no color zx spectrum 48k (rubber) composite mod

duro00611

I have a problem, I just got my 48k speccy and I am waiting for my keyboard mebrane to arrive, meanwhile I did the composite mod and on startup before the "1982 Sinclair Research Ltd" it doesn't show any colours (like the red stripes going down) its all in black and white, but when i move around the composite plug, i get color on startup...

balford

Sounds like the plug on the composite lead isn't making a good solid contact with the TV out socket, or the lead itself is iffy.

Best thing to do if you don't have any other means to diagnose is to get the membrane replaced, then write a short program to display some coloured text. You can then wiggle the lead to see whether or not the problem's related to the physical connection then.

B

rwap

Just an update here - the power supply failed shortly after this - hopefully it didn't damage the Speccy - I wonder whether that might have had a bearing on this....

balford

Oh dear :( If the PSU output was low then no colour would be a symptom of the LM1889 not getting +12v, which has obvious implications for the 4116's.

Fingers crossed there's no damage done.

B

duro00611

i replacet the PSU and i can hear the buzzing....
now i dont get output of any kind...

rwap

He has at lease now confirmed that the Spectrum is starting up - connecting one pin on the 5 pin molex connector with a pin on the 8 pin molex connector gives repeated clicking from the speaker (as though a key is pressed).

So that means the problem should be down to the video circuit.....

Any more ideas?

duro00611

i replaced the lead, and still nothing...

rwap

It is hard to pin down problems in the video circuit - any suggestions on the best way to proceed?

duro00611

i think that i overheated the composite hole on the board

duro00611

and I really can't afford to send the speccy to UK

duro00611

i found the problem,i have a broken track beetven the composite hole and its other end...
but still no color :/

duro00611

i fixed it :D
aand my power socket is loose, it loses contact when i move arround the plug

duro00611

i get color when i put half of the power plug in the socket, but when i push it to the end, it becomes black and white

rwap

Ah - be careful - if the power socket is loose, that may be what blew the previous power supply....

At least it now looks like all you need is a new power socket - I may have some in stock, otherwise dataserve-retro.co.uk has some...

1024MAK

If there are problems with the power supply, or power socket, it can cause all sorts of weird faults.

If in doubt whether there is a poor contact in the existing power socket, renew it.

Mark

duro00611

dataserve-retro does not ship to Bosnia.. :/

balford

The part is a 2.1mm PCB mount power socket - they're a pretty standard component. You should be able to source this locally if needs be.

B

duro00611

i allready looked for it, nobody has it in my town... so I should wait for Riches answer