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Seriously, look at this.

I pulled this out of the back shed at my parent's place tonight.

At least it's a sign of "life", though - I'm hoping it might just be a dirty cart port.

It's also showing a black screen, and giving repeated patterns of three beeps. I remember that means something, but I can't remember what... does anyone know what the three beeps mean?

photo.JPG (821.94 KB)

At least one address line to VRAM is corrupt, making text that usually accesses

`ABCDEFGHI

look like:

``BBDDFFHH

So, yeah, VRAM or its lines are corrupt.

I seem to recall the three beeps meaning something to do with RAM.

Hmm. I guess that's not fixable, then...?

I ended up getting an SC-3000 Survivors Multi-cart to boot, but again, all the text and graphics were garbled.

Sorry, I realise now I probably should have posted this in Development, too...

(edited from email reply to gregglesaurus)

The 3 beeps is a VRAM failure. The Basic IIIB ROM does some simple read / write tests on memory and VRAM and if the data that is read back doesn't match what is written, then you get the 3 beeps.

The VRAM is made up of eight 2KByte chips that are soldered onto the SC-3000 motherboard. Since the program in the cart ROM has executed correctly and we just have display glitches, it is likely that it is a failure of one or more of those chips.

I can see multiple failures in the VRAM there. The main one is in the least significant bit (IC17). See how most of the letters are one out? eg. 'ver' is 'wdp' and '1983' is '0882' and the vertical line character is just one less than the horizontal line character. But there are other VRAM errors too. eg. the + instead of the - says that bit 4 is sticking periodically (IC13), and the missing part of the vertical line beside that first + says that bit 2 is sometimes incorrect (IC15).

So you probably have multiple VRAM chip failures. If you are handy with a soldering iron they are fairly easy to replace. Use desoldering braid to remove the chips and solder a 16 pin socket in place. Then either carefully remove chips from another dead SC-3000 or buy some replacements off eBay.

Cheers

Author	Message
gregglesaurus Joined: 15 May 2006 Posts: 53 Location: Sydney, Australia	My SC-3000H is a zombie Posted: Sat Apr 07, 2012 1:45 pm
	Seriously, look at this. I pulled this out of the back shed at my parent's place tonight. At least it's a sign of "life", though - I'm hoping it might just be a dirty cart port. It's also showing a black screen, and giving repeated patterns of three beeps. I remember that means something, but I can't remember what... does anyone know what the three beeps mean? photo.JPG (821.94 KB)

ccovell Joined: 26 Dec 2004 Posts: 374 Location: Japan	Posted: Mon Apr 09, 2012 12:30 am
ccovell Joined: 26 Dec 2004 Posts: 374 Location: Japan	At least one address line to VRAM is corrupt, making text that usually accesses `ABCDEFGHI look like: ``BBDDFFHH So, yeah, VRAM or its lines are corrupt.

gregglesaurus Joined: 15 May 2006 Posts: 53 Location: Sydney, Australia	Posted: Mon Apr 09, 2012 7:15 am
	I seem to recall the three beeps meaning something to do with RAM. Hmm. I guess that's not fixable, then...? I ended up getting an SC-3000 Survivors Multi-cart to boot, but again, all the text and graphics were garbled.

gregglesaurus Joined: 15 May 2006 Posts: 53 Location: Sydney, Australia	Posted: Mon Apr 09, 2012 8:12 am
	Sorry, I realise now I probably should have posted this in Development, too...

honestbob Joined: 03 Oct 2011 Posts: 188 Location: New Zealand	Posted: Mon Apr 09, 2012 10:32 pm
	(edited from email reply to gregglesaurus) The 3 beeps is a VRAM failure. The Basic IIIB ROM does some simple read / write tests on memory and VRAM and if the data that is read back doesn't match what is written, then you get the 3 beeps. The VRAM is made up of eight 2KByte chips that are soldered onto the SC-3000 motherboard. Since the program in the cart ROM has executed correctly and we just have display glitches, it is likely that it is a failure of one or more of those chips. I can see multiple failures in the VRAM there. The main one is in the least significant bit (IC17). See how most of the letters are one out? eg. 'ver' is 'wdp' and '1983' is '0882' and the vertical line character is just one less than the horizontal line character. But there are other VRAM errors too. eg. the + instead of the - says that bit 4 is sticking periodically (IC13), and the missing part of the vertical line beside that first + says that bit 2 is sometimes incorrect (IC15). So you probably have multiple VRAM chip failures. If you are handy with a soldering iron they are fairly easy to replace. Use desoldering braid to remove the chips and solder a 16 pin socket in place. Then either carefully remove chips from another dead SC-3000 or buy some replacements off eBay. Cheers

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