<Actually, I find most precautions such as anti-static and so forth to
<be baloney. I must have done every illegal thing in the book, and the
<only things I haven't gotten away with was plugging chips in
Well it's really pay me now or later. While at DEC we (participated) did
and ESD study and we found even TTL was susceptable. It accounted for a
very significant number of boards that shipped good and failed on install
or very shortly afterwards. ESD can damage devices without immediately
failing them. It contributed to many burned in and tested at the facory
only to fail in the field boards and made for a high incidence of failures
in chips associted with interconnects (edge connectors and plugs/sockets).
When a program of ESD grounding was instituted the failures drom 20% over
a year and would continue to drop for several years and habits were
broken.
The problem is difference in charge so try to maintain contact to keep the
static charges equalized/dissipated especially on the
cold dry days were have up north here.
Also handling edge connectors is long term not good. Oils and salts from
the hands are not good even for gold plated connectors.
Allison
First, Uncle Roger declared...
>I have [music] CD's going back to the mid-80's. They all work fine.
>(P.S., never buy an Aiwa CD player.)
Max responded with...
>Why do you say this? I found an AIWA all-in-one thing (radio,tape,
>phono,cd) in the trash a few years ago, and it has worked fine. Does
>it damage CDs or something?
I think I know what Roger may be referring to, Max. About a year and
something ago, I bought my mate an Aiwa 3-disc CD player/changer that also
sported a SCSI port for the benefit of using data CDs.
The thing was new, still in the box. After about a month, it died. I sent
it off to Aiwa, they repaired it under warranty. It came back, lasted for
about another year, then the mechanicals in the transport died. Permanently.
Needless to say, I'm not impressed with Aiwa's later stuff (after 1993 or
so).
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Bruce Lane, Sysop, The Dragon's Cave BBS (Fidonet 1:343/272)
(Hamateur: WD6EOS) (E-mail: kyrrin(a)jps.net)
"Our science can only describe an object, event, or living thing in our own
human terms. It cannot, in any way, define any of them..."
I am right now sitting in a room containing a few interesting parts...
There's an 11/70 here, and 11/44, and 11/83.
And that's not all.
Lining the back wall are VAX 7650, 8530, 11/785...
There's other DEC stuff around... There's apparently a RSX/11M
distrib RL02 pack around, but it's been lost in a sea of XXDP+ packs...
Numbersome MicroVAXen...
I am talking to you right now from the 785! Truly impressive!
The room also holds an AlphaServer 7100, and a lot of Windoze boxen.
This is ATS's lab, where they test things!
Already scored a lot of manuals, PDP-11, VAX, and PDP-8 stuff.
Maybe I can talk them out of this 785, or maybe a DELUA or something... :)
See ya later, I'm gonna see what else I can find!
PS: NONE of this is trash! They actually USE all this stuff to test equipment!
-------
On Sat, 14 Mar 1998, Bill Yakowenko wrote:
> As near as I can tell, the classiccmp web site has been down for
> months now. I've tried probably fifty times since I-don't-know-when,
> but haven't got it to come up. Do you have the inside scoop on that?
> Without that, referring people to the FAQ isn't going to help much.
Oh, sorry. That does tend to be a big problem. And yes, that web site
has been flaky as hell for months now. I believe there is a mirror site
somewhere that carries the FAQ.
Can someone help Bill out? Anyone have a copy of the FAQ lying around?
Sam Alternate e-mail: dastar(a)siconic.com
-------------------------------------------------------------------------------
Computer Historian, Programmer, Musician, Philosopher, Athlete, Writer, Jackass
Coming Soon...Vintage Computer Festival 2.0
See http://www.siconic.com/vcf for details!
On Mar 13, 16:54, Keith Whitehead wrote:
> Ok...here's the problem
> The machine come up with garbage on the screen.It would also seem that the
> video is inverted, I can see the retrace lines etc, so the horizontal
> blanking is not working either by the looks of it.
>
> What I suspect is wrong is that either U42 (the 6845 labeled in my machine
> as a motorola SC80757P) or U102 (the 4.3 video support chip) is faulty (or
> both?).
The 6845 isn't much more than a programmable video timing generator. Since you
have *some* video, it's unlikely to be at fault.
It could be a memory-addressing problem, or a bad connection, or... My first
suggestion would be to *gently* prise each socketed chip from it's socket, and
reseat them all. This helps clean any oxidation off the pins at the point of
contact. Used to be a favourite problem with Apple ]['s, but it's a
widely-applicable technique.
