New Member, long time Dragon 32 owner

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SpaceFlightOrange
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Joined: Wed Jan 22, 2020 12:33 pm

New Member, long time Dragon 32 owner

Post by SpaceFlightOrange » Wed Jan 22, 2020 12:42 pm

Hi.

Just wanted to introduce myself. The Dragon was my first computer when i was a kid. I'll admit, i wanted a Spectrum, but my dad was paying, so...

I learned to program on the Dragon, but then a few years later i moved to the BBC Micro, then the Amiga, and by '92 i was on PC's

I still have all my original machines, but a little over a year ago, i donated the Dragon and the Amiga to my friend for his retro computer collection. I kept the beeb because it has special sentimental value for me, so i nursed that back to health and suddenly found myself collecting retro machines! since then i've collected and repaired 2 Spectrums, a BBC Master, an Oric Atmos, and a ZX81, plus a few handheld i'd owned in the past and regretted selling on. I also started to regret giving my friend my Dragon and Amiga. He kindly agreed to give me them back, I've now got both machines again! Sadly, the Dragon is missing a key :cry:

I haven't touched it since getting it back, but i want to restore it back to its former glory, so a strip down and clean, but i also need to source an "S" key. My friend is still looking for it, but with no luck, we think it might be in the kids massive lego box!

I don't intend to do much beyond the restoration, other than find some means of loading software without using a cassette player.

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robcfg
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Location: Stockholm, Sweden

Re: New Member, long time Dragon 32 owner

Post by robcfg » Wed Jan 22, 2020 9:44 pm

Welcome to the Archive!

Thanks for sharing your story, it's always interesting.

I almost lose my first computer, an Atari 800XL, because my parents gave it to a neighbour's daughters. Luckily, they weren't interested and managed to get it back too, as it has also a high sentimental value.

Regarding means to load software, you can take a look at the CASduino if you want to load tape images, or the DragonMMC, CoCoSDC or Drivewire, if you want to load tape/disk/rom images, either from a SD card or from a modern computer.

Good luck finding the missing key.

By the way, is your Dragona 32 or a 64?

Cheers,
Rob

SpaceFlightOrange
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Joined: Wed Jan 22, 2020 12:33 pm

Re: New Member, long time Dragon 32 owner

Post by SpaceFlightOrange » Thu Jan 23, 2020 10:19 am

robcfg wrote:
Wed Jan 22, 2020 9:44 pm
Regarding means to load software, you can take a look at the CASduino if you want to load tape images, or the DragonMMC, CoCoSDC or Drivewire, if you want to load tape/disk/rom images, either from a SD card or from a modern computer.
I didn't know there was an MMC reader for the Dragon! I'll check that out. My friend has a CASDuino (or similar) that he uses on his 800XL. might try and borrow it for a trial.
robcfg wrote:
Wed Jan 22, 2020 9:44 pm
Good luck finding the missing key.

By the way, is your Dragona 32 or a 64?
Thanks. I keep prodding him, but he's not found it yet. its really frustrating. he blames the kids, but he has about 10 machines in his collection and this is the only one its happened to. he does feel really bad about it. It has to be there somewhere. but I've had no luck finding replacements online.

it's a Dragon 32

SpaceFlightOrange
Posts: 9
Joined: Wed Jan 22, 2020 12:33 pm

Re: New Member, long time Dragon 32 owner

Post by SpaceFlightOrange » Mon Feb 03, 2020 7:12 pm

He’s found the key!!

I’m so happy. Going to get it in the week!

SpaceFlightOrange
Posts: 9
Joined: Wed Jan 22, 2020 12:33 pm

Re: New Member, long time Dragon 32 owner

Post by SpaceFlightOrange » Mon Feb 03, 2020 7:13 pm

I’ve been doing a bit of work on the dragon and I have a question.

I verified the voltages from the power board and turned on, and connected it to the TV both via composite and RF. I get flickering on both and a weird shifting of the screen on composite. The TV appears to switch from PAL to SECAM when this happens. I admit I haven't yet tried it on another screen, but I run my composite modded spectrums and many other machines through this TV without issue.

I've recapped the motherboard and the power board, one cap on the power board had leaked and and one 100uF on the board, though no damage. That said all caps appeared to be working, though they were out of tolerance.

the Recap has made no difference to the image either on composite or RF. I was wondering if anyone had any idea. I have been speculating that the Op-Amp (SFC2318DC) my be at fault, but I can't find a data sheet online for it, so I haven't tried probing it with the scope yet.

Here is a video of the issue. The video starts with the TV on RF input.

