but it was unable to spin the platters. I removed the top drive cover, and found the platters to be stuck. With a little careful encouragement I was able to free them up. I applied power and she whirred up to speed, but still gave error codes, a second attempt and no codes. Put the lid back on with just enough torque for the rubber gasket to seal and connected to the 8 bit controller (I'd installed the card/controller in my 386 test machine).

First time, no 1701 from the controller, but then NO ROM BASIC (386SX33 with no EPROM sockets spare, and they still use this meessage), rebooted again with a floppy drive connected and it started chattering away booting DOS. I think the card requires a working floppy drive to be installed (possibly to complete it's A -> C boot sequence).

It is the loudest hard drive I have heard in a long time but it is happy now. It booted MS DOS 5 and started up an old version of Direct Access (the menu system). As usual I had a browse to see what programs were installed - see what the machine was used for - I didn't look at any personal documents. The usual programs like Wordstar,Fastwire and XtreeGold were on there, but the most interesting was MS QuickBASIC (not QBASIC) and source code for a project which appears to be designed to run the scoreboard at Eden Park.

I'm going to contact the owner and see if he wants anything retrieved, but at some stage this hard drive will get a low level format.

Floppy drive is up next, although I suspect after a clean it'll run perfectly. Monitor I can't test until the power supply is repaired.
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Re: ITT Xtra

Postby tezza on Mon Dec 10, 2012 9:16 am

It's good to hear about how this unit fared. I'm looking forward to some pics.
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Re: ITT Xtra

Postby SpidersWeb on Thu Dec 13, 2012 9:05 am

Will do some modelling shots in the weekend, and put up a little video footage (the psu going pop and me jumping is at least amusing).

I had a look at the monitor the other day. It appears to be DC operated. It has two leads, 9 pin and 3 pin. The 3 pin goes in to the back of the PSU and those leads end up in the internal low voltage section - I'm expecting the monitor is fed 12V or possibly 24V (like the fan is). Originally I thought the monitor had a mains plug, but realised yesterday it was just an IEC power cable that was wrapped around it!

I also believe it is a normal MDA display, not mono CGA. I was confused because every resource I found said '640x200' which is a CGA resolution, but the software on the hard drive was all configured for Hercules Monochrome graphics. The card has seperate MONO and COLOR outputs.

Will find out the real answer when it's running.
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Re: ITT Xtra

Postby SpidersWeb on Thu Dec 13, 2012 9:35 pm

Floppy drive has a dead short, 0 ohms, no visibly dead caps so I'll have to just remove (and take note) of parts until I find the faulty item.
It's a half height drive, but belt driven like the old Tandon's - so I'm keen to get it running!
Boringly the 1.2Mb I got off trademe recently worked first time.

I also tested the keyboard on a 5160 - no keyboard error but no keystrokes come through. On startup the num lock light flashes, so going to need to look in to that one as well. I want this entire unit running with it's OEM gear.

I've been unable to determine the input voltage for the monitor, its definately DC but that's all I know (from taking resistance tests and comparing with known point).
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Re: ITT Xtra

Postby SpidersWeb on Sun Dec 16, 2012 5:02 pm

Pulled out the floppy drive today and started removing capacitors directly on +5 to GND. After the fourth one, we had no more short!
Connected it to my 386 with a 360KB DOS boot disk, and she booted straight up. Didn't even need a clean, just a few leaky capacitors.

Power supply is showing good resistance on outputs and inputs, no shorts, so I'm confused. Being so close to christmas taking it to a professional probably wont help my cause just yet, so might be a while before a bootup.

Found my digital camera charger, so will do some pictures later, the machine is currently disassembled but I'll try put up something tidy.
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Re: ITT Xtra

Postby SpidersWeb on Mon Dec 17, 2012 8:35 am

Machine, less the drive carrier:
Image
Screen is the "amber" monochrome model. Has a 3 pin power cord which goes in to the PSU. Knob is brightness.

The original QumeTrack floppy drive (1984), I love the little arrows, and hard drive holder hiding a 30Mb Miniscribe RLL drive (1989) - currently connected to the 386 for testing and drive whiping (my 386 is actually booting off this setup at the moment). The drive uses a belt setup, it's the only half height drive I've seen that does.

Image

The motherboard takes up the entire case. This case is identical to the case used by the Acer 710 (made about 4 years later). Notice the white block - this what the power supply slots in to to provide power. Resistance measurements are making me feel optimistic about start up. ROM is dated late 1983. CPU is an Intel 8088 4.77 and two banks of 64Kbit memory (128KB total). On-board floppy as standard. Two sets of DIPs, I suspect the settings will be the same as the 1983 5150 board from IBM.

Image

The video card installed in the case (I put this in when resistance testing the +12 rail). Note the battery, and ROM chip. Up top near the middle there is also a UART, and at the bottom a COM1/2 jumper, but I don't think the header near the monitor ports is for a 25 pin serial.

Image

NB: I haven't cleaned the motherboard yet, you can see quite a bit of 'growth' on it near the empty RAM sockets.

