[Coco] Weird CoCo3 problem...

Brian Blake random_rodder at yahoo.com
Sat Jan 2 13:25:27 EST 2010 

If I had one, I'd try it - besides games the only other paks I have are the S/SC & O90.

I followed Bob's advise and looked over the motherboards closely - no broken traces or anything like that.

With my limited knowledge, I'm leaning towards swapping the CPU and seeing where that takes me.

I reviewed everything again this morning and I did make a mistake last night (it helps when you're actually awake...)... pin 6 of the 138N is actually /SLENB, pin 9 is /SCS. I still get a HI signal all the time from pin 9, at power up and during the looped POKE statement. The frequency from pin 9, tho, is in the 192-kHz range. Nothing I can think of can explain the difference in freq between last night and today, except maybe fatigue (tho the reading on pin 6 WAS correct for my readings just a few minutes ago at 15-kHz)...



________________________________
From: Mike Pepe <lamune at doki-doki.net>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Sent: Sat, January 2, 2010 12:35:18 PM
Subject: Re: [Coco] Weird CoCo3 problem...

I've never seen this particular issue before, but from what you describe the only thing I can think of is the SCS signal is not making it into the cartridge itself. I wonder if a different I/O pak such as the RS232 pak is functional on this system or not.



> -----Original Message-----
> From: coco-bounces at maltedmedia.com [mailto:coco-
> bounces at maltedmedia.com] On Behalf Of Brian Blake
> Sent: Saturday, January 02, 2010 6:05 AM
> To: CoCoList for Color Computer Enthusiasts
> Subject: Re: [Coco] Weird CoCo3 problem...
> 
> Hi Mike,
> The answer to both of those is 'yes'.
> 
> I tried Tetris and it worked fine.
> I also tried the POKE on the CoCo3 with the C9 512k upgrade and the
> Drive 0 light did come on.
> --- On Sat, 1/2/10, Mike Pepe <lamune at doki-doki.net> wrote:
> 
> From: Mike Pepe <lamune at doki-doki.net>
> Subject: Re: [Coco] Weird CoCo3 problem...
> To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
> Date: Saturday, January 2, 2010, 2:10 AM
> 
> 15KHz sounds about right for a loop like that. Every poke to that
> address should drive SCS low momentarily.
> 
> Two other things come to mind for checking- if you put this
> controller/drive on another machine, does the poke make the drive
> activity light come on? Second thing is- do any other cartridges work
> on this machine? Any game paks to test with?
> 
> 
> > -----Original Message-----
> > From: coco-bounces at maltedmedia.com [mailto:coco-
> > bounces at maltedmedia.com] On Behalf Of Brian Blake
> > Sent: Friday, January 01, 2010 9:08 PM
> > To: CoCoList for Color Computer Enthusiasts
> > Subject: Re: [Coco] Weird CoCo3 problem...
> >
> > Hi Mike,
> >
> > Here's what I did - not sure if it was correct:
> >
> > 10 POKE &HFF40,1
> > 20 GOTO 10
> > RUN
> >
> > I then checked pin 6 of IC9 - which according to my schematic is the
> > /SCS line - HI reading on my DMM in logic mode (<1 = LO, >2 = HI, in
> > between it shows the voltage).
> > I then checked pin 40 on the 6809 - the /HALT line - and got a
> reading
> > of 1.545vdc.
> > Not sure if my DMM would react fast enough, I changed to Frequency
> mode
> > and checked pin 6 of IC9 again - got a reading of about 15-kHz.
> > I hit the break key and checked pin 6 again, and it was still HI.
> > Shut of the CoCo, waited a few seconds and turned it back on, checked
> > again and it was still HI.
> > Checking pin 36 on the slot yielded similar results, except the
> > frequency was very different ~110-kHz.
> >
> >
> >
> > ________________________________
> > From: Mike Pepe <lamune at doki-doki.net>
> > To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> > Sent: Fri, January 1, 2010 9:45:14 PM
> > Subject: Re: [Coco] Weird CoCo3 problem...
> >
> > I'd put that POKE &HFF40,1 into an endless loop and look to see if
> the
> > SCS line on the cartridge port is stuck high or if it pulsates.
> >
> > Radio Shack used to sell a pretty decent logic probe for about $20.
> Not
> > sure if they still do, but it would help diagnose the problem in this
> > case.
> >
> > The latch at $FF40 should function independently of a blown out 6809
> > HALT line which is what usually indicates a CPU replacement.
> >
> > > -----Original Message-----
> > > From: coco-bounces at maltedmedia.com [mailto:coco-
> > > bounces at maltedmedia.com] On Behalf Of Brian Blake
> > > Sent: Friday, January 01, 2010 4:48 PM
> > > To: CoCoList for Color Computer Enthusiasts
> > > Subject: Re: [Coco] Weird CoCo3 problem...
> > >
> > > Nope - no logic probe. What kind of signal should be seen there? My
> > DMM
> > > has some logic functions built into it, but, I'm not sure off hand
> > what
> > > it's capable of...
> > >
> > >
> > >
