Hey folks,
I registered to ask this question. I didn't see it on the FAQs and hopefully it's not a repetition of something here already.
I've been having a problem with my NES where after the last time I cleaned its edge connector (I do this by opening it up and cleaning it WELL with lint-free cloths and isopropyl/water mix which I then dry off)... it worked perfectly (no odd insertions, etc.) as always after I put it back together, but the next day it exhibited silence instead of sound.
On the inside, I've discovered that the resistors (R3 and R4) that come off the board still have the sound just fine, as do the later-on R7/R8/R9. The last cap (C23) just before the 7404 and the 7404 itself are where the buck stops. The unamplified sound (that the 7404 will amplify back up to normal levels) does show up on one leg of that capacitor, but not on both. The leg the sound appears on is showing .02 volts when tested with a multimeter, while the leg that shows 5 volts is the dead one. The unamped pin of the 7404 that the sound goes into still lets you hear the sound, but the sound doesn't come back out of the "amplified" side. At first I thought the 7404 alone was the culprit, since the sound goes in but doesn't come back out. However, then I saw that the capacitor had .02v on the leg that worked and 5v on the leg that didn't. The unamped pin also shows .02v (and something DOES go in there), and the amped pin shows 5v (but nothing comes out sound-wise)... the 7404 itself "registers" as okay when tested for resistance using its ground pin and its other pin.
I've spent a while to get to finding this much out, since I've sort of learned some stuff about voltage and resistance along the way. My friend who actually has the multimeter suspects that the capacitor before the 7404 is not getting fully energized and the 7404 is trying to amplify a signal but that it's just too weak a signal... however, I wonder if the fact that you CAN hear something (with the volume bleedingly loud) going in means that you shouldn't at least still hear it at that volume coming out instead of losing it altogether.
I have two specific questions. Firstly, is the .02 voltage reading NORMAL? The .02 (whereas working components read as 5) has me thinking that the cap, or possibly the cap and the 7404, are at fault. I'm trying to see if one or both components are at fault by finding out if those voltage readings are normal. One leg of the cap is .02, the other leg is 5, and the 5 leg is the one that doesn't provide sound. The 7404 seems to be working other than sound, since there isn't anything else wrong with the system's performance. I want to see if one or both components are rating normally or if one or both are the culprit. I'm considering component replacement and this would be good to know. (though I'm also considering routing the audio from R3/R4 in a sort of homebrew fix, I'd like to be able to use the system as before if possible)
The second specific question is what may have caused this. Naturally, I opened my NES and may have done something to it. However, it still had sound that night. I *was*, however, using a Honeybee converter with a Famicom cartridge of Final Mission (SCAT over here)... and it went through several reboots when I tried using that, even though the converter worked okay for other Famicom cartridges. I'm wondering if the 5v shock that the Honeybee and other "illegit" things use to knock out the security chip might've had the effect of shorting out one or both components of these components on my NES... especially if the system was also going through rapid rebooting with said shocks. Could this be the culprit?
Sorry if that went long - I tried to sum up all the relevant history so far as briefly as I could. I realize this may not be a repair forum, but if anyone here knows the answer to either of the two questions above, I would appreciate the help.
I registered to ask this question. I didn't see it on the FAQs and hopefully it's not a repetition of something here already.
I've been having a problem with my NES where after the last time I cleaned its edge connector (I do this by opening it up and cleaning it WELL with lint-free cloths and isopropyl/water mix which I then dry off)... it worked perfectly (no odd insertions, etc.) as always after I put it back together, but the next day it exhibited silence instead of sound.
On the inside, I've discovered that the resistors (R3 and R4) that come off the board still have the sound just fine, as do the later-on R7/R8/R9. The last cap (C23) just before the 7404 and the 7404 itself are where the buck stops. The unamplified sound (that the 7404 will amplify back up to normal levels) does show up on one leg of that capacitor, but not on both. The leg the sound appears on is showing .02 volts when tested with a multimeter, while the leg that shows 5 volts is the dead one. The unamped pin of the 7404 that the sound goes into still lets you hear the sound, but the sound doesn't come back out of the "amplified" side. At first I thought the 7404 alone was the culprit, since the sound goes in but doesn't come back out. However, then I saw that the capacitor had .02v on the leg that worked and 5v on the leg that didn't. The unamped pin also shows .02v (and something DOES go in there), and the amped pin shows 5v (but nothing comes out sound-wise)... the 7404 itself "registers" as okay when tested for resistance using its ground pin and its other pin.
I've spent a while to get to finding this much out, since I've sort of learned some stuff about voltage and resistance along the way. My friend who actually has the multimeter suspects that the capacitor before the 7404 is not getting fully energized and the 7404 is trying to amplify a signal but that it's just too weak a signal... however, I wonder if the fact that you CAN hear something (with the volume bleedingly loud) going in means that you shouldn't at least still hear it at that volume coming out instead of losing it altogether.
I have two specific questions. Firstly, is the .02 voltage reading NORMAL? The .02 (whereas working components read as 5) has me thinking that the cap, or possibly the cap and the 7404, are at fault. I'm trying to see if one or both components are at fault by finding out if those voltage readings are normal. One leg of the cap is .02, the other leg is 5, and the 5 leg is the one that doesn't provide sound. The 7404 seems to be working other than sound, since there isn't anything else wrong with the system's performance. I want to see if one or both components are rating normally or if one or both are the culprit. I'm considering component replacement and this would be good to know. (though I'm also considering routing the audio from R3/R4 in a sort of homebrew fix, I'd like to be able to use the system as before if possible)
The second specific question is what may have caused this. Naturally, I opened my NES and may have done something to it. However, it still had sound that night. I *was*, however, using a Honeybee converter with a Famicom cartridge of Final Mission (SCAT over here)... and it went through several reboots when I tried using that, even though the converter worked okay for other Famicom cartridges. I'm wondering if the 5v shock that the Honeybee and other "illegit" things use to knock out the security chip might've had the effect of shorting out one or both components of these components on my NES... especially if the system was also going through rapid rebooting with said shocks. Could this be the culprit?
Sorry if that went long - I tried to sum up all the relevant history so far as briefly as I could. I realize this may not be a repair forum, but if anyone here knows the answer to either of the two questions above, I would appreciate the help.