NES-001 cap replacement guide for the av power module

[jcarlos]

What is the external RF switch?

This thing:
https://images-na.ssl-images-amazon.com ... L1024_.jpg

The thing that lets you use a TV that doesn't have a SCART or A/V cinch jacks.

Ah OK

I had seen this power supply, but I do not know if it has that switch

One of these: https://en.wikipedia.org/wiki/Switched- ... wer_supply

I don't see the polarity, but I think it doesn't matter.

Polarity indeed doesn't matter because of the bridge rectifier inside the AV modulator unit.

[jcarlos]

But a good switched source is very complex and must also be very expensive. The sources of the style that I have shown you are switched, and if not, do they have any advantage over the original transformer?

[lidnariq]

But a good switched source is very complex and must also be very expensive. The sources of the style that I have shown you are switched, and if not, do they have any advantage over the original transformer?

Between power efficiency regulations and how expensive it is to wind a transformer, I think switchers have basically taken over the world. I don't think I've seen any new "transformer in a box" power supplies for years now.

[jcarlos]

My brother uses an external RF switch, for an old television dedicated to the NES. So I wonder will it work properly when using the 9V DC source?

[lidnariq]

Good question. I don't know.

The voltage there is for phantom power for the not-passive RF switch. (See the bottom half of the schematic https://console5.com/wiki/File:NES-001- ... Switch.png )

A mechanical RF switch (like what came with the Atari 2600) should work fine regardless of the phantom power voltage. Alternatively, if the TV is only used with the NES and no other devices, you should be able to connect the RF-out RCA jack on the NES via a DC-blocking capacitor to the RF-in Belling-Lee.

[jcarlos]

I can see the 150 Ohm resistance R24, the capacitor to ground C36 and the coil L8, the latter, in my RF module, goes through a diode to the RCA jack for the RF output. The scheme is similar to that of my RF module but not the same, Those 13V DC, it takes it from the filtered power output (2200uF capacitor), then they must have a ripple. If instead of power with alternating voltage (original transformer), I do it with the 9V DC source, this voltage of 13V DC falls around 4V or more, and I don't know what effect it would have on the RF output or on the external RF switch. But if I power with a 12V DC source, it will be much closer to 13V DC and I guess the external RF switch will be much less affected. These are all just assumptions, but I will do the tests with the mainboard and the RF module that I am trying to repair and a universal source of 2.125 A that I have, when I can repair them, if possible. What I do believe is that the external RF switch will not be damaged by lowering that 13V voltage by 4V or more. I would like to know if someone who powers his NES with 9V DC, sees his NES well when he connects it through the external RF switch to his television.

[lidnariq]

Obviously the RF modulator itself differs - it has to modulate audio and video to different frequencies for PAL vs NTSC. But the RF switch should be pretty similar.

[jcarlos]

My brother has one, but I don't think he has screws to open it, so I don't know his electrical scheme.

[jcarlos]

I have replaced the PPU with the UA6541

[jcarlos]

And the part of the CPU has been like this (The memory that is seen is damaged):

[jcarlos]

I get the following signals:

Pin 4 CPU:

[jcarlos]

It seems to have varied from before changing the PPU

[jcarlos]

PIN 4 CPU before changing the PPU:

[jcarlos]

CPU Pin 29: Not change

[jcarlos]

CPU Pin 31: Not change