Nan Tan Computer NTC 6251 101-key Enhanced Keyboard
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(https://deskthority.net/wiki/NTC_KB-6251)


KB-6251 S/N:960600015
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* Controller chip: C32321AE CHICONY VER-M 105-08049-130 9507 MT1 © INTEL 1980

* PCB: 6251M VER10 001-06251-003

* Key switches: White stem. No brand visible. Probably Aristotle Cherry MX white clone (https://deskthority.net/wiki/Aristotle_Cherry_MX_clone)

* Cleaned August 13 2016: With top plastic removed, cleaned with compressed air; top and bottom pieces of plastic body and all key caps scrubbed with soap and water; black plastic plate/chassis onto which key switches are mounted cleaned with cotton and 100% isopropanol and then entire board blown with compressed air; keys that have poor electrical contact when pressed (arrow up, arrow down keys) were sprayed with 100% isopropanol

* Condition: Plastic casing is very yellowed; no cracks or damage. Electrical cord is in good condition; coil has not experienced stretching. Printing on key caps are not worn out. Mechanical switches are clicky and in good condition except for a couple of keys which were serviced as explained above. All three LED indicators are functioning.


KB-6251CH S/N:02176316
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* Controller chip: +B8952 NTC-6351A

* PCB: KB-6251CH V10

* Key switches: Blue stem. Has "Cherry" embossed on switches. Probably Cherry MX blue (https://deskthority.net/wiki/Cherry_MX )

* Cleaned August 15 2016: With top plastic removed, cleaned with compressed air; top and bottom pieces of plastic body and all key caps scrubbed with soap and water; black plastic plate/chassis onto which key switches are mounted cleaned with cotton and 100% isopropanol and brushed thereafter with a toothbrush and finally entire board blown with compressed air; with two ends sealed in plastic bags, the insulated electrical cord was washed with soap and water.

* Condition: Plastic casing has no cracks of damage. Electrical cord is in fair condition; coil has experienced extensive stretching. Printing on several key caps have been completely worn away from use. Mechanical switches are not clicky despite being apparently Cherry MX Blue--even keys that are rarely used. All three LED indicators are functioning. Zero key on numeric keypad occasionally has poor electrical contact--no repair done.


KB-6251 S/N:08102716
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* Controller chip: +B9006 NTC-6351A

* PCB: KB-6251 EA V3.0

* Two tamperproof stickers over screws of plastic casing: "Interlink Computer", "8-11-90" [date is handwritten]

* Key switches: White stem. Has "ALPS" embossed on switches. Probably Alps SKCM white (https://deskthority.net/wiki/Alps_SKCL/SKCM_series)

* Partially cleaned August 15 2016: With top plastic removed, cleaned with compressed air; top cover was scrubbed with soap and water

* Condition: DEFECTIVE! Electrical contacts of letters "R" and "V" are faulty--allowing 100% isopraponol to seep into the switch ineffective. Keyswitch of letter V was disassembled but electrical cannot be fixed. These switches must be replaced. Plastic casing has no cracks or damage but has a number of gouge-like marks. Electrical cord is in good condition; coil has not experienced stretching. Printing on key caps are not worn out. Mechanical switches are clicky and in good condition. Upper right corner of PCB is chipped off but no copper trace has been compromised. All three LED indicators are functioning.