February 14th, 2017, 01:11 PM
Hello, first poster here.. Found this site while looking around for info on my new machine, and decided I had to post this (plus I'm a big vintage computer fan with no forum memberships, so why not!)
I recently got hold of a strange machine that it took some real google-fu to figure out what was. I was told by the seller that it booted, he sent me pictures and I took a leap of faith.. What I got was a blackened, smudgy piece that smelled like someone that hadn't had a bath for a very, very long time..
Anywho, I cleaned it up, opened it up, took some pictures and tried it out - with the exception of the second floppy drive which is making some clanking noises, it works great!
My internet info consisted of http://www.vintagecomputer.net/raytheon/VT302/ and http://www.vcfed.org/forum/archive/i...p/t-13089.html (someone posted here a long time ago, apparently - but thread seemed to die out).
So, based on this and on my usage of it + the manual that came with it:
- This is a word processing computer (i.e. not really intended for general purpose - although internet suggests it runs BASIC)
- Intel 8085 processor
- Custom, really neat display processor - scrolling of text is super smooth, and some changes like looking at the full page or switching cpi makes the monitor interpret the signal differently (see pictures)
- SCSI printer interface (that's what it looks like to me, at least)
- Only date code I found was on the keyboard, which says May 83.
- Raytheon is the same as Lexitron, which made other word processors with what seems to be the same software (manual is from '81 and uses a VT1202 for illustration)
Nah, let's get on with the pictures!
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- The machine has an access panel in the back, so you can open it up and change logic boards without taking off everything
- The monitor is connected on a cable from inside the machine that's a bit tricky to remove and put in place.. I was careful when opening up, so thankfully nothing got broken
- Keyboard is REALLY comfortable - this is definitely meant to be a typing machine - also, there are tons of typing-specific keys on the keyboard. Wonder what switches those are As far as I know you didn't get Cherry switches at that time (05.83, when the keyboard chassis is timestamped)
- Disk drives are made by Qume - which also supplied the daisy wheel printer that came with it (computer says made in Japan, but disk drives are made in USA)
- When pressing the "full page" key, the monitor says "click" and apparently shows what I believe really is the entire video signal. When showing normal typing, it shows just a part of the page.
- Monitor has buttons to select print spacing, display spacing and character pitch - when switching to a lower character pitch, the monitor stretches the image horizontally to show less characters
- Changes are written to disk automatically - there is no manual save or undo. If you eject the disk, you get a warning beep and three seconds to insert it again. If not, document is cleared.
- As far as I know there is no soft reset - you're supposed to type on it, that's it. The manual says the computer can be left on all day with no problem.
- The monitor is extremely comfortable. No high pitched CRT noise, it seems to have some extra coating that makes it easier on the eyes (and most likely prevents phosphor burns as well)
- Scrolling is performed by arrow keys, but in an opposite (i.e. "modern") manner - you're moving the page, not the cursor, so up means move page up (= cursor down)
- There are at least three different ways to delete a character, but no way of a normal backspace (i.e. move cursor left, then delete character). The closest you have is similar to the DEL key on modern keyboards.
- You have a "direct mode" where you control the printer and the screen simultaneously. The printer types what you type, and when you move the page the printer does it as well - really cool! :P
Hope this was fun to read.. and if anyone can help me out, that would also be really nice. Because right now, I'm stuck with a few questions:
- How on earth can I get data off this thing? The only two connectors on the back are for the keyboard and the printer.
- What disk formats are used? Could I put some extra stuff here?
- Is it possible to still get ribbons for the printer? It's a Xerox branded cartidge, but I can't find any model number.
- Any tips on what could be the issue with the clanking disk drive? I'm a bit of a newbie on repair, so any tips would really be appreciated!
Have a good one, and what a nice forum you've got here!
February 19th, 2017, 08:52 AM
What floppies do you have for it? According to the links in your post, the existed a "word processor", "communications" and probably a "BASIC" program disk for this thing.
As for figuring out disk formats and getting data off, do you have another computer with a 5.25 inch drive in it?
February 21st, 2017, 10:28 PM
I have two copies of the word processing software (slightly different version number I think), in addition to a bunch of document disks. There is also a disk from the original dealer labeled "Lexitron MS-DOS disk" (or something similar - at the office right now but will check later) - however this doesn't boot, and I suspect that it is a way to somehow write documents to a disk readable by MS-DOS systems (I've seen a similar feature advertised in old magazines), but the word processing software doesn't accept it either.
I've got an Osbourne-1 in the living room which I'll try to use to read the disks. I also have a couple of XTs in the basement which I can try. Do you have any good tips on multi-purpose disk reading software?
February 22nd, 2017, 07:55 AM
This is the curiously labeled "MS-DOS" disk. I'll try to dig out an XT this evening and see if it might be able to read it.
February 22nd, 2017, 09:38 AM
Hopefully these posts end up in the correct order, as they have to be approved by a moderator first. Anyway, I checked the "LEXITRON MS-DOS" diskette and lo and behold, it seems like it is an MS-DOS formatted disk with Lexitron documents on it. Everything seems to reside in the WP_SPACE file. Why the Raytheon VT302 wouldn't read it I'm not sure - maybe I needed to use a newer version of the word processing program?
