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PostPosted: Fri Jan 20, 2017 5:40 am 
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Pilgrim
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Hi,

I'm repairing a dead 486 computer from 1992-1993 which is housed in a keyboard like the Amiga 1200. It's really nice and my goal is to make it my daily 486 battlestation. Sadly it doesn't boot so I'm looking for info about the motherboard to help me repairing it (I already recapped the power supply without success, it still doesn't boot so I'm fairly confident that the mobo could be the culprit).

Here's some info about the computer and motherboard:
  • Computer name: Keyboard Network Station
  • Computer maker: Advanced Interlink Corp
  • Motherboard manufacturer: KAIMEI (I suspect it is also JAMICON since the power supply is a JAMICON one and JAMICON bought KAIMEI in this era)
  • Motherboard model: INS-486SLC-1
  • The Motherboard as one 2.5IDE port, one odd 26 pins FDD port (the FDD is a TEAC FD335-FH), one 16bits ISA port and 3 connectors for the (proprietary) graphic card

Here some pics of the Computer for reference purpose:
http://imgur.com/vv8DmzC
http://imgur.com/Y599sfu

And now some pics of the Motherboard:
http://imgur.com/pPz2yBV
http://imgur.com/ZnHgf79
http://imgur.com/EjPRN1f
http://imgur.com/tyV4mdi

FYI the graphic card seats above the motherboard and take 2 connectors to one side and one in the opposite side, here's a pic of it
http://imgur.com/JjjbwgB

A motherboard manual would be great, otherwise any pinout info on the 26 pins FDD port or the graphical connectors would be very appreciated!

Thank you :)


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PostPosted: Fri Jan 20, 2017 11:46 am 
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Mobo-fu Master
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Did not notice a holder for a BIOS battery in any images. But thankfully, no "Dallas Real Time" chip noted.
Typical BIOS battery is 3.0 volts, older motherboards had different brands and types. Likely a small note on the board somewhere as to 'battery', near a 3 or 4 pin connector. When the battery is dead or missing, then the system real-time clock does not function.. and the board may not show life signs.
Hopefully, a member has seen that system and may help you. But check http://www.elhvb.com/ or http://www.stason.org/ sites for possible match.

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PostPosted: Fri Jan 20, 2017 3:02 pm 
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Pilgrim
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Thanks for your answer!

Yes the battery is on a separate board (lpt + 2 commport + speaker + battery) and I tested booting it with it, without success. The aforementionned website doesn't host any documentation for this mobo's model.


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PostPosted: Fri Jan 20, 2017 4:10 pm 
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Pilgrim
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Thanks for your reply!


Not pictured is a bord containing lpt + 2 x commport + speaker + battery (new, I've changed it) and hooked the mobo isn't starting neither.


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PostPosted: Fri Jan 20, 2017 4:43 pm 
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Mobo-fu Master
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The older motherboards required only a +5 volts, +12 volts, -5 volts and -12 volts supply. If you have a digital multimeter, check if those voltages are present. Should be within +/- 2% limits, 1% is ideal. Those minus voltage sources are very low current, only for reference or bias needs.
The keyboard lights should flash when powering on, and in about 5 seconds or so, flash again. This is a sign the POST process is active. If no second flash, then there is a critical error halting the power on sequence.
As to a floppy drive, the connector should be standard, no need of a floppy drive with "settings" for 'A' or 'B' drive. Just the twist in the ribbon end going to the 'A' drive. Look for a small arrow or mark at the connector, designating #1 pin.
The 2.5 inch hard drive series is powered through the data cable, two leads each for +5 volts and negative, at one side. The connectors should be keyed to mate only one way.
That system likely was a POS or point-of-sale terminal, and may not have great graphics or performance.

Did find one Kaiemei reference at this site.. http://www.elhvb.com/mboards/kaimei/Index.html
and another site which may be of help.. http://www.plasma-online.de/index.html? ... micon.html

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PostPosted: Fri Jan 20, 2017 5:20 pm 
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Pilgrim
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Thank you for your help!

I've got +-12V and -5V but no +5V.

The FDD cable is 3 inches long and only two female 26 pin connector on both ends, I asked TEAC for a service manual and/or pinout.

I already checked the websites, to no avail.


Last edited by Jonas-fr on Sat Jan 21, 2017 9:09 am, edited 1 time in total.

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PostPosted: Sat Jan 21, 2017 8:23 am 
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No +5 volt source? That is the most critical for older motherboards. A minimal load of about 3 amps is required on the power bus, to have it stabilize and regulate properly.
Check the pin connection for proper contact, as well as the pin itself on the board. The solder joint should be a bit shiny, not dull or 'crackled' looking. Possibly the power supply (PSU) itself is at fault, due to age or excess heat. Or there is a short-circuit somewhere on the board or other device, and the +5 volt source is suppressed by a current limiter.
Any older AT-style PSU could be used for testing, but ensure the voltages are on the proper leads for that motherboard.
Be cautious about opening a PSU and poking about inside. The primary (largest) capacitors and heat sinks can have 200+ volts DC on them!

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PostPosted: Thu Jan 26, 2017 3:05 am 
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The double connector to the video card looks like a header replacement for the standard ISA connector. The 26pin connector for the floppy drive sounds like it may be similar to notebook floppy connector with the power included in that header.

Jamicon SpaceStation INS 1100 sounds like the same beast, however on that one there's next to no information online as well. I'll keep you posted if i can find anything useful.

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PostPosted: Fri Jan 27, 2017 11:08 am 
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evasive wrote:
The double connector to the video card looks like a header replacement for the standard ISA connector. The 26pin connector for the floppy drive sounds like it may be similar to notebook floppy connector with the power included in that header.

Jamicon SpaceStation INS 1100 sounds like the same beast, however on that one there's next to no information online as well. I'll keep you posted if i can find anything useful.


Thank you very much for your answer! I didn't know about the Jamicon SpaceStation INS 1100 but since they designed the electronic and that KAIMEI was their name for the motherboard market it seems to be a clone of mine. Hopefully its mother board would be more populated than mine (it miss a 487 coprocessor and other goodies). I'll do some googling as well and post my results here, but don't hesitate to post yours too!

Regarding my problem I'm currently investigating the power supply.


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PostPosted: Mon Jan 30, 2017 1:15 am 
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Pilgrim
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The computer is now booting!! The problem was indeed a lack of +5V tension output by the power supply. I changed a transistor (TIP42C) and the fuse and now the computer is booting flawlessly! I'm very happy.

The only problem I've got now is that the 26pins pinout of the FDD connector on the motherboard doesn't seem to be standard also (I tried to replicate this pinout without any success). My goal is ti replace it with a standard FDD or a HxC since the original FDD is dead.

So right know I'm still looking for a datasheet of the motherboard (KAIMEI INS-486SLC-1) and/or the current FDD (TEAC FD335-FH).

PS: I'm also looking for a datasheet of the NEC DF1138H FDD since it the one inside the "Jamicon SpaceStation INS 1100" which is a close enough (clone enough ; ) computer of mine and so it would be a 26pins too (I hope).


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