>From: "Ethan Dicks" <dickset(a)amanda.spole.gov>
>
>On Thu, Nov 25, 2004 at 01:26:04AM +0000, Philip Pemberton wrote:
>> In message <200411250057.QAA03125(a)clulw009.amd.com>
>> Aside from being a "better KIM"? ISTR it was basically a KIM with a few
>> extras (oscilloscope output, a la the Poptronics Scopewriter) added. I don't
>> think it used the mask-programmed RIOT chips either, unlike the KIM, which
>> makes it (slightly) easier to fix if something goes wrong.
>
>It does not use mask-programmed RIOT chips... one of the reasons I'm happy
>to have a SYM-1 - no unobtanium ingredients.
>
>-ethan
Hi Ethan
One can wire the 6532 and EPROM chip in place of the 6530. It does
require a little mapping because the selects most likely won't
be compatable but the rest should work. There is a fellow in
France that is doing this for Pinball machines.
Dwight
On Dec 1 2004, 13:21, Jules Richardson wrote:
>
> I've got a board here with a short between ground and the +5V rail
> (actually not quite dead - I'm getting around 10 ohms between the
rails)
>
> Any useful tips for finding the fault? It's a large board,
multi-layer,
> lots of silicon on it unfortunately :-(
That's only about 500mA at 5V. Sure it's a short? Of course, it may
draw lots more than that under power, if your meter is not using enough
voltage to turn on junctions.
> Are there any particular components that are likely to fail in this
way
> that might be found across PSU rails? (decoupling caps, certain ICs,
> crystal modules etc.?)
Decoupling caps, TTL, and some MOS memory chips all can draw excess
current when faulty. I usually put them on a hefty 5V supply and feel
for what's hot (you can sometimes burn out the short in a decoupling
cap that way -- they often go bang). Point of reference: a BBC B board
normally draws about 2A at 5V, but the last one I had with a
particularly nasty set of faults drew over 10A at 5V -- and the faulty
TTL chips got hot enough to feel without actually touching them.
> Given a suitably sensitive meter is it sensible to assume I can try
and
> home in on the short location a little? (I've found readings between
> GND/supply on various LS chips of anything between 9.5 and 12 ohms so
> far)
You really want a current tracer. HP made a really nice one, and I'm
still annoyed I didn't bid high enough on the last one I saw :-(
--
Pete Peter Turnbull
Network Manager
University of York
the biggest culprit when it comes to older electronics is the good old
tantalum cap. I have seen these be a little resistive, dead shorts, etc.
good luck.
best regards, Steve Thatcher
At 08:21 AM 12/01/2004, you wrote:
>I've got a board here with a short between ground and the +5V rail
>(actually not quite dead - I'm getting around 10 ohms between the rails)
>
>Any useful tips for finding the fault? It's a large board, multi-layer,
>lots of silicon on it unfortunately :-(
>
>Are there any particular components that are likely to fail in this way
>that might be found across PSU rails? (decoupling caps, certain ICs,
>crystal modules etc.?)
>
>Given a suitably sensitive meter is it sensible to assume I can try and
>home in on the short location a little? (I've found readings between
>GND/supply on various LS chips of anything between 9.5 and 12 ohms so
>far)
>
>I've checked the board for particles of anything that might be causing
>the problem, plus I'm halfway through ruling out any of the socketed
>ICs. Of course if it's a problem with the multi-layer PCB itself... eek!
>(do these ever fail in such a way though? It's a commercial board which
>used to be fine)
>
>cheers
>
>Jules
>From: CRC <technobug(a)comcast.net>
>
>
>On 1 Dec 2004 09:43:56, Paul Koning <pkoning(a)equallogic.com> commented:
>
>>>>>>> "Jules" == Jules Richardson <julesrichardsonuk(a)yahoo.co.uk>
>>>>>>> writes:
>>
>> Jules> I've got a board here with a short between ground and the +5V
>> Jules> rail (actually not quite dead - I'm getting around 10 ohms
>> Jules> between the rails)
>>
>> Jules> Any useful tips for finding the fault? It's a large board,
>> Jules> multi-layer, lots of silicon on it unfortunately :-(
>>
>> 10 ohms means about 0.5 amps -- sounds like a perfectly respectable
>> amount of current for a board with "lots of silicon" to draw.
>> So... are you sure there is a short, rather than just circuitry?
>>
>> paul
>
>Unless there are passives (like terminators) between +5V and GND, 10
>ohms is a little low. 0.5 amps represents a minimum current that the
>board will pull. An ohmmeter will not normally cause the silicon to
>conduct and hence be counted in the total resistance. Some chips do
>have internal dividers, but the they are nomally in the 10K + range.
>
>I normally use a current limited supply at the required voltage and set
>the limit so that it starts to limit. I then use a 5 digit voltmeter to
>trace where the current is going. This is done by placing one probe on
>the +5V input and then measuring the drop as you trace out the
>distribution path. The path drawing the current will continually drop
>while non-drawing paths will remain at a constant voltage drop.
>
>On multi-layer boards you measure drops to the Vcc pins of the bugs and
>map the drop.
>
> CRC
>
>
Hi
I use a slightly different method. I use a current limiting
supply and set it to about an amp or two. I place the supply
across one of the power planes ( corner to corner on a solid
plane and end to end for E traces ). I do not place the supply
form power to ground, just across the one plane.
I then place one lead, of a meter that reads 5 digits on a
200 mV scale, from the opposite rail that is shorted two.
One then simply traces for a null on the plane with the
current flow across it. On a plane, I take
a piece of string to mark the line of the null and then
put the supply on 90 degrees, across the same plane. Where
the new null line cross the old string is the where the short is.
This method will even work if the short is +1K, if that is
the only current flow. I once showed using it on a burnin
board with a 10K resistor that was in wrong out of some
400 sockets and about 12 resistors per socket. I was able to
zero right into the exact resistor.
The principle is that one uses the plane as though it were
a variable resistor and the short was the contact. If one
measures along the resistor to the contact, the voltage
will be zero at the location where the contact is made.
This is much easier to read than CRC's method since you
are looking for a null, rather than a stop in the change of
the voltage. It also has the advantage that it won't blow
an intermittent short so you can find it. It is more sensitive
than the HP current probe for power planes ( having used
both methods ). It also is run at a very low voltage so
there is no chance of damaging other parts.
I publish this method every now and then but most people
don't think about how it works and will tend to forget it.
Such is!
Dwight
Hello, all:
I'm looking for recommendations on CS textbooks for myself...I'm
embarking on sort of a DIY CS degree :-)
Anyway, if anyone could recommend decent first-year and/or
second-year books on algorithyms and data structures in C/C++, I would
appreciate it.
Thanks.
Rich
Rich Cini
Collector of classic computers
Build Master for the Altair32 Emulation Project
Web site: http://highgate.comm.sfu.ca/~rcini/classiccmp/
/************************************************************/
On 1 Dec 2004 09:43:56, Paul Koning <pkoning(a)equallogic.com> commented:
>>>>>> "Jules" == Jules Richardson <julesrichardsonuk(a)yahoo.co.uk>
>>>>>> writes:
>
> Jules> I've got a board here with a short between ground and the +5V
> Jules> rail (actually not quite dead - I'm getting around 10 ohms
> Jules> between the rails)
>
> Jules> Any useful tips for finding the fault? It's a large board,
> Jules> multi-layer, lots of silicon on it unfortunately :-(
>
> 10 ohms means about 0.5 amps -- sounds like a perfectly respectable
> amount of current for a board with "lots of silicon" to draw.
> So... are you sure there is a short, rather than just circuitry?
>
> paul
Unless there are passives (like terminators) between +5V and GND, 10
ohms is a little low. 0.5 amps represents a minimum current that the
board will pull. An ohmmeter will not normally cause the silicon to
conduct and hence be counted in the total resistance. Some chips do
have internal dividers, but the they are nomally in the 10K + range.
I normally use a current limited supply at the required voltage and set
the limit so that it starts to limit. I then use a 5 digit voltmeter to
trace where the current is going. This is done by placing one probe on
the +5V input and then measuring the drop as you trace out the
distribution path. The path drawing the current will continually drop
while non-drawing paths will remain at a constant voltage drop.
On multi-layer boards you measure drops to the Vcc pins of the bugs and
map the drop.
CRC
Several of the programs I try to run on my "classic dos" machine give
the error message:
<filepath\filename>:not coff (check for viruses)
I don't yet have a virus scanner, but these files were downloaded from
trusted sources
I don't think I have a virus. What is this error message?
A nice site on the IBM Composer:
http://www.ibmcomposer.org/
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
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In case anyone wondered what became of him . . . very sad.
FLORIDA CRIMINAL HISTORY RECORDS DEPARTMENT OF CORRECTIONS
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