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aha, i worked out a possible way of doing that with wilf rigters external chr$ circuit, making it 'programmable', i never got round to building the thing to try it, if i can find the circuit (rough hand drawn) i'll scan it and post it here...
your machine has the earliest ula and this is lacking the 'back porch' part of the signal, so WILL give poor dark picture on a colour tv, even if its perfectly ok... it will usually be ok on a black & white set..the zxvid or zxccb will cure it by adding the back porch..dont worry too much about the ...
- Tue May 16, 2017 3:36 am
- Forum: Hardware
- Topic: ZX Spectrum Issue 3 repair
- Replies: 123
- Views: 18200
supposedly a -6 'shouldnt' work in an issue 6 , only -7, due to timing change, but might have been a 'selected' one that did !! -7 's are supposed to be used in issue 4 and above, except apparently samsung issue 4s which can handle -6 's .. ?!
if you do that, you wont be able to get a display as the video timings are derived from the clock, and yes, the cpu clock is half that of the resonator/crystal...you must keep it at 6.5mhz...although it IS possible to rig up a 'turbo' circuit, which runs the cpu at 6.5 mhz when running program code,...