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PET 2001 Fault

Thanks, I've PM'd Dabone about his board.

I'll also try swapping out the 6550's in the system RAM with video RAM, are they even needed with the ROMulator in place?
 
I can't tell from your pictures, but which way do you have pin one of the romulator installed??? to the left or the right?

If I remember correctly, the CPU socket pin 1 is away from the tape drive, and I think you have it towards the tape drive.
 
Yep, I checked mine after I got home, and you have it in the socket backwards. CPU pin one is to the right.



romulator.JPG

Pardon all the dust.... And this shows you the orientation of the video ram adapter I shipped today.. I hope you noticed that the ram chips faced towards the front when you were testing them.
 
dave_m said:
Dabone is 'Da Man'! Good catch.

Hopefully that will not toast his CPU...
Click to expand...
In cases of IC's that have power pins on opposite sides and on opposite corners of the IC, as many do, rotating the IC 180 degrees in the socket, reverses the power supply to the IC die, and is nearly always universally fatal to the IC. Even if it appeared to survive it, likely there would be latent damage and the IC should always be replaced IHMO.
 
dabone said:
Hopefully it's fine, VDD is pin 8, Vss is 21, so power isn't reversed.
Click to expand...
Though in other cases the die can receive power, when applied via input and or output pins via substrate diodes, it is possible to get lucky with some IC's that are accidentally plugged the wrong way and not get any damage at all, but probably that is the exception rather than the rule.
 
The OP was last on yesterday at 10:33 PM (presumably this is UK time - as this is where I am located), so they should have seen post #23...

Dave
 
Sorry for the radio silence, family stuff getting in the way...

Good news twice - the Romulator was in the wrong way and that was the whole fault. And after correctly orientating it no damage done, the PET is up and running 100%, passed the tests on the ROM.

Thanks for all the help, I would never have suspected the cause and would have assumed the whole system wouldn't have worked at all with the CPU in back to front.

Now finally I can go and enjoy the PET.

(yes, I am a total idiot, not an ideal intro to the forum!!!)
 
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