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DRAGON 32 RETRO COMPUTER

Desperado

Desperado

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Good evening everyone, I bought a strange used vintage computer, it's called Dragon 32! The computer is in good condition but when I connect it to the TV via antenna cable, it can't hook up the signal. If I try to connect it to an old CRT TV, you see a flickering image...
I wanted to try to make the composite din cable but the pinout I find online always shows a 5-pin din connector. My Dragon has a 7-pin din connector....can someone help me please?
Thanks!
 

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It's a UK machine, so I'd think the RF is PAL? I'm not sure if it was ever sold in the US?
Click to expand...

Yes, as "Tano Dragon" (or "Dragon Tano"), sold until recently. Of course not this exact model; but a NTSC one...

I wanted to try to make the composite din cable but the pinout I find online always shows a 5-pin din connector. My Dragon has a 7-pin din connector....can someone help me please?
Click to expand...

Perhaps, just perhaps, seems that you have a SECAM Dragon, so a french one. You can't use a PAL or NTSC TV to display its RF signal and the DIN5 standard cable doesn't works either with composite monitors. The pinout of these machine is totally different as it must send RGB signals to allow the use of a french Péritel (SCART) connection.
Not too much information about this; but check this page where someone has posted some info about this DIN7 pinout and how to create a SCART cable: Dragon 32 SECAM

If you open it and with a bit of luck, the PSU PCB silkscreen must have some clue about it being SECAM or not.
 
If it does indeed have RGB output, you may find it easier to skip the whole SECAM thing and just use that directly, if you can find a PVM or similar that will sync to the 625 line 50 Hz signal.
 
The very first portable cassette, radio and television I bought could be powered from either the mains or a +12V car battery and had support for PAL, NTSC and SECAM video Standards. That has been a really useful addition to my test equipment - as well as watching TV of course...

It would be worth reading the posts linked to in the second link of post #4. It contain a wealth of information that may be useful. More study required...

Dave
 
I made a din scart cable and finally I managed to get a decent enough signal..Unfortunately this Dragon has some problems...the basic writings are wrong and if I press any key, what appears on TV does not correspond. I checked all eight RAMs with the oscilloscope and I do not see blocked signals...
 

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It's Welsh :)!

Ah, maybe not, I can't see any 'L' or 'Y' characters..

Did you find the matching schematics in the end?

What screen do you initially get when your turn the machine ON? Let's work from that end.

It is not too far out:

1743701018069.png

So you should be able to work out which characters work and which characters do not and look at the bit differences between the two values (in ASCII). This is the same thing we did on a PET - but in PETSCII. Do you remember the tables?

Dave
 
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I worked that out from the start-up screen I just posted above.

Just because you don't see a 'stuck' signal on the DRAM doesn't mean it is all good of course.

Dave
 
daver2 said:
I worked that out from the start-up screen I just posted above.

Just because you don't see a 'stuck' signal on the DRAM doesn't mean it is all good of course.

Dave
Click to expand...
I suspect bad ram ics....
But with scope i can't see stucked signals....
 
>>> I suspect bad ram ics....

I don't, because there are only eight (8) of them and BASIC appears to be working (albeit the hardware is displaying incorrect characters). If a RAM was faulty, you probably wouldn't get the screen that you are getting, because the 6809 CPU would crash. The characters that are displayed are systematically incorrect...

I would poke around here:

1743702200243.png

Schematics: http://www.dragondata.co.uk/tech/circuit-diag/index32.html.

Good manual to read: https://colorcomputerarchive.com/repo/Documents/Books/Dragon/Inside The Dragon (Duncan Smeed and Ian Sommerville).pdf.

The 6847 (IC12) is the video generator and contains an internal 64-character character generator (when using 512 bytes of main memory (from memory address $0400 to $05FF). It looks like the data is latched from the DRAM to the video generator by means of IC13. It would be sensible to scope the Qn outputs of IC13 feeding IC12.

Dave
 
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As a quick off-hand analysis, it's not just a stuck bit. If it were, I'd expect either T (%0101 1000) or F (%0100 0110) to display, but not both (bit 4 is different between the two). Yet O (%1000 1111) also turns into F. So bit 3 is sometimes working, sometimes not.
 
You definitely have a problem with Q1, so I would start there.

A -> @ (Q1 in error (LOW)).
C -> B (Q1 in error (LOW)).
E -> D (Q1 in error (LOW)).
G -> F (Q1 in error (LOW)).
I -> @ (this indicates a problem with both Q4 and Q1 - but let's worry about Q1 for now).

Dave
 
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daver2 said:
>>> I suspect bad ram ics....

I don't, because there are only eight (8) of them and BASIC appears to be working (albeit the hardware is displaying incorrect characters). If a RAM was faulty, you probably wouldn't get the screen that you are getting, because the 6809 CPU would crash. The characters that are displayed are systematically incorrect...

I would poke around here:

View attachment 1298643

Schematics: http://www.dragondata.co.uk/tech/circuit-diag/index32.html.

Good manual to read: https://colorcomputerarchive.com/repo/Documents/Books/Dragon/Inside The Dragon (Duncan Smeed and Ian Sommerville).pdf.

The 6847 (IC12) is the video generator and contains an internal 64-character character generator (when using 512 bytes of main memory (from memory address $0400 to $05FF). It looks like the data is latched from the DRAM to the video generator by means of IC13. It would be sensible to scope the Qn outputs of IC13 feeding IC12.

Dave
Click to expand...
Pin 6 and 12 of IC13 they are stuck low!
 
Maybe IC13 is faulty.

But I would test the input pins (Dn) first before you warm up the soldering iron!

The Q1 output is driven by the D1 input.

Likewise the Q4 output is driven by the D4 input.

I have no idea how the details in post #18 came about...

Dave
 
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