My SC1224 just died :-( Help!
Αdοnis
working. No smoke, no indicative smell of burn just a black screen and
NO sound when loading a game which typically plays sound. I tried the
Atari on a friend's machine and it works fine.
I searched online but couldn't find anything useful other than a
couple of mentions that the GoldStar made SC1224s suffered from a dead
thermistor (TH901). (BTW TH902, a big black plastic box next to the
fuse, looks scratched up and not firm when I push it. What exactly is
that thing?) I don't know if there's a way to test a thermistor to see
if it's dead (can I test it like a regular resistor?) but if someone
knows the value, then I can buy a replacement and test. Other than
that, any hints as to the common failures of the SC1224s and if
there's anything else I could check? And why isn't sound working at
least?
And a note: when powering on the screen I can hear the typical CRT
"tsk" noise which I believe it from static electricity around the
screen or degaussing? Not 100% sure, but what I'm trying to say is
that it sounds like the high voltage stuff works.
Thanks in advance for any help
Derryck Croker
> I don't know if there's a way to test a thermistor to see
> if it's dead (can I test it like a regular resistor?)
Yes. It is basically a resistor whose value changes as the temp. goes
up or down. It can be used to limit the switch-on surge. As it heats up
it will allow more current to flow. As a WAG, if you can detect signs
of life (you might also be able to see the CRT filament glowing) then
it is most likely not down to this or your mystery black box.
Hmm, maybe there's a dodgy plug on the end of the video lead, or the
lead itself is faulty?
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Charles Richmond
I've been away from my Atari ST gear too long, but...
Is there *not* a way (via a converter circuit) to connect a VGA
monitor to an ST??? ISTM that it would be a sight easier to lay
hold of a VGA monitor that to find a *replacement* for the SC1224...
... that is, if the original poster is unable to fix his monitor.
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+----------------------------------------+
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Derryck Croker
> I've been away from my Atari ST gear too long, but...
>
> Is there *not* a way (via a converter circuit) to connect a VGA monitor
> to an ST???
Probably ;-) Wasn't the problem actually finding a monitor that would
sync to the Atari?
Mark Bedingfield
> On 2009-12-15 05:26:56 +0000, Charles Richmond <fri...@tx.rr.com> said:
>
>> I've been away from my Atari ST gear too long, but...
>>
>> Is there *not* a way (via a converter circuit) to connect a VGA
>> monitor to an ST???
>
> Probably ;-) Wasn't the problem actually finding a monitor that would
> sync to the Atari?
>
Not in Mono, only in colour. VGA and ST Hi res are nearly the same.
Mark
Ed Edelenbos
"Mark Bedingfield" <atar...@nomorespampleaseoptusnet.com.au> wrote in
message news:4b27f621$0$1783$afc3...@news.optusnet.com.au...
Only certain monitors had the right sync rates in either. I forget which
(Sony I think) but one multisync could do both with a simple switchbox
built into the cable. The ST had to be turned off, the switch set, and then
the ST re-booted.
I have 4 ST's (all upgraded to 4 megs and 1 with a 16mhz accelerator), 4
monitors, 4 hard drives, and a genuine Atari CDAR sitting on the shelf that
haven't been started up for years. I really need to break some of this
stuff out one of these days.
Ed
Mark Bedingfield
>
>
> "Mark Bedingfield" <atar...@nomorespampleaseoptusnet.com.au> wrote in
> message news:4b27f621$0$1783$afc3...@news.optusnet.com.au...
>> Derryck Croker wrote:
>>> On 2009-12-15 05:26:56 +0000, Charles Richmond <fri...@tx.rr.com> said:
>>>
>>>> I've been away from my Atari ST gear too long, but...
>>>>
>>>> Is there *not* a way (via a converter circuit) to connect a VGA
>>>> monitor to an ST???
>>>
>>> Probably ;-) Wasn't the problem actually finding a monitor that would
>>> sync to the Atari?
>>>
>>
>> Not in Mono, only in colour. VGA and ST Hi res are nearly the same.
>>
>> Mark
>
> Only certain monitors had the right sync rates in either. I forget
> which (Sony I think) but one multisync could do both with a simple
> switchbox built into the cable. The ST had to be turned off, the switch
> set, and then the ST re-booted.
Multisyncs could handle all Atari resolutions (well some could). Another
solution is a LCD TV with VGA input. Run composite to the AV input and a
VGA/ST converter into the VGA input. Then all you need is a switch on
the VGA converter to disable the hi res monitor detect line. Voila,
instant modern multisync. ;-)
>
> I have 4 ST's (all upgraded to 4 megs and 1 with a 16mhz accelerator), 4
> monitors, 4 hard drives, and a genuine Atari CDAR sitting on the shelf
> that haven't been started up for years. I really need to break some of
> this stuff out one of these days.
I know how you feel, I have 2 Falcons (1 with a CT2), a TT030, MegaSTE,
Ste, 6 STFM's, a 130XE, 2 800XL's, a 600XL (64k), a XEGS, a Jaguar, a
Lynx and a Portfolio. And to think my Wife calls me nuts. ;-)
I do have the MegaSTE and the stock Falcon on my desk tho, just not time
to use them.
Mark
xla...@cix.compulink.co.uk
derryc...@NOSPAMcix.co.uk said:
>On 2009-12-15 05:26:56 +0000, Charles Richmond <fri...@tx.rr.com> said:
>
>> I've been away from my Atari ST gear too long, but...
