Hi to everyone

[clwydog]

Amazing to such widespread, international interest in Dragon. I bought mine (D32) not long after they came out: copied games from mags, bought cassettes from local suppliers, and even wrote a game for my pre-teen sons that incorporated a machine code sub-routine to move sprites quicker around the screen (cribbed from Dragon User).
Well, after some 30 years in the loft I brought it down again. A chance viewing of a YouTube upload triggered nostalgia that wouldn't be ignored, so I set it up and switched it on. Surprise, surprise, it worked and my memories lit up along with the screen. 'Hello World' all over again.
Anyway, after a time I got a brief flash across the screen which slowly increased it's presence until... no signal.
I have approached local computer shops to get a repair but no-one is interested, so i thought I'd ask here for suggestions rather than just abandon it. I did very basic City & Guilds electronic servicing courses 1and 2 some 35years ago as it was an interest but a demanding job and life in general meant it remained just that.
Can anyone help

[Serenarian]

Hi, I'm sorry no one else has replied yet - and I'm no expert, but can I offer some hints.
If anyone else wants to chip in, then please do.

More often than not, in my experience, it is the video signal that needs tweaking but you don't give many clues, about the flash.
Are you using the monitor output, or the TV modulator?
Being cautious I assume that you have a multimeter and can check voltages.
If you open it up and unplug the 10 way connector that links the power supply board to the main board you can that the check supply voltages are all there.
(see the schematics and the photos of the D32 power boards for confirmation of the pin numbers.)
I think Pin 5 =GND, Pin2 =+5, Pin3=-5, and Pin1=+12.
If those are all present and you reconnect and then power on you should be able to hear a click from the cassette relay.
If so, then typing blind, press Return, then type "PLAY"ABCD" and press return. Does it make sound?

If none of the above then we need to think again.

[robcfg]

Hi, welcome to the Dragon Archive!

Sorry for the late reply, between vacations and life getting in the way, sometimes it's not possible to answer as fast as we'd like.

I'd check first the voltages supplied by the power brick and if they're ok, I'd check the voltages coming out of the power board.

You have the pinouts for the connectors here: http://dragon32.info/info/psu.html

It would also help if you post some pictures of the boards inside your machine, which will add some more context to help diagnose it.

You can also check our motherboard scans and our power board scans pages to see if they're already there, though pictures of your actual unit's boards will help further with the diagnostics.

Cheers,
Rob

[clwydog]

@Serenarian, robcfg

Thanks to you both for your responses.

My multimeter must be on the fritz as my readings on the 9pin connector were: 1) 1.6, 3) 14.4, and 5) 14.7.
But while I was exploring there was a small fzzt and I had a picture again. After more exploring I found that the on/off switch at the back was very intermittent in operating - sometimes I'd have to press it several times before the screen would show. Is the switch able to be dismantled and cleaned?
With a screen again, I tried the Dragonwriter cartridge I have and it worked. So I got the cassettes out and even after such a long period of inactivity I managed to load Dragon Chess successfully (although my little Bush cassette player's speaker failed whilst setting the volume level - such memories - but I fortunately had another player).

The flash I described initially was a horizontal band across the middle of the screen, like a faulty suppressor used to create. I have a photo of the board but how do I upload it?

[robcfg]

The voltages on the 9-pin connector are AC, not DC, so you need to set your multimeter correctly.

For the power switch, you can try sipping in some contact cleaner fluid, and press it a number of times so the fluid enters it and gets rid of some corrosion probably.

Regarding the pictures, maybe you can upload them to https://imgur.com/upload and paste the links here. I think you don't need even an account to upload pictures.

Nice that you got it working!

[Alastair]

You should be able to upload photos directly to the board. Either click on the "Attachments" tab and then on the "Add files" button, or just drag and drop the picture file in the message box.

[clwydog]

@ robcfg, I was on the ac range when I measured.

Thanks Alastair, I just dragged the pic into the message box as you said - easy when you know how.D32 board

[Serenarian]

It seems that you are almost there. That looks to be an Issue 2 board with the two banks of 16k chips -one above the other.
The voltages that I was suggesting that you check were all on the grey connector between the PSU board (on the right in your picture) and the main board and are DC voltages coming off the PSU board. Pin 1 is at the bottom in your picture. But no matter, it appears that the voltages are all there and the power switch is a bit "crusty". So try contact cleaner next.

[clwydog]

Mmm. applied contact cleaner and left to soak/dry out. After 2 trials the Dragon starts ok but after some run time a restart becomes iffy- until finally there is no display. I suspect a component is gradually heating up until it fails. Does that seem plausible?

[clwydog]

Another check. Although there is no display I get the DC voltages at the connector you described.
P1=12v, P2=5v, P3=-5v, P6=-0.4v, P7=18v, P8=8.5v, P9=2.4v.
I can hear and see relay RL1 operating.