A1200 SCART (yep, another one with 'issues')

Megatron-UK

Member
Joined
Jul 23, 2010
Posts
151
Country
UK
Region
Durham/Newcastle
Ok.

A1200 works great connected via RGB cable to a 1084, or via composite to anything with a composite input.

A500 works great connected via (either of) two RGB to SCART cables connected to any of my TV's, and also via RGB cable to the 1084.

A1200 will not display an image via either of the same RGB to SCART cables used by the A500, on any TV. The TV's I've tried will auto-switch to the SCART input when the Amiga is turned on, but all I get is a black screen and one flicker when I would expect workbench to show (I'm guessing it's the screen mode being initialised) - even the early boot menu can't be seen (so it's not a workbench prefs cockup).

I need a solution to this problem that does not involve buying more monitors or TV's - I've been through enough of them (both old CRT and new LCD and Plasma) to realise that it's not them that's the issue. I have got to get the A1200 displaying via RGB SCART as I want only a single monitor/tv solution for my retro game setup.

I'm currently trying to get all my retro stuff (which is all RGB SCART or VGA) displaying through a Samsung Syncmaster 710MP. So if anyone is using one of those with a SCART cable, I'd love to hear from you.

Please help!
 

danhans115

New member
AmiBayer
Joined
Dec 18, 2007
Posts
181
Country
UK
Region
Leeds
SCART is always a pain with the older machines I have found..

When I had a 1200 a while ago I struggled with the SCART, but after much fiddling around, I put +5vdc through pin 8 and bridged pin 8 and 16 with a 180ohm resistor to get a picture, this enabled RGB.

Ive had this setup working on a Toshiba 42" LCD, 50" LG Plasma, 21" CRT Sony and a 21" Bush TV, as well as on other systems (Amstrad CPC etc..)

Powering those pins iirc makes the TV select the AV automatically and also enables the signal input over RGB rather than composite.

Dan
 

Megatron-UK

Member
Joined
Jul 23, 2010
Posts
151
Country
UK
Region
Durham/Newcastle
What I can't understand is why the A500 works with the same cables!

Is the pinout different on the earlier machine? Perhaps the A1200 missing power on that pin?
 

danhans115

New member
AmiBayer
Joined
Dec 18, 2007
Posts
181
Country
UK
Region
Leeds
Sorry I should have said. The pins I am referring to are on the SCART connector, not the amiga video connector.

Im sure not as to the rest, thats just the config I got working for me.
 

Megatron-UK

Member
Joined
Jul 23, 2010
Posts
151
Country
UK
Region
Durham/Newcastle
Yep, found these:

http://pinouts.ru/VideoCables/AmigaScart_pinout.shtml
http://www.pavouk.org/hw/en_rgbscart.html

Which seem to confirm it. However, I've just taken the ends off both RGB to SCART cables I've got here, and they've each got pin 22 and 23 connected, ending at SCART pin 8 and 16 - so it appears the cables are wired correctly.

I need a new battery for my multimeter - I'm wondering if the 12v or 5v line on my A1200 RGB port is faulty - which could be why the A500 works, but I get no display via the 1200.
 

Megatron-UK

Member
Joined
Jul 23, 2010
Posts
151
Country
UK
Region
Durham/Newcastle
Got a new 9v battery for the multimeter.....

On the SCART plug, pin 16 (Fastblanking in / RGB enable) : 2.0v (supposed to be 5v from Amiga pin 23, dropped to 1-3v via a 100Ohm resister).

On the SCART plug, pin 8 (Status / AV select) : 0.0v (supposed to be from 12v on Amiga pin 22)

I'll measure at the socket for actual output in pin 22.

But isn't pin 8 just autoswitching? If I select the SCART input manually (which I can do, actually it autoswitches anyway) then if it's 0v then it doesn't matter. RGB enable seems to be active... so it should all be working.

