PhilC's H4 Mongrel edition build x 3

[PhilC]

Ok, so today I've removed the 75 ohm resistors in the rgb circuit and replaced them with 100 ohm.

This is the result.

20191212_180412.jpg

So it's better but still not right, like it needs a little more contrast and a bit more black if that makes sense.

Here's the previous screenshot as a reminder.

20191209_165110.jpg

[exxos]

Have you tried some series caps ?

[PhilC]

Have you tried some series caps ?

Not yet, just tried 150ohm which looks better:

15761745699406831421705161317499.jpg

So where do I need to place the caps?

150 is looking better colour wise

[exxos]

So where do I need to place the caps?

In series with those 100R resistors... Those SMT 100uF ceramics would be ideal, they were used on the H4 and the prototype DAC bodge boards.

[PhilC]

So presuming I've got these in the right place, theres 3 104 caps soldered from the left hand side of the resistors to pins 6, 7 and 10 on the atari video port(or where it should be)

Here's the results.

20191212_184453.jpg

20191212_184438.jpg

[exxos]

Its not right.. you need to lift one end of the 100R resistors and solder the cap on the resistor end and the now free pad...

Also 104 caps may not work, should be more like 100uF.

[PhilC]

Ok, I need to see what I can find then

[exxos]

Ok, I need to see what I can find then

There 3 large SMT caps on the H4 are what you need.

[PhilC]

Only problem is that I only ordered 3 of them.

But The Alpha DAC board comes to the rescue. And for the record, soldering those caps in there was a pain in the bum.

Anyway

20191212_193109.jpg

20191212_193102.jpg

Much better. 150ohm and whatever those caps were lol.

Only other larger caps I have are either electrolytics or tants.

[exxos]

But The Alpha DAC board comes to the rescue.

Did tell you that earlier ;)

Much better. 150ohm and whatever those caps were lol.

So do the caps make any difference then , ? We need to know 100% if they are doing anything or its the 150R just having a effect.