NES-001 cap replacement guide for the av power module

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jcarlos
Posts: 42
Joined: Mon Dec 21, 2020 11:38 pm

Re: NES-001 cap replacement guide for the av power module

Post by jcarlos » Thu Jan 07, 2021 3:31 am

lidnariq wrote:
Thu Jan 07, 2021 1:03 am
jcarlos wrote:
Wed Jan 06, 2021 11:23 pm
I have been researching. The problem seems to be in the graphic processor (PPU), with reference RP2C07A-0, of my mainboard and it is faulty, I know it because when comparing it with the mainboard of the same console of my brother that is good, it gives me wrong measurements.
Please say a little more about these measurements. Although broken PPUs are indeed heard-of, they don't usually seem to stop drawing a picture altogether. It'd be a shame if you desoldered it and put a new one in just to find something else also wrong.
Since my RP2C07A-0 is impossible to find.
Please see my page on the wiki: https://wiki.nesdev.com/w/index.php/Use ... _revisions
To wit: the RP2C07-0, RP2C07A, and RP2C07A-0, and UA6541 all exist and should be completely interchangeable.

Furthermore, the UA6538 should be close but not fully compatible.
It is precisely on your page where I have seen about the compatibility of PPUs. Thank you. I know that the board has more faults, but I'll explain my procedure to try to repair it. It's a bit long, but good. My brother has a complete NES-001 and I only used the mainboard of another one, just like he had when I was a child, the latter is the one that was seen with a pink screen for a long time. My brother playing, his NES-001 breaks down, he detects a burning smell then after a while his NES turns off and when he turns it on again he sees the game he was playing, according to him, but he turns it off again fear because I followed the smell. He gave it to me to try to fix it. The first thing we did is check the transformer of the source, but it is OK, after cleaning and adding more thermal paste in the AN7805 and when turning it on, it did not smell, it has already burned, but the game did not look good, it looked deformed and without color , we believe that a tiny surface mount capacitor at the input of the AN7805, which looks burned out, produces an ohmic resistance at the input of the 7805 that is not normal about 3KOhm, when on the other mainboard, apparently OK, it measures at ends of is SMD capacitor about 4MOhm. We think that this is the cause of the video not displaying correctly. We discard, for the moment, this module and replace it with the other one on the pink screen. But it did not give video or audio, there is no signal, so review 3 2SC1740 transitors that you have and one of them, the one that goes to the audio / video output, half ohmic resistance in both directions, both in base-emitter and base-collector, So I bought one and replaced it and now it's working perfectly. Then it seems that the failure of the pink screen damaged this transistor at the time and when we put it on my brother's it failed, it seems that it destroys this transistor. Now we have a complete NITENDO-001 working perfectly. And we tested the other mainboard (pink screen) with burned-out SMD capacitor video / audio module. And the pink screen is still showing and we have seen a screenshot at first with strange characters and then again the pink screen again, and we have observed that at least one 2SC1740 transitor has been destroyed. So we decided to fix the latter using the one that is OK as a reference. We separate the mainboard from the video module in both. When measuring impedances and capacitances between Vcc (5V) and ground, without connecting power to the mainboards, we observe in the good mainboard we obtain about 1.75K and 33nF and in the other 11 Ohm and negative capacitance measurements, this is not normal, we disconnect the Vcc (5v) pin of the PPU RP2C07A-0 and the impedance rises a lot and it is this PPU disconnected from the mainboard that has the 11 Ohm between Vcc and ground. We think this PPU is out of order. We have also detected measurements, different from those of the good board, in both SRAM LH5116DY-10 memories, for example impedances in the data pins of the memories with respect to ground, which in the good mainboard, give the order of 3.5M and in the other infinite when they are on the air. In short, they are a series of breakdowns that we want to solve. Replace the PPU, the two SRAM memories, and the necessary 2SC1740 transitors. We think that would work. But in electronics there is never anything said, there may be something more. Sorry for the extension but I wanted to explain, more or less, how it happened. Greetings and thanks for the information on your page. So you also think that we can replace the RP2C07A-0 with a UA6541 because they are compatible?

jcarlos
Posts: 42
Joined: Mon Dec 21, 2020 11:38 pm

Re: NES-001 cap replacement guide for the av power module

Post by jcarlos » Thu Jan 07, 2021 4:19 am

lidnariq wrote:
Thu Jan 07, 2021 1:03 am
jcarlos wrote:
Wed Jan 06, 2021 11:23 pm
I have been researching. The problem seems to be in the graphic processor (PPU), with reference RP2C07A-0, of my mainboard and it is faulty, I know it because when comparing it with the mainboard of the same console of my brother that is good, it gives me wrong measurements.
Please say a little more about these measurements. Although broken PPUs are indeed heard-of, they don't usually seem to stop drawing a picture altogether. It'd be a shame if you desoldered it and put a new one in just to find something else also wrong.
Since my RP2C07A-0 is impossible to find.
Please see my page on the wiki: https://wiki.nesdev.com/w/index.php/Use ... _revisions
To wit: the RP2C07-0, RP2C07A, and RP2C07A-0, and UA6541 all exist and should be completely interchangeable.

