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Hi,

I'm a new/old user of the SC-3000 ... I grew up with the CPC464 but a family friend had an SC-3000H that I would play games on - I still remember Pop Flamer and an adventure game loaded from tape that I spent a few hours on. So I was always a little nostalgic for it.

I got one on eBay a while ago now and stored it away - I need to rationalise what systems I have so I'm keeping the Yeno (yep, I got one of those) and finding the John Sands one a new home.

I made up a 5-pin DIN cable and it initially works fine - video & audio look good.

But after a few minutes - after warming up - it loses chroma and the image becomes B&W. I've done a few searches and I can't quite find any advice about.

I actually managed to capture the problem when it starts happening - the image shows the BASIC IIIB cartridge after the machine has been on for a little while. When I switched it off and put the IIIA cartridge in it was totally B&W. Returning to the IIIB cartridge was also B&W only.

(Sorry the preview image is sideways - it's oriented correctly on my computer ...)

Where should I start?

Thanks.

2020-11-29 13.03.48.jpg (4.85 MB)

BASIC IIIB slowly losing colour

Likely bad capacitors.

gtawerfg wrote

[...]I'm keeping the Yeno (yep, I got one of those)[...]

The question is a bit offtopic, but I would be interested to know what Yeno you have? I think you mean the chess computers, right?

Bodhi1969 wrote

gtawerfg wrote

[...]I'm keeping the Yeno (yep, I got one of those)[...]

The question is a bit offtopic, but I would be interested to know what Yeno you have? I think you mean the chess computers, right?

There was a guy on eBay a few years ago here in Australia who had a large number of NOS "Yeno" badged SC-3000Hs - came with the machine, Euro 9V DC supply (in French), SCART video cable plus two blank cartridges. It may also have come with BASIC IIIA.

That's what I meant by "one of those" ;)

Maxim wrote

Likely bad capacitors.

Dah, of course. Will check them out.

Well well well - I had a look at the 4095 daughterboard and this 10µF capacitor C112 immediately caught me eye - corrosion on the legs.

Checking the schematic, it's connected to pin 13 of the LM1889 "TV video modulator" ... pin 13 has the chroma subcarrier.

I also took the opportunity to replace the 7805 linear regulator & heatsink - should run a lot cooler and for many more years now.

2020-11-30 09.58.02.jpg (2.89 MB)

C112 on 4095 daughterboard

Still having the issue - interestingly (for me at least) different cartridges are affected differently - Congo Bongo is mostly fine, but put BASIC IIIB in and it'll be B&W ... switch back to Congo Bongo - colour ... back to BASIC - B&W.

With the BASIC cartridge, I can see the colour switch between green & grey after a few minutes, but Congo Bongo remains fine for quite a while.

Anyway, swapped out all-but-one electrolytics on the video daughterboard:

C103 - 0.47µF 50V - no spare at the moment
C104 - 1µF 50V - replaced
C105 - 22µF 16V - replaced
C112 - 10µF 16V - replaced
C113 - 10µF 16V - replaced
C114 - 2.2µF 50V - replaced
C116 - 47µF 16V - replaced
C117 - 47µF 16V - replaced
C118 - 47µF 6.3V - replaced

Continuing ...

It could be that the 4.433MHz Crystal on the daughter board which generates the colour subcarrier frequency has aged and is drifting out of spec, or the components around the Crystal are causing it to drift out of spec.

Have a look at C110,C111,TC101,R117,R118,R119, TR103 and their connection to each other and to ground (for the ones that connect to ground). Check for any dry joints.

If you know someone where a frequency counter get them to check the crystal frequency.

gtawerfg wrote

Bodhi1969 wrote

gtawerfg wrote

[...]I'm keeping the Yeno (yep, I got one of those)[...]

The question is a bit offtopic, but I would be interested to know what Yeno you have? I think you mean the chess computers, right?

There was a guy on eBay a few years ago here in Australia who had a large number of NOS "Yeno" badged SC-3000Hs - came with the machine, Euro 9V DC supply (in French), SCART video cable plus two blank cartridges. It may also have come with BASIC IIIA.

That's what I meant by "one of those" ;)

I see, I thought you meant one of these famous chess computers.

Author	Message
gtawerfg Joined: 29 Nov 2020 Posts: 6 Location: Port Macquarie, NSW	Australian SC-3000H - video loses colour after a few minutes Posted: Sun Nov 29, 2020 5:56 am
	Hi, I'm a new/old user of the SC-3000 ... I grew up with the CPC464 but a family friend had an SC-3000H that I would play games on - I still remember Pop Flamer and an adventure game loaded from tape that I spent a few hours on. So I was always a little nostalgic for it. I got one on eBay a while ago now and stored it away - I need to rationalise what systems I have so I'm keeping the Yeno (yep, I got one of those) and finding the John Sands one a new home. I made up a 5-pin DIN cable and it initially works fine - video & audio look good. But after a few minutes - after warming up - it loses chroma and the image becomes B&W. I've done a few searches and I can't quite find any advice about. I actually managed to capture the problem when it starts happening - the image shows the BASIC IIIB cartridge after the machine has been on for a little while. When I switched it off and put the IIIA cartridge in it was totally B&W. Returning to the IIIB cartridge was also B&W only. (Sorry the preview image is sideways - it's oriented correctly on my computer ...) Where should I start? Thanks. 2020-11-29 13.03.48.jpg (4.85 MB) BASIC IIIB slowly losing colour

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14745 Location: London	Posted: Sun Nov 29, 2020 10:47 am
	Likely bad capacitors.

