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Vtech Laser 386SX/2E

lschect

New Member
Joined
Sep 25, 2021
Messages
5
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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modem7

Veteran Member
Joined
May 29, 2006
Messages
7,894
Location
Melbourne, Australia
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.
 

lschect

New Member
Joined
Sep 25, 2021
Messages
5
Location
Cincinnati,Ohio
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.
 

Slawterr

New Member
Joined
Jun 22, 2017
Messages
1
Location
Columbus, Oh
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.
 

oldpcguy

Experienced Member
Joined
Sep 23, 2021
Messages
223
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.
 
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