Furthermore, the UA6538 should be close but not fully compatible.
As for the SRAM memories, the references of those that are on the damaged mainboard are a Motorola MCM2018AN55 and the other Sharp LH5216AD-10L. The mainboard that works are the two Sharp LH5116DY-10. We have found SRAM memories with the Sharp reference LH5116D-10 and they are the ones that we are going to place in the damaged mainboard. As you can see, a Y is missing with respect to those of the mainborad that works. But I think they are all compatible, even the ones with reference 6116 are also valid. If you know anything about it, we would be very grateful. Thanks and best regards.

lidnariq
Posts: 10068
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: NES-001 cap replacement guide for the av power module

Post by lidnariq » Thu Jan 07, 2021 2:56 pm

jcarlos wrote:
Thu Jan 07, 2021 3:31 am
When measuring impedances and capacitances between Vcc (5V) and ground, without connecting power to the mainboards, we observe in the good mainboard we obtain about 1.75K and 33nF
I really would have thought that the isolated NES mainboard should have much more capacitance than that. There's multiple 100nF and 10nF decoupling capacitors all over the board...
So you also think that we can replace the RP2C07A-0 with a UA6541 because they are compatible?
The UA6541 is officially a clone of the PAL PPU. I have no personal experience with this, being from NTSC-land.
jcarlos wrote:
Thu Jan 07, 2021 4:19 am
If you know anything about it, we would be very grateful.
As far as I know, all sufficiently slow 24-pin 2KB RAMs are fine here. Don't use a 10ns or faster one, however.


Since you seem comfortable with soldering, I'd recommend a very simple test:

Take the supposedly-damaged PPU out of the mainboard.
Put it in a breadboard.
Provide the PPU with a clock on pin 18.
Hook a sound system up to the video output on pin 21.
Provide the PPU by itself +5V.
Listen for a buzz. (The exact tones will depend on the clock you provide on pin 18).

If you have a standard "can crystal oscillator" that will work fine for the clock source. If you only have BJTs and cut crystals, you can use a simple driver.

jcarlos
Posts: 42
Joined: Mon Dec 21, 2020 11:38 pm

Re: NES-001 cap replacement guide for the av power module

Post by jcarlos » Thu Jan 07, 2021 10:24 pm

lidnariq wrote:
Thu Jan 07, 2021 2:56 pm
jcarlos wrote:
Thu Jan 07, 2021 3:31 am
When measuring impedances and capacitances between Vcc (5V) and ground, without connecting power to the mainboards, we observe in the good mainboard we obtain about 1.75K and 33nF
I really would have thought that the isolated NES mainboard should have much more capacitance than that. There's multiple 100nF and 10nF decoupling capacitors all over the board...
So you also think that we can replace the RP2C07A-0 with a UA6541 because they are compatible?
The UA6541 is officially a clone of the PAL PPU. I have no personal experience with this, being from NTSC-land.
jcarlos wrote:
Thu Jan 07, 2021 4:19 am
If you know anything about it, we would be very grateful.
As far as I know, all sufficiently slow 24-pin 2KB RAMs are fine here. Don't use a 10ns or faster one, however.


Since you seem comfortable with soldering, I'd recommend a very simple test:

Take the supposedly-damaged PPU out of the mainboard.
Put it in a breadboard.
Provide the PPU with a clock on pin 18.
Hook a sound system up to the video output on pin 21.
Provide the PPU by itself +5V.
Listen for a buzz. (The exact tones will depend on the clock you provide on pin 18).

