Cpc 464 not displaying the colour red

[Cribbyrhymes]

Hi everyone, first of all I'm excited to be back into cpc gaming and its great that a resource like this is here with like minded people with way more knowledge than myself. I've run into a problem though and wondered if anyone can assist. I got a cpc 464 off eBay listed as not working for a cheap price and it came with nothing just the base unit itself. I bought myself a joystick, scart lead with integrated power supply and some games. The 464 was completely dead when I tried it so I stripped it down cleaned it thoroughly with isopropyl etc and voila it lived again!! 29 years old and going strong! They definitely don't make them like they used too. The issue I have was when I was loading the original dizzy cassette to try it out and it loaded fine but I noticed the bland colouring and thought, hold on, didn't dizzy have red gloves and feet?? When the game loaded the spider was missing aswell as the tree and platform from the opening screen and on checking old screenshots all these items are red in colour. I just don't know where to start troubleshooting, is it a main board issue, scart issue or tv issue?? I have tried other games which all load fine but the colour issues persist. Any help would be much appreciated!

[Bryce]

Hi CribbyRhymes,
     welcome to the Forum.

First question: What test equipment do you own? Multimeter at least?

I doubt it's a TV problem, but I can only give you further tips when I know what you can test.

Bryce.

[Munchausen]

Sounds like the red connection is broken somewhere - in the scart cable or the cpc itself (possibly even the red ground line in the scart cable). You'll need a multimeter to test the board traces and cable. It might be good to try a different TV as a sanity check, or try a DVD player or something on the same scart socket and make sure that shows red - as long as you are sure that the DVD player/whatever is using RGB video (scart can carry several different formats of video using different pins - amstrad uses the RGB ones).


Bryce or one of the other hardware gurus will probably see this and be able to help more...


EDIT: Ninja'd 

[Cribbyrhymes]

Thanks for the quick replies guys, the tv scart socket works fine connected to a DVD player. The tv is a small 15" LCD and the manual for it lists the socket as RGB scart.
I have a multimeter any advice on what to test and how would be appreciated

[Bryce]

Ok, first test (with CPC completely unplugged). Measure the resistance between pin 36 of the Gate Array (40pin IC top left on the PCB) and the red output pin (on RGB socket). You should get somewhere 220 ohms. Then measure the resistance between the red output pin and the 5V rail, you should get around 680 ohms.

While you're at it, clean the RGB socket pins and check that the solder joints of the sockets don't have any cracks / dry joints.

Bryce.

[Cribbyrhymes]

Thank you bryce, I'm at work at the minute but will do this when I get home tonight and report back.
Thanks again

[TFM]

Hi Cribby, welcome here! To me it sounds like you have to clean the contacts with alcohol thoroughly. Actually only the pin for red.

[CanonMan]

My money is on cracked solder joints on the socket.

[Cribbyrhymes]

Couldnt find my multimeter when I got home but decided I would try cleaning again with isopropyl and if it didnt work get a new multimeter tomorrow and carry out the resistance tests as bryce suggested.  After I stripped it down and cleaned it I put it back together again but without any of the motherboard or case screws in just to do a quick test and.......IT WORKED!! Dizzy had his red gloves and feet back! Unplugged it all again and put all the screws back in where they should be, connected it up and the problem was back    This time I tried removing the two motherboard mounting screws that are nearest the monitor socket, left all the rest in fired it back up and fixed again!    I can only assume/guess with my limited knowledge that the board does have a bad connection which is coming into play with the pressure the mounting screws are putting on the board because without those two screws it is working great.  By no means a perfect fix and this board may die on me at some point but in the meantime Im going to enjoy it in full colour! Thanks to everybody for replying to the post and helping me out.

[Bryce]

Sounds like you have a dry joint somewhere between pin 36 of the CRTC and the RGB socket. I'd re-solder the socket and all the other pins associated with this signal: Pin 36 of CRTC, R125, R126 and that should fix it. There's no reason the CPC should die anytime soon. They seem to go forever

Bryce.

[Cribbyrhymes]

Thanks Bryce,
I would do what you suggested but my solder skills are non-existant and I'd be scared of ruining the board completely!

[Bryce]

Pin 36 is the only risky one. Then leave it out, but the other solder points are all relatively safe. Even the most hamfisted beginner could safely re-solder these.

Bryce.

[Gryzor]

Too late to the party, but let me give you a warm welcome to our community - hope you stay and like it!


My first thought on the missing red, upon reading the thread title: Sugar is a known Thatcherite, so maybe he built in a red-removal bug to be activated when she died

[Cribbyrhymes]

Thanks guys
Just waiting on some desoldering braid to arrive in the post and i will attempt to resolder!

[ralferoo]

Just waiting on some desoldering braid to arrive in the post and i will attempt to resolder!

Where are you based, out of interest? There might be someone local who can help...

[Cribbyrhymes]

I managed to fix it    Resoldered everything as suggested on Saturday and it is working great.  I wouldnt say the soldering was textbook but I got there in the end and so far so good!

[Bryce]

Congratulations. Another CPC brought back to life.

Bryce.

[00WReX]

Nice one Cribbyrhymes, always good to hear another CPC resurrection story 

Cheers,
Shane