Introduction

Read This Warning!

Seriously.

If you want more memory, the wisest course is to contact the people at Times2Tech. While I haven't used them, I've heard very good things about them and their product is definitely cost effective. Mack at Times2Tech was helpful answering a couple questions I had about the 200LX - Thanks!

Ask yourself these questions if you're still interested in doing this modification: Do I solder well? Do I have the right equipment to solder on small parts? Will it be okay if I accidentally destroy my PDA?

Discussion

In a nutshell, the 200LX board has been designed to take a daughter card that contains memory. I've soldered a memory chip directly to the pads on the connector that would normally hold the daughter card. The DRAM chip that I used was a Samsung KM416V1200BJ-6.

The speed of this part is a little quicker then I really needed, but it is the architecture that's important. The 416V1200 is a 1M x 16 DRAM with 1K refresh blocks. Amusingly, a 4K refresh block size would have dropped current consumption by half, but the 200LX isn't set up to handle that part.

Procedure

Next, I soldered leads to all the pins on my DRAM, except for the No Connects (N.C.). Here's a table of the pin numbers and signal names on the DRAM:

KM416V1200BJ-6 SOJ-42 package Pinout

1	Vcc	42	Vss
2	DQ0	41	DQ15
3	DQ1	40	DQ14
4	DQ2	39	DQ13
5	DQ3	38	DQ12
6	Vcc	37	Vss
7	DQ4	36	DQ11
8	DQ5	35	DQ10
9	DQ6	34	DQ9
10	DQ7	33	DQ8
11	N.C.	32	N.C.
12	N.C.	31	LCAS_
13	W_	30	UCAS_
14	RAS_	29	OE_
15	N.C.	28	A9
16	N.C.	27	A8
17	A0	26	A7
18	A1	25	A6
19	A2	24	A5
20	A3	23	A4
21	Vcc	22	Vss

I used prestripped wirewrap wire that I clipped very short on one end. During the first part of the process, I taped my DRAM down to my work surface (pick one that is heat proof - a desk may not be a good idea). I added a small amount of solder to three or four pins at a time, then attached the wirewrap wire that I had prepared. A good test to check your soldering is to give the wire a good yank. If it pops out, it probably would have popped out anyway - so no loss.

Once the long-legged, DRAM beast was created, I was ready to solder it to the motherboard. I Ohmed out the connector with 200LX's DRAM already on the board and came up with the following conversion chart:

200LX Memory Connector Pinout

connector	416V256	416V1200	Signal Name
1	21,35,40	22,29,37,42	Vss/_OE
2	2	2	DQ0
3	3	3	DQ1
4	4	4	DQ2
5	5	5	DQ3
6	34	36	DQ11
7	33	35	DQ10
8	32	34	DQ9
9	10	10	DQ7
10	31	33	DQ8
11	??	??	RAS2_
12	29	31	LCAS_
13	26	27	A8
14	25	26	A7
15	24	25	A6
16	23	24	A5
17	22	23	A4
18	20	1,6,21	VCC
19	20	1,6,21	VCC
20	19	20	A3
21	18	19	A2
22	17	18	A1
23	16	17	A0
24	28	30	UCAS_
25	13	13	W_
26	??	14	RAS1_
27	15?	28	A9
28	40/21,27	22,29,37,42	Vss/_OE
29	9	9	DQ6
30	8	8	DQ5
31	7	7	DQ4
32	36	38	DQ12
33	37	39	DQ13
34	38	49	DQ14
35	39	41	DQ15
36	40/21...	22,29,37,42	Vss/_OE

This table describes the pin out of the connector - numbering pin 1 as the corner pad closest to the crystal and the rest of the pins continuing counter clockwise around the connector footprint. The pin numbering for the 416V256 is in a TSOP II package, the pin numbering for the 416V1200 is in a SOJ-42 package. The good side of the SOJ-42 package is that it is easier to solder to then a TSOP II package; the bad side is that it is almost too tall to fit inside the 200LX case. I rerouted my wiring around the part (rather then over it) to give me a little more clearance. The first time I put it together, the keyboard actually bulged a little where the chip had been placed. (gack!)

Once the part was wired up, I rigged up my power supply and reconnected enough of the innards to test it out. It worked on the first try, so I was pretty pleased.

Conclusion

The other disappointing side of things is that the current design is ancient electronically speaking. The 200LX should be redesigned for power savings and speed.

General 200LX Stuff

This should be turned into a FAQ...

Keyboard Problems

A:

Easiest solution:

It's most likely a key failure. Sometimes the keys get a little soggy and don't contact with a regular press-- sometimes you really have to push them down hard to get it to work. Try doing a keyboard test, or try using the Fn key and see how hard you have to press to get it to show up. The good news is, if it IS a key failure, they're usually completely fixable by cleaning out under the contact pad.

A bit more involved:

I recently had the SAME problem: resolved that easily by using a so-called 'contact-spray'.

Switch off the machine, use the spray gently around the key. Press the key a couple of times (30-40) and then power on the machine and see whether problem is solved. In my case I had to repeat the above descriped step a second time. Afterall problem resolved within 2 minutes.

More involved yet: (but it solved the problem for me!)

I had similar problems. It turned out to be a bad keyboard connection. If the problem occurs again, just put some pressure on your case in the lower right corner, where 0.=+ is located. If this solves your problem, you first should check, if the screws of your case are loose. Fix them and the problem should go away. If the screws are fix, you might have to open your palmtop and clean the keyboard connector cable. However this is not simple and you should do it only, if you know how to open the palmtop. The speed upgrade comes with a detailed explanation.

(Note: I used 2-propanol to clean the gold contacts on the keyboard connector then reassembled. It even worked with the memory upgrade that I performed a year ago!)

I found out, that the 32MB upgrade, which sits just under the number block, adds a little 'belly' to the keyboard and could be the reason for a bad keyboard connection, which works on pressure between the case and the motherboard.

Rudy Moore