Edit: just realised "Qume" was owned by ITT from 1978 to 1995ish, so that explains all the Qume bits.
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Re: ITT Xtra

Postby tezza on Mon Dec 17, 2012 10:19 am

Yes, it seems a bit dusty. Quite a few dip switches on the motherboard there?
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Re: ITT Xtra

Postby SpidersWeb on Mon Dec 17, 2012 10:22 am

Two sets. I haven't checked, but I suspect they're the same as the 5150 256KB board - one set for DRAM, the other set for configuring display type, floppy count, etc.

That dusty part is where the inlet on the case is, behind the louvers there is a plastic sheet to encourage air over the memory. There is a lot of 'growth' etc, so I need to remove the board and give it a light brush with isopropyl, but I'm trying not to touch the motherboard until I've applied power (so if something is wrong, I can tick off a handling-error as a possible cause), I have brushed off the rust dust though and tested for shorts - measurements were in range (compared to IBM boards).

Edit: although looking at the photos again, I should at least scrub up that area before applying power, which could be next weekend or over the holidays (I have to track the power lines to find the correct voltages, and then wire that to a spare ATX supply OR fix the original PSU)
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Re: ITT Xtra

Postby Carcenomy on Wed Dec 19, 2012 11:30 pm

Looks kinda like a Commodore PC board of that era with integration to that degree. I like it.
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Re: ITT Xtra

Postby SpidersWeb on Sun Dec 23, 2012 9:51 am

This company continues to amaze me with their engineering.

I removed the lid off the monitor to determine the voltage required. Two easily accessed screws under the screen (so you don't see them) and then everything slides apart. Unlike some of the mechanisms by IBM, HP, and Compaq it was easy to work out, easy to put back together, and still very strong.

Monitor runs on 12V DC, but the input is simply labelled V+. There is a big power transistor it feeds in to (JE3055), I'm not sure if this is used to downstep the voltage with switching, or a simple turn-on device. I know 12V DC is safe, so at some stage I'll attempt to use 12V. I measured the resistance from the emmitter lead of the transistor to the case and got a respectable 790 ohms.

The monitor interior is emaculate, it looks brand new in there. The base is completely empty - I suspect this case was only used because it's the same as Qume's old terminals which had circuitry in there.

Until I can buy a proper desoldering tool I've had to put the power supply to one side. Instead I've hacked open a 350W ATX supply, it fits inside easily. For the moment it's just using motherboard plastic feet but if I keep it in there for more than a test session then I'll be making a bracket. The actual challenge here is finding a way to connect to the motherboard without damaging it (so no soldering). None of the normal crimp terminals fit right, so I'm off to JayCar now...
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Re: ITT Xtra

Postby SpidersWeb on Sun Dec 23, 2012 3:39 pm

All done, ATX wired in. Motherboard cleaned too.
However I can't do anything now, because +5 on the motherboard is now showing only 14 ohms. Needs to be 100 ohms absolute minimum.

There is a tonne of caps on the 5V line, so putting the project down for the day, when I feel inspired again I'll go hunting for the bad cap. I guess before that I'll try using a toothbrush to go around the board just in case something got on it during cleaning. I wish I had a constant current power supply :/ That'd find the little bugger.

Oh and FYI, the connector, 3 x 3 with 3.94mm spacing between pins.

Code: Select all
BACK OF PC
+5   GND   +12
+5   GND   GND
+5   -12   GND

FRONT OF PC


-5 volts is produced on the motherboard, probably from the -12 line. There is no "Power Good" signal or anything like that, just 12,-12,5 and GND.

Edit: it's actually the power supply at 14 ohms, motherboard showing around 130ish, PSU wont power up (guessing short circuit protection) - how annoying!!
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Re: ITT Xtra

Postby SpidersWeb on Sun Dec 23, 2012 4:51 pm

Nevermind, I'm a bit spastic sometimes, I forgot the fuse and 13-14 ohms only adds up to around 300mA of current - but is a sign this PSU needs some cap replacements (a few don't look terribly healthy).

But the good news... IT BEEPED AT ME... just a single beep too, not an "I've lost my mind" beep-a-thon.
Now to pop in a video card and see what it says.
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Re: ITT Xtra

Postby tezza on Sun Dec 23, 2012 5:14 pm

SpidersWeb wrote:But the good news... IT BEEPED AT ME... just a single beep too, not an "I've lost my mind" beep-a-thon.
Now to pop in a video card and see what it says.


A single beep is good! :)
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Re: ITT Xtra

Postby SpidersWeb on Sun Dec 23, 2012 5:20 pm

Usually it is! I was excited but unfortunately no luck after popping in a video card.
It gives a single beep but no text on screen, then nothing happens for a while, then it repeats (as if it failed on something and wants to try again)

I guess I'll need to fire it up with the LanSoft ROMs and see if it responds to those.

The fact it's beeping to me means that the LanSoft ROMs should work, because we know the CPU / ROM part is working.
ROMs are 27128 x 2 - pretty sure I already have some with the LanSoft image installed.
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Re: ITT Xtra

Postby SpidersWeb on Sun Dec 23, 2012 9:17 pm

Split the 256kbit version of the LanSoft ROM in to HI and LO files, and doubled them up so I can just use 27C256 chips (because I have heaps of those and they're easier to program - less write current means I don't have to compensate for a poor power supply design in my burner).

Now just waiting for my EPROM eraser to do it's business.....
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