SOLVED: W&W Rambox 32k current drain

[Hiwi]

Hi all,
i recently bought an old used W&W rambox 32k which was described as not working (defective and unknown state)

The box is an old version with dip switches for toggling the rampages / write protection

The HP-41 did not come up if the rambox is inserted. So i physically disabled all the pages and the HP was back to live.

The next step was to replace the backup battery. This was a fairly tricky part but at least it was sucessful.

I put a new Rambox32 module on the page 8 and the box was working fine. All rampages were enabled again and initialized. The builtin testroutine found no errors.

But it seems to me, that the box draws to much current. If i put in fresh batteries in the HP-41 it lasts only about 14 days until the BAT indicator comes up.

This does not seem be be normal, or does it?

Has anyone the shematics of this box or some more technical specs of it? May be a diode for switching internal or external battery is faulty, so it sucks the HP41 battery empty.

Ralf

[Hiwi]

Hi all,
i had contact to the developer of the Rambox and got some schematics.

I have the Rambox version II. The voltage / battery regulation in both versions I&II are the same.
There are some diodes and transistors, shutting the Rambox down when the HP-41 goes to sleep.
Here i will start investigation.

The current drain should only be some uA. Actually my box draws more than 10mA so i suppose the Rambox does not go to powerdown mode or there is a leakage current.

The other problem could be the switches, they are pulldowns and oxidation could cause higher current drain.

Ralf

[PeterP]

Hiwi, would you mind sharing the shematics you got? I think they would be interesting to a number of people, me included.

[Hiwi]

Yes but i have to ask, regarding the copyright.
Ralf

[Hiwi]

Hi all,
the problem is solved. There was one of the blocking smd ceramic c defect. It has some resistance about 2-3 kOhm so there was a current drain even when the box was shut down. The internal battery and the battery of the HP-41 went empty within a couple of days.

I obtained the box as a gift from a collector's friend. The box was sold over ebay some month ago. Sold as fully functional, only empty battery at a yery huge price about 400$. Thats more than new! It was announced with something like "Last time I was using it, it worked" :-) But it turned out, that it was broken.

I found out, that it s a 64K Box , not only 32k!

There are 3 types of Ramboxes in the magnetic card reader case

First generation was build with over 24 discret ic's from the 4000 series. This is the 32k only version.
Second generation from 1888/89 was build on a foil circuit board with a custom made gate array and ram. 32k and 8k chips (8bit+2bit = 10bit needed for the HP-41)
There are 32k and 64k Versions. The additional Ram was mounted on the top of the foil

Third generation, especially for the Halfnuts (which has a different power management)
has 3 stacked circuit boards with gatearray and 64k Ram.

Ralf