February 25th, 2017, 12:24 AM
Time for PSU
So I had been thinking for some time that perhaps I should check the power supply, since this thing is pretty old. My skills are limited, however, and although I know capacitors (and other components) can and will fail over time (and tremendously so in a power supply), this is a scary field to me.
But was it really necessary? I started to check the voltages - 5v was 5.1, 12v was 12.1 - so all seemed stable and nice. I don't have any oscilloscope, so was (and still am) totally oblivious to any dangerous spikes.
However, the machine has two 24V fans - and these were both fed 33V! Running fine though.. however I assume that's not quite as intended. So time to have a look at the power supply.. It's a huge, heavy brick in the middle of the machine, stretching from left to right. Shielded like hell (as is the rest of the machine), and my magnetic screwdriver started wobbling so much close to it that I tended to miss the screws (a bit overstated perhaps, but you get the idea ).
In order to detach all cables I had to also remove the CPU/RAM board and the Video card. I had a blissful break enjoying them:
Note the "Boot 0.1" - I assume this actually means 1.0, since the machine was bought in-store and is not a prototype. Or maybe when developing the ROM, it worked on first try
OK, fun's over.. The PSU was clamped shut and obviously not meant to be serviced too often. This is as open as I could get it without getting too creative.
187V-264V 50/60Hz goes here (yes, that is the acutal rating on the machine):
Is that C107 a bad cap?
And what's this switch?
The "gentle" side of the power supply. I guess these output 5V, 12V and 24V, respectively.
Let's one thing be clear. This thing absolutely TERRIFIES me. I'm pretty sure 33V on the 24V rail means I have to do something, though. I'm a bit desperate for some hand-holding here - any help would be greatly appreciated! I love this machine now, I use it regularly, but I have no idea how long it will last unless I do a proper inspection and replace whatever needs replacing.
February 25th, 2017, 08:54 AM
C107 does look pretty "bulged", indicating that it's either bad or about to go bad. You might consider replacing all of the electrolytics in the PSU, given the system's age.
February 26th, 2017, 07:10 AM
Chuck(G), you nudged me in the right direction I guess.. so I've taken out and opened the PSU and removed all the electrolytic capacitors.
Seems like the power supply has replaceable modules for the three voltage levels:
This is the main part of the power supply:
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I managed to remove all the caps after a few hours of toying with my soldering iron and the internet at my side. One of the caps (C107, the most damaged one) left its legs behind, but I guess I can just piggyback a new one on top of it?
So back to the caps - I noted down their position, capacitance, voltage levels and max temperature. However, some of them didn't have voltage, but "WV" - for example, "2200µF 50WV". What does this mean? And are there any other parameters I should have noted down? Some of the capacitors are marked "3UC" and "3BP" in addition to the model number, if that has anything to say.
Brand is Marcon. I've understood that brand is not in production anymore. Is there any specific brand I should choose if I want something of top quality?
March 19th, 2017, 08:51 AM
I've recapped the PSU now - my first recapping, so I stood ready with fire extinguisher and a lump in my throat - but it all went rather well. Only issue is some caps are larger than the original, so it got a bit cramped in there. Note the "Kemet" cap, I've never heard about this brand and it was horribly expensive.. $5 or so per piece! They look like a relic from WW2.. but at that price I have to assume they're able to survive anything??
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So, originally I started recapping because what I expected to be a 24V rail read at 33V. However, after swapping parts and putting the PSU together for test, it showed 31V -- still high. There are 4 potentiometers, one "main" and one on each daughterboard. However, no matter how much I turned them I couldn't get it lower than ~28V. The only one that did any adjustment was the main pot, two of the others did nothing and the third one adjusted the 12V.
So that got me thinking, either there is something else that is worn in the PSU, or I might be wrong assuming the 5/12/24V configuration. The reason I thought 24V was because the two fans are labelled as such. All three voltages go to the motherboard from where the monitor is powered as well. Could it be that 30-33V in fact was correct? The fans have been wired in a weird way, as if they wanted to hook them up in serial, so that could be an indication:
One of the two fans seems to have died since last time, though - so who knows. I opened up the monitor to see if there were any clues regarding input voltage, but couldn't see any. Maybe better trained eyes can spot them?
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Is there any typical standard voltage these old CRTs run on? I'm really longing for booting this baby up again but I'm worried I'll be tearing it away with that PSU.
March 19th, 2017, 10:18 AM
As a note, the second fan isn't dead - it seems to try to spin but apparently doesn't get enough juice. I tried to check how much I could crank up the voltage, but didn't get higher than about 34V, which didn't help. I am increasingly getting the suspicion that this power line shouldn't be 24V, however I haven't heard about anything requiring a voltage in the 28-34V range.
Note that the power given to the motherboard seems to be +5V, +12V, 0V, -15V and +15V. No -5V or -12V. The -15/+15 seems to directly correlate with the 30V output to the fans.
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