Atari 800 System Repair Schematics or Manuals

[pseverini]

Atari 800 Owners,

 

Does anyone have a copy of the 800 system repair manuals or schematics? I'll take a copy of the SAMS or Atari original. I can't seem to figure out why my SIO port is not working with my 810 disk drive. Has anyone come across a bad SIO port on the 800? Any pointers? The 810 drive and cable work fine on another system I own. The 800 systems seems to power on and work fine except when I need to access the 810 disk drive.

 

Thanks.

Edited June 5, 2010 by pseverini

[Sub(Function(:))]

Atari 800 Owners,

 

Does anyone have a copy of the 800 system repair manuals or schematics? I'll take a copy of the SAMS or Atari original. I can't seem to figure out why my SIO port is not working with my 810 disk drive. Has anyone come across a bad SIO port on the 800? Any pointers? The 810 drive and cable work fine on another system I own. The 800 systems seems to power on and work fine except when I need to access the 810 disk drive.

 

Thanks.

 

 

Is this OK?

 

[+Stephen]

[quote name=Sub(Function()' date='Sat Jun 5, 2010 3:24 PM' timestamp='1275765890' post='2026260]

Atari 800 Owners,

 

Does anyone have a copy of the 800 system repair manuals or schematics? I'll take a copy of the SAMS or Atari original. I can't seem to figure out why my SIO port is not working with my 810 disk drive. Has anyone come across a bad SIO port on the 800? Any pointers? The 810 drive and cable work fine on another system I own. The 800 systems seems to power on and work fine except when I need to access the 810 disk drive.

 

Thanks.

 

 

Is this OK?

Awesome - thanks for posting.

[pseverini]

[quote name=Sub(Function()' date='Sat Jun 5, 2010 3:24 PM' timestamp='1275765890' post='2026260]

Atari 800 Owners,

 

Does anyone have a copy of the 800 system repair manuals or schematics? I'll take a copy of the SAMS or Atari original. I can't seem to figure out why my SIO port is not working with my 810 disk drive. Has anyone come across a bad SIO port on the 800? Any pointers? The 810 drive and cable work fine on another system I own. The 800 systems seems to power on and work fine except when I need to access the 810 disk drive.

 

Thanks.

 

 

Is this OK?

Awesome - thanks for posting.

[pseverini]

Perfect. Thanks everyone. Does anyone have the SAMS version as well?

[1050]

Has anyone come across a bad SIO port on the 800? Any pointers?

Thanks.

Yes, yes, and you are welcome. I have 4 800s and three of them needed me to replace their tired old worn out 6520 PIA chips with the new and better built Hitachi 68B21 PIA chip. After that they work like new again. The Jameco chip is cheaper than the JDR one and I'm sure others can be found with a little effort.

 

Since this doesn't seem to happen to 800XL I can only surmise that in the very earliest days the silicon used could not stand up to the test of time and thus the high failure rate among 800s. The PIA handles the SIO interrupt requests which is why the drive works fine elsewhere, the drive is NOT the problem.

[pseverini]

Great, thanks. Is there any way to test that chip to see if it's failing? Is the chip located on the main board? What diagnostics can I do to confirm it's the 6520 PIA besides swapping out the chip with a new one? Would the SALT diagnostics tell me anything? What's the best utility for diagnosing the 800?

 

While I have your attention...I just replaced an 810 DS side board in my drive to repair it. Have you identified any chips which are going bad in the side boards?

 

I appreciate the help.

[Rybags]

PIA handles the COMMAND line for SIO, it's "Interrupt" and "Proceed" functions are generally not used by peripherals.

 

You can test the input of the PIA easily enough, just a quick BASIC program:

 

10 ? STICK(0),STICK(1),STICK(2),STICK(3):GOTO 10

 

Try a joystick in each port in turn, that'll verify the input is working.

 

To test the output is a bit more complex, some sort of loopback is probably used by programs like SALT, and you'd need a suitable cable to do so.

