FIC PT-2200 missing resistor array R1 \ VOGONS

FIC PT-2200 missing resistor array R1

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First post, by majestyk

Posted on 2023-01-01, 14:30

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I just repaired a PT-2200 that was in very poor condition. After thoroughly cleaning everything I had to replace all 4 SIMM sockets, all the 470µ and 1000µ electrolytics and 3 small 10µ ones. They all had been torn out. The battery holder was missing and about 20 traces on the backside had been cut. The flashed BIOS was not one supporting this board.
I also upgraded L2 cache with 2 additional 32Kx32 PB-SRAM chips for a total of 512K and added the second TAG chip plus a zero Ohm resistor to enable it.

Now I´m reworking the area around the USB header. I already added a missing inductor in the 5V rail and still need to replace 2 missing 47pF ceramic capacitors.

Then there was a (4x) resistor array that´s missing also. One end of each resistor is connected to +5V, the other ends are connected to 2 pins of the DIN-KB connector and 2 pins of the PS-2 KB-connector (not populated) via 4 inductors. Between each inductor and the respective KB-pins there´s a capatitor going to GND:

What do you think is the resistance of the array "RN1"? Here is the best pictures I could find:

Last edited by majestyk on 2023-01-02, 17:18. Edited 5 times in total.

Reply 1 of 5, by weedeewee

Posted on 2023-01-01, 14:55

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4k7 seems like a nice value for a ps2 pullup from +5v

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Reply 2 of 5, by Horun

Posted on 2023-01-01, 19:04

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Somewhere in my boxes have a PT-2200 but cannot find it yet... if I do will try to take a close up picture of that area..
added: found it. Is a 103 quad SMT, so 10k quad. my 4 year old Iphone SE actually can take half-assed macro pictures 🤣

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Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 3 of 5, by majestyk

Posted on 2023-01-01, 19:55

majestyk Offline

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Thanks a lot!
Will insert a 10K array tomorrow.

Your PT-2200 is revision 2.2 I guesss, R5 and R9 are not populated.

Reply 4 of 5, by Horun

Posted on 2023-01-01, 20:03

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Corner of board says 2.1, it has the 512k cache and most likely needs the 1000 and 470 mf caps replaced like yours, though booted fine last year.

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. Stuff: https://archive.org/details/@horun

Reply 5 of 5, by majestyk

Posted on 2023-01-02, 09:54

majestyk Offline

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I found a nice 8K2 array for "RN1" and also replaced "L9". The only components still missing are "C3" and "C4"(47pF).
The pcb around the mounting hole was scratched all over and most components were damaged or missing, someone had tried to remove the mainboard from the case by rotating the whole board countless times without removing the screw first.