Schematic for PAL SNES

jkarma

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I have problems with the S-CLK chip, on pin 4 (XOUT) it generates an incorrect signal that you can see in the link below. I think the correct signal would be a square wave between 0 and 5V of about 21 Mhz

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I have problems with the S-CLK chip, on pin 4 (XOUT) it generates an incorrect signal that you can see in the link below. I think the correct signal would be a square wave between 0 and 5V of about 21 Mhz
 

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tech3475

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I have problems with the S-CLK chip, on pin 4 (XOUT) it generates an incorrect signal that you can see in the link below. I think the correct signal would be a square wave between 0 and 5V of about 21 Mhz

--------------------- MERGED ---------------------------

Have you checked the input voltages and capacitors?

On my recent MD/Gen repair the capacitors 'looked' fine but some were bad so a visual inspection alone may not be enough.
 

JaapDaniels

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Have you checked the input voltages and capacitors?

On my recent MD/Gen repair the capacitors 'looked' fine but some were bad so a visual inspection alone may not be enough.
yes, all the through hole caps could be having a leak and you might not smell or see it when that happens, and check the DC bridge, i had a few pal snesses where one diode of the four had shorted over time (it's one component with four legs).
 

jkarma

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Let me tell you. I have measured all three source voltages and they correctly measure 4.96V, 12V, and about 10V (instead of 9V) for the audio amplifier. This console worked fine but had noise, like hum, in the sound, I changed 4 capacitors from the power supply which gave wrong measurement with capacitance meter, then the hum or noise disappeared. But when assembling the console, nothing appeared, just snow on the TV. I measured, with the oscilloscope, the clock signals to the S-CLK outputs and they all gave correct except pin 4 (XOUT) which gave a continuous 0V, that is, it did not give any signal. So I followed the Snes PAL schematic of the circuit that surrounds the S-CLK and saw that a connection was missing, pins 8 and 9 were linked but they came out and I connected them to the junction of C3 and R3, as in the diagram, and there it is when i received the signal i have shown you on pin 4 of the S-CLK this signal is supposed to be the master clock of the system and it should be a square wave from 0 to 5V and around 21Mhz but it gives that weird signal superimposed to an alternate signal. The other outputs of the S-CLK are correct (pin 5, 6 and 7). Now with this XOUT signal I get video but it is a black screen and nothing else. Maybe I should change the S-CLK chip? Well, I have measured the rest of the components and they are fine. I also don't know how to get this S-CLK chip.
 
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