Re: 1502 TDR project - using bench supply

Tom Gardner

On 13/12/19 02:54, ehsjr via Groups.Io wrote:
On 12/12/2019 3:59 PM, Mark Pilant wrote:
So, here is a list of what I tried and whether or not it "worked":
    1)   Used the TekWiki cap/resistor replacement for the battery.  Did not work.
Two things come to mind on that.
First, do not attempt to power on the 1502 immediately after plugging
in the AC cord or wall wart supply.  Give it a few seconds to charge
the cap, then turn the 1502 on.

Second, the cap may be too small.  I used 4700uF which works
fine for me - I think the wiki recommends 2200.
The problem is that if the capacitor is too large it takes too long to charge up. The PSU interprets the low voltage as a failed cell, and shuts down.

The required C (and R) seems to be select-on-test, varying from one 1502 to another. Even if suitable values are found, it makes me wonder if it will switch on /next/ time :(

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