Re: How do i check the clock circuit?

On 09/24/2013 11:20 AM, Joel Griffin Dodd wrote:
> Thanks Ed.
>
> So far I have verified all voltages on the PSU and AR2 boards and they
> all fall within the required specs.
>
> Next I do indeed plan to make my way through all of the socketed chips
> for cleaning and reseating.
>
I'd invest in a Logic Probe for your first tool. There might even be one
built-in to your DVOM (Digital Volt Ohm Meter). This will either use
blinking lights/LEDs or beeps/chirps to indicate the presence of digital
signal (High/Low) on the trace in question.

I find the old HeathKit logic probes to be the best, although I have a
pile of Kurz-Kasch probes that we also use when the HK probes are all
hiding.

Read up on using Logic Probe, heck there are kits to make your own
(great practice!). It is the first tool I had years ago and it is still
one of the first I turn to for checking things like Clock, Reset, and
other critical signals.

As I went on I got a few more tools...and even started a mail list on
tech tools. Which seems to be mostly Fluke gear these days - but that is
another story.

John :-#)#
>
> On Tue, Sep 24, 2013 at 10:34 AM, Ed Henciak <ehenciak@gmail.com
> <mailto:ehenciak@gmail.com>> wrote:
>
> Hi Joel,
>
> Sorry for the delayed reply.
>
> You might want to insure your power supply is completely stable
> first and foremost. A bad power supply can cause even more damage
> to the main board.
>
> Atari does a pretty good job detailing the voltages you should
> expect to see. I'd disconnect the main board from the power
> supply first and make sure the voltages look reasonable. If you
> want to "overkill fix" your power supply, you might want to
> replace the electrolytic caps on the power supply. They can be
> had for fairly low prices. Also, someone out there may sell a
> "get well kit" for Atari power supplies. These are similar to
> those kits of electrolytic caps and deflection transistors for
> vector monitors.
>
> I'd certainly start there if you're not that well versed in
> PCB repair :-). If you blow that power supply board up, it's a
> heck of a lot easier/inexpensive to shotgun replace every
> component on a power supply vs doing the same on a main boards for
> a video game :-).
>
> One other suggestion ... a friend reminded me of this ... you
> should pull all socketed chips from the mainboard, clean the legs
> off, and reinsert them. The electrical connections in sockets get
> pretty gnarley over time. Use something like a pencil eraser to
> get the gunk off and clean up residue with a bit of rubbing
> alcohol on a cotton swab. I would also clean off the edge
> connectors with alcohol/cotton swab.
>
> And one other thing ... you might want a bench top power supply
> when you move to debugging the main board. The power is cleaner
> and more stable. I forget the voltages required for Star Wars
> though they can be found on the schematics. A bench top supply
> isn't 100% necessary, but it certainly helps a lot!
>
> Ed
>
>
> On Tue, Sep 24, 2013 at 12:05 PM, Joel Griffin Dodd
> <griffindodd@gmail.com <mailto:griffindodd@gmail.com>> wrote:
>
> Pat. Yep I have no illusions about what I am taking on, and
> maybe I will get to the point where I just have to know I am
> beat.
>
> I am documenting my experiences over at KLOV in the hope that
> anything I learn is of benefit to others in my shoes, even if
> that lesson is 'know when to fold em'.
>
> Talon2000 over at KLOV has agreed to give me coaching via PM
> as I try and progress, this is good as he is considered an
> excellent repairer especially with regards to these boards.
>
> For me this hobby has always been about pushing myself to
> learn new things and stretch my abilities, I really do enjoy
> that aspect and whether there are victories or losses I always
> have fun on the journey. Heck, I never would have thought I
> could have built a color XY from scratch, but this passed
> weekend I fired up my creation and she is working, such a
> thrill and very satisfying.
>
> Here's the KLOV thread following the board repair part of my
> journey.
> http://forums.arcade-museum.com/showthread.php?t=288626
>
>
> On Tue, Sep 24, 2013 at 8:58 AM, Joel Griffin Dodd
> <griffindodd@gmail.com <mailto:griffindodd@gmail.com>> wrote:
>
> Thanks for all the feedback guys.
>
> I'll definitely look into a solder reworking station if I
> start to need to remove unsocketed chips.
>
> I am currently looking for a nice used O-Scope but I'm
> having to learn what functions I will need it to perform
> so I don't get something unsuitable. So far I just know
