This was a little confusing, but I will try to explain the symptoms as I understood then. 1) Garbled characters. This can have several causes depending on the pattern. If the screen characters are totally random, then the processor may not have completed it's power-up sequence. Check the reset on the processor and the addressing and response on the ROMs at H3, H4 and H7. If there seems to be a pattern to the garbled characters, check for bad screen RAM at C3 and C4 or the driver at B4. If it appears to write to the screen, but the characters are wrong, check for a bad character ROM at A2. 2) Cassette doesn't read or write. Check the 6522 at A5. 3) Bad power supply for display. The power for the display is tapped of the main transformer separately from the power supply for the logic board. There is a full wave rectifier(4 diodes) and voltage regulator on the display board. Loss of signal in the video driver section can also result in a blank screen. Also, loss of horizontal driver can result in a bank screen, as the horizontal return is rectified and used to provide the high voltage for the video drive. There are four versions of the video board that I know of, so I can't be more specific. - This message was sent through the cbm-hackers mailing list. To unsubscribe: echo unsubscribe | mail cbm-hackers-request@dot.tcm.hut.fi.
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