Analogue-sequencer

Hi Hans,

> This is what my tech told me while testing the unit,
> The sequencer seems to work fine until  you put the litium battery ( +VB
in
> the schemes) to memory storage. Then the displays shows strange,cloudy.The
> leds turns on randomly and it sends midi messages without any order or
> logic.

That sounds very odd.
The DS1210 IC is basically acting as a voltage controlled switch.
It has two power inputs - one from the normal 5 volt supply (pin 8), and one
from the battery 3.6 volt supply (pins 2 & 7 - it can have a backup backup
battery). There is a power output to the RAM ICs and the decoder (pin 1),
and an enable output (pin 6) that enables the decoder. The decoder selects
the RAM IC for the current address the CPU wants to read.
When the +5v supply falls below a certain threshold, the DS1210 switches
the power output over from the +5v source to the battery source, and turns
off the enable line. This puts the RAM into standby mode.

> He tested it without the battery, and having short circuited the C12
> capacitor, the machine works fine again, his suspects are than the DS1210
> doesn´t work properly, he reports that that piece is connected
> to the feed of the memory chips and a decoder/ multiplextor.

It could be a failed DS1210. Check that you see the following voltages at
each pin of the 1210 (with reference to 0 volts/ground).

Pin    Voltage
1       5v with power on, 3.6v with power off
2       3.6v
3       0v
4       0v
5       0v
6       0v with power on, 3.6v with power off
7       3.6v
8       5v with power on, 0v with power off

If that all checks out OK, let me know, and I'll send you another DS1210 to
try.
This is probably an insult to your tech, but you do have the battery holder
in the right way round ?

Cheers,
Colin f



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