VT101 8085 CPU Fault

Matt Burke matt at 9track.net
Sun Feb 22 07:55:51 CST 2015

On 21/02/2015 18:59, Robert Jarratt wrote:
> So what sort of value is reasonable for leakage?

You need to look at the datasheet for each capacitor to find out what
the maximum leakage should be. Here is an example taken from the
Panasonic M Series datasheet:

DC Leakage Current: I <= 0.01CV or 3uA after 2 minutes (whichever is

So if C321 on the monitor board was a Panasonic M series then the
leakage would be:

I = 0.01 x 1000uF x 16V = 160uA

You need to connect a DMM with mA (or better uA) range in series with
the bench supply and capacitor so you can check that the leakage falls
below this value. You may find that it takes a while to reach this value
if the capacitor has not been reformed recently.

Once you've done a few of these you may not need to look at the
datasheet every time as you will get to know what reasonable values are
for a given capacitance and voltage.


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