Hires graphics problem

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Hires graphics problem

Text is fine. When you enter hires mode, all you get is random text on the screen. I've swapped out all of the chips with a working apple, but it is still the same. I've attached some pics. (note: the distortion you see in the pictures is just reflections. I think it was the only sunny day we've had in 3 weeks). You can see once I type hgr, the random text shows up.

I'm not sure what the apple uses to switch it to hires mode.

 

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High resolution graphics is

High resolution graphics is switched in by decoding soft switch addresses $C05x by the 9334 in socket F14.

That is the same socket where the Videx 80 column softswitch PCB gets

installed so that socket could have issues from wear.

That's how it works in a standard Apple II+. Not sure with a Unitron clone.

 

Larry G

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Hi Larry,Right you are. Pin 4

Hi Larry,

Right you are. Pin 4 was not making a connection. This machine came with an 80 column card that had 2 wires put into the socket before the chip was put back in, I assume for the softswitch of 40 to 80. When I removed it, I assume the wire had pushed the socket open too much and it didn't make a connection. Replaced the socket and all is well. I've attached a picture of the wires in the socket as I got the machine.

Thanks again

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johndegroot wrote:Hi Larry
johndegroot wrote:

Hi Larry,

Right you are. Pin 4 was not making a connection. This machine came with an 80 column card that had 2 wires put into the socket before the chip was put back in, I assume for the softswitch of 40 to 80. When I removed it, I assume the wire had pushed the socket open too much and it didn't make a connection. Replaced the socket and all is well. I've attached a picture of the wires

 

I have seen this a few times on systems where the owner tried to squash wires into a socket along with a 9334 pin. The original Videx SoftSwitch board itself can damage old sockets, too. Pushing a pair of 8p stacking headers into the socket ahead of the 9334 usually restores enough continuity to solve the issue. 

 

Most notably, the socket wiper widening tends to cause a marginally faulty connection, that results in HGR crashing into text if the machines are bumped when being used. 

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Get some clips!!

It's a bad idea to ram signal wires into a socket along with the chip.

You've discovered why that is so already.

 

Get yourself some breadboard jumpers.  A kit like this will do:

Amazon link to related product

And some chip clips - either an IC grabber like this:

Digikey link to IC grabber

or some test clips like this:

Amazon link to test clips

 

 

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Thanks for the replies. Yes,

Thanks for the replies. Yes, myself, I would never jam those wires into the socket. Those test clips that clip on the chips was what I used on my first computer which was a commodore pet. I was learning assembler (assembled by hand on paper), type it in, sys(mem address) and the computer would lock (until you got the bugs out). Found an article (in Compute I think), and the 6502 had a NMI to interupt the cpu. Change a couple of registers and you could continue without retyping everything.

 

That was a long time ago. Probably pushing 40 years ago I think.

 

Thanks again for the replies

John

 

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