On 11/26/2012 04:26 PM, email@example.com wrote: > > On 2012-09-12, at 18:37, Gerrit Heitsch wrote: > >>>>>> Otherwise... I had C90 got bad on a 250407. No capacity left at all, resulting in +12V for VIC and SID being only +8V. System worked, but I only got a b/w picture. That one was a light blue 407µF/25V made by GRAND SONIC. >>>>> >>>>> I have one board that boots to B/W picture when "cold". After some time colour pops in. It also quite often hangs (after some seconds) when cold. With time it also becomes more reliable. Voltages on the regulators/stabilisers look good. Don't have scope at hand to have some more close look but maybe this rings a bell for someone? >>>> >>>> Can you provide some extra information about the kind of board? Assy number, which voltages were checked and where... >>> >>> 250425 board. Voltages checked at regulators, VIC, SID, CPU and few other points for the "second" +5. >> >> Still, if you have a matching one, you could replace C90 anyway. Otherwise, since it's a 250425... If you have one, try a different 8701. > > Got this one fixed. Crashing was unrelated to the lack of colour. Crashing was caused by broken KERNAL socket - replaced and crashes disappeared. Lack of colour was a bit more tricky though. I was hunting it for some time until I started watching the chroma waveforms on different boards recently, including the one in question. I noticed that on other boards trimming the crystal frequency leads to loss of colour and setting it back brings the colour back. But on this board no.. So I replaced the trimmer and adjusted it so that I get colour every time now. It sorts of explains also why the colour was more likely to appear after some time and less likely when cold - frequency drifting due to temperatrue difference. Hm, never had one of those go bad... But then, it's hardware, it will fail sooner or later for someone. Gerrit Message was sent through the cbm-hackers mailing listReceived on 2012-11-26 19:01:18
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