On 31/05/11 16:40, Rich Mellor wrote:
I just need to pick your brains if you don't mind (and maybe your spares
pile)...
I have replaced the TV lead from inside the power unit, and I get a picture on
my TV.
However, if the TV is tuned in properly - I get a black and white picture,
otherwise the start up screen is very blue.
Is there anything I can do - I had to remove the ROM and memory chips and reseat
them to get even an ounce of colour on screen, but it may just be the TV needs
tuning.
It has been a long time but if I remember correctly the TV signal was
always very dodgy. First the lead from the power plug on the Sam to the
PSU wasn't screened so the signal could be too poor to carry the colour
part. I often used to shorten the power lead to about 18 inches to
overcome this.
The other frequent problem I recall was on the Sam main board. On the
left hand side (see attached image) C43 and L1 used to cause loss of
colour. C43 needs to be the blue component, not the brown one, and L1
should not be in a metal can. Don't even think about trying to change
these if you're not fully equiped with years of soldering experience and
a good temperature controlled soldering iron. The Sam PCB will lift
tracks and be destroyed more easily than almost any other!
And anyway I can't think where you would get spares from.
The best solution is and always has been, to use the scart lead.
There were two SCART leads with the computer, but neither seem to give an
output.
I seem to recall reading that the SCART is very different to normal.
The sam scart lead only goes one way. That is there is a Sam end and a
TV end. Put it the wrong way and it won't work.
If you need to check your leads then the tech manual gives the pin
connections but not the cable details. I think it goes like this (but
no guarantee that I'm right)
signal sam TV signal
Audio Right Out 01 02 Audio Right In
SPEN 02 NC Audio Right Out
Audio Left Out 03 06 Audio Left In
Audio Ground 04 04 Audio Ground
Blue Ground 05 05 Blue Ground
Blue TTL Out 06 NC Audio Left Out
Blue 07 07 Blue analogue
Red TTL Out 08 NC 4:3 / 16:9
Green Ground 09 09 Green Ground
Green TTL Out 10 NC not used
Green 11 11 Green analogue
+5V In 12 NC not used
Red Ground 13 13 Red Ground
CSync Ground 14 14 Fast Blanking ground
Red 15 15 Red analogue
CSync 16 16 Fast Blanking
C.VID Ground 17 18 Video in Ground
+12V In 18 NC Video Out Ground
C.Vid Out 19 20 Video In
Bright TTL 20 NC Video Out
Ground 21 21 Ground
NC = No Connection / not used
Hope this is of some help
Nev
