Icky's H4 Mongrel edition build x 2

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PaulJ
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Re: Icky's H4 Mongrel edition build x 2

Post by PaulJ » Sat Dec 14, 2019 5:22 pm

Icky wrote:
Sat Dec 14, 2019 4:35 pm
Below is a comparison of the original H4 circuit on the left and the revised 100R with caps in series on the right. As you can see its darker but still not as dark as the original ST. I will get a comparison pic of the original a bit later.
H4-Normal and Caps.png
Icky, what's going on... that jump looks like Phils dogs got to it. :dizzy:

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Re: Icky's H4 Mongrel edition build x 2

Post by Icky » Sat Dec 14, 2019 5:50 pm

@PaulJ - soldering iron got a bit aggressive with the jumper when I was desoldering the 75R's

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Re: Icky's H4 Mongrel edition build x 2

Post by Icky » Sun Dec 15, 2019 9:31 pm

Hmm - I still think there is something not quite right with the video circuit. My board currently has 100R and Caps in series. The colour has got darker but I am getting flickers and and pulsing on the screen. This is using my rock solid monitor / TV. Am going to make a video to show this in action. I have yet to try the 100R and cap combo on the monitor I was getting complete white out.

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Re: Icky's H4 Mongrel edition build x 2

Post by Icky » Tue Dec 31, 2019 6:16 pm

@exxos has been helping me test out the 1.44 HD Floppy part of the H4.

After initial problems with finding a HD floppy that actually worked and having to format it on my TT. We can confirm that it works, see photo below total bytes add up to 1440508 on the A Drive on the H4.

I'll stick up a guide on how to tomorrow.

IMG_4705.jpeg
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Re: Icky's H4 Mongrel edition build x 2

Post by PhilC » Tue Dec 31, 2019 7:13 pm

Cool, well done Icky, is it a gal or ATF we will be needing?
If it ain't broke, test it to Destruction.

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Re: Icky's H4 Mongrel edition build x 2

Post by Icky » Tue Dec 31, 2019 7:15 pm

@PhilC - you need a GAL22V10C

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Re: Icky's H4 Mongrel edition build x 2

Post by PhilC » Tue Dec 31, 2019 7:17 pm

Cool, got plenty of those.
If it ain't broke, test it to Destruction.

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Re: Icky's H4 Mongrel edition build x 2

Post by kodak80 » Tue Dec 31, 2019 10:44 pm

Icky wrote:
Tue Dec 31, 2019 7:15 pm
you need a GAL22V10C
Could GAL22V10D or GAL22V10B also be used? Datasheet looks similar. What speed or does this not matter?
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Re: Icky's H4 Mongrel edition build x 2

Post by Icky » Thu Jan 02, 2020 1:33 am

Thought I would post a pic of the H4 1.44 HD floppy test rig.

You may notice Flashy Clock V3 (FCV3) is in one of the expansion sockets (not the Flashy Clock socket one as I haven't got round too sorting that out yet). The PLCC CPU has been removed and DIP 68K is in use on the FCV3. In addition there is an extra lead coming out from the FDD drive that is used for the HD select.

IMG_4713.jpeg
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Re: Icky's H4 Mongrel edition build x 2

Post by exxos » Thu Jan 02, 2020 2:05 am

:bravo: as long as you don't make a habit of shoving things in the wrong hole :lol:

I may at some point see if I can route the 2 1772 lines which goes via resistors though the gal instead. Might save 2 resistors and could be classed as a bit more eligent I guess.

Incidentaly, the H4 could likely work without the 3 large smt caps. I mean there's enough smaller caps across the board that they may not actually be needed. It would have to be looked into properly though, not just a test of if it boots or not.
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