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Vtech Laser 386SX/2E

lschect

New Member
Joined
Sep 25, 2021
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Location
Cincinnati,Ohio
This is the first computer I purchased from Micro Center in 1992. I also bought a Laser 486DX2 purchased from Micro Center later. After upgrading to faster computers I packed both up in plastic wrap and placed in storage for a verrry long time. I recently retrieved them both from my storage locker. The 486 worked great but the 386 posted a beep code indicating keyboard controller failure. I pulled everything out of the computer and found the motherboard is clean with no corroded traces. Both units have new BIOS batteries. I have included photos of this computer and have no idea where I could find a new keyboard controller. Need suggestions on a fix please or a replacement availability. Thanks, Larry
 

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The 486 worked great but the 386 posted a beep code indicating keyboard controller failure.
Regarding POST codes. People are often misled, because they go to the Internet and see something like, "List of AMI POST codes", and not realise that AMI/Phoenix/IBM, and the like, changed their POST codes periodically. Unless you have a list that you know for for fact matches the particular BIOS, then you could be being misled.

I pulled everything out of the computer and found the motherboard is clean with no corroded traces.
Something worthwhile to do is to re-seat all socketed chips.
Also, a thorough visual inspection can sometimes reveal a problem.

I have included photos of this computer and have no idea where I could find a new keyboard controller. Need suggestions on a fix please or a replacement availability.
Assuming a faulty keyboard controller:

There is a good chance that your controller is an Intel 8042 (or 8742) chip that has been suitably programmed for what the motherboard needs the controller to do.

IBM's keyboard controller (IBM part number 1503033) may work. A common way for people to obtain one, is by acquiring a blank Intel 8742, then using an EPROM programmer to program the 8742 with the code used in IBM's controller (code at [here]). Or see if a person/company at [here] can provide that service.

In the thread at [here], a member successfully used an P8242 chip.
 
I did remove the 2 BIOS chips and the keyboard controller chip. I cleaned the contacts and reseated them. The post code is listed in the manual for the Laser 386. Yes, I do have all the original paperwork and accessories for this computer since it is a one owner. It did work before it went into storage. I removed the external batteries before storage So I don't know what happened, just age of the chip I guess. So I will try to get a chip and get it programmed for the computer. I will check the solder around the motherboard before I reinstall it again. This computer is seemingly kinda rare, I have only seen one more like it for sale. Thank you for the reply.
 
How are you coming along with the keyboard controller? I have a Laser 386SX model (Also from Microcenter) that may have a compatible controller. If time permits, I could tear it down and check the controller type. Unsure on the specifics or ability to dump and reprogram these controllers however.
 
I did remove the 2 BIOS chips and the keyboard controller chip. I cleaned the contacts and reseated them. The post code is listed in the manual for the Laser 386. Yes, I do have all the original paperwork and accessories for this computer since it is a one owner. It did work before it went into storage. I removed the external batteries before storage So I don't know what happened, just age of the chip I guess. So I will try to get a chip and get it programmed for the computer. I will check the solder around the motherboard before I reinstall it again. This computer is seemingly kinda rare, I have only seen one more like it for sale. Thank you for the reply.

I would look at things that tend to go bad with time: Batteries and capacitors are two of the most likely culprits. You've already eliminated the former so I would look at the latter, especially electrolytic capacitors. Don't forget those in the power supply. Chips can fail but I would focus on the capacitors first and, once eliminated, investigate the keyboard controller. If the supporting circuitry is not functioning properly you could be misdiagnosing the problem.
 
I recently got a Laser 386SX PC that I am working on. It boots to BIOS but because the CMOS battery is dead it won't boot from the ST3120A disk. What battery is used here? I think my first PC has a clip of 2 AA batteries.
 
I recently got a Laser 386SX PC that I am working on. It boots to BIOS but because the CMOS battery is dead it won't boot from the ST3120A disk. What battery is used here?
Why can't you just open up your computer and see what the dead CMOS battery is ?
 
Good idea. I'll post a photo when I get from travel. What exactly is a Dallas RTC module? I saw reference to this on youtube.
 
Typical Dallas DS1287 (real time clock)... integrated battery and timekeeping circuitry.
 

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I hope it's not a Dallas chip. That can be more of a challenge. I have a relative of the VTech, a PC Partner by Leading Technology. It uses a header pin connection with a wire to a four-pack of AA 1.5v batteries. I am also able to get into the BIOS CMOS settings after an initial boot message even if the battery is dead or missing. The key combo for BIOS is <Ctrl><Alt><S>. I was able to use the system with a dead battery that way for quite some time.

Seaken
 
Yes, "if you have decent soldering skills." I just had one of my Pentium 150 systems stop booting and traced it to a bad Dallas chip. I guess I'm going to have to get at least "decent" at soldering. Up until now I have managed to avoid it (that is soldering on chips on a PC board). Thanks for the link.

Seaken
 
Yes, "if you have decent soldering skills." I just had one of my Pentium 150 systems stop booting and traced it to a bad Dallas chip. I guess I'm going to have to get at least "decent" at soldering. Up until now I have managed to avoid it (that is soldering on chips on a PC board). Thanks for the link.

Seaken


Practice on several boards (that are of no value) first. Solder wick+low temp solder+tacky flux make the job 100% easier. Been soldering almost 50 years now... still learn something new frequently. True rework equipment is the best solution, but prohibitively expensive for most folks not doing it for a living (like me).
 
I've see these "suckers" that look like a cross between a little vacuum and soldering iron. What do you think of those. Are they one of the "prohibitively expensive" tools?
 
I've see these "suckers" that look like a cross between a little vacuum and soldering iron. What do you think of those. Are they one of the "prohibitively expensive" tools?

No. Those aren't very expensive, but again....you get what you pay for. For a minor job they'd be fine after someone got proficient with it.

This is what I mean by expensive (but well worth it if you're paycheck depends on it):

 
OK, now I see what you mean. Yes, $2500 is a little steep for a few old hobby computers that may need a chip once in a while. :) I would like to get a better soldering iron though and probably one of those suckers.

Seaken
 
I would like to get a better soldering iron though and probably one of those suckers.

Seaken

Again the other "not-so-expensive" items I'd recommend:


Obviously for "difficult" solder areas



Low-temp solder is added to the existing solder joint to lower the overall melting point and make removal of the solder easier.


Tacky flux is used in conjunction with the low-temp solder (which is very "dry", since it has no internal flux). It also makes for a very clean via-hole for soldering back the pins. I usually clean up with isopropyl alcohol after finishing.
 
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