The error code 6500 indicates that an internal error has occurred which may be resolved by resetting the printer. Please follow these steps for isolating and resetting the printer:
1. Open the printer's front cover, and then open and close the print head lock lever (do not remove the print head).
2. Make sure all ink tanks are seated properly.
3. Make sure all packing materials have been removed.
4. Make sure no paper is jammed in the printer.
5. Disconnect the printer cable from the printer.
6. Close the front cover and turn the printer off.
7. Unplug the printer from the power source, and then plug it back in after five minutes.
8. Power on the printer.
If the error returns, the printer will require service options. Please use the following link to reach a Canon representative who can provide you with your service options. Contact Us.
The canon service manual, containing information on maintenance and troubleshooting of the PIXMA MP530, states the following description for the error code 6500:
Cycles of blinking in orange (Alarm LED) and green (COPY button):
*Other hardware error
* The PCI bus error is detected by the ASIC.
Solution (Replacement of listed parts, which are likely to be faulty):
* Logic board
This means the logic board should be changed. But check first to see if the machine has died by reaching its product life span:
Specified print volume (I) or the years of use (II), whichever comes first.
(I) Print volume: 17,000 pages
(II) Years of use: 5 years of use
I can confirm that replacing the logic board fixed this error for me. Luckily I had a couple of spare logic boards from old MP830 printers.
Unfortunately after replacing the board, another issue became apparent, and that is that the printer complained "Release the scanner lock switch and turn the power off and back on." The lock switch was not in the locked position though.
I re-plugged all the cables to the logic board, as this had once fixed that error for me. In so doing, I noticed that the ribbon cables were badly worn at the ends of the connectors, and this would no doubt be the result of a lot of plugging/unplugging while diagnosing a previous fault, and this one.
Most of those ribbon cables are a friction fit, meaning that each time you re-plug them, they get worn. Evidently they are not made to be re-plugged many times (cheap cables) and so after a while, many of the ribbons simply don't make connection any more. This resulted in the printer assuming that due to a lack of connection, the lock switch was unlocked. Unfortunately there's not much that can be done to replace the ribbon cables - each one is a different length and width, and getting to the other end of each cable would mean a very lengthy job disassembling both the scanner unit and the duplexing unit. Far more trouble than it's worth!
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