Quantcast

Page 130 of 130 FirstFirst ... 3080120126127128129130
Results 1,936 to 1,947 of 1947

Thread: GUIDE: Telling apart good Genesis 1s and Genesis 2s from bad ones.

  1. #1936
    isolated enthusiast Death Adder's minion Heavy Viper's Avatar
    Join Date
    Apr 2014
    Location
    Western Australia
    Posts
    14
    Rep Power
    0

    Default

    Yup! Cleaning the slider with some isopropyl was my first port of call - I usually go for the easy fix first. :V

    I'll take a look at that 1uF cap over the weekend when I have some spare time. As an aside, I did dig up this thread from AtariAge during my googling, and the issue sounds remarkably similar. Could it be the volume slider itself that's gone? Would there even be a way to check without actually doing a swap from a donor board?

  2. #1937
    Creator of the Mega Amp Raging in the Streets Ace's Avatar
    Join Date
    Jun 2008
    Location
    Montreal, QC, Canada
    Age
    27
    Posts
    3,706
    Rep Power
    41

    Default

    You should be able to take some resistance measurements with a multimeter. Set it to resistance mode (ohms, indicated by an Omega symbol) then poke around the slider to see if the resistance changes as you move it. If you see the resistance doesn't change or is extremely jittery, you will need to replace the slider.
    HATES ATGAMES WITH A PASSION


    Mega Amp: An all-new audio circuit for your Sega Genesis/MegaDrive and clones.

    Note: If you want to contact me on Skype, identify yourself or your contact request will be rejected.

  3. #1938
    isolated enthusiast Death Adder's minion Heavy Viper's Avatar
    Join Date
    Apr 2014
    Location
    Western Australia
    Posts
    14
    Rep Power
    0

    Default

    Okay! Spent some time tonight to take some measurements of the slider and the 1uF cap on the faulty VA4. For comparison, I took measurements from another Japanese VA4 board I managed to land with working sound.

    --------
    GOOD VA4:

    - 1uF cap: 17.93k ohms (slider max) -- 25 ohms (slider min.)

    - Slider: MAX setting - 25 ohms / MIN. setting - 17.93k ohms

    FAULTY VA4:
    - 1uF cap: 30.4k ohms (slider max) -- 75.9k ohms (slider min.)

    - Slider: MAX setting - 37 ohms / MIN. setting - 45.5k ohms
    --------

    I did do some checks while moving the slider as well, but I'm hesitant to trust them given the shaky claw grip I had to keep the probes in place. :B For what it's worth, the readings did seem smooth on the faulty VA4's slider.

    At this point I'm leaning towards the slider, given the readings there.

  4. #1939
    Wildside Expert
    Join Date
    Sep 2014
    Location
    Conservative enclave in California
    Posts
    167
    Rep Power
    7

    Default

    The 1uF cap's impedance looks awfully high (almost 2x higher than the 'good' VA4 on max slider) so I'd replace that for good measure.

  5. #1940
    isolated enthusiast Death Adder's minion Heavy Viper's Avatar
    Join Date
    Apr 2014
    Location
    Western Australia
    Posts
    14
    Rep Power
    0

    Default

    Hm, I'll leave this on the backburner for now. Made an attempt to get the 1uF cap off but just could not get the solder out of one of the holes. Might be a bit above my skill level, looking at it. Thankfully I at least have one with decent HP audio.

    Thanks to y'all for the feedback/ideas, regardless!

  6. #1941
    isolated enthusiast Death Adder's minion Heavy Viper's Avatar
    Join Date
    Apr 2014
    Location
    Western Australia
    Posts
    14
    Rep Power
    0

    Default

    Quote Originally Posted by Heavy Viper View Post
    Hm, I'll leave this on the backburner for now...
    ...and it came off the backburner today! And it turns out it was the slider! Seems it was my iron temperature that was too low, not my skill level. :V

    I replaced the 1uF cap first (C58), which sadly made no difference: still distorted and loud out of the HP jack, no response from the slider. I then went about removing the volume slider, and took measurements while it was removed:

    "Bad" slider: minimum setting - 45.2k ohms // maximum setting - 33 ohms

    Compare this with the replacement slider, taken from an Asian PAL VA6:

    "Good" slider: minimum setting - 44.3k ohms // maximum setting - 18 ohms

    Once the replacement was soldered in place, I fired it up with headphones plugged in and the slider at minimum. Nothing! Until I slowly moved the slider up and got nice, steady, clean output. ;3

    So yeah - slider was busted! Quite chuffed I managed to fix up my new "lucky" VA4. Not sure what happened to cause the problem, though - first time I've seen it. Hopefully it was just some idiot plugging power into the jack or something.

  7. #1942
    Hedgehog-in-Training Hedgehog-in-Training JamesF's Avatar
    Join Date
    Sep 2017
    Posts
    16
    Rep Power
    0

    Default

    Hi fellows, I've been waiting for a month for activation but I finally got activated to join this great site!

