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#1 2012-04-17 11:21:10

neal beard
Nibbler
From: Portsmouth
Registered: 2010-10-19
Posts: 43
Website

Blank Screen? Have I killed her?

I've been modding my beloved 64c -

with dual SID
audio out x2
video out
feedback x2

and inactive x's 4 pot http://www.prophet64-forum.com/viewtopic.php?id=1935

It had been working though with crazy amounts of what sounds like scan noise through both audio outs.

I had been checking the audio in to ground connections (through 1uf capacitor and 100k R) but that didn't cure the noise so I tried adding a ground loop islolator.

But when I turned it on I got a strange squeeky noise followed by a dead screen.

I looks like Msisah loads for about a nano second before the screen goes blank through both RF out and video out.

I checked the mssiah cart in another machine and it's fine.

Any ideas what's happened and if I can fix it?

Or is it time to rip out my mods and start on another machine...

although I think this time I'll make break out boxes for as much of it as possible as it's so depressing to put lots of work into something that F's up!

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#2 2012-04-17 18:04:21

neal beard
Nibbler
From: Portsmouth
Registered: 2010-10-19
Posts: 43
Website

Re: Blank Screen? Have I killed her?

I've just put the sid2sid with the same two 8580 sid chips into another 64c machine.

Mssiah loads and both Sids working though there is still an un-bearable amount on noise out of both audio out's.

There are no mods on this machine, just audio out x2 with both audio in's grounded through 1uf cap and 100k R.

I wondered if it is possible to bugger up Sids causing them to become effing noisy whatever machine they're put in?

Last edited by neal beard (2012-04-17 18:04:59)

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#3 2012-05-04 17:32:05

neal beard
Nibbler
From: Portsmouth
Registered: 2010-10-19
Posts: 43
Website

Re: Blank Screen? Have I killed her?

A happy ending.

My modded machine magically started working again.

I have no idea why the screen went dead but I am very happy to have it back!


As far as the noise goes I think this was simply me forgetting that c64's quirky old beasts and inherently noisy, possibly due to the sid chip not being isolated from other areas of the machine..?

As discussed on this thread and probably elsewhere....

http://www.prophet64-forum.com/viewtopic.php?id=90

Anyhow to get the best possible sound I have:

Grounded the audio ins on both sids.
Started using a DI box in between the c64 and my mixer.
Made sure I blank the screen when recording.
Used expansion/compression.
And EQ'ed as much of the background sound out as possible...
I might also try the inverted noise idea from the thread above.

Any other recording ideas welcome, but in essence I am very very very happy to be back making music, and any quirks of the machine are things to embrace sonically, which is why I wanted to make music on a c64 in the first place - AUTHENTICITY - Mssiah rocks!

Last edited by neal beard (2012-05-08 17:28:18)

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