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Dec wt78

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MossyRock

Experienced Member
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Dec 6, 2016
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I've acquired a WT78, RX02 dual drive, a DECPrinter III, and its mobile cart/rack. Attached is a stock photo of a WT78 system unit.

It's all been in storage for about 20 years, I estimate. There's some corrosion and rust here and there on the peripherals and mobile cart/rack, so the storage environment was not ideal.

I powered on the WT78 with no peripherals connected and the "CPU OK" and "DC OK" LEDs illuminated, but there was nothing on the CRT, even after several minutes of warm-up. I did hear a high-voltage whine from the CRT transformer(s). I turned up the CRT intensity and it blew the 3A fuse. I replaced the fuse with one of exact specifications and it did not blow. The original fuse had probably become brittle. However, nothing ever appeared on the CRT - no cursor, no raster, even after a generous time for warm-up.

There was no smoke or sparks, no unusual smell.

I can find no archived service manuals on the WT78. The closest manual I can find is one for a VT52. The WT78 is a VT52 with an added motherboard and other parts to make it a computer.

The VT52 service manual says that a blinking cursor should appear after power on and 30 second warm-up.

Does anybody know if the WT78 behaves in the same way - should a blinking cursor appear power on and warm-up, or perhaps a BIOS message?

I'm not experienced in working with CRTs, and as such I am not going to attempt anything inside the unit. If there's trouble here, I'm going to donate it all to a local computer museum.

Thanks.
 

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Neat find on the WT78 as it appears to be complete. Personally, I think that design (ie VT52) is timeless. I commend you for not attempting to go inside and look around. There are fewer and fewer of us left that are (or used to be) competent to go into a potentially lethal high voltage CRT circuit. I remember having a VT52 at one point hooked to a PDP-11/23+. You had to have a large desk and a strong back as I recall. I guess this old DEC stuff is like antique cars, there are still some great barn finds out there. Best of luck with it. Perhaps someone near to you will jump into it with you to get it fired up.

-Ken
 
Chuck,

It is difficult to see without taking the whole thing apart. Opening the top cover doesn't completely do it as there is an additional shroud inside that covers the CRT assembly, and there is only a small opening in this shroud, in the yoke area.

However, in darkness, through the opening, I can see no signs of a heater glow in the neck of the CRT.
 
Thanks, Chuck,

"I'm not experienced in working with CRTs, and as such I am not going to attempt anything inside the unit. If there's trouble here, I'm going to donate it all to a local computer museum."

I've notified Living Computers + Labs Museum that I'm willing to donate it to them. It will take them a while to respond, or they may never respond...

In the meantime, I'll extend this to anyone else in the Seattle area: If you want this system, will give it a good home, and not destroy it/part it out, send me a PM.
 
Well, I'm sure it'll go to a good home.

But that's par for the course on these old bits of kit--it's better than an even bet that there's something wrong with them.
 
pbirkel,

You are correct in that it wasn't a WT78! However, upon closer inspection, I've determined that my photo is actually a VT78.

I'm not sure of the differences between a WT78 and a VT78.

Thanks.
 
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I emailed him the question of what the differences were.

I would assume it would be the same hardware but with different software. From http://www.old-computers.com/museum/computer.asp?st=1&c=369 :

"The VT78 came with a FORTRAN, a BASIC compilers, the PAL-8 assembler and various other utilities."

Probably the WT78 omitted these and included the word processing programs, but could also run end-user programs such as legal management software packages. I know mine did as it was in a laywer's office in Portland, OR, and came with a legal management software package manual.

I reassembled the items that I had apart and cleaned everything up. It's now just a static artifact. The DECPrinter III is not pictured as it is in the worst shape and hasn't been attended to yet. Pictures attached.
 

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Vince responded to my question about what the differences are between a VT78 and a WT78, and he gave me permission to post his response in this thread:

Q: "Do you know what were the differences between the VT78 and the WT78? Was it just software differences, i.e., the exlcusion of compilers, etc., and inclusion of the word processing software?"

A: "The VT/78 was an early micro (6100 based) PDP-8 that came with floppies and ran the standard OS/8 software, including PAL/8, Fortran, etc.

The WT/78 is the same hardware, except for some labeling. I believe it was shipped with a version of WPS, the menu based "office software" operating system.

Later 6120 based Decmates have the brain-dead terminal interface, and various attempted software kludges that CJL is so offended by.

So, yes, I think your characterization is correct. I wish I knew of an authoritative place to confirm what software shipped with the WT/78, but everything I have seen so far supports the theory that it came with office (rather than scientific) software."
 
So imagine that’s basically just a primitive word processor, still it would be a great system to have and play around with a word processor that’s running on a PDP-8, got lots of newer system that can compile and run DEC code but a signal function DEC word processor that’s floppy disk base would be sweet! Would the operating system be in ROM with the disk just as a storage medium? Or would you have to load the operating system each time you start the workstation?
I would want to have one of those systems just for that function. Wonder how it would compare to an early PC running Word Star? Can’t think it would compete with a later product like Microsoft Works.
 
The VT/WT78 does do more than run WPS. It's not a single function word processor. It does run OS/8 and therefore can run the basic interpreter and fortran compiler. It is the forerunner to the VT278 (Decmate) which I have a few of and does the same (but the 278 has a full 32kW of memory). Although the VT278 has the screwed-up device 03/04 interface, it still runs OS/78 just fine. Albeit slow, the 278 will run Adventure.

I would like to find a VT78 myself someday. I have the experience of working on CRTs safely and would be able to keep it going. Such things don't seem to show up in the metro NYC area though.

Lou
 
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