Compaq SLT/286 Prototype Revival

[compaqportableplus]

I can't believe it finally happened! I finally found a prototype Compaq SLT/286, something I've wanted for years now. I have a prototype SLT 386s/20 (signed by Rod Canion himself!) as well, which some of you may remember my post about. The SLTs are one of my favorite computers.

My oldest production Compaq SLT/286's serial number is 1842HU40184, meaning it was made in the 42nd week of 1988 (the 2nd, 2rd and 4th digit of the serial is the manufacture date.

When this one popped up on eBay I had a closer look and saw that the serial is 1837ZU3Z0271! That means this laptop was made in the 37th week of 1988, which makes it very early for an SLT/286. The two letter Zs in the serial pointed to it being a prototype as well. I'm not sure what they mean, but the only other SLT/286 I know of with two letter Zs in the serial is another (even earlier) prototype owned by a computer museum. Those two letter Z's are letter H's on the production models.

Here's some photos of the unit.











It is missing the rear port door unfortunately, but I'm not too worried about that.

One thing odd you may notice is that the label on the rear with the FCC ID and model number belongs to an SLT 386s/20! I was initially perplexed by this, but I noticed something under the sticker so I peeled it back and here's what I found.




I gasped when I saw that, because this 100% proves it is a prototype. That is leftovers from the old sticker that said something to the effect of "Property of Compaq Computer Corporation NOT FOR RESALE." I saw a pic of another prototype one that had sold on eBay many years ago with a label of that exact size in that exact location. I believe it also said something about the machine not having proper FCC approval yet from what I remember.

Really not sure why someone felt the need to peel that off and install a ID label for an SLT 386s/20, but oh well.

Another slightly unfortunate thing is that someone completely removed the original hard drive. They even took the entire drive enclosure and all of the screws! Thankfully, I had an extra drive enclosure and spare 20MB Conner drive, so I threw that in there. It's a Conner CP-3024, so it's not the exact drive it came with, but close. The original Conner CP-3021s are very hard to come by unfortunately, but I'll find one someday.

Time for some system board photos now. I thing I'm close to my attachment limit for one post, so I will continue this on in a second post.

 

[compaqportableplus]

So here's some pics of the system board where several differences from the production model can be seen.









Notice how the CPU is socketed? Production models had soldered CPUs! Notice there are quite a few bodge wires as well. And those light blue connectors for the internal PSU and LCD is another sign of it being a prototype. One computer magazine that reviewed the SLT in 1988 had a prototype test unit, and their system board looked EXACTLY like mine!

Here's a link to that (it's not in English, but you can see the pics of the board).

http://www.digitanto.it/mc-online/PDF/Articoli/080_102_107_0.pdf

Pretty incredible I think!

Oh, and the internal PSU had been replaced with a slightly newer one (black font on the switch), but I had a more appropriate older one with the white font on the switch I installed.

So there you have it, a prototype SLT/286! This is definitely one I'll never get rid of. Was in a pretty sad state when I received it, but we got it all fixed up! Only thing I haven't done is modded the Dallas chip, and I may not bother. Since it's such a special unit I don't mind running the diags on each cold boot. It's not like this will be my daily driver or anything.

 

[compaqportableplus]

Here’s another difference I noticed as well.

On the left is the handle of my early production SLT/286 made in the 42nd week of 1988. On the right is the prototype.



Notice how the rails on the production handle are a dull silver finish, but the rails of the prototype handle appear to be chrome plated!

Not entirely sure what the deal with that is or why they chrome plated the rails of the handle on the prototype. It does look super cool though!

 

[compaqportableplus]

Oh, something else I completely forgot to add, is that someone upgraded the ROM chips in this unit at some point. You may notice they have 1989 copyright dates on them.

The chips contain BIOS version 12, but I believe this would have had version 6 originally. I swapped them out for a version 7 set that I had, which gets it fairly close to original at least.

 

[compaqportableplus]

Found another small difference on this SLT!

