[ICOM] IC-2AT diode matrix question

[K6STU at aol.com]

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
In a message dated 3/20/2005 7:48:24 P.M. Pacific Standard Time,  
vhfplus at bmg50.com writes:

(Reposting with the correct model number indicated)


I have  been given an IC-02AT HT for my son, who recently 
passed his Tech exam and  is waiting for the license to be 
issued. This HT has been slightly  modified by someone who, I 
believe, was trying to change the frequency  coverage so got 
into the diode matrix. The PC board where the diode pairs  
were mounted has been damaged and the surface mount diodes
can no  longer be mounted in their original locations. My 
question is  this:

What is the proper diode matrix configuration for stock  
2-meter operation? The manual copy which I have shows two 
identical  4-diode diagrams for IC-02A/AT (AU/AE) and IC-02AT 
(SA/SAT) utilizing half  of D-2 and D-3 and both sections of 
D-7 (marked D-402, 403 and 407 on the  diagram). Are these 4 
diodes all that are required to make the rig  work?
The schematic is not clear on this matter and it appears 
that  there were more than just 3 diode pairs mounted on the 
PC board. The only  diodes mounted on the board presently are 
the original D-407 pair which  check good with a DMM.

Any assistance would be  appreciated.

Thanks and 73,

Jack, AE7DX

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