HK Famicon - Appears working but no AV output.

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

HK Famicon - Appears working but no AV output.

Post by inabityo » Wed Sep 09, 2020 8:39 pm

I have 1998 Famicom HVC-CPU-GPM-02 with a BN5060i Pal conversion for Hong Kong (not from Nintendo).

I have a power supply branding says is compatible, rated as below:
Input AC 110-240V60Hz
Output: DC9V-850mA
(+)--(0--(-)
After testing with my multimeter, it outputs 9V. I don't wish to cut the cabling, so it is difficult to measure the amps.
One point of note is that HK (where I am) has a 50HZ AC power supply - will this make a difference?

It is attached to a modern LCD. the TV reports to be tuning to PALi - between the right frequency bands. I have had black screens appear twice (which I suspect are from the famicon), both times after recently opening to console both times around the (edited from orginal typo of 60mhz) 600mhz range, however after turning the console off to reseat the game. No output.

I have tested the regulator. And this does appear to output higher than its supposed to. It outputs at 5.11v's (could this be variance on the multimeter?). The regulator is on the modded board - would this be an issue?

The CPU and the GPU, both get warm - I don't think I'd call it hot. No hotter than my mobile phone has been before. The vOut on both chips both show a 5.11v's. The front controller port also shows the correct output voltage.

I have tested all the wiring for continuity. It all seems fine, as do the switches and everything else that looks like an obvious candidate for disruption.

Can anyone provide me with some pointers as to where to look next? Perhaps the power supply issue?
How do I Test the RF out? I don't have any spare CRT's laying around! Are there any tests I should/can do with my multimeter?

Please Help! I have attached images below but can supply more upon request.

I have 1998 Famicom HVC-CPU-GPM-02 with a BN5060i Pal conversion for Hong Kong (not from Nintendo).

I have a power supply branding says is compatible, rated as below:
Input AC 110-240V60Hz
Output: DC9V-850mA
(+)--(0--(-)
After testing with my multimeter, it outputs 9V. I don't wish to cut the cabling, so it is difficult to measure the amps.
One point of note is that HK (where I am) has a 50HZ AC power supply - will this make a difference?

It is attached to a modern LCD. the TV reports to be tuning to PAL - between the right frequency bands. I have had black screens appear twice, both times after recently opening to console both times around the 60mhz range, however after turning the console off to reseat the game. No output.

I have tested the regulator. And this does appear to output higher than its supposed to. It outputs at 5.11v's (could this be variance on the multimeter?). The regulator is on the modded board - would this be an issue?

The CPU and the GPU, both get warm - I don't think I'd call it hot. No hotter than my mobile phone has been before. The vOut on both chips both show a 5.11v's. The front controller port also shows the correct output voltage.

I have tested all the wiring for continuity. It all seems fine, as do the switches and everything else that looks like an obvious candidate for disruption.

Can anyone provide me with some pointers as to where to look next? Perhaps the power supply issue?
How do I Test the RF out? I don't have any spare CRT's laying around! Are there any tests I should/can do with my multimeter?

Help please! I have attached images below but can supply more upon request.
IMG_3544.JPG
IMG_3540.JPG
IMG_3573.jpg
IMG_3568.jpg
IMG_3567.jpg
Last edited by inabityo on Wed Sep 09, 2020 10:29 pm, edited 1 time in total.

lidnariq
Posts: 9659
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

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

Post by lidnariq » Wed Sep 09, 2020 9:07 pm

inabityo wrote:
Wed Sep 09, 2020 8:39 pm
I have 1998 Famicom HVC-CPU-GPM-02 with a BN5060i Pal conversion for Hong Kong (not from Nintendo).
Looks like it's using the same MK5060 IC used in the official HK Famicom.
One point of note is that HK (where I am) has a 50HZ AC power supply - will this make a difference?
With a supply that can run at 110-240V, you can be reasonably confident that's a switching power supply, and those don't really care about input frequency much at all. 50Hz should be fine.