> that 100mhz and above is good and an XY input is a nice
> added option for vector work without monitors.
>
>
> On Tue, Sep 24, 2013 at 8:48 AM, Jimmy Ipock
> <jipock@gmail.com <mailto:jipock@gmail.com>> wrote:
>
> I would highly recommend at least a low end
> oscilloscope. It made troubleshooting my space duel
> vastly easier. Plus, you can hook it to the x and y
> out and play the game sans vector monitor ;>
>
> I actually found a reasonably good one on ebay for 60
> bucks once..
>
>
>
> On Tue, Sep 24, 2013 at 9:52 AM, Pat Danis
> <patdanis@verizon.net <mailto:patdanis@verizon.net>>
> wrote:
>
> Joel:
>
> I salute your dedication in attempting to get your
> board set working. You might have considered
> starting on something a little bit easier. I have
> been doing this for at least 10 years and my skill
> set at fixing boards is what I consider "very
> basic". That is, running the self test and
> replacing chips identified as bad. After that, if
> you do find something that is wrong, chances are
> you will not have the parts you need to fix it.
> There are the very common chips scattered
> throughout he board that are easy to find, it is
> the unique parts that might give you the fits.
>
> If you do find the problem, you need to be certain
> you know what you are doing when replacing chips.
> Can you cleanly desolder chips without ripping
> pads or traces and reinstall a socket? If not,
> You might stop now and consider sending the board
> off to a "pro" (Not me) and let them tackle it.
> It costs more in the long run for them to fix
> other people's screw ups. It is certainly
> admirable to learn to fix things yourself but it
> might be better to start on a simple board like a
> pacman etc.
>
> There is a Star Wars trouble shooting guide
> available and a ton of information on the web
> about star wars issues. Who knows, you might get
> lucky and find the problem and change a chip and
> be up and running. (I doubt it) Based on my
> experience with SW board sets, you have a long
> road ahead of you. I know two guys who fix them
> and I consider them brainiacs when it comes to
> board repairs. They still have problems sorting
> out all the issues.
>
> Best of luck in your endeavors.
>
> Pat
>
> On 9/24/2013 8:32 AM, Joel Griffin Dodd wrote:
>> Thanks guys, the info on spotting a clock
>> visually was especially helpful. Sometimes the
>> skill level of guys that have been doing this
>> work for such a long time skips past many of the
>> most basic yet useful pieces of information that
>> a newbie simply doesn't yet know. Now at least I
>> know what to look for on the PCB in the 'real'
>> world as well as the schematic.
>>
>>
>> On Tue, Sep 24, 2013 at 2:08 AM, Andre Huijts
>> <a.huijts@upcmail.nl
>> <mailto:a.huijts@upcmail.nl>> wrote:
>>
>> The clock signals are generated using
>> crystals. They are easy to ID, usually a flat
>> aluminum colored can:
>>
>>
>>
>>
>> More modem versions look like this, if you
>> see these, the crystal has probably been
>> replaced in more recent years:
>>
>>
>>
>>
>> This may sound weird but your first work
>> should be visual. Check if the crystals are
>> there at all and if they are still firmly
>> soldered. I actually started measuring for a
>> clock signal only to discover some seconds
>> later that it was missing :) The crystals
>> often get damaged or broken off during
>> stacking PCBs or transport because they stick
>> out high above all the other parts. This is
>> also why I prefer to replace them with the
>> smaller modern types.
>>
>> A general visual inspection is always a good
>> idea. Look for damaged tracks, bad sockets
>> etc. in case of SW PCB set, make very sure
>> the interconnection board is on really tight.
>>
>> Verstuurd vanaf mijn iPad
>>
>> > Op 24 sep. 2013 om 10:49 heeft Andrew
>> Welburn <andy@andysarcade.net
>> <mailto:andy@andysarcade.net>> het volgende
>> geschreven:
>> >
>> > You need to get the manual and schematics
>> and read them, they you will know where all
>> these things are...
>> >
>> > Andrew Welburn
>> > http://www.andys-arcade.com
>> >
>> >> On 23/09/2013 23:33, Joel Griffin Dodd wrote:
>> >> Thanks Ed!
>> >>
>> >> No problem on waiting for the probe to
>> arrive, I'm moving house this
>> >> week so I have plenty to keep me busy.
>> >>
>> >> How do I physically identify a
>> clock/chip/oscillator on a board? Also
>> >> how do I know which line out is the clock
>> line?
>> >
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>> <mailto:chris@westnet.com>
>>
>>
>
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