Help with Frontloader

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

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gecko702
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Joined: Thu May 09, 2024 8:46 pm

Help with Frontloader

Post by gecko702 »

Hello, I just recently joined in because of an issue, so my front loader is not working anymore, I got it a sale for $20, it actually worked but suddenly one day wouldn't turn on, all I got was a black screen on A/V and RF, I replaced all the caps to no avail even voltage regulator and the rectifier, motherboard caps, and even with an OEM power supply wouldn't budge, not sure if it the aftremarket supply messed it up? all it does its a red solid light and black screen, I disabled the security chip and nothing as well could it be the RF modulator? or a faulty PPU or CPU? my power modulator is a Mitsumi TDK-T31V, all I all I have is a multimeter, if it it was the CPU or PPU shorted it would've gone off but I get no sounds only when ground is touched, pins are good and its OEM and I tested continuity and the whole pin assembly is fine, thanks any help is appreciated
lidnariq
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Joined: Sun Apr 13, 2008 11:12 am

Re: Help with Frontloader

Post by lidnariq »

Since the red LED is glowing, you have power. The LED is driven by the CIC.

Measure the voltage supplied to the CPU and PPU.

If you plug the NES's "video" output RCA jack into your TV's "audio" input, do you hear a loud 50/60Hz buzz?

It's going to be hard to give useful diagnostics with the normal cheap multimeter, unless it includes a frequency meter.

See also my previous outlines:
viewtopic.php?p=260390#p260390
viewtopic.php?p=263220#p263220 (PAL NES, but that only means the exact frequencies change)

Disabling the CIC is basically irrelevant; the kind of situation where it refuses to work usually is a situation where the PPU or CPU is already going to have problems.
gecko702
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Joined: Thu May 09, 2024 8:46 pm

Re: Help with Frontloader

Post by gecko702 »

lidnariq wrote: Fri May 10, 2024 1:25 am Since the red LED is glowing, you have power. The LED is driven by the CIC.

Measure the voltage supplied to the CPU and PPU.

If you plug the NES's "video" output RCA jack into your TV's "audio" input, do you hear a loud 50/60Hz buzz?

It's going to be hard to give useful diagnostics with the normal cheap multimeter, unless it includes a frequency meter.

See also my previous outlines:
viewtopic.php?p=260390#p260390
viewtopic.php?p=263220#p263220 (PAL NES, but that only means the exact frequencies change)

Disabling the CIC is basically irrelevant; the kind of situation where it refuses to work usually is a situation where the PPU or CPU is already going to have problems.
No, There's no hums or buzzes just solid black screen, and you know what? the PPU feels a bit more hot than the CPU maybe the PPU is faulty, but like you said I need a frequency meter to find out.

EDIT: so I actually checked voltages CPU pin 40 measures 4.90V PPU pin 22 measures 4.90V too I press reset and voltage goes down but goes back to that same voltage, PPU feels hotter than CPU so maybe a faulty PPU?
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Ben Boldt
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Location: Minnesota, USA

Re: Help with Frontloader

Post by Ben Boldt »

A black screen over RF (instead of snow) tells me that it IS putting out a video signal?? Please correct me if I’m wrong on that.

CPUs and PPUs are usually warm. They just shouldn’t burn your finger.

Modern TVs don’t always work well with NES. Maybe it’s your TV.

Also, the TV might not play audio if it doesn’t have a good video signal. You might try hooking up something else that puts out composite video (I.e. dvd player, Xbox, etc), and plug the NES’s video into the tv’s audio at the same time.
gecko702
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Re: Help with Frontloader

Post by gecko702 »

Ben Boldt wrote: Fri May 10, 2024 8:15 pm A black screen over RF (instead of snow) tells me that it IS putting out a video signal?? Please correct me if I’m wrong on that.

CPUs and PPUs are usually warm. They just shouldn’t burn your finger.

Modern TVs don’t always work well with NES. Maybe it’s your TV.

Also, the TV might not play audio if it doesn’t have a good video signal. You might try hooking up something else that puts out composite video (I.e. dvd player, Xbox, etc), and plug the NES’s video into the tv’s audio at the same time.
I tried it on a CRT, both A/V and RF and still a black screen no sound at all
Fiskbit
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Re: Help with Frontloader

Post by Fiskbit »

Just to clarify, the suggested test is plugging the console's composite video output into the TV's audio input to see if the video signal can be heard as a buzz. The way you describe it makes it sound like you're just passing video as video and audio as audio, so I want to make sure you understood it correctly. This test would help us understand whether the PPU is outputting a video signal or not. A functional PPU will output a solid color when powered on, though what color that is will vary usually from console to console, and it may be black. Other things to check for might be the TV resyncing to the video signal every time the reset button is pressed.

The heat you describe doesn't sound like a problem to me. I believe the PPU normally gets hotter than the CPU (and very early PPUs had serious heat problems requiring heat sinks or heat spreaders, though this wasn't a problem anymore by the time they released the NES in North America). I find that some PPUs can get uncomfortably warm, but painfully hot would point toward a problem.
gecko702
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Re: Help with Frontloader

Post by gecko702 »

Fiskbit wrote: Fri May 10, 2024 10:34 pm Just to clarify, the suggested test is plugging the console's composite video output into the TV's audio input to see if the video signal can be heard as a buzz. The way you describe it makes it sound like you're just passing video as video and audio as audio, so I want to make sure you understood it correctly. This test would help us understand whether the PPU is outputting a video signal or not. A functional PPU will output a solid color when powered on, though what color that is will vary usually from console to console, and it may be black. Other things to check for might be the TV resyncing to the video signal every time the reset button is pressed.

