HK Famicon - Appears working but no AV output.

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inabityo
Posts: 16
Joined: Mon Sep 07, 2020 10:10 pm

Re: HK Famicon - Appears working but no AV output.

Post by inabityo » Sat Sep 12, 2020 6:59 pm

Some success!! Thanks guys, I’ll do a proper mod later.

Again, huge thanks for your help!
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55C605F0-E3D1-4828-95ED-1866424E6CE0.jpeg

inabityo
Posts: 16
Joined: Mon Sep 07, 2020 10:10 pm

Re: HK Famicon - Appears working but no AV output.

Post by inabityo » Mon Sep 14, 2020 12:10 am

Thanks again - I have done a quick bit of soldering and now am able to get a steady picture, with sound and *some* colour. So big step forwards. Relieved to know that everything seems to be working ok.

So, the picture is ok, there as an auditable hum coming from the microphone controller two (I assume) the black stuff (graphite?) on the slider switch is worn off completely, so this will need replacing I guess.

The image itself is ok, not great, but I am ok with great. The colour however is super washed out. So I am assuming this is why AV mod's are a lot more complicated!

Before I start unsoldering parts, do you have any recommendations on the best AV mod to follow?

Thank you and I will stop bothering you for a while after this!

lidnariq
Posts: 9676
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: HK Famicon - Appears working but no AV output.

Post by lidnariq » Mon Sep 14, 2020 12:24 am

inabityo wrote:
Mon Sep 14, 2020 12:10 am
I have done a quick bit of soldering and now am able to get a steady picture, with sound and *some* colour. [...] The colour however is super washed out. So I am assuming this is why AV mod's are a lot more complicated!
Would help to know exactly what you mean by "some" color. Also where on the board you're currently getting the video from.
So, the picture is ok, there as an audible hum coming from the microphone controller two (I assume) the black stuff (graphite?) on the slider switch is worn off completely, so this will need replacing I guess.
Or just removing it entirely. As I understand, not that many games use the microphone. Replacing the microphone with a button might be the best user experience.
Before I start unsoldering parts, do you have any recommendations on the best AV mod to follow?
Usually we just suggest a single-transistor PNP emitter-follower, or recapitulating the US NES's video output.
https://wiki.nesdev.com/w/index.php/PPU ... deo_Output

You could read this thread if you want lots more details: viewtopic.php?t=18508

No TVs that I know of will decode NTSC3.6 at 50Hz, so if you use the above mod you will have to leave the switch at whatever position means "60Hz". If you want to be able to switch between 50 and 60Hz you'll have to take video from the MK5060 instead.

inabityo
Posts: 16
Joined: Mon Sep 07, 2020 10:10 pm

Re: HK Famicon - Appears working but no AV output.

Post by inabityo » Mon Sep 14, 2020 1:06 am

I just soldered onto the pins that carry the respective video/audio to the RF board - I was not intending for this to be a fix, simply so that I could test everything and ascertain that you know, it all works, controllers and such like.

In terms of colours, hard to describe - There are some of each colour, but only large area's. Mushrooms will appear red/pick, Pipes and such (SMB3 is my testing cartridge) will appear green, but the sky will appear white or a light grey. Black is also a darker grey.

Ok, I have YouTubed enough - and I think I can do that mod without too many difficulties. My only question is if you think that it is necessary to lift the pin 21? I have seen people do both - conscience that I a newb.

lidnariq
Posts: 9676
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: HK Famicon - Appears working but no AV output.

