Yellow Screen

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mrr19121970
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Yellow Screen

Post by mrr19121970 »

I have beautiful 1983 VIC20cr here with the original purchase receipt from 10-Dec-1983 (Boots the Chemist, Chelmsford, UK), bought from the original owner. It has a Eurostile keyboard and the case is as yellow as a canary. The mainboard is spotless. However, it doesn't work.

When I turn it on the screen is yellow, there is a high pitched tone. Pressing the reset, the tone becomes abit deeper. The diagnosis cart won't start, but after a few resets Avengers will finally kick in. I think the colours might be abit off, and the sounds are not quite right (there is no firing sound, but there is a explosion sound).

All chips are soldered in. Anyone seen this before? I am thinking VIC-I for sure is done.
Last edited by mrr19121970 on Fri Mar 11, 2016 6:19 am, edited 2 times in total.
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mrr19121970
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Re: Yellow Screen

Post by mrr19121970 »

https://youtu.be/2AqdkDnEIQ4

After many resets I finally got the test cart to appear on the right place on the screen and without scrambled chars.

Seems there is no issue ??? Rofl
Last edited by mrr19121970 on Fri Mar 11, 2016 6:14 am, edited 1 time in total.
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mrr19121970
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Re: Yellow Screen

Post by mrr19121970 »

No tips on what causes the screen to be yellow and the high pitched tone sound?

Adding an expansion rom and loads of resets I can get to a screen full of garbage characters which after each reset changes position. Sometimes I even get a black screen with yellow border and text and can type in a small basic program that runs. Sometimes I have even managed to get a white screen with cyan border too.

This weekend i will start desoldering and testing chips. Based on my limited experiences. I will start with the VIAs, RAMs and maybe logic chips.

I am still suffering from the Chinese new year backlog with limited supplies of sockets.

UPDATE


I have also asked for help on a German forum, here they have told me 100% is is the electrolyte capacitors (but not mentioned which one). Mike has the following to say on the matter:
Mike wrote:However, before you begin with the replacement of all Elkos, you should know whether it is really necessary.

I suppose you have a multimeter at hand. With this, you can not only measure if the voltage at the +5V rails is within the allowed range (+4.8 V .. +5.2 V) but you can only measure the ripple of the same voltage by setting the multimeter to VAC and putting the probes at the +5V rail, and also at the supply pins of all ICs (be cautious not to short anything!). If that ripple exceeds, say, 0.1 V, then this would be no good.
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mrr19121970
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Re: Yellow Screen

Post by mrr19121970 »

Seems to be the VIC-I putting the chip in a known working machine I was able to recreate this weird behaviour.
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vicist
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Re: Yellow Screen

Post by vicist »

Well done for seemingly sorting this out all by yourself. :)
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mrr19121970
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Re: Yellow Screen

Post by mrr19121970 »

As @ken says "anyone can fix a VIC20" :evil: this is #6 now

What I'd like to understand deeper is the "why". With memory expansion and a few resets the VIC-I works. I don't know anything about the internals of the chip, but on a logic point of view I'd say the ability to address the smaller address spaces is damaged. I don't suppose it can be repaired, but I might keep it as a backup (instead of casting in resin).

I bought a new VIC-I (NOS) for 20.49gbp posted. More than the complete in box VIC-20 itself.

http://www.mutant-caterpillar.co.uk/sho ... ts_id=3689
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mrr19121970
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Re: Yellow Screen

Post by mrr19121970 »

So 6561 arrived this week. It's raining so why not a vic day ?? Popped it in. Works. Man s-video is needed here.....

As you can see the plug and play cable is also backwards compatible.
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