 

Testing the COMMAND line would probably be easiest to accomplish with a multimeter with the probes inserted to the relevant pins of an attached SIO cable, use something like this to toggle the COMMAND line on/off at short intervals:

 

10 POKE 54019,52:GOSUB 100:POKE 54019,60:GOSUB 100:GOTO 10

100 POKE 20,0

110 IF PEEK(20)<60 THEN 110

120 RETURN

 

Put the GND probe against pin 4 of the SIO cable, positive end against pin 7

Edited June 7, 2010 by Rybags

[pseverini]

Thanks. Good stuff. What type of ouput levels should I see on the meter?

[Rybags]

Should be your normal TTL levels... so under 1 Volt = logic 0, over about 3.5 Volts = logic 1.

 

Commmand, IIRC, is active low, so by default should output logic 1 when inactive.

 

You could also test the serial output, although a little trickier... you can run SIO at an extraordinarily low rate which should be measurable by a multimeter.

[Chris Strong]

(1) If it is the 800 that is bad, I would try swapping out the POKEY chip (CO12294B on the motherboard).

 

(2) BUT, it could be the drive. If so, the failure would depend on the drive. The electrolytic capacitors on the power supplies are dying quickly on these things anymore; I have two Happy 1050's here, both of which have dead caps. I've started to see it on the 800s as well.

[atariksi]

I have some custom cables that have internal connections between the joystick ports/command line/proceed line/data-in/out.

 

POKE 53775,131 can be read as zero on Data Out line

POKE 53775,3 can be read as one on Data Out line

I have the command line tied to a joystick pot line so POKE 54019,52 reads as a "228" and POKE 54019,60 reads as a "0" on the pot line (pin 9).

Some other connections as well but with a PC w/parallel port it's easier to diagnose.

[pseverini]

(1) If it is the 800 that is bad, I would try swapping out the POKEY chip (CO12294B on the motherboard).

 

(2) BUT, it could be the drive. If so, the failure would depend on the drive. The electrolytic capacitors on the power supplies are dying quickly on these things anymore; I have two Happy 1050's here, both of which have dead caps. I've started to see it on the 800s as well.

 

The 810 works like a charm on another 800. What leads you to believe the POKEY chip might be the issue? Thanks.

[pseverini]

Should be your normal TTL levels... so under 1 Volt = logic 0, over about 3.5 Volts = logic 1.

 

Commmand, IIRC, is active low, so by default should output logic 1 when inactive.

 

You could also test the serial output, although a little trickier... you can run SIO at an extraordinarily low rate which should be measurable by a multimeter.

 

Thank you.

[pseverini]

[quote name=Sub(Function()' date='Sat Jun 5, 2010 3:24 PM' timestamp='1275765890' post='2026260]

Atari 800 Owners,

 

Does anyone have a copy of the 800 system repair manuals or schematics? I'll take a copy of the SAMS or Atari original. I can't seem to figure out why my SIO port is not working with my 810 disk drive. Has anyone come across a bad SIO port on the 800? Any pointers? The 810 drive and cable work fine on another system I own. The 800 systems seems to power on and work fine except when I need to access the 810 disk drive.

 

Thanks.

 

 

Is this OK?

Awesome - thanks for posting.

[atariksi]

Has anyone come across a bad SIO port on the 800? Any pointers?

Thanks.

Yes, yes, and you are welcome. I have 4 800s and three of them needed me to replace their tired old worn out 6520 PIA chips with the new and better built Hitachi 68B21 PIA chip. After that they work like new again. The Jameco chip is cheaper than the JDR one and I'm sure others can be found with a little effort.

 

Since this doesn't seem to happen to 800XL I can only surmise that in the very earliest days the silicon used could not stand up to the test of time and thus the high failure rate among 800s. The PIA handles the SIO interrupt requests which is why the drive works fine elsewhere, the drive is NOT the problem.

 

I never heard of the 68B21 PIA. Where is that available? I replaced the 6520 with a 6521 from WDC and it was worse than the original PIA. It was slower in switching between input and output modes and thus incompatible with some software unless you only use it for software that use it for input. Also, the original PIA allows you to do input while in output mode which the new PIA from WDC doesn't.

 

As far as SIO interrupt goes, it's handled by POKEY not PIA. The PIA interrupts caused by proceed and interrupt lines are not used by the 1050/810 drives. I have had rare failures of PIA chips but only on 800XLs so far. I would also say that the Atari 800 has the superior hardware over the 800XL when it comes to PIA external hardware support.