bricked dragon 32...

[jedie]

I have a new, used Dragon 32 buyed at ebay, because my origin Dragon i have used for tons of years is bricked.
When I was little, I have insert into the cartridge port a non-matching cartridge Think i have made some short-circuit

Now the Dragon will had the screen full of various characters when started it.

So it seems that is not completely bricked.

Is there any chance for repair ?

[Rink]

I'd say yes, but how difficult it would be is hard to guess.

Incidentally, I've done that many times while messing on with DIY cartridge builds and been lucky enough not to damage anything. But what you describe sounds a bit like you may have caused a conflict on the data or address bus and blown out a ROM or memory chip. Without diagnosing the problem properly, I'd suggest trying replacing those one by one (starting with the system ROM).

Since this has happened, have you tried plugging a proper Dragon cartridge in and seeing if it plays?

[Rink]

Also, do you have access to an oscilloscope?

[jedie]

Since this has happened, have you tried plugging a proper Dragon cartridge in and seeing if it plays?

No i haven't any origin Dragon cartridge eBay prices are to high

I haven't a oscilloscope... But used oscilloscope in my education time. Would be great to have one. But think the price will be too high, isn't it?

EDIT:

I'd suggest trying replacing those one by one (starting with the system ROM).

That's what I've thought. I only fear then to have two bricked dragon

[sixxie]

The "Hantek" digital oscilloscopes are relatively cheap and quite usable. Check out OpenHantek for free software to talk to them. I have the lowest-end one, the DSO2090 and it seems fine for most things Dragon.

Also, I can recommend the Saleae Logic 16 - I've used it for decoding RAM addressing RAS/CAS and it's really rather nice. Software not "libre", but "no cost" and available multi-platform.

[jedie]

The "Hantek" digital oscilloscopes are relatively cheap and quite usable. Check out OpenHantek for free software to talk to them. I have the lowest-end one, the DSO2090 and it seems fine for most things Dragon.

Oh wow, USB oscilloscopes with OpenSource Software! Great!

But i can't find a list of supported devices by OpenHantek.

On eBay a DSO2090 costs ~120€ ... But a "HANTEK PC USB 2CH Digital Oscilloscope 20M Hz 48M Sa/s 1M Byte/CH" on amazon costs 79€: http://www.amazon.de/gp/product/B00EEXC ... e=&seller=

There exist a few "Hantek USB" -> http://www.heise.de/preisvergleich/eu/?fs=Hantek+USB


Beside the oscilloscope: Is it really save to put the EEPROM from my working dragon into the bricked one? Or can the EEPROM also bricked there?

[jedie]

Most of the time, i start the bricked one, the screen looks like this:







But occasionally it vary and can look similar to this:





On the xroar page here http://www.6809.org.uk/dragon/xroar-man ... ng-started says:

If you just get a strange checkerboard pattern of orange and inverse ‘@’ signs, it probably failed to find any ROM images

So maybe i have a bricked EEROM ?

[acsi]

Hi

This looks very similar to what my Dragon 32 was doing.

Turned out to be a faulty VDG chip. Got a replacement off eBay and it worked fine afterwards. At least until the SAM chip failed later on

Anyway here is the link to my posts about it.

viewtopic.php?t=1889

Hope it helps.

[jedie]

In my case, the screen is clearly and stable. So i think the Video Display Generator (VDG) should be ok.

[Rink]

If you turn it on and let it run for a few seconds, does the display change? Characters and colours changing, for example.

Trying to think of what else might help you figure this out without requiring any more equipment.

You could try typing the Dragon's beep command or CLOAD "" and pressing enter. If you heard a relay click or beep then it might suggest a fault in the VDG or one of the RAM chips. I wouldn't expect this to actually work but it helped me with a faulty MSX once.

If not, then you might want to try and check whether the CPU is running (the VDG might try to work whether the CPU is dead, don't know). But I can't think of an easy way of doing that without a scope.

BTW As long as you've removed the cartridge which did the damage , you should be safe putting another ROM in there to check.