dragon 32 not displaying anything on screen

[starfrog]

I have two Dragon 32's that are not displaying anything, the psu that I use from my dragon 64 (a dragon 32 psu) works okay and the two PSU's that I had with the dragon 32's works on the dragon 64 so I know the PSU's are working. When I switch on at the back I get a click from the main motherboard so it looks like some sort of power is getting through but no image is displayed on screen. i have tried both displays using the modulator and the composite lead (which work when used with the dragon 64). what should I be looking for as nothing appears to have blown. any help is very welcome.

[tormod]

Do you hear the relay click if you type "motor on" and "motor off"?

[starfrog]

Yes I hear a small click from the motherboard when I type Motor on and motor off

[starfrog]

I have also noticed that while my 64 works and and entering exec 48000 works it only does it in monochrome from my composite out connection ? maybe all my Dragons are beginning to fail ? I assume its something to do with the video chip ?

[Rink]

Did that TV used to work with those Dragons?

I don't know but it seems a little odd that two 32s and a 64 all have video problems. I'd try and test with another display before worrying too much about the VDP.

Edit: Not all modern TVs like the old signals from computers like the Dragon. And you don't say where you're from so we can't guess if its likely to be regional issue (PAL vs NTSC etc).

[starfrog]

I'm from scotland but as I'm using composite it shouldn't matter ? The TV is good as I use it for a sinclair spectrum, the 64 works fine other than its mono and I've had that since 1988 and seem to recall that it was only mono previously. I've only every used the composite adapter for all three machines. The 32's just don't give any picture at all (I've only recently acquired them) one of the 32's did give me a picture for a brief time when first trying it out but it was scrambled and after the 2nd time of powering it up I've had nothing. Really appreciate the help and would be great to get them back working. maybe its a VDP issue ? but how does one easily change that chip out as its soldered onto the board ?

[Rink]

I'm from scotland but as I'm using composite it shouldn't matter ?

Composite video is still offered in standard formats such as NTSC, PAL, SECAM etc. But since you're in Scotland, there shouldn't be any problems with you using Dragons.

Might as well ignore the RF modulator at this stage. Those things just introduce even more problems.

I've only every used the composite adapter for all three machines.

When you say 'composite adapter', what do you mean exactly? I'm assuming you're just connecting a composite video cable from the composite video out on the Dragons, to the composite video in on your TV?

I'd still try a different TV if you can - just because you want to narrow down every easy possibility before hitting the complicated ones.

From what you're saying, things don't sound good. But let's not give up hope just yet. Are you using the same cable as you're doing successfully with the Spectrum?

How are you with a multi-meter / soldering iron etc?

one of the 32's did give me a picture for a brief time when first trying it out but it was scrambled and after the 2nd time of powering it up I've had nothing. Really appreciate the help and would be great to get them back working. maybe its a VDP issue ? but how does one easily change that chip out as its soldered onto the board ?

Yep, replacing the VDP is non trivial. That's if you can even find a replacement. Someone was selling ones built with FPGAs, but they're like $90 or something.

[starfrog]

Hi Rink,

I tested on 3 TV's 1 older CRT model, two modern LCD's same result from all of them, only display from the 64, the 32's nothing, nada, zilch I'm just using a standard Dragon Monitor out cable to composite on the TV's

I can use a solder iron but multimeters and the like are voodoo magic to me having said that I can type into google so that might assist me with knowing how to use one I think the replacement VDP chip is only 8 quid on ebay.

[robcfg]

I'd test the machines with a composite cable and a standard tv cable.

Maybe some cable broke or there's a dry solder on the cable connector. Just to rule out that there's something wrong with the machine.

[starfrog]

already tested both display modes and the cables that I am using work on the Dragon 64 fine when I try the same on the 32's they give me no display what so ever but they do respond to motor on / motor off