If you have a standard "can crystal oscillator" that will work fine for the clock source. If you only have BJTs and cut crystals, you can use a simple driver.
Does the oscillator have to be of an audible frequency? Is it worth around 10 kHz, for example?
When you say clock on pin 18, do you mean this pin to ground?
Last edited by jcarlos on Thu Jan 07, 2021 11:18 pm, edited 1 time in total.

jcarlos
Posts: 42
Joined: Mon Dec 21, 2020 11:38 pm

Re: NES-001 cap replacement guide for the av power module

Post by jcarlos » Thu Jan 07, 2021 10:37 pm

jcarlos wrote:
Thu Jan 07, 2021 10:24 pm
lidnariq wrote:
Thu Jan 07, 2021 2:56 pm
jcarlos wrote:
Thu Jan 07, 2021 3:31 am
When measuring impedances and capacitances between Vcc (5V) and ground, without connecting power to the mainboards, we observe in the good mainboard we obtain about 1.75K and 33nF
I really would have thought that the isolated NES mainboard should have much more capacitance than that. There's multiple 100nF and 10nF decoupling capacitors all over the board...
So you also think that we can replace the RP2C07A-0 with a UA6541 because they are compatible?
The UA6541 is officially a clone of the PAL PPU. I have no personal experience with this, being from NTSC-land.
jcarlos wrote:
Thu Jan 07, 2021 4:19 am
If you know anything about it, we would be very grateful.
As far as I know, all sufficiently slow 24-pin 2KB RAMs are fine here. Don't use a 10ns or faster one, however.


Since you seem comfortable with soldering, I'd recommend a very simple test:

Take the supposedly-damaged PPU out of the mainboard.
Put it in a breadboard.
Provide the PPU with a clock on pin 18.
Hook a sound system up to the video output on pin 21.
Provide the PPU by itself +5V.
Listen for a buzz. (The exact tones will depend on the clock you provide on pin 18).

If you have a standard "can crystal oscillator" that will work fine for the clock source. If you only have BJTs and cut crystals, you can use a simple driver.
Can the oscillator be of any frequency or an approximate one? Is it worth about 4MHz for example?
When you say a clock on pin 18, do you mean from this pin to ground?
I know that the right thing to do is to extract both PPU's from the mainboards to be able to make those assumptions, but that is precisely what I try to avoid, desoldering both PPU's. At first, when measuring the impedance between Vcc and ground, they gave me very different measurements in both mainborads, if one is good in the other something does not work well, because the supposedly bad mainboard gave me continuity between Vcc and ground and the good mainboard did not . By disconnecting pin 24 (Vcc) from the PPU's on both mainboards, to isolate, in part, both PPU's from their respective mainboards. When measuring in both PPUs between disconnected pin 24 (open) and ground, the PPU that I assumed was faulty continues to give continuity while the other does not, everything makes me think that this PPU is faulty. When I decide to replace the supposedly damaged PPU and remove it from the board, I will try to do what you tell me to be sure. Thank you.
Last edited by jcarlos on Fri Jan 08, 2021 1:35 pm, edited 1 time in total.

lidnariq
Posts: 10068
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: NES-001 cap replacement guide for the av power module

Post by lidnariq » Thu Jan 07, 2021 11:51 pm

jcarlos wrote:
Thu Jan 07, 2021 10:24 pm
Does the oscillator have to be of an audible frequency? Is it worth around 10 kHz, for example?
It should be distinctly ultrasonic. The two frequencies that you will hear on the video pin will be (input clock ÷ 1705) and (input clock ÷ 531960). So to get something audible out, you should feed it at least 100kHz, possibly higher.
When you say clock on pin 18, do you mean this pin to ground?
Yes, relative to ground, the clock pin should oscillate between something around 0-1V and 2-5V.
jcarlos wrote:
Thu Jan 07, 2021 10:37 pm
I know that the right thing to do is to extract both PPU's from the mainboards to be able to make those assumptions, but that is precisely what I try to avoid, desoldering both PPU's.
I didn't say anything about desoldering both. Only the suspect one.

The problem is: right now, you really must check the main system clock first. There's a variety of ways you can do this, but it depends on what test equipment you have available.

(For example, if you have a shortwave radio, tune it to 26.6MHz and hold it near the NES mainboard. If you have an oscilloscope, you probably already know what to do. You can check if the CPU is running even a little bit, by using a logic tester on either of CPU pins 31 and 4 relative to ground and see if they keep changing between high and low.)

jcarlos
Posts: 42
Joined: Mon Dec 21, 2020 11:38 pm

Re: NES-001 cap replacement guide for the av power module

Post by jcarlos » Fri Jan 08, 2021 12:25 pm

lidnariq wrote:
Thu Jan 07, 2021 11:51 pm
jcarlos wrote:
Thu Jan 07, 2021 10:24 pm
Does the oscillator have to be of an audible frequency? Is it worth around 10 kHz, for example?
It should be distinctly ultrasonic. The two frequencies that you will hear on the video pin will be (input clock ÷ 1705) and (input clock ÷ 531960). So to get something audible out, you should feed it at least 100kHz, possibly higher.
When you say clock on pin 18, do you mean this pin to ground?
Yes, relative to ground, the clock pin should oscillate between something around 0-1V and 2-5V.
jcarlos wrote:
Thu Jan 07, 2021 10:37 pm
I know that the right thing to do is to extract both PPU's from the mainboards to be able to make those assumptions, but that is precisely what I try to avoid, desoldering both PPU's.
I didn't say anything about desoldering both. Only the suspect one.

