Icky's H5C1 build to document all C1 fixes

[Icky]

I thought I would start a thread to help with the H5 C1 board fixes and in particular the audio issues. @Bikerbob has been looking to resolve the audio issues and am going to walk through a new H5 C1 board that exhibits the same behaviour as his board here - viewtopic.php?p=82855#p82855

So below is a pic of the newly built board which does not have any fixes to the board so far. It has a TOS Decoder board to allow booting to TOS206 similar to the build in @Bikerbob's thread. I have installed an original ST floppy drive to help with capturing behaviour of the board pre-fixes. I don't normally use floppy drives have never seen the need and always use a gotek or other derivative but thats just my preference.

IMG_1460.jpeg (173.45 KiB) Viewed 4308 times

As I work through the fixes I will post in this top thread as a guide to them all and reference to the work threads on each done by @exxos. I will bump the thread as this top post gets updated.

Audio Fixes:

First job is to film a video of the noise coming from the floppy and reduction in volume. The board is displaying this behaviour so will post shortly.



In the video the first noises are the floppy disk but its actually the audio interference. Secondly when the title screen displays the gun blast the noise is loud and after that all the repeat titles blasts are quieter and quieter.

Now to start the audio fixes on the board.

First fix - H5 C1 YM AUDIO FIX - this fixes the fading audio

1K resistor in place:

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100nF ceramic cap in place on top of the 1K resistor:

IMG_1481.jpeg (117.06 KiB) Viewed 4236 times

After the fixes here is a video of the same game to compare. I can still hear the floppy interference sounds but the fading sound has gone away. When the title screen displays the gun blast the noise each time the sound level is the same



Second fix - C1 AUDIO FIX - FLOPPY NOISE ISSUES - does what it says on the tin

Take the capacitor C2A positioned under the audio circuit IC off. Add a bit of additional solder on the pads helps to remove it and place the removed capacitor on top of the 4th resistor along R77 from where the cap was removed:

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On with the next steps

Cut the track between the 2nd (R57) and 3rd (R74) resistors at the bottom right of the audio circuit IC:

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Once cut test that you have cut the track and there is no continuity between the the top of the 1st (R56) and 4rd (R77) resistors at the bottom right of the audio circuit IC. These two pads are where we solder a 100K resistor:

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Now to do some tests to see if the audio interference from the floppy drive has gone.

Success - no noise of any floppy interference even if I turn the volume up to max on the TV.

Now on to the MIDI sound fix - adding the S2 board

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[Bikerbob]

Thanks for posting Icky, I have been very busy over the summer ( my business is seasonal) so I am just getting the H5C1 back out now.

I will go and try the fixes. - I appreciate your illustrations.

I did not use the midi board in mine, but I did do a fix as per. viewtopic.php?p=87729#p87729

Viewing that thread I see that Exxos has also added much more to it since last I was on here to look.

Thank you both. I will work on this over the next couple of weeks (still busy at work) and try and get this resolved, and verify your great work.

James

[Bikerbob]

ok Icky, if you see my thread now. I have done everything up to the midi fix.
in that thread viewtopic.php?p=87729#p87729 I did the old fix

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I now see there is a NEW fix, and it is very much more than I WANT to do. Does the old fix actually fix? or do I need to do the new fix? OR should I just test what I have done, and see where I am at? I am not installing any S2 midi board.

James

[exxos]

I now see there is a NEW fix, and it is very much more than I WANT to do. Does the old fix actually fix? or do I need to do the new fix? OR should I just test what I have done, and see where I am at? I am not installing any S2 midi board.

You need to do all the new fixes. There are no shortcuts i'm afraid. I did it all as simple as I could already. They are really just one fix, which fixes noise on the power rails. So if you don't do them all, then the problems won't be fixed.

[Bikerbob]

I now see there is a NEW fix, and it is very much more than I WANT to do. Does the old fix actually fix? or do I need to do the new fix? OR should I just test what I have done, and see where I am at? I am not installing any S2 midi board.

You need to do all the new fixes. There are no shortcuts i'm afraid. I did it all as simple as I could already. They are really just one fix, which fixes noise on the power rails. So if you don't do them all, then the problems won't be fixed.

Well, I am going to call it a success!
I powered up the machine an I would say 95% of all noise has been removed with the old fix. YES if I crank the volume up to 100% there is a consistant background hum at say 70%+ and at about 90% if I click the mouse, or access the drive there is a change in the frequency of the hum. But no longer am I hearing the access or other noises, and when I loaded speedball2 I could hear the music of the game and nothing else really.

Does leaving it the "old fix" actually cause any issue? or is it just not the best way to completely cure the rail noise. 1 - I dont have spare SMD resistors lying around, and I have to buy 100 around here.. cant buy 4-5. 2 - I know you did it as simple as you could, but for a lot of us, each time you take the soldering iron out for a fix - is a risk.

James

[exxos]

Does leaving it the "old fix" actually cause any issue? or is it just not the best way to completely cure the rail noise. 1 - I dont have spare SMD resistors lying around, and I have to buy 100 around here.. cant buy 4-5. 2 - I know you did it as simple as you could, but for a lot of us, each time you take the soldering iron out for a fix - is a risk.

Not sure what your reffering as "old fix", do you mean the wires on the midi header ? It doesn't matter anyway.

You don't have to use SMT, but think it would quickly end in a mess with other parts. If you do a store order in the future then I can probably include some SMT stuff anyway, assuming I can find the stuff

[Bikerbob]

Not sure what your reffering as "old fix", do you mean the wires on the midi header ? It doesn't matter anyway.

So you're saying it does nothing? and I can just remove it???

[exxos]

So you're saying it does nothing? and I can just remove it???

Are you referring to this ?

viewtopic.php?p=92583#p92583

It mutes the volume of the MIDI board audio channels.. The new fixes correctly Bias the volumes of those links no longer required. Leaving them with just simply keep the audio channels muted. Makes no odds if you never plan to use the MIDI board anyway.

[Bikerbob]

So you're saying it does nothing? and I can just remove it???

Are you referring to this ?

viewtopic.php?p=92583#p92583

It mutes the volume of the MIDI board audio channels.. The new fixes correctly Bias the volumes of those links no longer required. Leaving them with just simply keep the audio channels muted. Makes no odds if you never plan to use the MIDI board anyway.

Got it.. SO if I have no plans to use the MIDI board then the MIDI fixes we just discussed above are not really required then? Good to know. Maybe I do them later if and when I decide to do the midi board.

[exxos]

Got it.. SO if I have no plans to use the MIDI board then the MIDI fixes we just discussed above are not really required then? Good to know. Maybe I do them later if and when I decide to do the midi board.

No.. That's not what I said. I said you need to do all the new fixes. Its irrelevant if you use midi or not as the noise is on the all circuit power rails for both YM and MIDI.