[volt-nuts] ...a guide to buying the HP/Agilent 3458A

[Mark Sims]

You should pay around $20 each for the DS1230 and $10 for the DS1220.  I bought mine from a local dealer.  Digikey also has them.  If you buy 24-36 of them the price drops to around $13/$7.

I don't think the internal voltage is available on those chips.  The Tek 1503B uses a DS memory keeper battery and external SRAMs.  The battery/power controller are the same as in the DS RAM chips. 

For the 2Kx8 device you could probably substitute a ferroelectric SRAM...  no batteries needed.   Somewhere there is a place that sells a small PCB with an FRAM on it to substitute for the DS1220 in some arcade games.  It should not be hard to build a DS1230 replacement.

I have also seen some small PCB's outfitted with a SMT 32kx8 ram and external battery that substitute for the DS1230 chips.  The batteries on these were much less capacity than the internal DS1230 battery,  but was changeable.

I do a lot of work on Tek TM500 series modules.  The DM5010 meter saves its cal constants in a RAM backed up by a 2 cell rechargeable NiCad (remember to use that meter occasionally or you will need to recal).  If one cell goes bad,  the RAM contents usually survive.  I built a device out of a battery and DIP clip that allows one to hot-swap the (soldered down) nicad battery without losing the memory.  I usually replace the NiCad with a lithium battery/series diode so you don't have to worry about keeping the thing charged.

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