NOS A1200 , screen flickers when accessing floppy
 

Hiya! :blased
a close friend of mine just got a NOS Commodore A1200 and uses it with a 1240 accelerator and an A500 "heavy" PSU. The screen flickers in regions when a floppy disk is accessed. We also tried without the 1240 installed, but nothing changed...
Is there a solution to this problem?

@keropi

Have you tried a different PSU with just the stock A1200 ?

It does sound like the PSU maybe struggling to provide a stable supply

TC :D

Hi keropi,

TC's suggestion really does sound like your best first step. I recently traced a similar display problem on my A1200 to a faulty PSU. The minor fault had been evident from new, but I only discovered the cause when I tried the Amiga with another PSU.

prowler

thanks for the suggestions, but unfortunatelly we have tried 3 PSU's... (1 from A1200 and 2 "heavy" A500 ones)
the problem does not go away... we even tried a different monitor :lol

@keropi

I had a feeling you might have tried it already, You say NOS A1200, If it was purchased form Amigakit then I suggest it goes back my friend.

I would say it has "Capacitor" issues & is unable to keep the supply stable when extra load is required, ie the floppy drive motor.

TC ;)

its my A1200 with the problem and I am Keropi's friend, so first af all hello everybody and thanks for the answers untill now. To give you a little tip so you may help me is that the A1200 is Commodore and not Amiga.inc it was brand new in its box almost never used for several years and I took off for the first time the sticker below the case. the board is ver ID.1 and we have the flickering problem my friend posted here.

you can see parallel lines going up and down every time the floppy drive reads a disk.

we have also check the A1200 plain without the 68040 and the problem remains.

The point is that I couldnt wait for long so I have allready orderd a refubished mobo from Amigakit. but if there is a way to make the board work I would appreciate it !

Thank you all !

@marag

Welcome to EAB & thanks for the history

My ID4 Mobo has the same issues whenever I use the floppy drive, I have to get round to replacing the Cap's on the Mobo, I just keep putting it off....;)

I'm 99% sure that's your problem too

TC :D

I think you have a point there, Keropi said the same thing from the begining but was not 100% sure. now we are :great

Look for "flicker fix" on Aminet. It's a hardware motherboard fix.

Does this fix affect Rev 1D1 Mobo's too ??

TC :confused

Nope, 1D3 onwards.

This is maybe the way solution for marag-keropi (hi guys) A1200 flik-prob..
but think he use tantalum cap,and this (also the electrolyte cap) has polarized + & -, the info dont tell nothing for this!

But their Mobo is a 1D1, no fix to apply, Change those Caps !!!!!

TC :D

just 1 question from me are you using the rf for TV or rgb for a monitor ?

rgb port for monitor...

ok thanks, as some rf units are doggie, well mine was years ago

today i fix one of my 2 A1200 ,with same problem.. the Mboard is 1.D4
all OK now, the flicker is no more ;)
i use one cap 1μF - 50V (smaller of guide but stronger voltage)
Edit: oh and polarized is: (-)on the left, (+) on the right.. :)
http://img212.imageshack.us/img212/6...mya1200lg1.jpg

@Anemos

Thanks for that my friend, a great place to start, glad it solved your problem, I think you've finally inspired me to get may caps changed ;)

TC :D

excellent anemos! :great

@keropi ,hope to solve your problem soon.. if i can help you i do in my forum,in greeks.. :)