Strange Issues with rev 2B A1200 and its Floppy Drives
 

I would suppose I have returned to being a noob again,

As I originally had a Commodore A1200 back in 1992/94. It was the Comic relief pack, with a HDD and expansion.

But sold it to buy a 486 DX4 100Mhz PC, to play Doom....


So recently I decided to get another A1200 for some retro gaming, as WinUAE wasn't cutting it, and managed to get an unopened AT 1200, without a HDD. So I have brought and installed 4GB CF, AGA MkII, ACA1232, Wifi PCMCIA Network card and PCMCIA Transfer Kit.

So here is my problems, it's a rev2B board which kinda sucks, and I am getting crashes and graphic glitches. So I am expecting to have to undertake the timing fix in the future.

But the main problem I am having, is when I try and format any floppy in WB, the A1200 thinks the disks are write protected, on both the internal and external FDD. Which has made it hard trying to install WB3.1 to the CF, and strange problem to troubleshoot.

The disks are write enabled, and they are original 3M DD disks. The internal FDD is a Panasonic, so I presume it's a HD FDD.

The only other thing I can think of is a Power supply problem, as it has the original black AT A1200 power supply with it!!!

Has anyone else had this problem.? Or any suggestions....

Cheers

I'm guessing this is not a NOS unit (new old stock)? If it isn't, then it is likely that it could have some broken traces on the MB due to corrosion.
Pin 7 on U7 provides the Amiga with the write protect status and if this connection is broken, it will not be able to see the write protect status of a disk, neither internal nor external.
You could try to measure the resistance between U7 pin 7 and pin 14 on the external floppy drive connector. It should be 68 ohms.

Edit: I see that you did write unopened, but it is still not unlikely that there's something wrong with it.

Maybe try to format HD disk, not DD.

could be the drive try switch cleaner on the little switches in the front.

could be duff disks

ive only ever encounted two 2b motherboards in the past and i really dident like them,they need timing fixes and the floppy dont read some disks properly(pc drive conversion i think)

Thanks for the responses, I didn't expect a quick reply

I have formatted the HDD ok without any issues,

I will check the pins for correct resitance... But I have a feeling it could be a power issue. To test this, I will remove CF, ACA1232 and report back. As it has written disks before for the previous owner

I have also checked inside the internal floppy and can see the Write enable switch move when the disk is inserted. Another thing to try would be to find an old PC FDD, I think i have one somewhere.

You write that it is the same problem with an external drive, so I think you can rule out the drive.

Ok I have removed the external drive, aca1232, PCMCIA, and joystick

So only Indivision AGA MkII and CF on the mother board, and it still failed.

The power supply is a black Amiga Tech supply which supplies 25W

I might go back to basics and take all the extra hardware off the board...

What is the best way to remove Indy AGA Mk II without damaging it?

Hmm, Panasonic a HD drive? Anyway make sure the the hole on the left of the floppy disk is covered.

possible red herring
 

these are mainly DD 3M disks.... so shouldn't be a problem... I have tried 10 different types of disk. All failed

if you can try the floppy in another amiga,and it doesent work it might be one of at's converted pc drives or just a failed drive.(but seeing as youve tried an external one,it doesent look this way)

if you try it in another amiga and it works,and of course youve tried demolitions advice.
you might have a faillng cia or paula.

the original power supplys (25watt)can power an 030 card and cf but not much else,thats if its fully functional.

good luck.

I have taken the amiga back to bare bones, and it still doesn't work. So I have brought another amiga, hopefully better than this one.

I would have been gutted if I had paid the eBay prices, (£145) for it...

Its a buggered computer, as I can't install the wireless drivers without errors, which is another strange thing.


But I have had more Guru errors with this 1200 in 1 month, than the whole time i had my previous amiga.


But i know it's nearly 18 years old.

So hopefully out of two I can make one good one....

try try again....
 

So I decided to dig out my A1200's again, i know it's been a long time...

So back to the Rev2B which is what this thread is about, well it had been opened, as I can see damage to the inside cover which looks like a pointy end of a compass, so a replacement sticker had been put on it.....

But I have noticed there is a faulty cap, which has leaked, and think is causing problems with the composite video. As the RGB works ok. C239 is the cap.

But when I looked at the underside, I noticed E123C and E125C is missing, so were timing fixes done in the factory? also the floppy fix looks like it been done... But there was still a Panasonic FDD in the machine so would that cause it not to work correctly.? :confused

EDIT: I will be replacing the caps before I do anything else...

It's possible that they were never fitted at the factory - there are often changes made at the factory without updating the PCB - extra components soldered to component legs or parts left out. Of course, the alternative is that it was actually used before and someone hasn't told you that.

As for leaking capacitors, yes, they can cause issues, especially when the electrolyte eats away the traces on the board. Replace *all* of the electrolytic capacitors as soon as you can - not just when they leak as at that stage it might be too late...