(If you'd somehow gotten a conventional unregulated transformer-based power supply, those have a minimum frequency at which they'll work; below that frequency they'll get hotter and generate less output power. I believe that's irrelevant here.)
It is attached to a modern LCD. the TV reports to be tuning to PALi - between the right frequency bands. I have had black screens appear twice (which I suspect are from the famicon), both times after recently opening to console both times around the 60mhz range, however after turning the console off to reseat the game. No output.
I've heard of a few situations where the HK Famicom RF modulator seems to have stopped working. Since HK is UHF-only, they needed a different design than the VHF modulators used in the rest of the world.
both times after recently opening to console both times around the 60mhz range, however after turning the console off to reseat the game.
You're probably accidentally receiving an overtone of the 21.5MHz crystal used inside. However, the HK Famicom should be modulating its video output somewhere at much higher frequencies - 470MHz or higher. In System I, this was referred to as channel "21" and higher.

Perhaps the power supply issue?
5.1V is a little high, but it also safely within spec, and is not going to pose the problems you're seeing here. I believe it's something else.
How do I Test the RF out?
Do you have any kind of general purpose radio receiver? For example, one of those cheap RTLSDR boards? If it's successfully modulating things, you should be able to receive the audio using that, or the 50/60/16kHz hum of the modulated video.
Are there any tests I should/can do with my multimeter?
Make sure that the 21.5MHz crystal is still operating at the right frequency. See if M2 and A0 are oscillating. Check if the 21.5MHz clock gets to the PPU.

After that, see if a random audio amplifier can detect audio on pins 1/2 (AUD1, AUD2) of the CPU, or audible 50/60 Hz on the PPU video output (VOUT).

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

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

Post by inabityo » Wed Sep 09, 2020 10:28 pm

I think I made a typo with the output frequency - 600mhz, no 60. I will edit the post now!

I will look that stuff up! I'm enthusiastic amateur so not 100% on how to do that.! But either way thanks so much for the reply! Big help - If you were anywhere near me in the world, I'd buy you a six pack! Thanks again :)

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

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

Post by lidnariq » Wed Sep 09, 2020 10:39 pm

inabityo wrote:
Wed Sep 09, 2020 10:28 pm
I'm enthusiastic amateur so not 100% on how to do that!
To check for things oscillating: if your multimeter has a frequency or logic tester, use that. Otherwise, measure both DC volts and AC volts. DC volts should be around 2 volts, AC volts should be more than 1 volt.

To use an audio amplifier: touch the center of the RCA jack or tip of the 3.5mm jack to the relevant pins.

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

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

Post by inabityo » Wed Sep 09, 2020 11:07 pm

Thanks man, I'll let you know how it goes!
(sadly, I need to go to work now)

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

Post by inabityo » Thu Sep 10, 2020 7:14 am

Ok - So - here are the results, I've written (flashing) to denote a steady flip between positive and negative. I'm hoping that's oscillation.

CPU
DC: (set to '20')
A00=3.8v
M2=0.1 (I assume 0)

AC: (Set to ACV200 - Lowest on the multimeter)
A00=2.4 (flashing on the multimeter)
M2=0.1 (Flashing negative and positive)

Audio:
No audio out from Pin AD1/AD2

PPU
PPU Clock AC=4.5v (Flashing)
No denotable audio from the VOUT.
Audio coming from PPU Clock (wave) - Accidental test!

Am I right in assuming that similar to the NES, it will still output video even if the game isn't working/seated correctly? I.e. if it is a fault with the game then it should still output video?.

Thanks again

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

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

Post by lidnariq » Thu Sep 10, 2020 10:25 am

inabityo wrote:
Thu Sep 10, 2020 7:14 am
Am I right in assuming that similar to the NES, it will still output video even if the game isn't working/seated correctly? I.e. if it is a fault with the game then it should still output video?.
You are correct. Even without a game at all, the PPU should still generate video, and you should be able to hear that as a 50 or 60 Hz buzz. (What position is the 50/60Hz switch in?)
CPU A0: DC3.8 AC2.4
That looks like that's working normally
CPU M2: DC0.1 AC0.1
That's weird, that looks like that's not working. If that's not working, I'm not certain how A0 could possibly be working. DC should be closer to 2.5V.
Audio coming from PPU Clock (wave) - Accidental test!
What did it sound like?

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

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

Post by inabityo » Thu Sep 10, 2020 6:06 pm

I see what I’ve done here (40-31=9. Let’s test the 9th pin from the edge) so that would be the IRQ. I will retest.

I’ll double check the audio pins too.

