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dafa_123

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Posts posted by dafa_123

  1. Posted

    Hello,

     

          I have a Sega Saturn that will not power up. I cannot find any schematic for the Yamaha XS205 Rev C power supply. I believe that the transformer is bad. I get continuity on the high voltage side but not on the low voltage side. On the high voltage side, I get ±160v DC but nothing on the low voltage. I am unable to find the part number of the transformer. The transformer is green and the number on top shows: XR909 A T64.

     

    Anyone know a replacement part number for that transformer?

     

    Thanks.

  2. Posted

    1 hour ago, Bratwurst said:

    I'd thought of doing this for a Neo Geo with bad sync output but was able to source a donor board to rob the replacement chip from it, so never bothered to try. With no explicit data sheet available that outlines what is going on in the chip die (because custom Nintendo package) there'd be a lot of guess work and trial and error.

    Indeed. I don't mind trying. I only need a schematic to built a 15kHz signal generator that can replicate the one on the SNES. I have a working SNES to compare the signal to. You don't have such a schematic by any chance?

  3. Posted

    As I suspected, on the defective SNES, I get no signal on pin 100 of PPU2 U3. When I compare to a working SNES (See picture), which gets a 15kHz signal on pin 100.

     

    Does anyone know if it would be possible to create a replacement 15kHz RSYNC using an external circuit? Would it work?

     

    Thnaks.

    PPU2 Pin 100.jpg

  5. Posted

    On 4/8/2020 at 8:02 AM, Bratwurst said:

    This model of SNES is notorious for failing video sync, possibly related to the BA6592F chip or other components in the video amp circuit or somewhere along the way through to the multi-out connector. An RGB cable probably will not fix the issue.

     

    Test the RF-Out connection.

    Do you know if pin 100 of U3 is the one doing the video sync?

  6. Posted

    I checked all the lines for the PPUs and RAM and everything looks fine. I also checked the grounds and VCC and they also llook fine. When I look at the electric diagram, I see pin 100 of PPU2 U3 that says CSYNC that goes to both the RF Module and the AV out connector. Does anyone know if that is what is used to sync the image on the TV? If U3 is not sending the correct signal out of pin 100, could that be the issue?

     

    Thanks.

  7. Posted

    4 hours ago, Bratwurst said:

    This model of SNES is notorious for failing video sync, possibly related to the BA6592F chip or other components in the video amp circuit or somewhere along the way through to the multi-out connector. An RGB cable probably will not fix the issue.

     

    Test the RF-Out connection.

    I have the same issue with RF.

  8. Posted

    10 hours ago, Thomas83Lin said:

    It looks like a sync issue too me, it's weird that you have the problem using composite. I normally see this with rgb when the sync isn't properly connected. I suspect a problem with a cap or the video chip. I think a good test would be to try RGB using Csync. if it still doesn't work most likely it would be the video\rgb chip.

    Do you know a good RGB Mod for the SNES?

  9. Posted

    6 minutes ago, Tanooki said:

    I've read of rare cases of CPU failure.  If it's not the RAM or PPU maybe you have something else messed up, small cap, resistor, a rotting trace, something is up.  Also the duh moment would be swapping out a fresh ac adapter(OEM) and video cable (RF and RCA to check both ports.)

    I have tested with a different PSU and cables. I have another SNES that works fine with the all my cables and both PSU that I have. Since I have the same issue with RF and RCA, the issues seems to be elsewhere.

     

  10. Posted

    2 minutes ago, Tanooki said:

    I'm wondering if it's a power issue or your chip(s) on board are failing.  Something isn't adding up.  Oh and Starfox uses the larger board FX1, it does demand a hair bit more power than a normal game but that shouldn't matter like it could with the SD2SNES.

    Power looks good according to the meter. Which of the chips could be causing the issue? Does not look like a RAM or PPU issue from what I saw on Youtube, but I could be wrong. Since all the tests pass on the diagnostic, I am not sure what what to look at next! It seems like there is something wrong with the video output.

  17. Posted

    Not sure were to post this.

     

    I have a SNES with the image continually flickering. The keeps going up, down, up, down like when we had an old TV with rabbit ears that was not properly adjusted. (See video)

    I have already checked the power, AV cables, replaced all the capacitors, try to adjust the little screw near the oscillator crystal, replaced the oscillator crystal and I keep getting the same issue with RF, composite and component cables.

    When I manage to run the test cartridge, all systems pass the test. I get no Fails.

    Any ideas what to look at next?