The plastic part (which is molded into the back panel) that fills in the notch behind the power switch is completely smooth and untextured, which is common on prototypes. It's the piece that has a red arrow pointing to it.



That part is textured to match the rest of the case on production models.

 

[wulp]

When I see and read this, you are truly an expert!
And then I have a question for you.... I have 2 SLT's 286. One has "Compaq" on the handle, the other does not.
Do you have an idea why?
Thanks!

 

[compaqportableplus]

When I see and read this, you are truly an expert!
And then I have a question for you.... I have 2 SLT's 286. One has "Compaq" on the handle, the other does not.
Do you have an idea why?
Thanks!

Thank you! I don’t know if I’d call myself an “expert,” but I definitely have tried to gather as much knowledge about these as I can.

Typically, it’s the earlier production models (47th week of 1988 or earlier) that don’t have the Compaq logo on the handle, although there are some VERY late (1991 to 1992) models that also don’t have the logo.

Starting in around the 48th week of 1988 they started putting the “Compaq” label on the handle, and continued that until around late 1990.

What’s the serial number on your two units? With that, I can tell you exactly when they were made.

 

[wulp]

I have 3 Compaq. A 386s/20 of which the label is no longer so clear, and two 286s, one with and one without 'Compaq' on the handle.
And so I wondered why that happened.
In attachment I added photos of the 3.
Thank you in advance!

 

[compaqportableplus]

I have 3 Compaq. A 386s/20 of which the label is no longer so clear, and two 286s, one with and one without 'Compaq' on the handle.
And so I wondered why that happened.
In attachment I added photos of the 3.
Thank you in advance!
View attachment 1267186 View attachment 1267187 View attachment 1267188

Excellent. The 286 on the top is one of those very late production units I was referring to, it was made in the 34th week of 1991.

The 286 in the middle was made in the 11th week of 1989.

And finally the 386s/20 on the bottom was made in the 21st week of 1991.

The SLT 386s/20s typically don’t have the logo on the handle, but some of the VERY early ones do. I have only seen a handful of those.

 

[wulp]

Thanks!

 

[rayman1968]

As someone who started working for Compaq in December of '88 at the tail end of the assembly line (known as clean and close), I can tell you a couple of tidbits about the SLT's. The blue wires on the boards are from a rework. Meaning there were issues found during production testing that required fixes. These fixes would be done in the form of these reworks and were allowed to ship with these wires installed. Future revisions or spins of the system board would incorporate these fixes. Another tidbit for you, the first digit of the serial number is for the site location it was built at. I don't remember all of the site numbers but can tell you 1 was for Houston. Early SLT production was done at the Sommermeyer location, a warehouse type setup that I worked in from 12/88 until 6/89, when we moved to a newly built CCM6. CCM6 was on the main campus located south of Tomball, TX. SLT 286's, 386's, LTE's and Presario all in one units would all come out of either CCM5/CCM6 through the early to mid 90's.
The poster above with a couple of serial numbers starting with 8, I think those might be Scotland built units.

 

[compaqportableplus]

As someone who started working for Compaq in December of '88 at the tail end of the assembly line (known as clean and close), I can tell you a couple of tidbits about the SLT's. The blue wires on the boards are from a rework. Meaning there were issues found during production testing that required fixes. These fixes would be done in the form of these reworks and were allowed to ship with these wires installed. Future revisions or spins of the system board would incorporate these fixes. Another tidbit for you, the first digit of the serial number is for the site location it was built at. I don't remember all of the site numbers but can tell you 1 was for Houston. Early SLT production was done at the Sommermeyer location, a warehouse type setup that I worked in from 12/88 until 6/89, when we moved to a newly built CCM6. CCM6 was on the main campus located south of Tomball, TX. SLT 286's, 386's, LTE's and Presario all in one units would all come out of either CCM5/CCM6 through the early to mid 90's.
The poster above with a couple of serial numbers starting with 8, I think those might be Scotland built units.

Wow, that’s so cool you worked on the assembly line back in the day! That must’ve been an awesome job.

