Conference hydra::amiga_v1

    You undoubtedly have fried one or both CIA chips (8520).  Cost each is
    $15.55 (retail).  Time to put it in (about 20 minutes in a 2000).  You
    did this damage because of 1 of two things: 1) You plugged you 25 pin
    "D" connector into  the parallel port instead of the serial port, or
    you have not protected the power pins on the 25 pin "D" connector on
    your Amiga.  When you get the 8520's replaced replace BOTH chips. 
    Don't settle for just replacing one!  The pull on one can affect the
    other.  Then build a cable to interface the two which isolates the
    power pins on the Amiga.
    
    Good luck, it should work.
    
    Clark

    I opened my 2000 and found the two chips labeled 8520A-1.  Is there any
    way to confirm that these are the culprits?  Would the 8520R2 chips in
    my Amiga 1000 work.  I could at least test them to see if it cures my
    problems and get my 2000 up and running until replacement parts arrive. 
    I could do a while without my 1000 a lot easier than my 2000.
    
    re -.1
    
    > You have not protected the power pins on the 25 pin "D" connector
    > ...build a cable to interface the two which isolates the power pins
    > on the Amiga.
    
    My power pins are likely not protected, since I have never heard that
    before.  What exactly does this cable look like that would isolate the
    power pins?
    
    Terry
    

    The A1000 chips will work, but I think you will loose Half-brite
    capability.  The 8520s are more static sensitive than most chips so
    please use a wrist strap.  You can make one easily by attaching a 1
    megaohm resistor to some copper tape and using velcro to secure it
    around your wrist with the copper tape touching your skin, then ground
    yourself with a wire from the other end of the resistor to the chasis
    of the A2000 (use the grounding shield attach points on the A1000). 
    Remove the two CIA chips (noting the orientation of the chip [notch in
    chip goes toward the rear of the A2000]).  Install the two new ones. 
    When removing the two new ones from the A1000 have some conductive foil
    ("tin" foil will work), to put the chips on while transporting them. 
    All of this assumes that you have removed the power supply chasis and
    have given yourself easy access to the 8520 chips on the A2000.  When
    removing the CIA chips, please note that a chip puller can warp the
    board badly.  Use even pressure if you're using a chip puller and if
    not, pry slowly on one end of the chips and then the other, to "walk"
    them out of the socket.  If youy need the chips and you are in the USA,
    then leave me E-MAIL and I'll send you two of them (for my cost and
    shipping of course).
    
    If you have questions or need some help E-Mail me at SDOGUS::Williams.
    
    Good luck, its really very easy if you take your time.
    
    Clark

Re: .3

>    The A1000 chips will work, but I think you will loose Half-brite
>    capability.

Shouldn't be a problem:  the version of the Denise chips controls
whether you have extra half brite mode.

    You're absolutely correct Randy, my error.
    Clark

    Well, I put my 1000 8520 chips into my 2000 and it worked.  Just for
    kicks I put my 2000 (blown) chips into my 1000, and it worked. I was a
    little suspicious, but happy to have my 2000 up and running again -
    until I connected everything back up to all the ports, then bye-bye
    2000 again.  I narrowed it down to the Supergen genlock and thought
    maybe it was bad.  When I turned the machine on with the genlock
    connected, the floppy drive lights come on now and stay on, and the
    machine never boots.  If I take the genlock off, everything is great.
    
    Suspecting the genlock was bad, I tried it on my 1000.  It worked
    flawlessly.  I then put an old Amigen genlock on my 2000, and the same
    symptoms appeared, drive lights stay on - no boot.  
    
    Anybody have an idea what might be causing this?  What could be
    different on the RGB port with a genlock attached?  What else could
    my modem have blown up on the RGBport?  Any ideas would be appreciated.
    
    Terry
    
                                                               

    Okay, try this.  Check the Jumper J300 and make sure that it is on the
    left two pins.  If not, move it to the left two pins.
    Number two, are you sure that you are hooking up the Genlock to the
    VIDEO?  I'm not trying to be a smart a*s, but the disk port and the
    video port are both 23 pin connectors, and just looking at the A2000
    schematics here, I'm not sure how the video could confuse the disk
    drive lights.  Check that everything is hooked into the PROPER ports!
    
    The only thing the video ports go to is the VIDIOT and thru some
    schmidts and then into Denise (yes you can substitute Denise, but you
    may loose HB) and XCLK and XCLKEN feed FANG, and I think GARY gets some
    of the floppy control.  You could try changing out Denise, Agnus and/or
    Gary.
    
    That is about all I can think of Terry.
    
    Hope some of this helps.
    