It sounded like a low frequency bur, going up and down in pitch but not evenly.
\ /\
\/\ /\/ \/\/
\/
Maybe like this? (Not sure if they ascii will hold out of the reply box.

I have the switch set to nearest to the power supply. It’s not marked so who knows? I think I’ve set it to which ever appeared to be joining to challenges as opposed to ‘off’

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

Post by inabityo » Thu Sep 10, 2020 6:38 pm

Opperator error on my part. Thanks for your patience!

AUD1
AUD2
and VOUT all produce a tone.
M2 also knocks out voltage.
M2-4.5AC - 2.5DC

So, would I be right in assuming that this means the issue is likely with the RF modulator?

lidnariq
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Location: Seattle

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

Post by lidnariq » Thu Sep 10, 2020 6:49 pm

inabityo wrote:
Thu Sep 10, 2020 6:38 pm
AUD1
AUD2
and VOUT all produce a tone.
That's probably 50Hz from mains around you. AUD1 and AUD2 should sound like parts of the video game soundtrack. As I understand it, VOUT should either sound like 50Hz or 60Hz depending on the switch in the back, and also whether the game has successfully booted and started drawing.
So, would I be right in assuming that this means the issue is likely with the RF modulator?
Either the RF modulator, or maaaaybe the MK5060 itself (which is responsible for both converting the NTSC PPU to 50Hz and also converting the colorspace from NTSC3.6 to PAL4.4)

Is an AV mod something you want? Or do you really want to get the RF modulator working? Can your TV accept NTSC3.6 at 60Hz?

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

Post by inabityo » Thu Sep 10, 2020 8:05 pm

I am ok with AV modding it - if that's the best solution. Part of me wants to keep it as it is, as it is interesting bit of gaming history. That being said, I may well be beyond my capability to fix!

I can solder ok, so that shouldn't be much of an issue, however with the AV mod, the easier ones mod from the RF board, but of course mine is a little different so its not clear where I should wiring things.

That being said, I have seen others that involve different wiring options - maybe an AV mod is best, that way I can improve the output and avoid having to tackle the RF modulator.

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 10, 2020 8:13 pm

All of the outputs sound right. the Aud1+2 output sounds similar to game sound (8bit frequencies I guess) one higher pitched then the other. The PPU gives a clear 50/60htz burr. Sounds similar to what is on YouTube.

lidnariq
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Location: Seattle

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

Post by lidnariq » Thu Sep 10, 2020 11:09 pm

Well, reassuringly it does sound like it's just the RF modulator that's broken. Hard to say where that's wrong. If you have a friend with some nicer test gear (oscilloscope, ham radio) they could probably narrow it down, but I don't know the first thing about RF engineering. It's also possible, given your intermittent vaguely-like-success, that one of the wires is no longer making good electrical contact.

RF modulators almost always take baseband audio and video as input, so you should be able to just tap those two pins - either temporarily, to verify that the MK5060 is working as intended - or permanently, as part of an AV mod. Using your pictures and Krzysiobal's schematics in this post, you should be able to get raw A/V here:
IMG_3573-rf-modulator-pins-indicated.jpg
These pins should give you baseband PAL4.4 at 50/60Hz.

Alternatively, if you want to do a slightly more invasive modification, you can just steal the wires that bring A/V to the BN5060 board:
IMG_3540-wires-named.JPG
In this case, you'll get baseband NTSC3.6 at 50/60Hz.

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

Post by nocash » Fri Sep 11, 2020 9:59 am

The section with the channel switch (or whatever it is) and the resistor and potentiometer next to the switch is looking rusty. If the potentiometer or switch aren't getting contact... that might cause nonsense channel selection.

RF output has kindy terrible quality (and channel searching is kinda terrible on its own), so AV mod would be really better, both for testing & daily use.

What do you mean by "Aud1+2 output sounds similar to game sound (8bit frequencies I guess)"? There are only half of the sound channels on each pin, but you should be able to hear the melody and sound effects from the game cartridge... not just one or two random random beeps.
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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 8:29 am

It was a continuous monotone I think. However I am not confident that the cartridge is loaded, I have pick up some ipa today to clean the cartridge, then test again. I will see if I can get an AV signal.

I though that two regarding the switch, resistor and potentiometer - I thought that too. I will lest in the morning and let you know how I get on!

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