The irq is working correctly ? in the pre-series 720 I used, the irq was coming from the power supply when we received it, the 720 was not working a chip was blown, this chip was used to generate the irq from the power line frequency (was fixed by generating the irq from another source) symptomes: no keyboard, no cursor -- didier On 19/10/2014 21:08, A. Fachat wrote: > Hi there, > > just a status on my CBM 720 repair - and maybe you can help as well :-) > > After replacing some capacitors in the original power supply, I checked the > first logic signals and found /RES continuously low. Traced it back to a 556 > timer chip with a broken output. Replaced it, and found from scope traces that > the CPU was working. > > Unfortunately after a few minutes the old power supply went south with a small > "plop"... I decided to not get further with it, and instead replace it with a > PC power supply. > > That worked well, and got some video output after adjusting the screen > brightness with the small knob on the back (I found video signals with the > scope, and then decided to check that knob, which in fact ... :-) > > Unfortunately it's not yet fully working, but much further. The CRTC gets > initialized, so that means the video output is working, the CPU as well (at > least to a considerable extent), but other stuff is still broken. > > Anyone knows the video pattern shown here? > https://www.flickr.com/photos/afachat/sets/72157647798386959/ > > Thanks > André > > Message was sent through the cbm-hackers mailing list Message was sent through the cbm-hackers mailing listReceived on 2014-10-22 09:00:03
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