Great info, thank you! Very cool to finally know what the first digit of the serial means. My earlier SLT serials all start with a 1 and my later ones start with a 6. I assume the “6” means a CCM6 built unit?

And what does a serial number that starts with “0” mean? The only other prototype SLT/286 I know of (owned by Computer History Museum) has a serial number that starts with a 0. It’s an older prototype than mine, made in the 30th week of 1988 if I remember correctly. I wish I could buy it from them!

 

[rayman1968]

Correct, serial #'s starting with 1 would indicate units built at that Sommermeyer facility and Serials with 6 would have come out of CCM6.
I'm guessing....Serials starting with 0 were prototype/non-production/non-revenue units.

I've had an SLT286 for about 20 years that one of my Engineers had set out for scrap. I neglected to grab the power supply that went with it as I really only wanted the laptop to set on a shelf as a memento. Recently I came across a seller on eBay who had crafted his own power supply for an SLT he was selling and I asked him to build and sell one to me. He did so and it works great. I had a lab tech I've known for many years do the battery mod for me to use a socketed coin cell and I'm currently waiting for two 1MB memory modules to arrive from New Zealand. My hard drive was erased by the Engineer who was scrapping it. I have another co-worker who's been helping me with creating disks and we'll be installing Windows 3.1 after the memory is installed. Basically I just want to be able to power it on and show it to these new hires coming out of college who haven't seen what 36 year old laptop technology looks like.

 

[compaqportableplus]

Correct, serial #'s starting with 1 would indicate units built at that Sommermeyer facility and Serials with 6 would have come out of CCM6.
I'm guessing....Serials starting with 0 were prototype/non-production/non-revenue units.

Interesting! I would love to know for sure what the 0 means, but we may never know. I have a couple of Compaq prototypes that start with 0, an SLT 386s/20 and an unreleased LTE 4/100cx (you can search here the forums and you'll see them), one prototype that starts with a 6 (an LTE 386s/20) and the prototype SLT/286 I started this thread for, which starts with a 1.

I wonder why some non-production units start with a 0 while others start with the more typical 1 or 6? Perhaps it's the earlier stage protos that are 0? I'm thinking that's probably it. For example, the SLT/286 I started this thread for is definitely a later stage prototype, though it does still have some definite differences to production models, such as the socketed CPU. And the remnants of the paper "Property of Compaq, Not For Resale" sticker is a dead giveaway also.

And also, do you happen to know exactly which week full production of the SLT/286 started? The oldest production unit I have seen was made in the 42nd week of 1988, and I actually happen to own it! I have yet to find or see an older one that isn't a prototype.

Here's the serial on that one.


It also has the more typical two letter H's instead of the Z's like both the newer prototype that I own, as well as the older prototype that CHM owns. I have never owned or seen any others with the Z's. That other proto SLT/286 that was on eBay years ago (that I foolishly passed on) probably had the Z's also, but I just don't remeber. It was almost just like mine though, and it still had the "Not For Resale" sticker fully intact. It was in the exact same location the peeled-off sticker on mine was.


Do you know exactly what those Z's and H's are for?

 

[compaqportableplus]

I've had an SLT286 for about 20 years that one of my Engineers had set out for scrap. I neglected to grab the power supply that went with it as I really only wanted the laptop to set on a shelf as a memento. Recently I came across a seller on eBay who had crafted his own power supply for an SLT he was selling and I asked him to build and sell one to me. He did so and it works great. I had a lab tech I've known for many years do the battery mod for me to use a socketed coin cell and I'm currently waiting for two 1MB memory modules to arrive from New Zealand. My hard drive was erased by the Engineer who was scrapping it. I have another co-worker who's been helping me with creating disks and we'll be installing Windows 3.1 after the memory is installed. Basically I just want to be able to power it on and show it to these new hires coming out of college who haven't seen what 36 year old laptop technology looks like.

Nice! Yeah, the PSUs are hard to find by themselves, you ususally have to buy a whole system to get one (which I have done many times). Good excuse to get another SLT!

