On Fri, Jun 19, 2020 at 11:49 AM Gerrit Heitsch <gerrit_at_laosinh.s.bawue.de> wrote: > > On 6/19/20 11:23 AM, Clockmeister wrote: > > > > > > C64 DRAM has a high failure rate but that's true of DRAM generally in > > all my vintage equipment these days it seems (yes some brands fare much > > worse like mT). I rarely had to replace was the 77xx logic on any > > Commodore computers though, I would say about the same rate as for other > > systems that used 74XX logic. > > I had a lot more dead 7708 (74LS257), 7709 (74LS258) and 7707 (7406) > than their 74xx equivalent. another data point agreeing with my experience :) > > > It is however my opinion that power supply ripple, not only over voltage > > is quite capable of damaging IC's in the long term including DRAM and C= > > supplies were notoriously rubbish back in the day and haven't gotten any > > better with age. > > A 78S05 (as used in the C= supplies) doesn't produce much ripple though, > at least as long as the large capacitor in front of it is still within > spec. You get a lot more from any switching regulator. That's what I've found too (as I was expecting) when I replaced a linear regulator inside a C64 power supply with my own switching design: https://youtu.be/oxxZgwm8lIs?t=880 I don't think the added ripple is an issue though. I'm using the DC-DC switchers on my C64 since a few years now. FrankReceived on 2020-06-19 12:01:59
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