Falcon repair

[candle]

I've managed to buy half of atari falcon (half, because its just motherboard with bottom of case and psu) as "unchecked"

ofcourse it doesn't work

so far i've managed to check combo ic for presence of various clocks outputs (and they are present), videl for any activity (only pixel clock is present), and cpu

reset seeems to work properly, bus control signals (active low) are high (BERR- and HALT-) so it should run, but it doesnt - there is NO activity on data or address bus on CPU

 

i've managed to get replacement CPU and get it replaced - no change whatsoever, so i'm back in the fog again

 

if anyone could shed some light on bus arbitration of mc68030 or falcon repairs in general (ie what to check next) it would be greatly apreciated

 

i've always wanted to have this computer, and it was out ouf my range

for this one i've paid quite a lot, but still bearable money, and really want to get it up and running

[Zerosquare]

A few pointers :

 

- reseat socketed chips by pressing firmly on them

 

- check that the RAM board is inserted firmly on connectors J6 and J17 (if it uses a SIMM RAM module, check that it is proprerly inserted too)

 

- if you don't have any accelerator board installed, a jumper should be connected between pins 20 and 22 on connector J20 (expansion connector)

 

- check that the solder points U46 and U47 are set correctly :

 

You can find the Falcon schematics, service guide and the developer documentation (which includes useful info on the hardware) here : http://dev-docs.atar...rch.php?find=_5.

 

Good luck !

Edited December 2, 2010 by Zerosquare

[JingleJoe]

I can't be the only one who saw this thread and visualized captain falcon repairing things; Falcon Solder!

[simbo]

youll probably find the dma ic is dead

 

this is the usual one that goes

 

if you connect a monitor to it

it mostly will power on the monitor

but it will come up as out of range

next check the DE signal to the videl

 

if you have a pulses on the DE pin

then check the bus grant chain

youl see that the combel has granted the bus to the dma

but the dma does nothing

 

you can also look with a scope at the mad bus {memory board pins}

 

what i did long ago was to make up a board that plugs into the expansion slot

it uses leds to monitor the address and data bus

 

usualy if the dma is being granted the bus the machines address bus will run to 1111 1111 1111 1000

or less

and the address strobe will not run past a few cycles

ie the dma is granted the bus but is unable to respond to FC 0,1,2

youll notice they toggle as far a 110 {ie fc 0 is the only one that moves}

last two falcons i did that were doa had busted dma

and i used that method to varify this before i ordered it

 

dont use a shotgun approch to repair take your time and make some signals charts

for boot reset and etc

if you have a test cart this is handy and will tell you over the serial port mostly

what the issue is if the videl has a problem

you can also notice that the yellow drive access led will flicker around in time to the address strobe

this is the first test i use

 

to make the board for led tests i use simple project board

{vero but not strip board dot board}

and lots of 2ma led's {use low current types}

each all leds are common and the main 1k resitor is a 1watt type on ground side of the led bank

 

its handy as the port gives other usefull signals for diagnosis

 

and one day ill make a project board for it on ss pcb

 

 

 

you need about 50 for signals and address and 16 for data bus + some for data signals

 

ive found in the past photos are handy

 

can you take some macro photos of three areas on the pcb left middle right

 

nice ones in daylight {sun if we ever see it again}

 

ill help you out for sure

if you slow down dont replace any more ic's and take your time

Edited January 8, 2011 by simbo

[candle]

thanks! this should keep me going