I found a IIe in the loft (PAL version) and it does not boot. Clock phases are correct and address/data lines look OK. Adr downstream of buffers 74LS244 also look OK and buffers test OK (in an LED & switch tester!). There is no beep.
Screen appears to show graphiccs (so IOU generating sync etc) but characters look as if text is being shown in graphics mode not text e.g. bit patterns repeat every 4 raster lines. A quick check with scope shows the MMU /C0xx line doesn't seem to be asserted. Following back to 74LS138 the enable on this seems stuck low and this is the CXXX line from the MMU. Checking with the logic analyser shows that A15-A12 are setting C and the line is resolutely low. I've changed the 74LS138 in case it was holding it down.
Do the MMU chips fail? Is there any other obvious test to try before having reluctantly to put this in the "non-fixable" pile since I presume the only source of the ASIC is another IIe.
(RAM & ROM tested in EPROM burner/silly little tester)