ICS64

[Chuck]

Check your solder joints one by one.  If you used the 'zip' soldering method where you quickly drag the soldering tip while applying solder to the pins of the chips it is possible to bridge two pins, and also possible to miss a pin.

The screen issue you talk about is most common caused by the PLA, but can be the RAM.  If you are using sockets, it's possible that a socket is not making a good connection.  That is really rare, but I have seen that before.

Hi,

    Follow-up.  I replaced the 6510 MPU (U7) with an new chip (MOS replacer) and the board is not freezing-up anymore.  Now I get "bad user port" and "bad U1" (CIA) on start-up most of the time.  I do get a clean diagnostic test occasionally.   It seems to run ok when I play some games or run basic programs.  Will keep working on it.  Need to try the SD2IEC card reader next.

     After replacing the L3 inductor the board it made it through 105 cycles of the 586220 diagnostic cartridge test, with the harness attached, with no errors.  Note:  I did temporarily place the old L3 back in the circuit and got the same bad U! and bad user port errors.   I’m calling it good.  Here is what fixed the problem in the unlikely event it happens to someone else.   The ICS64 is my favorite C64 mod.  Good stuff.
 
SYMPTOMS OF THE L3 INDUCTOR GOING BAD.
 
A device powered through user port (CN2) does not turn on (e.g. SD2IEC card reader). 
 
Erratic voltage readings when testing TP5 to CN2 pin 2. 
 
A dim LED compared to a properly working C64 when connected to pin 1 (ground) and pin 2 (5 volt) of CN2.  I used a red LED with a 220 ohm resister for the test.  Something was reducing the current.
 
Bad U1 (CIA), U2 (CIA), U7 (MPU) or user port indicated when running diagnostic test 586220 with the harness attached.
 
There is a significant voltage across L3.  The last voltage tests I did before replacing L3 was on pins 1 and 2 of CN2 (1.4 volts) and across L3 (3.6V).  All chips were removed from their sockets.    It appeared L3 was taking away the voltage from the expected 5 volts reading for the pins 1 and 2 of CN2 test (i.e 1.4v+3.6v=5v).