    Clark

    
    
    	Could it be a power problem ?  The Amiga uses +5 for the logic
    but needs +12 for the disk. If the modem hit the +/- 12  and blew
    something in the genlock that is now pulling on the +/- 12 volt
    it all ties together.
    
    		Steve P.
    		Wild guess are fun ...
    

    I thought that this 2000 had a hard disk.  If so and 12 volts were
    nailed, I don't think he would be able to boot.  Also the lights are
    controlled by the logic and that tends to lead me back to the CIA chips
    or Denise.
    
    Don't know.  Sure would be fun to look at it, but Utah is a long way
    from San Diego.
    
    Clark

    I'm presently back in Boston for Net U for the week so I won't be
    trying to fix my 2000 for a while.  Sounds like the problem is getting
    complicated enough I may have to take it in for service.  Yesterday my
    MIDI interface started getting flakey even though the serial port to my
    printer and old modem worked just fine.  Then out of nowhere, the green
    DMA light would come one while in the CLI (but not the light on the
    hard disk).  
    
    re -.2 Yes I am hooking into the RGB port, then the monitor works fine
    if I take out the genlock.  Also DCTV works fine off that port.  I
    should have the new 8520 chips when I get home and will replace the
    1000 chips I swapped.  If that doesn't do it, I'll just take it in and
    leave it for a few weeks at the local repair shop unless I come up with
    a better idea before then.  
    
    Thanks,
    Terry
    

    TERRY,
    I forgot to tell you about the cable.  On the Serial port pins 14 and
    15 carry power (I think, the 1000 had pin 25 with power, so you should
    check the 2000 book to make suer that I'm right about 14 and 15).  You
    simply make a cable that has pins 14 and 15 isolated (not connected). 
    Sometimes, when people plug a parallel printer cable with a 25 pin D
    connector on one end and a centronics connector on the other end
    (especially when the cable was built for a 1000 [same sex as the serial
    connector on an A2000]) the grounded pins on the parallel cable short
    pin 14, 15 and ground together.  Usually the result is that the CIA
    chips fry very quickly.
    
    To protect yourself you isolate pins 14 and 15 on your modem cable and
    you don't have to worry about how the manufacturer builds the modem. 
    You don't want to do this with everything hooked into the serial port. 
    Your printer, and or your MIDI, FAXs, etc may use more than just pins 1-7
    and 20.
    
    It is possible that you nailed Denise.  I'm just not sure without more
    information.  Before you take it in, lets try some things.  Send me
    Mail when you are back from NET U.
    
    Clark

    I called Digital Creations to see if they could give me hints why
    plugging in the genlock killed the machine.  They said to check for
    power on pins 21-23 on the video port.  I did.  Port 21 has -5V and the
    pins 22 & 23 which are supposed to have +12 and +5V have nothing.  My
    hard disk works fine and there is +12 on two pins on the serial port,
    so there must be power.  Did I blow a power supply or just something
    that provides power to the video port?  Any ideas?
    
    Terry,
    

    You should have +12 on pin 9 of the serial port 
                    -12 on pin 10 of the serial port   <-----****
    
    The +12 volts (called +12_USER) has the same source for the serial and
    the video ports.  If these voltages are not correct, then you could
    have fried the power supply or most likely just some small resistors
    inside the power supply (to limit user draw).  
    
    Hope this helps
    
    Jean
    

>   <<< Note 4950.13 by KAOFS::J_DESROSIERS "Lets procrastinate....tomorrow" >>>
> 
>     You should have +12 on pin 9 of the serial port 
>                     -12 on pin 10 of the serial port   <-----****
>     
>     The +12 volts (called +12_USER) has the same source for the serial and
>     the video ports.  If these voltages are not correct, then you could
>     have fried the power supply or most likely just some small resistors
>     inside the power supply (to limit user draw).  
>     
>     Hope this helps
>     
>     Jean
>     
> 

If your up for it, the back of your A2000 manual has schematics. Just trace
the power sources back from the connector.

john

There could be a small Pico fuse for those ports, that are not on the schematic.

I popped the one for the mouse port a while back.  It does not show in my
schematic.  I have it jumpered for now, there might be simmular fuses for 
the other ports.

I found mine by checking for +5V on both side of all the components around 
the mouse connectors. 

    To close out this note, I thought I'd let everyone know what the
    problem was.  I took my 2000 in to the repair shop.  They replaced a $2
    diode that was cracked and repaired a burnt trace on the video port. 
    Everything works great now.  They charged me $45 labor and returned my
    machine the same day (even though they quoted 2 weeks).  Since I DON'T
    solder and since my local VCR repair shop won't even look at my VCR for
    less than $100, I felt I got a good deal at $45.  
    
    I appreciate everyone's help.
    
    Terry