Apple-II beep but strange Video

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Apple-II beep but strange Video

Hi all

 

Try to get an Apple-II working, get the starting beep but there are only stripes and strange characters on the screen (see picture)

The four voltages are ok, tested also the RAM and 74xxx chips, all are working. Changed also the ROM's with a working system.

Any advise what could be wrong with the board?

Thank you for your help!

Thomas

 

 

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You've reseated the chips?

You've reseated the chips?

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Well, the missing chip at F14

Well, the missing chip at F14 is at least ONE of your problems. It's labelled as a 9334 but can be replaced with a 74LS259.

 

It is definitely causing you to go into mixed graphics mode and you might be looking at page 2 which is why things don't look right. The beep indicates that the CPU and mosty everything else is working fine!

 

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Shame on me ...

OMG, this was the typical "not seeing the wood for the trees" problem ... thank you jeffmazur, exactly the missing F14 was the problem, the system works now well!

Was this F14 removed, because this add-on board was originally installed? (see picture). Anybody knows this board?

Thomas

 

 

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80 Column Card

From the text on the pcb I would guess it's german manufactured 80 Column Card.

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I'm guessing it IS the reason that chip is missing.

As tolderlund pointed out, it's an 80 column card. I notice above ther ribbon cable is written "LS259" which is where it's plugging in on your board I'm guessing.

(I also googled the prominent Hitachi chip, and it's a "Non VGA Video Controller". Interesting! I wonder if, rather than having it's own Video port, it intercepts the Apple II video and inerjects it's own signal straight out the composite port? If so, it's a nifty idea.)

 

Chesh

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LS259 is the chip

If I may say the text LS259 belongs to the chip above.

If you notice alle chips have the text below them.

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Then what does it say below

Then what does it say below the ribbon cable? I can see "ER" but nothing else. 

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nick3092 wrote:Then what does
nick3092 wrote:

Then what does it say below the ribbon cable? I can see "ER" but nothing else. 

 It looks like the cable was meant to plug into the 259 socket and the chip above it is used to replace that. Not sure what signals they were grabbing from that chip, but this would have been the standard way to do that.

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jeffmazur wrote:nick3092
jeffmazur wrote:
nick3092 wrote:

Then what does it say below the ribbon cable? I can see "ER" but nothing else. 

 It looks like the cable was meant to plug into the 259 socket and the chip above it is used to replace that. Not sure what signals they were grabbing from that chip, but this would have been the standard way to do that.

 

 

The LS259 / 9334 chip has signals that control the color killer and the graphics / text modes.

The 80 column card you have has the equivalent of the Videx soft switch on board.  You'll notice two black transistors that handle the signals for 40 column and 80 column text and the relay no doubt switches the video between the two.

It's all dependent on signals from the 74LS259 for the card to know which mode the Apple is in.

 

 

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