>>
>> Is there *not* a way (via a converter circuit) to connect a VGA monitor
>> to an ST???
>
>Probably ;-) Wasn't the problem actually finding a monitor that would
>sync to the Atari?
That used to be the problem - only Multisyncs would work as the
Atari video was to PAL or NTSC TV standards using a 15.x kHz line
rate. Most computer monitors started at 30 kHz, so the converter
would need to be a line-doubler. However, some modern flat screen
monitors double as TV receivers, and most include frame stores
since their display is sequential rather than TV's interlace.
These may well accept the Atari's input signal, specially if they
have a SCART socket.
Regards, /Peter/
Αdοnis
with my SC1224. I don't want a VGA/multisync monitor, nor a flat panel
display (for those, this would be helpful:
http://www.retrocomputing.net/parts/atari/1040STF/docs/connettore_monitor_st.htm)
For far I found these links a tiny bit helpful:
http://groups.google.com/group/comp.sys.atari.st/browse_thread/thread/e49151f085ad96c8/69ee56414b59ac29?lnk=gst&q=dead+sc1224#69ee56414b59ac29
http://groups.google.com/group/comp.sys.atari.st/browse_thread/thread/5080d4f737d22c20/a5aeda733c7d302b?lnk=gst&q=rex+hebert#a5aeda733c7d302b
Unfortunately it's hard to understand people on the net these days,
because they stopped using grammar rules and writing properly (just
contrast the usenet postings above with the brain numbing "rivers of
words" below:
http://www.atari-forum.com/viewtopic.php?f=15&t=2117&hilit=black+screen
http://www.atari-forum.com/viewtopic.php?f=15&t=10579&p=84525&hilit=goldstar#p84525
Anyways, from the little bit that I "got", and from reading the
venerable electronics repair FAQs:
http://www.repairfaq.org/sam/tvfaq.htm
http://www.repairfaq.org/sam/monfaq.htm
I realized that there's no high voltage. There's a squeal when the
screen turns on, but it seems to be coming from the PSU. The filaments
don't light up and the voltages on the back of the tube are in the 50v
range instead of the 100+v range (I tested with a working SC1224).
Furthermore, I replaced the PSUs and the dead one wasn't Lazarus... So
it seems the problem is not in the PSU (and thus the infamous
thermistor - which I tested with a hair-dryer and cold-spray and it
seems to work, although the range was a bit "off" from the working
SC1224's TH901 thermistor). From partial decoding of the cryptic texts
in the atari-forum I'm thinking that maybe it is the LOPT/flyback, but
I'm not entirely convinced. I guess I have to measure more things to
come to a better conclusion. If anyone can give some pointers here,
they'll be appreciated.
Thanks
Jim DeClercq
is on the top of the board, next to a heat sink, where it bakes. And when
it does it kills the flyback.
When you replace both those things, put the cap on long leads, to the
bottom of the board, and toss it up front under the monitor face.
The flyback and cap should be able to get from BEST Electronics. That is
from fixing a 124, not a 1224. Anyway, if you get a new flyback
transformer, get the flyback capacitor, too. Check e-bay. Last I looked a
1224 was selling for 40 dollars.
Jim
=?ISO-8859-7?B?wWTvbmlz?= <4do...@gmail.com> writes:
: Right, so as I was saying, I want to try to figure out the problem
: Thanks
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Αdοnis
thanks for the helpful reply.
On Dec 17, 5:06 pm, Jim DeClercq <j...@panix3.panix.com> wrote:
> Been there, done that. The problem is that the frequency-setting capacitor
> is on the top of the board, next to a heat sink, where it bakes. And when
> it does it kills the flyback.
Dl you mean the capacitor that's at the top-left of the motherboard
(looking top-down), that's inside the flyback's protective shielding
(doesn't look much like a heatsink, not at the top-left corner
anyways). Or do you mean the big ol' capacitor that's directly to the
south of the flyback and indeed close to the heatsink that's got the
HOT attached to it?
And just to make sure, we're talking about the electrolytics here,
right? Because I also see some ceramic ones in the vicinity.
What I just don't understand is why I get no sound out of the
monitor... I mean, the Atari is indeed producing sound (I tested
this), and I also tested the voltages that come out of the main PSU
and go into the sound circuit. It puts out almost 18v. Then the next
leads over to the left are putting out 16v. (not sure what the nominal
voltages ought to be - according to the post below he's expecting them
to be 24v and 12v) Finally the left-most that feed the HV circuits
start at 117v when the HV is disconnected, but get pulled down to ~55v
when the HV circuits are connected. This is very similar to what these
other posters found out:
http://groups.google.com/group/comp.sys.atari.st/browse_thread/thread/5080d4f737d22c20/a5aeda733c7d302b?lnk=gst&q=rex+hebert#a5aeda733c7d302b
http://groups.google.com/group/comp.sys.atari.st/browse_thread/thread/c67bdbcb5d718227/32b29709ff03f7e6?lnk=gst&q=sc1224+voltage#32b29709ff03f7e6
But neither of them says what the real problem was... So it seems it's
something common enough, if they're getting similar behavior.
Lastly, there's a buzz coming out of the PSU when the HV circuits
aren't connected. It almost goes away when the HV is connected to the
PSU.
Edward S. Baiz Jr.
Best Electronics. I think it would be cheaper just to buy a new.
I have seen plenty on the Web for sale, so as cheap as $30...
Falcon030 with 16meg of ram