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AuthorTopic: Amiga Apollo 04 card wont boot  (Read 732 times)

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Offline retrostyle

Amiga Apollo 04 card wont boot
« on: April 18, 2022, 12:21:10 PM »
Hi folks

I recently purchased this none working Apollo card that had battery leak over the boot rom and jumpers i have cleaned it up but still no luck as i keep getting a black screen.
The cpu goes warm when i leave the Amiga on for a time and the fan spins on the card.

Any help would be grateful

I have checked for broken tracks but all look fine ???
 

Offline Pat the Cat

Re: Amiga Apollo 04 card wont boot
« Reply #1 on: April 20, 2022, 03:52:38 AM »
Looks like a PROM chip in the photograph - might be bad. Getting a replacement means burning a new copy of the firmware to an replacement EPROM chip.

Also worth changing the crystal, without a solid clock it would do a black screen.

Without a battery, you might have a dead Real Time Clock chip. The ROM code might lock for a clock and refuse to autoconfig if it can't find one (very unlikely but could be).

Would help to know which Apollo board for which Amiga. I'm assming something for an A1200?

EDIT: I think I found it, one like;-

http://amiga.resource.cx/exp/apollo1260
« Last Edit: April 20, 2022, 04:02:21 AM by Pat the Cat »
"To recurse is human. To iterate, divine."

A1200, Vanilla, Surf Squirrel, SD Card, KS 3.0/3.z, PCMCIA dev
A500, Vanilla, A570, Rev 5, KS 1.2/1.3 Testbench system
Rasp Pi, UAE4ARM, 3D laser scanner, experimental, hoping for AmigaOS4Arm, based on Watterott Fabscan Pi
 

Offline retrostyle

Re: Amiga Apollo 04 card wont boot
« Reply #2 on: April 20, 2022, 06:59:19 PM »
Hi

yes its for a 1200 machine
Have replaced the crystal a few times no luck
 

Offline retrostyle

Re: Amiga Apollo 04 card wont boot
« Reply #3 on: April 24, 2022, 09:07:53 PM »

Where can i buy a new F74 chip?
 

Offline Castellen

Re: Amiga Apollo 04 card wont boot
« Reply #4 on: April 24, 2022, 09:41:15 PM »
You can source a new part here:
https://www.digikey.co.nz/short/p7h428mq

I've repaired a few of these boards in the past with the same problems caused by battery corrosion.  There can often be open circuit tracks under the 74F74 as well, so I'd recommending removing the IC and carefully checking all tracks and vias underneath.  Since the IC has been subject to corrosion, it should be replaced even if it's working.  As I recall, it's used as a clock divider, so with a 50MHz oscillator, you should expect to see 25MHz on one of the two outputs.  I don't remember if only one or both elements of the flip-flop IC are used, though from looking at the 74F74 datasheet and connecting tracks on the PCB, it's not too hard to work out how the circuit operates.

I can also repair the board for you if the above detail is outside what you're comfortable with.

http://amiga.serveftp.net
 

Offline retrostyle

Re: Amiga Apollo 04 card wont boot
« Reply #5 on: April 25, 2022, 04:29:13 PM »
Hi

Thanks for the valuable information will remove the ic and check the tracks underneath in the next few days

cheers