Famicom av mod issues - dang…

[Tengugurl]

Hi friends! 

I am trying to do an AV mod on a famicom HV CPU GPM 02 and I am having a bit of issues.

I am super surprised as it seemed straightforward but dang...

TL;DR
Why do I have a really loud buzzing sound? Droning humm


I have installed the following caps and resistors

1) video line - 47uf 25v cap then resistor 120ohm resistor

2) audio line - 220uf 25v cap then 1uf ceramic capacitor


Video works, audio works but it has really bad humming that almost drowns out the audio.

I was good about making sure nothing is touching any other components on the board.

Sounds like Analog audio RF noise but I am not using Rf?

Any suggestions would be awesome thanks!

Ps the colors on the wire look reversed but I they are not. Probably need to change them if I crack into this in the future

[FAMICOM_87]

remove the second controller to check that the microphone is not the problem with the buzzing sound. If it is the case, clean the conductive traces with alcohol and the metal part of the mic slider with fine sandpaper.
BTW Are you are using this mod? https://www.youtube.com/watch?v=ky8rFPbzGMU

[Tengugurl]

Hi! Can do
Correct that is the mod I did.
Is it not recommended?

Just curious thanks for your help

[Tengugurl]

Okay just disconnected player 2 and it's still making a high pitched hum.

I am going to recap it soon, hopefully that helps

Any other ideas?

Appreciate them btw

[FAMICOM_87]

I did not tested this mod yet, but l have this pcb revision too so i will do it at some point. I like it because it is fully reversible
What about the sound true RF? Can you record a video?
Try to recap only the big capacitor on the power pcb.
BTW what power supply are you using?

[Tengugurl]

For sure! I am excited for when the caps come in.

Think that might help.

Psu wise using a famicom psu from retro gamesupply.com

[FAMICOM_87]

The link is broaken. Just tell me rhe power supply specifications. It might be weak and casing those sound issues.

EDIT:

I found it https://en.retrogamesupply.com/collections/nintendo/products/power-supply-for-nintendo-famicom

The specs are OK. So I am out of ideas. 

[Tengugurl]

Hi again! Sorry new phone
So typing is a mess.

It's the darn slider on the mic of controller 2.
When I av modded it, I cleaned the pcb traces just in case and I didn't take the volume slider knob apart but sure enough coated in gunk.
Cleaned it up and turned it all the way to the left Aka lowest volume and boom!

Works perfectly

Thanks so much for your help.
Going to recap it anyway.
Also got a new 7805 thinking wth while I am in there.
Basically make it a new Famicom.

[FAMICOM_87]

Nice to know that you fixed it
I do not recomend to change the voltage regulator and recap without any real reason. (old components are better quality then newer ones especially some capacitors brands, if they are not failed ofcurs)