I don't wish to teach my granny to suck eggs, but I'd also suggest you take
care that *all* the pins go back in the socket when you reseat anything; it's
not hard to bend a pin underneath sometimes. For many years I was a
component-level repair technician for an education authority, and I once had
someone bring me a malfunctioning machine which had that problem. When I
pointed it out, the response was "but NEARLY all the pins are in, and it
doesn't work AT ALL".
--
Pete Peter Turnbull
Dept. of Computer Science
University of York
In a message dated 98-03-13 21:22:35 EST, you write:
<< <And in my experience, IC's are not that easy to damage by overheating.
<I've soldered and desoldered hundreds of chips and never once overheated
<one. Yes I do use a temperature controlled iron, etc. >>
with all this talk of soldering and desoldering, is it possible for a layman
to do this with just a regular low wattage soldering iron? any tips from the
pros?
david
] From: Wirehead Prime <wirehead(a)retrocomputing.com>
]
] In repairing the SWTPC 6800 MP-A CPU board, I've discovered I THINK that
] a 7474 which is used to generate NOT HALT to the CPU (and to halt it
] under certain circumstances) is keeping the CPU halted all the time even
] though the bus says there's no reason for it to be halted.
]
...deletia
]
] Thanks...
]
] Anthony Clifton - Wirehead
> From: "Jack Peacock" <peacock(a)simconv.com>
>
> considering the low speed of a 6800, an LS (or even an HCT)
> should work...but, are you sure it isn't the case of a fast
> pulse on the D input when CLK is hit (on the falling edge if
> memory is correct)? and you aren't seeing it (using a logic
> probe or a triggered scope)? did you check the voltage in to D?
> maybe it's in no mans land (i.e. around 2v). Maybe its the IC
> driving the flip flop D input thats bad, or a fast pulse is
> hitting the R* input
>
> Anyway, I'd take it out and put in a socket if you think its
> most likely cause
> Jack Peacock
Do you have anything funky plugged into that box? Later SWTPC systems
had disk controllers doing DMA, but I'm not sure about the 6800.
Does it lock up all the time? If so, can you yank everything except
the MP-A and an MP-C or MP-S in port 1, and see if it still happens?
In that case, there should be nothing wanting to do DMA, so the HALT*
line should be permanently high - no possibility of sneaky fast pulses
on the HALT line that you might overlook. Then everything is simple:
If HALT* is still high on the SS-50 and low on the output of that
7474, then that 7474 is definitely ill. If the problem goes away
when you do this, then maybe the 7474 is okay and maybe you've got
some board doing spurious HALTs.
OTOH, to keep the CPU halted, you'd have to be getting one of those
sneaky pulses on the HALT line in every clock cycle; just one here
and there wouldn't keep the CPU totally halted. Just on that basis
alone, I'd say it's almost certain that the 7474's flip-flopping
days are over.
As for 7474 vs. 74LS74, since the output of this is only driving the
one CPU input, I expect it should be okay. I think the main concern
would be whether or not the replacement chip can drive as many inputs
as the chip it is replacing, and an LS output can certainly drive one
standard input. (Experts are welcome to correct me here!)
Cheers,
Bill.
At 06:53 PM 3/14/98 -0800, Sam Ismail wrote:
>On Sat, 14 Mar 1998, Max Eskin wrote:
>
>[In response to Uncle Roger's spontaneous anti-AIWA quip...]
>
>> Why do you say this? I found an AIWA all-in-one thing (radio,tape,
>> phono,cd) in the trash a few years ago, and it has worked fine. Does
>> it damage CDs or something?
>> >
>> >I have [music] CD's going back to the mid-80's. They all work fine.
>> >(P.S., never buy an Aiwa CD player.)
>
>This is an example of the kind of message that should go to private
>e-mail. Thanks.
>
>Sam Alternate e-mail: dastar(a)siconic.com
>-------------------------------------------------------------------------------
So is this.
No, Thank YOU
Les
>Well, obviously you use the right tools :-). Attacking any
computer board
>with a sheet-metal iron is going to do some damage. But I don't
>understand why a PC motherboard is any more fragile than (say)
a board
>from a minicomputer, workstation, or whatever.
Well, for one thing old boards used .1 inch traces, now with
surface mount it's .05 or .025. I don;t know about you, but my
hand (wasted from advanced age and hard living) isn't steady
enough to solder a surface mount IC.
Jack Peacock
