Back Porch circuit and a back porch generating ULA

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bola_dor
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Joined: Wed Oct 02, 2019 5:32 am

Back Porch circuit and a back porch generating ULA

Post by bola_dor »

Hi,
I've built the 555 based circuit By Ziggurat http://zx.zigg.net/misc-projects/
I plan to use it on a ZX80 but meanwhile tested it with my CZ1000.. with a Ferranti 2C210E ULA which grates an appropriate back porch.
20200521_211818.jpg
What I've noticed is a really crisp, steady and noiseless K cursor but with a black left border.. is this because the preexisting backporch added to the new one or did I messed up something?
20200521_211624.jpg
Ernesto
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1024MAK
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Re: Back Porch circuit and a back porch generating ULA

Post by 1024MAK »

A longer black porch will eat into the left hand side border...

Mark
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stroebeljc
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Joined: Thu Apr 23, 2020 6:02 am

Re: Back Porch circuit and a back porch generating ULA

Post by stroebeljc »

You should be able to reduce the duration of the back porch by changing the RC values on the 555. Of course, then it may not work so well on the older ULA. Maybe a way to switch in different R values?
John
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