Post by lidnariq » Mon Sep 14, 2020 1:10 am

inabityo wrote:
Mon Sep 14, 2020 1:06 am
In terms of colours, hard to describe - There are some of each colour, but only large area's. Mushrooms will appear red/pick, Pipes and such (SMB3 is my testing cartridge) will appear green, but the sky will appear white or a light grey. Black is also a darker grey.
My hunch is that you've got yours left in the "50Hz" position, and that's what your TV does when it receives NTSC at 50Hz. If you flip the switch, I think you should get to see more color. (Or else your TV will reject it entirely if it won't accept 60Hz video...) Better to check this before doing anything more invasive.
Ok, I have YouTubed enough - and I think I can do that mod without too many difficulties. My only question is if you think that it is necessary to lift the pin 21?
I don't think you need to touch the PPU at all. In fact, I'm pretty comfortable saying you can just reuse the wire you've already got soldered there.

inabityo
Posts: 16
Joined: Mon Sep 07, 2020 10:10 pm

Re: HK Famicon - Appears working but no AV output.

Post by inabityo » Mon Sep 14, 2020 1:20 am

The switch is see to 'off' which I assume is 60hz. If switched to on, then the TV screen will black out and flash on an off. The TV is a modern LCD. I'll google its spec now however it plays an Chinese knockoff mini famicon ok. So I would expect so. I defer to your better judgement though.

NTSC video out if fine, not bothered about the PAL output as a general note.

Good to know about the video pins. I have seen people wire capacitor onto the audio lines. Most of the reading I did suggested that capacitors basically help smooth out the signal?

inabityo
Posts: 16
Joined: Mon Sep 07, 2020 10:10 pm

Re: HK Famicon - Appears working but no AV output.

Post by inabityo » Mon Sep 14, 2020 1:24 am

The colours basically look like this in real life.

Darker scenes are better
A71798B7-9204-4E2E-90E5-D6ACD9DB3646.jpeg

lidnariq
Posts: 9676
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: HK Famicon - Appears working but no AV output.

Post by lidnariq » Mon Sep 14, 2020 12:20 pm

inabityo wrote:
Mon Sep 14, 2020 1:20 am
The switch is see to 'off' which I assume is 60hz. If switched to on, then the TV screen will black out and flash on an off.
Huh. I have no idea why that's the symptom you get in the other switch position.
I have seen people wire capacitor onto the audio lines. Most of the reading I did suggested that capacitors basically help smooth out the signal?
Capacitors let "fast" things through but not "slow" things. When wired in series:
In --- capacitor --- Out
it'll block the "slow" things (low frequency components), and permit high frequency things through.
When wired in a "shunt" position:

Code: Select all

In ---Resistor---+--- Out
                 |
             Capacitor
                 |
              Ground
they still let the high frequency things through the capacitor, which means that it doesn't show up on the output instead.

In the "wiring capacitors onto the audio lines" case, the capacitors are serving as a "DC blocker", to allow you to plug external audio in without getting a huge pop.

inabityo
Posts: 16
Joined: Mon Sep 07, 2020 10:10 pm

Re: HK Famicon - Appears working but no AV output.

Post by inabityo » Thu Sep 17, 2020 7:55 pm

Yeah recreated that circuit and soldered onto the corresponding wires, but I’m not getting any video out.
I’ve tried soldering directly onto the PPU pin 21, and the PPU ground, but to no avail.
I made two circuits (my soldering isn’t great) but neither have worked.
I’m wondering if I burnt out the Diode when removing it from the mainboard.
I think my next step is to follow a you tube tutorial (maybe more appropriate for my level, but before I do, I thought it worth sharing my experience and see if there is anything obviously wrong with my circuit...
The only deviation from the diagram, is that I’m using two resistors in series (100 and 10) as the store didn’t have 110...
838E7229-F86F-4577-AE3F-09733947C2DF.jpeg
BF93905D-6ED2-4101-8957-4D4B62B6DE3F.jpeg

lidnariq
Posts: 9676
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: HK Famicon - Appears working but no AV output.

Post by lidnariq » Thu Sep 17, 2020 8:00 pm

Yes, it's possible that burnt out the transistor.

inabityo
Posts: 16
Joined: Mon Sep 07, 2020 10:10 pm

Re: HK Famicon - Appears working but no AV output.

Post by inabityo » Thu Sep 17, 2020 8:09 pm

Transistor sorry*
Ok, will source a replacement.
Cheers

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