    I in the last few years I was an active member of the Vogons site which is the official forum of DOSBox emulator and retro PCs;
    My hobby lead me to acquire few real hardware Pentium 1 machine and Sound Blaster cards to have the real deal to compare with DOSBox, and there was indeed not-so-small difference between the real hardware and dosbox emulation.

    I acquired my very first Sega Genesis systems last month which are Model1 VA6 and Model2 VA4 along with Mega Everdrive X5, to play with and compare to emulators which I play for almost 15 years now.
    And indeed there was differences between the hardware and emulators mainly in audio emulation and smoothness of gameplay, but the differences are smaller than in DOSBox vs real PC especially with Genesis Plus GX emulator in Retroarch.

    Now for a technical question.
    Can someone please list the deficiencies of Model2 VA4 in the Sound department compared to Model1 VA6?

    Thanks!

  8. #1943
    Wildside Expert
    Join Date
    Sep 2014
    Location
    Conservative enclave in California
    Posts
    167
    Rep Power
    7

    Default

    Welcome JamesF!

    Well the Model 2 VA4 has some excessive low-pass filtering implemented on its onboard sound mixing/amplification circuit. When compared side by side the Model 2 VA4 sounds noticeably more muffled. On my VA4s I also noticed some clipping on loud sounds too. Other than that it's not THAT bad, and it still sounds much better than pre-VA2 Model 2's.

    One thing though, Model 2's of VA0~1.8 and VA3 and later use an ASIC FM which has less YM2612 FM quantization noise, which may subtly (or in some cases, not-so-subtly) alter the timbres of some games that deliberately try to modulate this noise. Whether this matters is up to personal taste.

  9. #1944
    Hedgehog-in-Training Hedgehog-in-Training JamesF's Avatar
    Join Date
    Sep 2017
    Posts
    16
    Rep Power
    0

    Default

    Hi Eep386!

    To my ear the YM2612 has more prominent "ladder effect" distortion that sounds like a BZZZzzzzzshh type of sound when notes decay or quiet notes.
    But on the YM3438 it still exists but much more restrained and quieter in relation to the decaying note, although still not as clean as an emulator.

    Indeed the Model2 VA4 is more filtered (2nd-order lowpass) but frankly I like how it sounds better than the Model1 because PCM sounds have terrible quality on the Genesis and benefit greatly from higher order lowpass filtering.
    Moreover, most of my friends in the 90s had Model 2 which I'm more familiar with, although I don't recall distortion or noise from back then mainly because everyone played through low quality TV speakers.

    Can you please share on what loud sounds you hear clipping on the Model2 VA4?
    Sega Genesis Model1 VA6 & Model2 VA4 + Mega Everdrive X5

  10. #1945
    Hedgehog-in-Training Hedgehog-in-Training JamesF's Avatar
    Join Date
    Sep 2017
    Posts
    16
    Rep Power
    0

    Default

    I just got my Composite cable, now I see and remember how the Genesis looked back then, with dithering and jaggies like it should.
    Genesis games use so much dithering that many objects look like a bunch of vertical lines, it actually a big improvement using the Composite output instead RGB, IMO.
    I will not use the Scart(RGB) cable anymore besides for testing because it looks too much like an emulator.
    Sega Genesis Model1 VA6 & Model2 VA4 + Mega Everdrive X5

  11. #1946
    Raging in the Streets Thierry Henry's Avatar
    Join Date
    Dec 2008
    Location
    SA
    Posts
    2,501
    Rep Power
    75

    Default

    Quote Originally Posted by JamesF View Post
    it's actually a big improvement using the Composite output instead of RGB, IMO.

    Quote Originally Posted by soviet View Post
    We believe! SEGA Empire will live again, like the Jews re-establish their Israeli, GOD will never forget his people, SEGA will never forget his fans.

  12. #1947
    Hedgehog-in-Training Hedgehog-in-Training JamesF's Avatar
    Join Date
    Sep 2017
    Posts
    16
    Rep Power
    0

    Default



    Yeeesss.. Composite has MORE colors on screen without ugly jailbars all over the picture, but it's less sharp.

    I should add that the previous user of my Model1 VA6 never even used the DIN output jack, only the RF, as the RF was scratched and beat around it while the DIN was in pristine condition.
    Sounds strange but how much people (kids) back in the 90s used the RGB output of the Genesis/Mega-Drive?; Not very much I assume.
    It's only in recent years the 'kids' can read about RGB on the internet and afford a BVM, for the perfect Genesis experience, but far from nostalgic.

    Don't negate the possibility that developers actually intended the games to be seen using the Composite signal of the Sony CXA1145, or worse, the RF signal.
    Last edited by JamesF; 10-13-2017 at 03:23 AM.
    Sega Genesis Model1 VA6 & Model2 VA4 + Mega Everdrive X5

Thread Information

Users Browsing this Thread

There are currently 3 users browsing this thread. (0 members and 3 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •