M&R Enterprises Sup'R'Terminal 80 column card

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M&R Enterprises Sup'R'Terminal 80 column card

Hello,

I have an Apple II M&R Enterprises Sup'R'Terminal 80 col card which doesn't work. I type pr#3 and there is no output signal to the monitor (lcd).

I have checked the eprom and 6845 crtc chip which are fine. Does anyone have any schematics that I could use to trace through the circuits ?

The 2114 ram is also fine.

Thanks

Andy

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Just to be sure...

Hello,

You are using the little adapter that plug into the C2 IC socket on the motherboard, right ?

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Yes. The Apple II works well

Yes. The Apple II works well in 40 column mode and after being put into 80 column mode with PR#3, it  responds to Esc Q which resets the screen back to 40 column. This makes me feel the board is executing code from the dedicated EPROM OK.

Just here is no composite signal. As I don't have a circuit diagram I am almost on the verge of  having to go down the road of pulling chips (desoldering) and testing they work OK.

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OK, I have managed to get it

OK, I have managed to get it working. The video RAM was bad as were a number of associated IC's. What also foxed me was the composite output is different  compared to that from the Apple motherboard - my LCD TV see's no signal (no issues with the Apple II motherboard output) but when i plug it into a scart/composite to hdmi video converter box I get a display.

what determines the output frequency - is it the crtc chip for example ?

 

Thanks

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what determines the output

what determines the output frequency - is it the crtc chip for example ?

The HD46505 datasheet indicates it gets its frequency (dot clock) on input pin 21 (CLK). The Sup'R'Terminal advertisement says that this is synchronous with the Apple II, so without a schematic my guess is that it is derived from pin 36 of the slot (7M CLOCK).

The horizontal and vertical sync signals are output from the CRTC based on what is written into its horizontal and vertical size registers. They are under control of the CPU, so would be set by the code in the EPROM.

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Thanks.... it works but I am

Thanks.... it works but I am not a Video signal expert and still do not comprehend why the frequency is out of range and need scart to hdmi converter. The rom is a 50hz which is correct - tried a 60hz and no change. Ummm....

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