Bodhi1969 Joined: 01 Oct 2020 Posts: 32 Location: Gummersbach, Germany	Posted: Sun Nov 29, 2020 7:16 pm
	gtawerfg wrote [...]I'm keeping the Yeno (yep, I got one of those)[...] The question is a bit offtopic, but I would be interested to know what Yeno you have? I think you mean the chess computers, right?

gtawerfg Joined: 29 Nov 2020 Posts: 6 Location: Port Macquarie, NSW	Posted: Sun Nov 29, 2020 8:35 pm
	Bodhi1969 wrote gtawerfg wrote [...]I'm keeping the Yeno (yep, I got one of those)[...] The question is a bit offtopic, but I would be interested to know what Yeno you have? I think you mean the chess computers, right? There was a guy on eBay a few years ago here in Australia who had a large number of NOS "Yeno" badged SC-3000Hs - came with the machine, Euro 9V DC supply (in French), SCART video cable plus two blank cartridges. It may also have come with BASIC IIIA. That's what I meant by "one of those" ;)

gtawerfg Joined: 29 Nov 2020 Posts: 6 Location: Port Macquarie, NSW	Posted: Sun Nov 29, 2020 8:36 pm
	Maxim wrote Likely bad capacitors. Dah, of course. Will check them out.

gtawerfg Joined: 29 Nov 2020 Posts: 6 Location: Port Macquarie, NSW	C112 failed on 4095 daughterboard? Posted: Sun Nov 29, 2020 11:31 pm
	Well well well - I had a look at the 4095 daughterboard and this 10µF capacitor C112 immediately caught me eye - corrosion on the legs. Checking the schematic, it's connected to pin 13 of the LM1889 "TV video modulator" ... pin 13 has the chroma subcarrier. I also took the opportunity to replace the 7805 linear regulator & heatsink - should run a lot cooler and for many more years now. 2020-11-30 09.58.02.jpg (2.89 MB) C112 on 4095 daughterboard

gtawerfg Joined: 29 Nov 2020 Posts: 6 Location: Port Macquarie, NSW	Posted: Mon Nov 30, 2020 7:32 am
	Still having the issue - interestingly (for me at least) different cartridges are affected differently - Congo Bongo is mostly fine, but put BASIC IIIB in and it'll be B&W ... switch back to Congo Bongo - colour ... back to BASIC - B&W. With the BASIC cartridge, I can see the colour switch between green & grey after a few minutes, but Congo Bongo remains fine for quite a while. Anyway, swapped out all-but-one electrolytics on the video daughterboard: C103 - 0.47µF 50V - no spare at the moment C104 - 1µF 50V - replaced C105 - 22µF 16V - replaced C112 - 10µF 16V - replaced C113 - 10µF 16V - replaced C114 - 2.2µF 50V - replaced C116 - 47µF 16V - replaced C117 - 47µF 16V - replaced C118 - 47µF 6.3V - replaced Continuing ...

asynchronous Joined: 14 Aug 2000 Posts: 742 Location: Adelaide, Australia	Australian SC-3000H - video loses colour after a few minutes Posted: Mon Nov 30, 2020 11:32 am
	It could be that the 4.433MHz Crystal on the daughter board which generates the colour subcarrier frequency has aged and is drifting out of spec, or the components around the Crystal are causing it to drift out of spec. Have a look at C110,C111,TC101,R117,R118,R119, TR103 and their connection to each other and to ground (for the ones that connect to ground). Check for any dry joints. If you know someone where a frequency counter get them to check the crystal frequency.

Bodhi1969 Joined: 01 Oct 2020 Posts: 32 Location: Gummersbach, Germany	Posted: Mon Nov 30, 2020 4:26 pm
	gtawerfg wrote Bodhi1969 wrote gtawerfg wrote [...]I'm keeping the Yeno (yep, I got one of those)[...] The question is a bit offtopic, but I would be interested to know what Yeno you have? I think you mean the chess computers, right? There was a guy on eBay a few years ago here in Australia who had a large number of NOS "Yeno" badged SC-3000Hs - came with the machine, Euro 9V DC supply (in French), SCART video cable plus two blank cartridges. It may also have come with BASIC IIIA. That's what I meant by "one of those" ;) I see, I thought you meant one of these famous chess computers.

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