[ICOM] IC-2AT diode matrix question

[Jack/AE7DX]

K6STU at aol.com wrote:

> 
>hi jack you are correct. there are only 4 diodes in the matrix. there are 4  
>horizontal and 4 vertical lines that make up the matrix. the 4 vertical lines  
>are from left to right are R10, R11,  R12, and R13. the 4 horizontal lines  
>are from top to bottom R23, R22, R21 and R20.
>it looks like a larger version of tick tack toe diagram.D407 consists of  two 
>diodes. Diode one The cathode/bar connects to line R23 and the Anode  
>connects to R12. The second diode the Anode connects to R12 and the cathode/bar  
>connects to R22.      D402 the bar connects to R21 and  the anode connects to R11. 
>D403 the bar connects to R20 and the anode connects  to R12.
>     The diode matrix connects to the left side of IC  401 which is located 
>above the speaker on the logic board. the pin out on on IC  401 is from top to 
>bottom 65 through 80. 66/R10, 67/R11, 68/R12, 69/R13, 70/R20,  71/R21, 72/R22, 
>73/R23. 
> When you have the unit open with the speaker half on the left and the  the 
>other half that has the  controls on the top look at he  bottom left you will 
>see the memory back up  battery. Just to the  lower left of this battery is the 
>CPU reset switch. With the power switch on  press the reset switch and this 
>will reset the CPU.
>If this doesn't fix it I  don't know what to tell you.
>Good Luck.
>Mike, K6STU
>  
>
Thanks, Mike! I'll give the reset a try since the 4 diodes are in the 
right places (well, 2 IN4148's the I installed and the original D-407). 
I just hope that the attempt to extend the range of the '02AT didn't 
result in more PC board damage than is visible from the top of the 
board. I did do a continuity check with a DMM in the "diode check" mode 
and all the traces seem to be intact from the original matrix diode 
locations to IC-401 so I 'll keep my fingers crossed!

My son got the call KE7DAE and is anxious to get something on the air 
(aside from using my call on HF). I told him that his call will be a 
nice one for running contests on CW...I'm actually envious :>)

73,

Jack, AE7DX