I did try to post this as a new thread but it kept giving me an error

SpaceFlightOrange
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Joined: Wed Jan 22, 2020 12:33 pm

Re: New Member, long time Dragon 32 owner

Post by SpaceFlightOrange » Sun Feb 09, 2020 1:56 pm

Hi.

Couple of updates. The Dragon has been stripped, re-capped, cleaned and re-assembled.
IMG_0746.JPG
IMG_0746.JPG (2.33 MiB) Viewed 978 times
IMG_0777.JPG
IMG_0777.JPG (2.45 MiB) Viewed 978 times
IMG_0781.JPEG
IMG_0781.JPEG (1.51 MiB) Viewed 978 times
The Logo I printed myself in lieu of getting a nice replacement. It's not obvious from the picture but the case would benefit from being retrobrighted a little, so I'm leaving this badge on until I retrobright it, then I'll put a proper one on.

I fiddled with the 2 pots on the picture output and managed to improve the image on composite, but the picture is a bit rubbish, with green ghosting to the right. On RF it's really bad.

Monitor output
IMG_0784.JPG
IMG_0784.JPG (2.07 MiB) Viewed 978 times
RF output
IMG_0785.JPG
IMG_0785.JPG (1.86 MiB) Viewed 978 times
I cant seem to get a decent picture on both. Any tips? im certain its not this TV as it's brilliant on my other machines (Spectrum, Amiga, Oric Atmos) on both composite and RGB.

Thanks

sorchard
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Location: Norwich UK

Re: New Member, long time Dragon 32 owner

Post by sorchard » Sun Feb 09, 2020 11:08 pm

Your composite output actually doesn't look too bad for a Dragon. The MKII machines had a sharper image than the earlier models thanks to an improved circuit. Not sure what would cause the ghosting on the right, other than the video signal being too high and causing a bit of saturation somewhere. It might be worth removing the LM1889 from its socket to disable colour and seeing what the mono image looks like.

The dot crawl down the left and right edges can be tweaked with the green trimcap below XL1.

The RF output does look pretty poor, and it shouldn't be a lot different to the composite. I don't have any sensible suggestions I'm afraid, other than adjusting the level via the trimmer next to the modulator, which you've already tried. I guess it's possible someone tried to tune the video before you and messed with the adjustments in the modulator. If so it might be a challenge to put them back where they should be.
Stew

Alastair
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Joined: Fri Jul 18, 2008 11:33 pm

Re: New Member, long time Dragon 32 owner

Post by Alastair » Sun Feb 09, 2020 11:11 pm

For the RF problems it could be that the modulator needs adjusting - no guarantees but it's a possibility. For information on how to test and adjust see my first post in the following thread:

viewtopic.php?f=8&t=5613&p=15904


P.S. I still don't know what 'cable compensators' do!

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robcfg
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Re: New Member, long time Dragon 32 owner

Post by robcfg » Sun Feb 09, 2020 11:22 pm

Can I ask you for some nice pictures of both sides of the board?

I just checked and we don't have your board pictured here: http://archive.worldofdragon.org/index. ... d_Pictures

We have the Issue 6 board with the "(P/N 48127)" marking though.

SpaceFlightOrange
Posts: 9
Joined: Wed Jan 22, 2020 12:33 pm

Re: New Member, long time Dragon 32 owner

Post by SpaceFlightOrange » Mon Feb 10, 2020 1:33 pm

sorchard wrote:
Sun Feb 09, 2020 11:08 pm
Your composite output actually doesn't look too bad for a Dragon. The MKII machines had a sharper image than the earlier models thanks to an improved circuit. Not sure what would cause the ghosting on the right, other than the video signal being too high and causing a bit of saturation somewhere. It might be worth removing the LM1889 from its socket to disable colour and seeing what the mono image looks like.
I'll give that try tonight. literally just whip the chip out and power back on?
sorchard wrote:
Sun Feb 09, 2020 11:08 pm
The RF output does look pretty poor, and it shouldn't be a lot different to the composite. I don't have any sensible suggestions I'm afraid, other than adjusting the level via the trimmer next to the modulator, which you've already tried. I guess it's possible someone tried to tune the video before you and messed with the adjustments in the modulator. If so it might be a challenge to put them back where they should be.
I've had this fella from new so the only fettling that happened inside is by me the other night :D

I think my biggest issue is lack of understanding on what the 2 pots do. I was focusing on trying to resolve the jumping issue i have (See Here) and i thought i had it sorted, but it came back!! It may be the TV, I'll try it on a different one tonight and do another adjustment to try and bring the RF back in.

Thanks

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