Black Screen

Symptom: Screen remains black (monitor) or
         no video signal (TV).
Target : C-64

WARNING! This diagram is INCOMPLETE yet!

More links for the instructions to come! - have to write script for that first, since otherwise this flow chart would be impossible to maintain :-)

        |
        V
  +----------------+  no      +---------------+  no      Replace PSU fuse,
  | Power LED lit? |------->  | 5V at PSU ok? |------->  if that doesn't
  +----------------+          +---------------+          help, get new PSU
        |                             |
        | yes                         | yes
        |                             |
        |                             V
        |
        |                     Replace extremely
        |                     hot chips (OUCH-hot)
        |
        |
        V
  +----------------+                             +-------------+
  | Does LOAD"$",8 |  yes                        | Still black |
  | seem to work?  |------->  Swap VIC  -------> | screen?     |
  +----------------+                             +-------------+
        |                                               |
        | no                                            | yes
        |                                               |
        |                                               V
        |                                            [later]
        |                                         
        |                                         
        |                                         
        |
        |
        V
  +------------+         +--------------+
  | Reset line |  no     | Reset switch |  no      Replace
  | HIGH?      |-------> | okay?        |------->  reset switch
  +------------+         +--------------+
        |                        | yes
        | yes                    | (or no switch
        |                        | present)
        |                        V
        |                 +-------------+
        |                 | Reset line  |  yes     Try pull-up
        |                 | level > 0V? |------->  resistor
        |                 +-------------+
        |                        |
        |                        | no
        |                        |
        |                        V
        |
        |                   Replace CIAs,
        |                   SID, and CPU
        |                   until reset
        |                   level is > 0V
        V
  +--------------+
  | Phi 0 in at  | no
  | CPU present? |------->  Swap VIC-II
  +--------------+
        |
        | yes
        |
        V
  +--------------+
  | Phi 2 out at | no
  | CPU present? |------->  Replace CPU
  +--------------+
        |
        | yes
        |
        V
  +--------------+                                   +--------------+
  | Interrupts   | no                                | Interrupts   |
  | from CIA #1? |------->  Replace CIA #1  -------> | from CIA #1? |
  +--------------+                                   +--------------+
        |                                                   |
        | yes                                               | no
        |                                                   |
        V                                                   V
     [later]                                         +---------------+
                                                     | /CS at CIA #1 |
                                                     | alternating?  |
                                                     +---------------+
                                                            |
                                                            | no
                                                            |
                                                            V         
                                                         [later]

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