The problem is: right now, you really must check the main system clock first. There's a variety of ways you can do this, but it depends on what test equipment you have available.

(For example, if you have a shortwave radio, tune it to 26.6MHz and hold it near the NES mainboard. If you have an oscilloscope, you probably already know what to do. You can check if the CPU is running even a little bit, by using a logic tester on either of CPU pins 31 and 4 relative to ground and see if they keep changing between high and low.)
I don't have a logic analyzer but I have a 200 Mhz oscilloscope with two channels.
The problem is that I only have the mainboard at home and nothing else, the transformer of the NES-001 is at my brother's house and gives an alternating signal of 9.9AC and 1.3A. Unless I used a 2.125A universal DC power supply that I have. I could put it at 5V and power only the mainboard. The question is, I have the RF / RCA video module desoldered from the mainboard, I don't know if I should solder it and power it with your factory transformer (9.9AC and 1.3A) to do the test or do the test only with the mainboard powering it with 5V DC from my universal source. This last option would be more comfortable for me, since I would not have to go to my brother's house for the transformer, since he lives quite far away, nor would I have to solder the RF / RCA video module, to possibly have to desolder it in the future. I say because the pads and electrical connections suffer with temperatures. Another issue is that I have one of the 2K static memories unsoldered from the mainboard, because I think it is also damaged, although the image appears half unsoldered, it is now completely unsoldered. I think it will not influence, to measure the system clock, when powering the mainboard and doing the test.
Attachments
IMG20210105165229[2].jpg

lidnariq
Posts: 10068
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: NES-001 cap replacement guide for the av power module

Post by lidnariq » Fri Jan 08, 2021 1:51 pm

jcarlos wrote:
Fri Jan 08, 2021 12:25 pm
I have a 200 Mhz oscilloscope with two channels.
That's more than enough.

Check the following locations:
CPU pin 29 (26.6MHz)
PPU pin 18 (26.6MHz)
CPU pin 31 (1.66MHz)
CPU pin 4 (415-830kHz)
PPU pin 19 (50Hz)
jcarlos wrote:
Fri Jan 08, 2021 12:25 pm
Unless I used a 2.125A universal DC power supply that I have. I could put it at 5V and power only the mainboard.
That's fine. My (NTSC) NES operates correctly on as little as 4V.
The question is, I have the RF / RCA video module desoldered from the mainboard, I don't know if I should solder it and power it with your factory transformer (9.9AC and 1.3A) to do the test or do the test only with the mainboard powering it with 5V DC from my universal source.
You don't need it. It only regulates 9V down to 5V and amplifies video and audio.
Another issue is that I have one of the 2K static memories unsoldered from the mainboard, because I think it is also damaged, although the image appears half unsoldered, it is now completely unsoldered. I think it will not influence, to measure the system clock, when powering the mainboard and doing the test.
Correct, that's fine.

jcarlos
Posts: 42
Joined: Mon Dec 21, 2020 11:38 pm

Re: NES-001 cap replacement guide for the av power module

Post by jcarlos » Fri Jan 08, 2021 2:54 pm

This is another question I have, which is not related to the above. My brother's other NES-001 that now works perfectly, but I don't want the same thing to happen to him again, the AN7805, which is in the RF / RCA video module, got hot and the NES turned off, I suppose it is the overheating protection system of AN7805. I changed the complete video module for the one that had this board to which I am going to do the test that you have told me, because the RF module was intact except for a 2SC1740 transistor that gave incorrect measurements and I changed it. But why did the other AN7805 get so hot? The first thing we did is measure the effective voltage of the transformer and it gave 11.66 V AC. Isn't that a bit high, should we measure 9V or 9.9V AC approximately? and the second change the thermal paste of the AN7805 to the heatsink. Now everything works correctly but could it happen again because the transformer is high or because of the deterioration of the thermal paste or for another reason?

