Timing fix for A1200 1.D4 motherboard?

[jj]

I was under the impression that you shouldnt have a problem with blizzard cards and timing problems, thats because the bus is buffered.  That is why apollo cards are generally faster but prone to timing issues.

I would look elsewhere for the problem

[Stedy]

@Monami

My Rev 2B A1200 was modified back in 2002 to work with my Apollo A1240. I had a rev 1D1 motherboard before this. I bought the A1200 rev 2B motherboard as it had Kickstart 3.1 ROMS and worked out cheaper than buying the ROMS on their own!

So all I did was remove E123C or R, remove E125 C or R, and changed R118 to 220 ohms. You can remove E123/5 resistor (R) or capacitor (C) as all the timing fix does is break the AC terminator on 2 clock signals to give a few nanoseconds more timing.

@Painkiller
The A1200 floppy connector PCB traces are not rated at much more than 1.5 Amps so do not use this to power your A1200.

Get some electrical cleaner and clean the A1200 power connector, the CPU slot and the connector on the CPU card. Dirty connections can cause many issues.

If you are not afraid to use a multimeter, measure the actual +5V supply on the A1200 motherboard. To do this pick a 74 series, 14 pin TTL device and measure across pins 7 and 14. From experience, the +5V supply on the A1200 needs to be in the range of 4.85V to 5.15V DC.

For the startup issue, look for test point/connector CN17 (Only present on REV 2 motherboards). Connecting pin 3 (KBRESET) to pin 7 (GROUND) will send a reset pulse to the Amiga. There can be issues with the Reset circuit of older Amigas with age as some use R/C networks :evil:

There is a guide on Aminet for the Keyboard test socket but I do not appear to be able to access Aminet at this time.

I can't think of much else to suggest.

Ian

[twizzle]

i have had a few mem simms go faulty on me with the same symtems?
worth a look.

[Painkiller]

@Painkiller
The A1200 floppy connector PCB traces are not rated at much more than 1.5 Amps so do not use this to power your A1200.

I'm not powering the whole board from there, just additional power supply to keep the whole board in steady power supply. They even addvise to do this in BVision manual.

Anyways I got the board working now as I removed E123C and E125C capasitors.

[golem]

I installed a quite new Fujitsu 2.5" 60Gb drive to my 1200 1.D4 with Blizzard 1260. I also have a 4xEIDE buffered interface connecting the hard drive to the IDE header. This set up exhibited the same weird crashing as you experienced (total system lock up, mouse pointer stuck and no Guru). I think I've nailed it down to the Elbox 4xEIDE.driver software. I cut this out the startup-sequence and I've had no freezes from cold or otherwise for now. I think it's strange that this should be the case but it seems to be so.  

[Treadwheel]

Having similar issues with a ID.4 motherboard. Just blacks out/reboots randomly with a Blizzard 1260, Lyra, Indivision, Subway on clockport, Microys, & 2.5 hard drive attached.
Funny thing is the ACA232 has them all working. I thought the timing fix
was only for this accelerator.
It may be capacitors. I think the fix was done on this board hence ACA working better than Blizzard.

It is not the heat issues as the crashing happens the most when I cold start the machine. (Which now leads me to thinking that some of the capasitors needs to be replaced).

I have also tried to refit the board couple of times to see if it is a bad contact.

The problem it self just freezes the Amiga with no guru or anything just freezes the screen. Sometimes I can go hours and sometimes it crashes in a few minutes or imidiately after boot up.

[Leifern]

I have a small question regarding timing fixes. I have a 1d4 motherboard that worked fine with a Blizzard 1260. I sold the 1260 a few years ago, and now I'm considering an ACA1232.

If my botherboard worked with the 1260, will it work with the 1232? I am not capable of doing these fixes and I really cannot afford to send my motherboard to UK or GER for fixing.