I'm not at all surprised to hear it fired right up and works fine, because you CANNOT kill the SLTs! They are some of the most reliable systems I have ever touched. For example, I have spent far more time using my SLTs than I have spent reparing them. Not to mention the SLTs are easy to service and look great. Nice form factor too and the removable keyboard is just the coolest thing ever. I first discovered the SLT back in 2011 and they have been one of my favorite vintage laptops ever since. Compaq made such great stuff back then!

 

[rayman1968]

Interesting! I would love to know for sure what the 0 means, but we may never know. I have a couple of Compaq prototypes that start with 0, an SLT 386s/20 and an unreleased LTE 4/100cx (you can search here the forums and you'll see them), one prototype that starts with a 6 (an LTE 386s/20) and the prototype SLT/286 I started this thread for, which starts with a 1.

I wonder why some non-production units start with a 0 while others start with the more typical 1 or 6? Perhaps it's the earlier stage protos that are 0? I'm thinking that's probably it. For example, the SLT/286 I started this thread for is definitely a later stage prototype, though it does still have some definite differences to production models, such as the socketed CPU. And the remnants of the paper "Property of Compaq, Not For Resale" sticker is a dead giveaway also.

And also, do you happen to know exactly which week full production of the SLT/286 started? The oldest production unit I have seen was made in the 42nd week of 1988, and I actually happen to own it! I have yet to find or see an older one that isn't a prototype.

Here's the serial on that one.

View attachment 1275276
It also has the more typical two letter H's instead of the Z's like both the newer prototype that I own, as well as the older prototype that CHM owns. I have never owned or seen any others with the Z's. That other proto SLT/286 that was on eBay years ago (that I foolishly passed on) probably had the Z's also, but I just don't remeber. It was almost just like mine though, and it still had the "Not For Resale" sticker fully intact. It was in the exact same location the peeled-off sticker on mine was.

View attachment 1275277
Do you know exactly what those Z's and H's are for?

Sure, full break down of your serial:
1 8 42 HU4H 0184
1 Is site build location, 8 is 1988, week 42, HU4H is the model number of the unit and 0184 is the 184th unit built that week for the particular model.
Compaq launched the SLT 286 publicly on October 17th, 1988 which was week 42 of the year. I don't what was the week cutover between prototype and production but I would guess somewhere around 2-3 weeks before launch since you would want product on hand ready to sell at time of launch. (So the serial number we broke down above was indeed built the week that the SLT286 was announced).
On your other serial, I suspect the Z's also represent that it's a prototype unit, I but I do not know that for certain.

 

[compaqportableplus]

Sure, full break down of your serial:
1 8 42 HU4H 0184
1 Is site build location, 8 is 1988, week 42, HU4H is the model number of the unit and 0184 is the 184th unit built that week for the particular model.
Compaq launched the SLT 286 publicly on October 17th, 1988 which was week 42 of the year. I don't what was the week cutover between prototype and production but I would guess somewhere around 2-3 weeks before launch since you would want product on hand ready to sell at time of launch. (So the serial number we broke down above was indeed built the week that the SLT286 was announced).
On your other serial, I suspect the Z's also represent that it's a prototype unit, I but I do not know that for certain.

Very cool! Thanks again for the great info. I can’t even express how much I appreciate you sharing your knowledge here that may have otherwise been completely lost to time! I had pretty much figured out the date code in the serial after owning so many Compaqs and those numbers constantly matching up with internal date codes, but I had absolutely no clue what the rest of the serial meant! And I would have never know without someone like you informing me, so again, I thank you!

Yep, that week 42 SLT so far is the oldest production one I have seen. If I ever see an older one you can bet I’ll buy it though, lol!

Another thing I have observed with the SLT/286, is an “HU4H” is a model 40 and the “HU3H” is the model 20. Every “HU3H” I have owned has a 20MB drive, and every “HU4H” has a 40MB. The model 40s seem to be a lot more common than the 20s.