On the Discord, grievre disassembled a Famicom's RF modulator and converted that into a schematic.
Here's the PCB stackup, BOM, and schematic in KiCAD and PDF format
Schematic of one Famicom RF modulator
Moderator: Moderators
Schematic of one Famicom RF modulator
- Attachments
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- famicom_rf_kicad.7z
- (6.84 KiB) Downloaded 47 times
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- famicom_rf.pdf
- (63.04 KiB) Downloaded 152 times
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- famicom RF mod bom - Sheet1.csv
- (372 Bytes) Downloaded 50 times
Re: Schematic of one Famicom RF modulator
The last 3 missing cap values filled in:
C2 and C29 - 0.01 uF
C18 - 1000pF
C2 and C29 - 0.01 uF
C18 - 1000pF
Re: Schematic of one Famicom RF modulator
Some more info:
This is from an HVC-CPU-07 unit. I have a few open right now and some of them have this layout while some of them have a slightly different layout. I think the one posted here is the older version as the other layout has the refdes silkscreen removed for the unpopulated components, and also has fixed components in place of some of the adjustable ones.
I didn't mark this on the schematic, but I believe the channel switch selects channel 1 when connected to 5V and channel 2 when connected to ground. Unlike on the NES modulator (or some of them at least), the switch isn't directly in the RF oscillator circuit, but rather forward biases the diode D1 to switch the extra inductor and cap into circuit.
This is from an HVC-CPU-07 unit. I have a few open right now and some of them have this layout while some of them have a slightly different layout. I think the one posted here is the older version as the other layout has the refdes silkscreen removed for the unpopulated components, and also has fixed components in place of some of the adjustable ones.
I didn't mark this on the schematic, but I believe the channel switch selects channel 1 when connected to 5V and channel 2 when connected to ground. Unlike on the NES modulator (or some of them at least), the switch isn't directly in the RF oscillator circuit, but rather forward biases the diode D1 to switch the extra inductor and cap into circuit.