  19. Posted

    Hello,

     

           I know that I am in the Genesis section, but can't seem to find a SNES section. I have a SNES that had no video but the sound was working. After looking at the schematics and doing some diagnostic, I found out that D1 was dead. I've replaced the diode and now I get the image but it's continuously flickering (See attached video). I've managed to run a burn-in test and everything passes.

     

          I am thinking that I may have a bad capacitor somewhere. I am looking at ordering a replacement kit but I would love to have a second opinion on this issue.

     

    Thank you.

    IMG_20200222_131401.jpg

  21. Posted

    2 hours ago, ChildOfCv said:

    You should probably actually connect it to the inner side of C88 (relative to the RF box) instead.  As mentioned, C100 (under the RF box) separates the C88 point from pin 2, and pin 2 exposes you to the oscillator that modulates sound for the RF.  C100 also acts as an attenuator, so your sound may not be as strong there.  If you do use pin 2 though, then yeah use a capacitor, like maybe that 10uF that you pulled from your other circuit.  Again, + side towards pin 2

    I used pin 2 of the RF box with a 10uF capacitor and it works great. Image and sound are crystal clear. Completed reassembly and cleaned the two very dirty controller that came with the console and voilà! Just like new, well... almost ;)

     

    Once again, thanks for helping revive this dead console and saving it from the scrap yard.

    IMG_20200118_165248[1].jpg

    • Like 2

  22. Posted

    3 minutes ago, ChildOfCv said:

    In fact, for building the minimum circuit that will "work", leave out C1 and C2.  The circuit will do its basic job without either.  C1 is intended to improve the response so that it outputs a more accurate signal.  C2 is intended to smooth power and clean up issues related to temporary higher power requirements.  But the most basic circuit has only R1, R2, C3, and (R3/R4).  And power and ground, of course.

     

    Also, if you soldered this all together rather than beginning with a breadboard, make sure you don't have any solder bridges.

    Replaced C2 with the 85nF and it works. Super clear and sharp image.

     

    For the Audio, should I connect the RCA directly to pin 2 of the RF box or should I put a capacitor or some other component between pin 2 and the RCA connector?

  23. Posted

    3 minutes ago, ChildOfCv said:

    Looks like you just have a 12V oscillator.  Did you build the circuit yourself, or do you have a local source for one of the pre-built ones?  We may need to look at the wiring.  Also, the datasheet for the 318 says that C2 should be 0.1uF, which should be easier to find as a ceramic.  So I don't know where they came up with the idea that 10 would be an improvement.

     

    Make sure the electrolytics have the correct polarity in your circuit.  The + on the 470 needs to face pin 6, the minus on the output side.

    Purchased the parts and build it myself. C3 - pin is facing the 75 ohm resistor and the + side is on pin 6. For C2, I have some ceramic 85nF on hand, would that work or should I go back to the store and get 0.1uF?

     

    The IC I got from the store is a LM318P

     

    I checked the schematic, and everything appears Ok.

  24. Posted

    10 hours ago, ChildOfCv said:

    You're correct.  Pin 2 of the RF box should give you exactly what the sound modulator is seeing, but it would also mess with/weaken the RF audio output and may also collect artifacts from the audio modulation circuit.  C88 is on the other side of a capacitor from the RF box, so better protected from that.

     

    It may still be better to have an audio buffer between the AV out and C88 though, but nobody seems to bother.

    I may need your guidance once more.

     

    I followed the schematic but replaced C3 with a 470uF as you mentioned and put a 10uF at C2. Unfortunately, the store did not have any ceramic 10uF so I got the electrolytic one for now. I don't get an image when connecting to the TV. I took some oscilloscope reading on the input at pin 6 of the RF box and the RCA output. The input signal seems different when the AV Mod is connected. I don't know if it's normal.

     

     

    Input AVMOD.jpg

    Input no AVMOD.jpg

    RCA Output.jpg

  25. Posted

    2 hours ago, nick3092 said:

    A friend of mine actually designed that mod many years ago. At the time I don't think he knew that was the best place to pull the audio from. Although back then, I don't think it mattered because it mainly affects the SGM, and it didn't exist back then.

     

    I believe the preferred spot now days is to pull audio from the leg of C88 closest to the modulator. As I understand, pulling it from the chip directly causes low volume on anything from the expansion port (module 1 or SGM - but since module 1 doesn't mix with the Coleco sound the way SGM does, it doesn't matter as much for that). Not sure if pulling it from the RF box pin header/connector causes the same issue.

    I will try it. I will get the missing components tomorrow and try to built it this week end. I'll keep you posted on my progress.

     

    Thanks.

     

    Daniel

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