Amiga A520 TV modulator problem

[Half-Saint]

I recently bought a used A520 at the flea market. The problem is that the output is only in black&white, sound works fine. I tried messing with the little pots to no avail. Any other suggestions? The Amiga is not defective.

Thanks

 

[carlsson]

Are you using the RF or composite video output from the A520? Have you tried both?

 

[Half-Saint]

I only tried RF out. You think I should try composite?

 

[carlsson]

Well, if you get colour out from the composite you have at least one fault source less to suspect. I don't know how a 520 looks like on the inside, but I'd suppose it consists of a RGB to composite circuit and then an off-the-shelf RF modulator which takes the composite signal, mixes with audio in and outputs the antenna signal.

 

[Half-Saint]

Thanks for the suggestion. I'll give it a try and report back!

 

[Zeela]

I only tried RF out. You think I should try composite?

Any chance it's a NTSC A520? Then you'd get B&W picture from it on a PAL TV.

 

[Half-Saint]

I don't know. How can you tell? Different part number?

 

[Half-Saint]

I took the time and tested all three A520 units that I have.

Here's the result:
1. RF - color, Composite - color
2. RF - color, Composite - no picture
3. RF - black & white, Composite - black & white

2nd and 3rd are exactly the same model and part number.

 

[Druid6900]

RF modulators are usually tuned to one of 2 channels (2 and 3, 3 and 4) and may even be switch selectable on the unit. Try going up and down one channel on the TV and see what you get. The output of the computer should over-power a broadcasted signal in case the channel is in use.

 

[Half-Saint]

What puzzles me is that I don't get anything on Video Out for the 2nd modulator.

My TV is a Sony KDL-40EX500 and it has separate digital and analog input. Since we have digital free2air TV, I had to scan through all analog channels and the TV only picked up one. I don't remember which of the three modulators was plugged in when I did this (either No. 1 or No. 2). I tried all three on this same channel. Maybe I should try re-scanning with the No. 3 plugged in but I'm afraid the end result would be the same.