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Hi all,
I'm restoring an Apple IIe PAL/Euro.
Six month ago, I replaced all RAM IC and the computer works well.
Last week I powered it and it's gone bad.
I'm stuck on a display fault after a fairly thorough round of testing. Sharing the full detail in case anyone can offer input, or with some luck has a spare IOU to test.
**Symptom**
The machine boots normally and gives the usual beep, but the screen shows a frozen pattern (see attached photo): some times I got a "Apple '" banner at the top of the screen (correctly written by the boot ROM), followed by a repetitive pattern alternating between two states on almost every line below, with a few fragments of coherent text poking through here and there.
This pattern is identical on every power-up, and Ctrl-Reset does not change it at all.
**Components identified and tested off-board (all good)**
- - CD ROM: 342-0135-B - Tested with RCT PRO CRC OK
- - EF ROM: 342-0134-A - Tested with RCT PRO CRC OK
- - Keyboard ROM: 342-0153-A - Tested with RCT PRO CRC OK
- - Video ROM (French character set): 341-0163-A - Tested with RCT PRO CRC OK
- - 6502 CPU: confirmed good by substitution (same fault with the original CPU and with a known-good CPU)
- - RAM: confirmed good - Tested with RCT PRO with March test
**Oscilloscope measurements (4-channel, 200 MHz, no logic analyzer)**
On the IOU's RA0-RA7 outputs (UC8 on the schematic, pins 17-24 per my reading of sheet 3 "Timing/Video"): correct amplitude, 5V peak-to-peak on all 8 bits. No output stuck at a fixed level.
**What still looks healthy**
- Clean, sharp character rendering (the "Apple" banner is legible, some times)- Stable screen sync (no rolling, no erratic flicker)
**My question**
Without a donor board or a logic analyzer, I can't push the diagnosis further on the "video address generation inside the IOU" theory. Does anyone have:- a working 344-0022-A IOU I could try as a substitute (even temporarily)?- another test achievable with a standard 4-channel scope before I go hunting for this component, which seems to be rare?
Thanks in advance for any help, happy to run any additional test or measurement.