9 May
2020
9 May
'20
5:13 p.m.
The spikes are 400mV. The probes are set to x10 and the scope is set for
them to be x10.
Regards
Rob
-----Original Message-----
From: Jon Elson <elson at pico-systems.com>
Sent: 09 May 2020 17:45
To: rob at jarratt.me.uk; Rob Jarratt <robert.jarratt at ntlworld.com>; General
Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
Subject: Re: MicroVAX 3100 Model 95 Ripple
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-ps
> u-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