Schematic of one Famicom RF modulator

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

Moderator: Moderators

Post Reply
lidnariq
Posts: 11432
Joined: Sun Apr 13, 2008 11:12 am

Schematic of one Famicom RF modulator

Post by lidnariq »

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
Attachments
famicom_rf_kicad.7z
(6.84 KiB) Downloaded 47 times
famicom_rf.pdf
(63.04 KiB) Downloaded 152 times
famicom RF mod bom - Sheet1.csv
(372 Bytes) Downloaded 50 times
famicom_rf_solderside.jpg
famicom_rf_componentside.jpg
grievre
Posts: 3
Joined: Tue Sep 06, 2022 12:31 pm

Re: Schematic of one Famicom RF modulator

Post by grievre »

The last 3 missing cap values filled in:

C2 and C29 - 0.01 uF
C18 - 1000pF
grievre
Posts: 3
Joined: Tue Sep 06, 2022 12:31 pm

Re: Schematic of one Famicom RF modulator

Post by grievre »

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.
Post Reply