A520 - No Colour?

[EreWeGo]

Hi all,

I'm having some problems getting an A520 modulator to display colour using the RF output. I'm hooking up my old Amiga 500, (I have an A1200 already, but just wanted to hook up the 500 in another room for the odd quick game).

I'm using a PAL Amiga, and I think a PAL A520, (I bought it from someone in England, and the crystal inside is a 4.43 MHz, so I'm pretty sure it's PAL).

Now, on two different TVs, I can connect the A520 to the aerial/RF port, tune the channel, and get a nice, clear image...but only in black and white! I know the composite port will only display b&w, but shouldn't the RF be in colour?

The A520 didn't come with the RF lead, so I am only testing using one I made, (attached an RCA connector to a standard TV aerial, plugs in okay etc), and also tried a standard aerial lead, (just held the lead in place at the A520 end to make contact).

Do I need the actual A520 RF lead, or is it pretty standard? (except for the RCA type connection obviously)...

Any help/ideas would be very much appreciated!

[alexh]

Do you get colour out of the Composite video output on the side of the A520?

Have you tried the A520 with the A1200 is that also B&W?

You of course do not need an A520 specific RF aerial lead, after all it's just a bit (two bits) of wire.

I'd put money on either the A520 being broken, or the A500 being broken.

[EreWeGo]

Hi Alexh, thanks for the reply mate. I believe that getting b&w from the composite is normal for the A520, but I did try using the RF output with my A1200 as well as the A500 as you suggested, and I get b&w on the A1200 too...so I guess I must have a broken A520?

Shame, as I said, the image is fine, except there's no colour. Does anyone know if there's a solder joint or diode etc that I could check to do with the colour, or am I just barking up the wrong tree so to speak?

Anyway, I appreciate your suggestions, guess I'll be looking at another A520 then...

[davideo]

@EreWeGo

You should definately get colour on the Composite output if your A520 is working correctly.

That's how I connect my systems up - I don't use the aerial lead.

Dave G

[EreWeGo]

Originally Posted by davideo

You should definately get colour on the Composite output if your A520 is working correctly.

Really? Thanks for the correction Dave.

Bugger, ah well, at least I won't waste any more time trying different leads/cables and searching the net for answers. Thanks for your help guys, really appreciate it.

[TheCorfiot]

The Colour Sub Carrier frequency needs slight tweaking inside the A520 possibly that or the Colour Encoder circuit has failed.

TC

Looking around for a schematic to see if we can point you to the right adjustment

[EreWeGo]

Hey TC, thanks mate. I was just about to give up, then thought I'd have another look after your reply, and after Dave mentioned that I should get colour even with the composite port...

I had a look inside again, gave everything a clean with contact cleaner, then tried tweaking some of the little "pots", and I can get colour now! It's a little "twitchy", (if I bump the unit a bit it can take a bit of moving it to get colour back), but it's going. I'l clean the main contacts, and see if I can get it a bit more stable, but it's going at least!

Thanks a lot guys, awesome stuff, and a very helpful forum you guys have here!

[TheCorfiot]

Excellent Stuff

One of my A520's behaved the same, Slight tweak, Ahem, All Ok.

TC

[Overdoc]

On the A-520 it happens quite often that some solder joints on the pins get loose. This can also lead to a b/w pic.
Just resolder them and it will be ok again.