Conference 7.286::atarist

The printer port is connected directly to the AY-3-8910 sound chip. 
(It has an extra parallel port on it for this function.) Your
symptoms indicate that one or more data bits in the printer port section of
this chip was "blown".  The part is available at Radio Shack for about $7.50.

My suggestion would be to replace this part, and if it still doesn't work,
persue more expensive repair options.

Unfortunately, this part is not usually in a socket.  It's a 40-pin part.

    
    	Have you given the ST the ol' FLEX? Holding the computer by
    the sides, flex the case a couple times, left and right. Don't
    laugh...every once in a while, the chips in my 520 would get loose.
    I read about this flexing in a magazine, and it seemed to work.
    I used to get junk on my screen, and this solved the prob.
    	In Nashua, the only place I know of is White Mountain computer.
    I can't recall what street it's on, but it's across from ComputerTown.
    I can't quote their prices or reliability, but it's a place to start.
    
    
    					Les Fister
    					Andover Cal Lab
    

    Each output line for the printer port is coupled through an odd,
    three legged, capacitor like componet that is actually an LC circuit.
    There is an inductor between the outer two leads with a capacitance
    coupled to both from the center lead, which is grounded.  Recently I blew
    out one of these LC circuits (for data bit 02).  The local Atari
    repair shop told me that those components were impossible to get
    but they were able to make repairs by simply bypassing the circuit
    with a piece of wire run between the two outer holes!  If you can
    determine which bit is bad, it is possible that this circuit has
    gone bad, and not the chip.  
    
    BTW, if anyone knows what this component is and where to get it
    I would really like to know.

    Drop fix and Flex fix... I can't believe people actualy recommend
    these ways to fix a "delicate" piece of equipment like a computer.
    
    YES it may fix the problem (ie: reseat loose chips) and yes maybe
    it hasn't casused any damage to your computer yet. BUT NO I don't
    think it's a very good way to fix your ST or any other piece of
    computer equipment. It could very easily break something much more
    costly (or difficult) to fix than loose chips. Flexing could cause
    etch to break, causing hairline cracks that can be very difficult
    to see and interrmittent, making them hard to trouble shoot. Dropping
    can physically damage chips, I have seen less shock cause complex
    (ie: expensive) chips to stop break.
    
    I've been supprised in the past to hear that even some ST repair
    shops recommended and used these same techiniques to repair ST's.
    
    I don't mean to knock anyones intelligence on the subject I'm just
    trying to pass along views based on my experience in manufacturing
    and hardware engineering.
    
    	Ray

    
    Hello,
    	Another 4c's worth, or is it 2c? . There are recuurent stories
    that some Atari printer driver chips cannot drive certain printers
    successfully. This is due as stated earlier, to lack of proper driver
    ccts on the outputs of the printer chip. The "fix" is to replace
    the termination resistors IN THE PRINTER with other resisters of
    a different value, to enable the Atari chip o/ps to switch. I have
    heard that one ST will drive a particular printer, but another ST
    would not drive the same printer, the margin is so close.  
    	You should be able to see whether you have an intermittent or
    DEAD line bu sending the printer a Known Test character set and seeing
    whether the corruption is constant ie picking or dropping an ASCII
    bit.                                             
    Cheers
    
    Pat K. 
                                                      

Pat,

The problem you are referring to is the connection of the HP DeskJet to
the Atari.  I am actively engaged in solving this very problem.  I have
for several months now (on and off) been trying to figure out why the HP
Desk Jet works in MY house, but not in Chris Paulus's house.  (Same
printer, same cables, and believe it or not, same computer.)

At this point I am convinced that this story about terminator resistors is
NOT true.  The reason I am not convinced is that I built a signal buffer
that amplifies the signals coming out of the Atari to 74LS244 levels,
which are easily strong enough to drive into 2Kohm terminators, and whose
inputs are sensitive enough that the Atari should have NO TROUBLE driving
them from the MOS outputs of any Yamaha chip.  With the buffer installed,
the printer STILL works at MY house, and STILL fails at Chris's.

For this reason, I think the terminator resistor thing is wrong, and that
the actual problem is TIMING, rather than LOAD.  I've been meaning for a
couple of weeks to put a scope probe on it in order to check the set-up
and hold times around the data strobe, but I've got a rear-mounted laser
and extended cargo bay in my Cobra MK III now, and 1500 credits to my
name, and I'm getting ready to buy myself a mining laser and fuel scoop so
that I can start harvesting asteroids :-).  (You can blame my brother for
this, he's the one that bought me a copy of Elite for Christmas.)

Oh, since you are all going to ask about it anyway, we've determined that
the mains at Chris's run a bit low at about 116v, and mine a bit high at
122 v, and that somehow this 5% variation must be responsible for the
problem.

    hi Jeff,
    
    re .6, This is very interesting!! There was a lot of obviously useless
    info in the ST World magazine a few issues ago!!. What happended
    was a guy had an intermittent printer on his ST, so he senrt it
    for repair, the repair shop "fixed" it and charged him an arm and
    a leg, about $250 I think. However the printer now would not work
    at all!!!!. The guy had a lot of aggro from the repair shop, so
    he was asking for help from the readers of the Mag. In the next
    issues were lots of helpful? advice including several who mentioned
    the driving capability and the resistors. There was even an article
    from the UK stockists of the NEC 2200 saying that unless you bought
    a NEC from them which was modded to the atari ST driver requirement,
    any Grey imports (ie cheapos Nec 2200's, not sold by them) would
    DEFINATELY not work. Funny enough I bought a Cheapo from a box shifter,
    IT WORKS GREAT!                                                                 
    So who do you believe !!                  
    I believe you, but I dont understand your problems!!!
                                              
    Cheers                                    
                                              
    Pat Keane.                                
                                                             

    JUST TO CAP OFF MY ORIGINAL QUESTION ... I DID BUY THE RADIO SHACK
      PROGRAMMABLE SOUND CHIP ($7.50 ) AND ADDED A SOCKET WHILE I WAS
    AT IT IN REPLACING THE ORIGINAL CHIP.  THE PROBLEM HAD BEEN THAT
    BITS 0 AND 1 WERE ETERNALLY ON, AND AFTER THIS REPLACEMENT EVERYTHING
    IS FINE.  THANKS FOR THE ADVICE ... YOU SAVED ME A REPAIR BILL.
     HOPE IT HELPS SOMEONE ELSE.
    DAVE
    

Thanks for reminding me about this note.

Further research shows that the DeskJet problem might be some sort of
software problem.  No idea what components are involved - I'll defer to
Chris to explain how he get's it to work.

    Chris does that mean that finnaly after what seems about six months
    you finaly got your deskJet to work? What was the problem?
    
    	Ray