I have this dead XT here, and I wanted to replace its motherboard with a
newish ATX beastie. Anyone know where I might be able to find some
pointers?
Peace... Sridhar
Tony wrote:
> Do you have a logic analyser? If so, then I would try looking at the 8080
> address bus. See what bit of the program it's executing, see if it does
> the right things when you press the keys, etc.
I have, it's a Biomation K100-D. When I first set it up Sunday afternoon,
and turned the LA on, the screen moves vertically. So I had to get the LA
in good working order first! As I have the operator & service manual, the
location of the vertical freq. adjustment was quickly found. The screen is
now steady.
I connected the pod B, 8 data inputs to the ROM address lines A0-A7, and
gave it a manual trigger to capture all it sees. At first I got too much
detail (address repeats several times), but after setting the clock of the
LA to sample at 10 ?s I got almost always consecutive addresses.
That depends on the length of the instruction. Anyway, I see the addresses
60-110 (octal) in the correct order and see the address jump at 101 to the
address 335 (a subroutine). I see the complete execution of the subroutine
and the return. Indeed going to address 105. That means the stackpointer
and the memory must be OK! ReturnPC stored in RAM, and retrieved correctly.
However, I can not check everything. Need to connect pod A, and have 8 more
data input lines to measure interesting things. And trigger facilities!
It's time to read the user manual of the LA, to do advanced measurements.
I still haven't got a clue what's going wrong ...
- Henk.
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At 09:57 07/11/2005 -0500, you wrote:
>Re: " What does a single vertical line in the middle of a display indicate?"
>
>This is a symptom that is normally never seen.
>
>It would, in theory, indicate loss of horizontal deflection. The problem is
>that loss of horizontal deflection in virtually all monitors also causes
>loss of high voltage, which keeps you from seeing ANYTHING. [The high
>voltage is obtained from the horizontal output transformer ("flyback"
>transformer) in virtually every TV set and monitor made.)
>
>One possibility: If the horizontal deflection yoke was open, there could be
>a loss of horizontal deflection while you still had output from the
>horizontal output transformer. Usually, an open yoke would shut down the
>horizontal output and high voltage, but it's the only way I can think of
>that you might get loss of horizontal deflection and still have high
>voltage.
I have a MAC Plus with the same symptom - seemed odd to me as well, so I asked
a local guy who used to repair monitors. He didn't think it was that odd, here
is what he responded with (I haven't had time to look further at it yet):
>#2 - I've got a Mac Plus which displays a thin VERTICAL line - I've not
>seen this before, because since it has HV, the horizontal oscillator must
>be running! - any guesses?
This obviously has separate circuits for EHT and horizontal
drive/deflection, and the deflection circuit has a bad drive component or
bad solder joint. Usually the HOT goes due to high ESR caps in the primary
side of the transformer driving the HOT, or the solder joints go bad because
of the high drive currents and heat. Also check the flyback transformer
(actually, all) solder joints with a 10x loupe. You really need an ESR
meter and to go through all the electrolytics on the board. I regret selling
mine a few years back; that was an invaluable piece of test gear.
Regards,
Dave
--
dave04a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.parse.com/~ddunfield/museum/index.html
>
>Subject: TI 99/4A Power Supply
> From: "Harriman, JT" <jharriman at waff.com>
> Date: Mon, 07 Nov 2005 12:34:39 -0600
> To: <cctech at classiccmp.org>
>
>Good afternoon
>
>
>
>Can you tell me if the TI 59 calculator requires a DC or AC wall-wart?
>
>
>
>Thanks
>
>
>
>JT
The 99/4a is AC the 59 is DC
Allison
Hello folks,
somebody has uploaded some useful information about these drives to
bitsavers - thank you!
There is only a kind of technical overview manual for my drive at the
moment.
But I still and urgently need the schematics for the 7978 drive. My
power supply has broken down and I cannot get it back working. I also
don't know how to repolace it because I don't know where to connect
+/-12V and power good etc....
Thank you very much!
Philipp :-)
P.S.: Shouldn't my Honeywell software be hosted on bitsavers, too?
I forget. What does a single vertical line in the
middle of a display indicate? It might be something
entirely different from an image that collapses into a
horizontal line, but I seem to remember one of them
representing a definitive component failure. If it
makes a difference, the unit is a compact Mac, a
Classic I think. Can any (and all) *new* display
components still be had for such a unit. Substitutes?
Reasonable facsimiles? Yo thanks.
__________________________________
Yahoo! FareChase: Search multiple travel sites in one click.
http://farechase.yahoo.com
Hi,
I seem to remember that I have a copy of the UCSD p-System for a PC. I also
have a z-80 cross-assembler for that environment.
I'll have a look in the storage room tonight and see if I can find the
media. From memory, it was distributed on 5.25", 360K floppies.
What are the re-distribution rules? I believe that UCSD still exists, so it
is probably not abandonware.
Regards
Doug Jackson
Hey, does anyone here have a black 1.2MB floppy drive? I'm going to
make it a permanent addition to my current PC for data transfer to/from
my pdp-11 and DECmate.
I have a Digital Equipment Corporation AlphaServer 1000 4/266 for sale.
The price is negotiable, but I'd really like to get around $100 for it if
possible.
This unit has a StorageWorks SCSI expansion chassis as well as a ton of
manuals - mostly VMS.
It comes with the owners manual and VMS CDs.
The unit worked perfectly when pulled from service but we had to junk the
drives in order to protect sensitive data thereon (per previous threads.)
The unit takes common SCSI drives, however, so getting it going will be a
snap. All of the drive caddies for both the system unit and the
StorageWorks cabinet are present.
Here's the rub - the unit is heavy, Especially with all of the manuals,
so this is a pick-up only deal in San Jose, CA. I don't have any time to
pack and ship this beast.
Please email me directly with offers.
Thanks!
--
Erik Klein
www.vintage-computer.comwww.vintage-computer.com/vcforum
The Vintage Computer Forum
With all of this ragging on audio nut who spend obscene amounts of money on
wire, I decided to at a look. I don't know why we call them crazy, they
don't have 1975 computer running in the basement.
The guy in the next office is in to high end audio. (Although he claims that
he is in the lower end of the people in his audio club.) I asked if he had
a power cord so I could take some pictures. He had a spare PS Audio xStream
Statement Power Cable, the 2 meter version lists for $550. This is 6 gauge
oxygen free copper with machined connectors. The cord has a ferrite
impregnated jacket.
Here is my short review of the power cord
http://www.swtpc.com/mholley/MP_F/PS_Audio.htm
I took it home and hooked it up to my new custom case computer which also
cost me about $550. It is a modern 3 GHz Pentium that looks like a 1975
SWTPC 6800.
http://www.swtpc.com/mholley/MP_F/MP_F.htm#NewCover