---------- Post added at 16:54 ---------- Previous post was at 16:35 ----------

To test I have bridged SCART pins 8 and 16, so they are both at 2.0v. There is no difference in output. The screen still autoswitches to SCART and goes black, flickers a couple of times during bootup and nothing gets displayed :dry:

---------- Post added at 17:07 ---------- Previous post was at 16:54 ----------

Ok, measured voltages at the A1200 RGB connector:

Pin 22 : 0.0v (should be +12.0v)
Pin 23 : +3.90v (should be +5.0v)


This doesn't appear to be good :(

---------- Post added at 18:15 ---------- Previous post was at 17:07 ----------

I'm wondering if I should try another A1200 motherboard - I'm sure when I first got the system it worked via RGB SCART without any problems, but when I first tried it after moving in to my new house I had these issues and resorted to picking up a 1084S to get a display.

I've not noticed any bad caps on the board, but wonder if something has been damaged during the years in storage (well, clearly there has, as there is no +12v output from the RGB port!).

Anyone got a working A1200 motherboard they'd like to sell or donate?

---------- Post added at 19:13 ---------- Previous post was at 18:15 ----------

Trying to track down components E263, E264 and E265, which should be where the RGB power lines come from (+5v, +12v etc). Can't seem to find them on my rev 2B board.

Could someone point them out?

---------- Post added at 19:34 ---------- Previous post was at 19:13 ----------

Found the components:

1200rgb.jpg


I've labelled them as they should be. However, the actual measured voltages are:

-11.90v
0.0v
+2.19v

I'm guessing the components are surface mount resistors? Whatever they are, on the RGB connector ('output') side, the voltages are the same as measured on the connector pins. On their 'input' side, I do not get any readings.
 

Megatron-UK

Member
Joined
Jul 23, 2010
Posts
151
Country
UK
Region
Durham/Newcastle
Hmmm... interesting. Could the missing +12v be a red herring then? Perhaps the issue is that I am not seeing a full +5v?
 

rkauer

Amiga fanboy
Joined
Dec 17, 2007
Posts
10,337
Country
Brazil
Region
São Leopoldo, RS
The brown SMD ones are capacitors. The resistors are in the other side of the board.

Check the one for the +12V line: I bet it is broken.
 

johnim

New member
VIP
Joined
May 18, 2010
Posts
13,051
Country
England
Region
birmingham
i was having problems with my genlock and found this out was fine on my 600 pain really
 

Megatron-UK

Member
Joined
Jul 23, 2010
Posts
151
Country
UK
Region
Durham/Newcastle
The brown SMD ones are capacitors. The resistors are in the other side of the board.

Check the one for the +12V line: I bet it is broken.

Thanks! I've checked the other side and I've found a single lifted trace leading to pin 22 of the RGB connector (the voltage from the resistor was +12v) . Unfortunately it's lifted between the first and second row of pins, so I don't think I'll be able to repair it in-situ.

I have some kynar wire - would that suffice to make a patch wire to the other side of the board so that I can solder directly to pin 22?
 

Merlin

Ministry of Retr0bright and Street Judge
VIP
Joined
Nov 24, 2007
Posts
15,597
Country
UK
Region
Manchester
Yes, Kynar wire will be fine - it's been used for many a repair on here.

(y)
 

Megatron-UK

Member
Joined
Jul 23, 2010
Posts
151
Country
UK
Region
Durham/Newcastle
Done. SCART pin 8 now has +12v. Still no joy from the screen though. Sigh...... :mad:

---------- Post added at 22:16 ---------- Previous post was at 21:40 ----------

Just for kicks I tried a patch lead direct from the +5v power line to Pin 23 on the RGB port (the one that is supposed to go SCART pin 16 at between +1.0-3.0v).... et voila! the screen sprang straight in to life.

Sorry, no pics... but you all know what a kickstart screen looks like :)

Looks like the 2-point-something volts on that line are not enough anymore. Perhaps a component on that line is going bad and not supplying enough juice anymore... Anyway, I'm back to work tomorrow, so it's too late to do any more soldering. I'll find another +5v line that isn't straight from the PSU and solder that in tomorrow; hopefully that should be it fixed for all tv's now!
 

ptp170

R Tape loading error, 0:1
AmiBayer
Blogger
Joined
Aug 20, 2010
Posts
715
Country
UK
Region
Devon
Don't know about anyone else but I'm unable to see any of the pictures you're posting...
 

Megatron-UK

Member
Joined
Jul 23, 2010
Posts
151
Country
UK
Region
Durham/Newcastle
Sorry, I've been redoing my website lately and my misc folder where my forum attachments go was moved. Should be back now.
 
Top Bottom