A600 Floppy Access Dimming/Flicker

[hamsterbasher]

My A600 Revision 2D board has a strange issue. Everything seems to be working fine and I am considering installing a Furia into it as I just love the compact design of it but it desperately needs more muscle... problem is that the screen slightly dims on every access by both internal and external floppy drives and that has made me nervous to spend the money on the Furia until I can get this resolved. So far my troubleshooting has been.

1. I have tried a few different drives internally (Sony + Chinon and Toshiba) and they all do it.

2. Does it on both RGB and Composite feeds and have tried both the OSSC and my Retrotink5 and both show the issue. Dont think its a video issue.

3. If I attach a 250MB or a 120MB physical HDD there is no dimming on access so this only appears to be impacting the power to the floppy circuits.

4. I have the same power supply for my A1200 + Accelerator, A500+ and another A500 and none of them show anything like that on floppy access so I don't think this is a supply issue. Also if I put a scope on the +5V rail I can see the rail dipping by about 0.2 - 0.3V each time the floppy clicks.

5. Recently recapped the A600 using a kit from Console5 and the problem remains so I think that rules out all the electrolytic caps being a cause.

At this stage I am mostly out of ideas. Anyone have any suggestions to try?

Regards
Hans

[Jpor]

Originally Posted by hamsterbasher

My A600 Revision 2D board has a strange issue. Everything seems to be working fine and I am considering installing a Furia into it as I just love the compact design of it but it desperately needs more muscle... problem is that the screen slightly dims on every access by both internal and external floppy drives and that has made me nervous to spend the money on the Furia until I can get this resolved. So far my troubleshooting has been.

1. I have tried a few different drives internally (Sony + Chinon and Toshiba) and they all do it.

2. Does it on both RGB and Composite feeds and have tried both the OSSC and my Retrotink5 and both show the issue. Dont think its a video issue.

3. If I attach a 250MB or a 120MB physical HDD there is no dimming on access so this only appears to be impacting the power to the floppy circuits.

4. I have the same power supply for my A1200 + Accelerator, A500+ and another A500 and none of them show anything like that on floppy access so I don't think this is a supply issue. Also if I put a scope on the +5V rail I can see the rail dipping by about 0.2 - 0.3V each time the floppy clicks.

5. Recently recapped the A600 using a kit from Console5 and the problem remains so I think that rules out all the electrolytic caps being a cause.

At this stage I am mostly out of ideas. Anyone have any suggestions to try?

Regards
Hans

When you say you recapped the board. You haven’t damaged anything or lifted any pads on the mainboard?

When you mention Power Supplies. Have you tested other power supplies on the A600?

On testing other floppy drives. Did you also try a different power and Floppy data cable?

I have in the past had trouble with the Rev 2D A600 board but using the A604N 1MB chip board where it would’nt work correctly. I take it you don’t have another revision of A600 board to test your components on? Such as a 1.3 or 1.5 revision?

[hamsterbasher]

Originally Posted by Jpor

When you say you recapped the board. You haven’t damaged anything or lifted any pads on the mainboard?

The board was dimming when I bought it and one of the reasons I decided to try a recap as a possible solution. I didnt see any obvious leaking or bulging but decided it was worth a shot to try that. I was very careful so fairly confident the recap was good. It also didn't change anything with the dimming which was the same after the recap.

Originally Posted by Jpor

When you mention Power Supplies. Have you tested other power supplies on the A600?

Yes I have two 'modern' supplies. One from KeeLog and the other from Electroware. Both exhibit the same dimming. I am not seeing any dimming with any of my other Amiga's when using either of these supplies so I assumed that they were producing enough current for at least an A1200 with accelerator to run good. Does the A600 draw more than a 1200?

Originally Posted by Jpor

On testing other floppy drives. Did you also try a different power and Floppy data cable?

Yes. I took one of the drives straight out of my A1200 and hooked it up with its cables to my A600. No dimming when in the A1200 but dimming in the A600. I also have two external floppy drives. Both those show the same issue.

Originally Posted by Jpor

I have in the past had trouble with the Rev 2D A600 board but using the A604N 1MB chip board where it would’nt work correctly. I take it you don’t have another revision of A600 board to test your components on? Such as a 1.3 or 1.5 revision?

No unfortunately not. This was my first A600 and I basically put it together from parts sourced from ebay after someone gifted me just a shell which was in excellent condition. Not an Amiga I thought I would ever end up owning but its been fun finding the parts for it and then getting it all running. Apart from this damn dimming issue its been all good so I was hoping to track down this issue on the board and then look at an accelerator for it as she is "slow" compared to my 1200. I would hate to have to spend money on another 600 board when this one is so close to being perfect.

Thanks for the questions and advice. I am pretty sure the issue is on the board somewhere but its probably going to be a mare to track down. I read a few posts that suggest something similar was the CXA1145M or the Band Pass Filters misbehaving when there was small voltage drops on the 5V rail. Since the effect is a video level dip it could be a candidate for this issue. There are various replacement IC's you can use for that 1145 so I may take a look at that next to see if it helps.

Thanks again.