9 May
2020
9 May
'20
4:44 p.m.
On 05/09/2020 11:32 AM, Rob Jarratt via cctalk wrote:
Hello,
I have recently been trying to improve the ripple on the output of my
MicroVAX 3100 Model 95 PSU because occasionally it would fry a memory
module. I replaced a bunch of capacitors, some of which had started to leak.
However, the ripple does not seem much better. There is a scope trace here:
https://rjarratt.files.wordpress.com/2020/05/microvax-3100-model-95-psu-ripp
le-after-re-capping.png
Ch1 is the 12V output and Ch2 is the 5V output. I had an old RD53 connected
as a dummy load. It is possible that the memory was breaking because of
occasional spikes that are worse, but I don't know. Does that seem OK?
These spikes are very likely not real, but a result of probe
ground impedance. There likely ARE
some spikes and ripple, but not to the extent of the giant,
sharp vertical spikes. If you are using a X10
probe, does the 200 mV / div on the scope trace reflect that
attenuation?
In other words, are the spikes 400 mV or 4 V?
Jon