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D64 with new Dragon PSU issue

Posted: Fri Jan 14, 2022 4:55 am
by acsi

I'm a bit confused with this but I received and built up a new Dragon PSU board from DragonPlus (BTW nice kit) and installed it in my Dragon64 after testing the voltages and setting up the -12v as instructed.

However with it installed my Dragon will now only work with the SuperSprite plugged into the cartridge port? It will not work with the floppy controller plugged in or with nothing plugged into the cartridge port.

I tested it wasn't just a display issue by typing MOTOR ON and MOTOR OFF and listening for the relay click but nothing.

The D64 has a DragonPlus board installed and has a 6809 CPU

Voltages measured at the board connector are

-11.69 (same with SuperSprite plugged in)
4.85 (4.80 with SuperSprite plugged in)
11.67 (11.56 with SuperSprite plugged in)

Old PSU board


Anyone have any ideas where to start with this?

Re: D64 with new Dragon PSU issue

Posted: Fri Jan 14, 2022 9:34 am
by sorchard
I would use an oscilloscope to see how much ripple there is on the supplies. The fact that it works when more current is drawn suggests one of the supplies is moving to a more stable region, which in turn suggests an incorrect component value.

A component value could be incorrect because it was put in the wrong place, or the wrong one was supplied in the kit (or from anywhere in the supply chain), or you are unlucky and a component is faulty.

With that in mind I would carefully check that the capacitors and inductors are the correct values. An error here can cause unstable operation. You may as well check the resistors too while you're at it.

You didn't specifically mention it: does the old PSU still work when you put it back in?

Re: D64 with new Dragon PSU issue

Posted: Fri Jan 14, 2022 12:54 pm
by acsi
Unfortunately I don't own a scope.

All components appear to be correct and yes the original PSU board works when I put it back in.

I've tried 4 different power supplies just in case. One actually turned out to be dead but no change with the other 3.

I decided to swap it into my Dragon32 (after swapping JP1 to the D32 position) and it works fine.

Possibly the D64 is more picky?

Re: D64 with new Dragon PSU issue

Posted: Fri Jan 14, 2022 2:25 pm
by sorchard
Curious that it works in a D32. Can't really say much else without seeing a schematic and more detailed measurements.

Assuming you've followed the build instructions to the letter, the ball is very firmly in the court of the supplier and/or designer.

Re: D64 with new Dragon PSU issue

Posted: Fri Jan 14, 2022 7:40 pm
by robcfg
I'd check the orientation of any component with polarity, like capacitors, diodes, etc.

Take care when connecting it to the 32, as I don't know if the -12v are automatically converted to -5v and that can cause damage to components.

Re: D64 with new Dragon PSU issue

Posted: Fri Jan 14, 2022 11:44 pm
by acsi
Yep I've been over it with a fine tooth comb. All orientations are correct and there is a jumper to change from -12v D64 to -5v D32 which so far I haven't forgotten to change although I may just leave it in the D32 now.

Re: D64 with new Dragon PSU issue

Posted: Tue Jan 18, 2022 11:59 pm
by dublevay
Hi - I've only just seen this, sorry. You can always email me directly via the contact page on the DragonPlus page. From your description though, it certainly is rather a mystery. I've only seen Dragons stop working when the SuperSprite is inserted, usually due to an overloaded PSU, or the power jumper being set incorrectly on the SS FM+ board. I've never known the SS FM+ to be the 'enabler'!

Re: D64 with new Dragon PSU issue

Posted: Wed Jan 19, 2022 12:10 am
by dublevay
I've just noticed that you say you also have a DragonPlus board in the same machine. I've never actually tested SuperSprite with a DragonPlus board, as not sure it would all fit with the Oojamaflip, and thus I couldn't also connect a disk solution. But the DragonPlus can be a finicky beast with respect to it's connection into the SAM socket. I wonder if when the SS FM+ board is inserted, it is slightly moving the motherboard position and somehow reseating the DragonPlus board?

Is your SS FM+ power board using the internal power when it works with the new PSU - or is it using external power?

Re: D64 with new Dragon PSU issue

Posted: Thu Jan 20, 2022 8:31 pm
by acsi
Yep I was only plugging the super sprite board into it directly.

I am now having trouble with my Dragondrive. It will load Flagonbird from a VDK fine but if the VDK has bigger files like Flex or a ADG games disk it fails. It does better in the D32 but still not great.

I'm pretty much at the point that I've decided to part with them as they are beyond my skill set.

Re: D64 with new Dragon PSU issue

Posted: Fri Jan 21, 2022 4:50 pm
by dublevay
Please do feel free to contact me via the website if you want. From my records of sales, I think I know who you are. ;)

The website seemingly crashed yesterday and I did not know, but it is back up and running again now.