UH3/9 - 5.3V
UH3/1 - 1Mhz confirmed - see attached
UG5/7 - ditto
UH3/8 - 16Mhz confirmed by the scope, but as a sine wave not a square wave
https://drive.google.com/file/d/1efE...ew?usp=sharing
However, I can get no readings on UH3 pins 3,4,5,6, 11,12,13.
Colin.
Quote:
Originally Posted by SiriusHardware
Quote:
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UH3-9 should be mostly high, but I haven’t been able to find the source of this signal in the schematics yet.
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Me neither! It would be easier to find the Scarlet Pimpernel. Every chip pin I can find on the INIT line on sheets 6, 7, 8 is a reset or CLR input or a 'state input' to a flip-flop. But on sheet 6, lower left, the line is held high by R12, a 1K resistor. The INIT line just goes to more inputs on sheets 7,8.
In the absence of any obvious chip output driving the INIT line maybe it is just supposed to hold all the connected ICs off until the +5V supply is up? The main thing is that it should normally be high, ~ 4-5V, held in that state by R12.
As per Mark:
Check for +5V on UH3 pin 9
Check for 1MHz on UH3 pin 1 - if not there, look for it on UG5 pin 7.
Check for 16MHz on UH3 pin 8
UH3 pins 3,4,5,6, 11,12,13 should all have 1MHz waveforms on as well. |