> > > ________________________________
> > > From: Mike Pepe <lamune at doki-doki.net>
> > > To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> > > Sent: Fri, January 1, 2010 7:39:58 PM
> > > Subject: Re: [Coco] Weird CoCo3 problem...
> > >
> > > That's pretty strange. If you have a logic probe you can do some
> more
> > > investigation. The LS138 chip may be faulty.
> > >
> > > > -----Original Message-----
> > > > From: coco-bounces at maltedmedia.com [mailto:coco-
> > > > bounces at maltedmedia.com] Ong happens accept an I/O error - not
> > light,
> > > no
> > > > disk activity, nothing...
> > > >
> > > >  Behalf Of Brian Blake
> > > > Sent: Friday, January 01, 2010 3:24 PM
> > > > To: CoCoList for Color Computer Enthusiasts
> > > > Subject: Re: [Coco] Weird CoCo3 problem...
> > > >
> > > > Tried the POKE and no drive activity light came on. Anytime I try
> > to
> > > > access the disk, nothin
> > > >
> > > > ________________________________
> > > > From: Mike Pepe <lamune at doki-doki.net>
> > > > To: CoCoList for Color Computer Enthusiasts
> <coco at maltedmedia.com>
> > > > Sent: Fri, January 1, 2010 6:08:28 PM
> > > > Subject: Re: [Coco] Weird CoCo3 problem...
> > > >
> > > > I suspect the 6809 as well. But if you do a poke &HFF40,1 the
> drive
> > 1
> > > > activity light should go on. If not something else may be wrong.
> > > >
> > > > > -----Original Message-----
> > > > > From: coco-bounces at maltedmedia.com [mailto:coco-
> > > > > bounces at maltedmedia.com] On Behalf Of Brian Blake
> > > > > Sent: Friday, January 01, 2010 2:36 PM
> > > > > To: CoCoList for Color Computer Enthusiasts
> > > > > Subject: Re: [Coco] Weird CoCo3 problem...
> > > > >
> > > > > Hi Arthur,
> > > > >
> > > > > Unfortunately, it's not socketed. Tho, I have about 9 6309's
> and
> > > > plenty
> > > > > of sockets... hmmmm.... maybe tomorrow....
> > > > >
> > > > >
> > > > >
> > > > > ________________________________
> > > > > From: Arthur Flexser <flexser at fiu.edu>
> > > > > To: CoCoList for Color Computer Enthusiasts
> > <coco at maltedmedia.com>
> > > > > Sent: Fri, January 1, 2010 3:56:15 PM
> > > > > Subject: Re: [Coco] Weird CoCo3 problem...
> > > > >
> > > > > I vaguely recall something like this happening to me years ago
> > that
> > > > was
> > > > > fixed by replacing the 6809.  If this machine and one of your
> > > others
> > > > > has had
> > > > > the 6809 socketed, it would be easy enough to swap in a 6809
> from
> > > one
> > > > > of the
> > > > > other machines and see if the problem goes away.
> > > > >
> > > > > Art
> > > > >
> > > > > On 1/1/10, Brian Blake <random_rodder at yahoo.com> wrote:
> > > > > >
> > > > > >
> > > > > >
> > > > > > All of these new developments on the CoCo front finally lit
> the
> > > > fire
> > > > > under
> > > > > > my arse to set up real hardware again. Besides my repack
> > project,
> > > I
> > > > > have 3
> > > > > > other CoCo3's, two with 512k upgrades (one C9 and one PBJ)
> and
> > > one
> > > > > 128k. The
> > > > > > one with the C9 upgrade works fine - can load and play
> > > Sockmaster's
> > > > > Donkey
> > > > > > Kong.
> > > > > >
> > > > > > The one with the PBJ upgrade, not so... At boot, it comes up
> as
> > > it
> > > > > should
> > > > > > with the proper display. However, any floppy commands are met
> > > with
> > > > no
> > > > > > response from the floppy drive (with an FD-502 controller) at
> > > all.
> > > > > Almost
> > > > > > like the drive is off. The drive responds as it should in the
> > > other
> > > > > two
> > > > > > machines. Upon removing the top case and k/b, I saw two
> wires,
> > > each
> > > > > had been
> > > > > > soldered to opposite sides of R23. Now, under the keyboard,
> is
> > > > > another wire
> > > > > > with alligator clips on each end, and the clips are holding
> on
> > to
> > > > the
> > > > > bare
> > > > > > end of the wires soldered to R23, effectively bypassing the
> > > > resistor.
> > > > > I'm
> > > > > > looking for the PBJ instructions, pretty sure I have them, to
> > > find
> > > > > out if
> > > > > > this is called for. I can also see where C65 & C66 have been
> > cut
> > > > and
> > > > > > re-soldered. I have reseated the GIME and the PBJ memory
> chips,
> > > and
> > > > > cleaned
> > > > > > the 40 pin connector.
> > > > > >
> > > > > > Any other suggestions? My 100MHz o'scope bit the dust so I
> > don't
> > > > have
> > > > > that
> > > > > > tool any more (anybody have a CRT for a Leader 3 channel
> 100MHz
> > > > > scope??)
> > > > > >
> > > > > >
> > > > > > Thanks,
> > > > > >
> > > > > > Brian
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > --
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> > > > > >
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> 
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