Analogue-sequencer

> the 62256 RAM IC's arrived this morning and i replaced them, but no
> change...so the last thing i'm now waiting for is the ds1210 battery
> backup circuit. so by now i've resoldered & quadruplechecked all
> solderpoints on the mainboard and replaced just about all IC's on it
> with new ones. i have to admit i'm starting to think about just
> giving up and using the thing as a really expensive nightlight.. :(

Hi Chiel,

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.

If you still can't get it working, you can ship the main board to me and
I'll check it out thoroughly on the scope/logic tester.
If all other ICs have been ruled out, it's possible there could be static or
shock damage to one of the CPU lines.
Have you checked continuity of all the CPU, decoder, DS1210 and SRAM lines
against the schematic, with the ICs removed ? Maybe there could be a broken
track ?

Cheers,
Colin f

--- In analogue-sequencer@yahoogroups.com, "Colinf" <colin@c...> 
wrote:
> 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...
 
> If you still can't get it working, you can ship the main board to 
me and
> I'll check it out thoroughly on the scope/logic tester.

i guess i could do that but i'd much rather sort it out myself so i 
can try to learn a bit and understand what it is exactly that i'm 
doing..

> If all other ICs have been ruled out, it's possible there could be 
static or
> shock damage to one of the CPU lines.

is there a way to check this without a scope?

> Have you checked continuity of all the CPU, decoder, DS1210 and 
SRAM lines
> against the schematic, with the ICs removed ? Maybe there could be 
a broken
> track ?

i'll be doing this (again..) tonight. thanx again for the tips Colin.
grtz Chiel

--- In analogue-sequencer@yahoogroups.com, "Paul Maddox" 
<Paul.Maddox@s...> wrote:
> Cheil,
> 
> > is there a way to check this without a scope?
> 
> As colin said, continuity check all the lines from the CPU to the 
74hc138,
> 574, DS1210 and RAM chips.
> it sounds like a bad track somewhere.
> 
> Paul

thanks Paul, I was thinking bad track myself by now.. i'm going to 
check 'em all tonight. and i think you mean 573 instead of 574? (U4?) 

grtz Chiel

Cheil,

> is there a way to check this without a scope?

As colin said, continuity check all the lines from the CPU to the 74hc138,
574, DS1210 and RAM chips.
it sounds like a bad track somewhere.

Paul

Chiel,

> thanks Paul, I was thinking bad track myself by now.. i'm going to 
> check 'em all tonight. and i think you mean 573 instead of 574? (U4?) 

hehe, yeah that chippy thing with legs :-)

Paul

> > 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

--- In analogue-sequencer@yahoogroups.com, "Colin f" <colin@c...> 
wrote:

morning guys,

> 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.

i've tried this, as well as a continuity check on all IC's concerned; 
i did find a broken track between pins 7 & 2 of the ds1210, and a few 
other dodgy points i wasn't too sure about which i fixed.
i feel i may be getting somewhere now; jumpered as described (U6 pin8 
> U3 pin1/ U6 pin5 > U6 pin6), i'm still getting the '??/??' above 
bank on the first row in the LCD, but above FTS it displays 'G# !' 
which looks like it refers to a scale to me. 
also, last night when i had the p3 jumpered the same way, i got an 
interesting response; when powering up, i first got a bad chksum 
message and the boot/flash screen. when i then hit boot(f1) i got 
what i believe to be the startup-LED sequence (also the 1st time i 
saw the tricolour leds go red!), the RAM test fail messages followed 
by the (by now) usual '??/?? ?? play' display. when i then re-
uploaded the latest firmware version the LED sequence didn't show 
again and the display went straight to the RAM test fail messages.
also, occasionally, generally when i've just re-jumpered the ds1210, 
i get a part of the Memory Layout screen. last night, with the LED-
sequence thing, i even got a complete memory layout screen for a 
second, including the 3 XxX choices for a short second. it didn't 
last though, and continued to the 'RAM test fail!' display.
i'll wait and see what the new ds1210 is going to do tomorrow.

i also have a few questions;
- what is the usual display after a firmware upload? should it be 
the 'checksum' and 'boot/flash' screen? because i'm just getting a 
blacked out top line..it does respond to the F1 'boot'-key though.
- is there an easy scope-less way to check if the CPU is functioning 
properly? i ask because i'm not getting continually consistent 
responses to stuff im trying; a few times the display'll show me one 
thing, and the next it's something completely different..i'm getting 
kinda concerned that the CPU might be busted.

grtz Chiel