The heat you describe doesn't sound like a problem to me. I believe the PPU normally gets hotter than the CPU (and very early PPUs had serious heat problems requiring heat sinks or heat spreaders, though this wasn't a problem anymore by the time they released the NES in North America). I find that some PPUs can get uncomfortably warm, but painfully hot would point toward a problem.
Tried that and no buzz, but actually I plugged the video onto the console, then instead of plugging the other end to the TV I measured its voltage and measured 0.32V even the audio measured 0.01V, could it be an issue with the modulator itself? I switched to another set of AV cables same result
lidnariq
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Re: Help with Frontloader

Post by lidnariq »

The RF modulator can die, but it's not the most common failure mode I remember hearing. You could see if touching the center of the RCA jack directly to PPU pin 21 (video output) produces a 60/50Hz buzz.

Otherwise, it's going to be hard to give any useful instructions without having access to some kind of test equipment.
gecko702
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Joined: Thu May 09, 2024 8:46 pm

Re: Help with Frontloader

Post by gecko702 »

lidnariq wrote: Sun May 12, 2024 10:33 am The RF modulator can die, but it's not the most common failure mode I remember hearing. You could see if touching the center of the RCA jack directly to PPU pin 21 (video output) produces a 60/50Hz buzz.

Otherwise, it's going to be hard to give any useful instructions without having access to some kind of test equipment.
Oh I'll try that, touching as in actually touching? Only tool I have is just a multimeter a cheap one though, but ill try to do that, also testing the PPU with video out from console and plugging it to the audio of the CRT? And touching at the same time? Hopefully it's a dead modulator probability good excuse to install that Merlin shaw board, I have soldering skills too it'll be easy
lidnariq
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Re: Help with Frontloader

Post by lidnariq »

No multimeter for this test: just try touching an audio amplifier of whatever sort onto PPU pin 21, which is the one that emits video. If you hear something that sounds like video, the PPU at least sort of works, and the fault is somewhere between there and the RCA jack on the outside.
gecko702
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Joined: Thu May 09, 2024 8:46 pm

Re: Help with Frontloader

Post by gecko702 »

lidnariq wrote: Mon May 13, 2024 12:56 am No multimeter for this test: just try touching an audio amplifier of whatever sort onto PPU pin 21, which is the one that emits video. If you hear something that sounds like video, the PPU at least sort of works, and the fault is somewhere between there and the RCA jack on the outside.
Well i tried finding that hum/buzz but couldn't get anything, i tried that touching method with the A/V cables, is there any other tests i can try? Only thing i get it's just this loud pop sound whenever i turn it on with black screen and horizontal white lines too but that's when it's plugged video to video and audio to audio, Meantime I will invest in a more reliable multimeter and with frequency meter, while it arrives i shall try any other methods you recommend, also what is the frequency the CPU and PPU output? To have an idea when I do that test and is it Khz or hz? Thanks for the help :beer:
lidnariq
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Re: Help with Frontloader

Post by lidnariq »

If there's no 60Hz buzz from the PPU, either the clock is dead or the PPU is dead :(

If the clock and CPU work and the PPU is dead, then you'll be able to detect 1.8MHz on CPU pin 31.

If the clock is dead, it's hard to detect anything else. There will, or won't be, 21.5MHz on CPU pin 29, PPU pin 18, and cartridge pin 37. But that's high enough frequency that you may not have hardware that can detect it.
gecko702
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Joined: Thu May 09, 2024 8:46 pm

Re: Help with Frontloader

Post by gecko702 »

lidnariq wrote: Tue May 14, 2024 12:01 am If there's no 60Hz buzz from the PPU, either the clock is dead or the PPU is dead :(

If the clock and CPU work and the PPU is dead, then you'll be able to detect 1.8MHz on CPU pin 31.

If the clock is dead, it's hard to detect anything else. There will, or won't be, 21.5MHz on CPU pin 29, PPU pin 18, and cartridge pin 37. But that's high enough frequency that you may not have hardware that can detect it.
Well out of curiosity i probed PPU pin 21 with multimeter and says 0.02V shouldn't it be outputting 0.07? Or more?
lidnariq
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Re: Help with Frontloader

Post by lidnariq »

If you didn't hear a 60Hz buzz, you won't measure an interesting voltage either.
gecko702
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Re: Help with Frontloader

Post by gecko702 »

lidnariq wrote: Wed May 15, 2024 12:04 am If you didn't hear a 60Hz buzz, you won't measure an interesting voltage either.
Ok so my new multimeter has arrived and checked out with the frequency meter ok so here's what I gotten (not sure if I measured correctly)

CPU pin 31: 1.376hz (but has an m to the hz) CPU pin 29: 26.81hz ( this one with a k to the hz and no its an NTSC NES) PPU pin 18: 17.54hz (k too)

and finally cart pin 37 15.83hz (k as well) are these numbers somewhat OK? sorry first time measuring HZ and such but I'm learning a lot thanks for the help :beer: :beer: hopefully this can be fixed and it was $20 off some old guy selling it I know I had to rescue it
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