lidnariq
Posts: 10068
Joined: Sun Apr 13, 2008 11:12 am
Location: Seattle

Re: NES-001 cap replacement guide for the av power module

Post by lidnariq » Fri Jan 08, 2021 3:01 pm

jcarlos wrote:
Fri Jan 08, 2021 2:54 pm
But why did the other AN7805 get so hot?
Because that's what 7805s do, unfortunately. And in case of damage on the low side, such as a transistor that's drawing extra power, all that extra power produces even more heat in the 7805.
The first thing we did is measure the effective voltage of the transformer and it gave 11.66 V AC. Isn't that a bit high, should we measure 9V or 9.9V AC approximately?
These old power adapters that are just a transformer provide extremely non-constant voltage. The unloaded voltage is often 150% of the nominal, and you only expect to see the nominal output at the rated output current. (In the NES's case: you should see 9Vrms AC when 1.2A are drawn)
and the second change the thermal paste of the AN7805 to the heatsink. Now everything works correctly but could it happen again because of the transformer or because of the deterioration of the thermal paste or for another reason?
Thermal paste doesn't just disappear, you're probably fine. The original assembly had none.

jcarlos
Posts: 42
Joined: Mon Dec 21, 2020 11:38 pm

Re: NES-001 cap replacement guide for the av power module

Post by jcarlos » Sat Jan 09, 2021 7:44 am

lidnariq wrote:
Fri Jan 08, 2021 1:51 pm
jcarlos wrote:
Fri Jan 08, 2021 12:25 pm
I have a 200 Mhz oscilloscope with two channels.
That's more than enough.

Check the following locations:
CPU pin 29 (26.6MHz)
PPU pin 18 (26.6MHz)
CPU pin 31 (1.66MHz)
CPU pin 4 (415-830kHz)
PPU pin 19 (50Hz)
jcarlos wrote:
Fri Jan 08, 2021 12:25 pm
Unless I used a 2.125A universal DC power supply that I have. I could put it at 5V and power only the mainboard.
That's fine. My (NTSC) NES operates correctly on as little as 4V.
The question is, I have the RF / RCA video module desoldered from the mainboard, I don't know if I should solder it and power it with your factory transformer (9.9AC and 1.3A) to do the test or do the test only with the mainboard powering it with 5V DC from my universal source.
You don't need it. It only regulates 9V down to 5V and amplifies video and audio.
Another issue is that I have one of the 2K static memories unsoldered from the mainboard, because I think it is also damaged, although the image appears half unsoldered, it is now completely unsoldered. I think it will not influence, to measure the system clock, when powering the mainboard and doing the test.
Correct, that's fine.
I have performed the test and it seems that the CPU gives the correct measurements and the PPU pin 18 seems to be, but the other pin 19 is not correct, it gives a continuous of 4.88V the same as Vcc, also I have observed that the PPU gets quite hot when it is a while, while the CPU does not heat up.

CPU pin 4: intermittent square signal, readings different frequencies: 554.3Khz, 833.3Khz, 277.1Khz (These were difficult to capture, as the signal appeared and disappeared intermittently and changed frequency).
Attachments
CPuPin4B.jpg
CpuPin4A.jpg
Last edited by jcarlos on Sat Jan 09, 2021 8:20 am, edited 1 time in total.

jcarlos
Posts: 42
Joined: Mon Dec 21, 2020 11:38 pm

Re: NES-001 cap replacement guide for the av power module

Post by jcarlos » Sat Jan 09, 2021 7:48 am

CPU pin 31: Fixed square signal, frequency reading: 1.66Mhz
Attachments
CpuPin31B.jpg
CpuPin31.jpg

jcarlos
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Joined: Mon Dec 21, 2020 11:38 pm

Re: NES-001 cap replacement guide for the av power module

Post by jcarlos » Sat Jan 09, 2021 7:50 am

CPU pin 29: Fixed sinusoidal signal, frequencies reading: 26.6 Mhz, 26.74 Mhz
Attachments
CpuPin29B.jpg
CpuPin29.jpg

jcarlos
Posts: 42
Joined: Mon Dec 21, 2020 11:38 pm

Re: NES-001 cap replacement guide for the av power module

Post by jcarlos » Sat Jan 09, 2021 7:53 am

PPU pin 18: fixed sinusoidal signal, frequency reading: 26.6 Mhz
Attachments
PpuPin18.jpg

jcarlos
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Joined: Mon Dec 21, 2020 11:38 pm

Re: NES-001 cap replacement guide for the av power module

Post by jcarlos » Sat Jan 09, 2021 7:54 am

PPU pin 19: fixed practically continuous signal, frequency reading: -
Attachments
PpuPin19.jpg

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