Analogue-sequencer

> > You could bypass the backup controller temporarily to test whether 
> it is the
> > problem.
> > Take it out the socket, and just jumper a wire from the +5v supply 
> to the
> > Vcc supplies on the RAM chips. This would be a wire from pin 1 to 
> pin 8 of
> > the DS1210 socket.
> 
> hm...this is kind of strange; i just tried this, and with the ds1210 
> removed the response is the same as before, i.e. 'RAM TEST FAIL'on U2 
> & U3, boot sequence, then ending in a top line saying 'tempo=149' and 
> the usual bank/fts bottom line. with the ds1210 in place however, i 
> get the 'RAM TEST FAIL' and boot sequence, but it ends in a screen 
> saying '??/?? ??   PLAY' which looks like a much more normal response 
> to a RAM test failure, with the '??'s referring to 'out of range' 
> i.e. nonexistant or unreadable data.
> i'm quite a bit more hopefull after this...

Oops ! I forgot you'll also need to jumper the chip enable line that
runs from the DS1210 to the 74HC138.
This line is used to deselect the '138 that enables the RAMs when the
power goes down.
That might explain the difference...

In normal operation the CE line should be 0v, so jumper pin 5 of the
DS1210 socket to pin 6, then try again.
Since it's potentially possible the track from pin 6 of the DS1210 to
pin 4 of the 74HC138 (U5) could be the problem, check the continuity
between U5 pin 4 and ground once you've put this jumper in.

Hope this helps !
I'm sure there's probably just going to be one dodgy connection spoiling
your fun !

Cheers,
Colin f