Results 1 to 9 of 9

Thread: CM8833 Black screen

  1. #1
    Amibayer! dougal's Avatar
    Join Date
    Nov 2009
    Country
    Malta
    Age
    38
    Posts
    2,436
    Feedback
    50 (100%)

    Default CM8833 Black screen

    I've got a Philips CM8833 which used to work perfectly until about a year or two ago.

    Rather than throw it away I kept it in my garage. I'd love to fix it but don't really have any experience with repair of CRT's.

    The problem is that there is a totally black display. No light, nothing.

    The monitor power light comes on and sound works from the speakers but no image.
    A4000D '040@33mhz 16MB OS3.9 Picasso II - A2000'030@25Mhz 8Mb KS3.1 - A1200 '030@50Mhz 64Mb OS3.9 - A600 2Mb Chip + 4Mb fast ,2gb CF HD KS/WB 3.1 - A500 Plus 2mb chip + 2mb A590 + Gotek - CD32 + Analogic FDD - CDTV With joy/mouse ports

  2. #2
    Beavis's Avatar
    Join Date
    Nov 2013
    Country
    Netherlands
    Region:
    South
    Posts
    551
    Feedback
    57 (97%)

    Default

    Philips is quite infamous about bad solder joints, so you should check the board first.
    When the power is on, and you move your hand close to the screen, do you feel something like hairs getting drawn to the screen or not?
    Hard to explain, but I hope you get the drift.

  3. #3
    Amibayer! Marmes's Avatar
    Join Date
    Sep 2011
    Country
    Portugal
    Region:
    Amadora
    Posts
    1,738
    Feedback
    226 (100%)

    Default

    wich monitor is it mk1 or mk2?
    if you have a soldering iron, just resolder as Beavis said. If that doesn't work, go to a tv shop repairer, it will be better.

  4. #4
    Amibayer! dougal's Avatar
    Join Date
    Nov 2009
    Country
    Malta
    Age
    38
    Posts
    2,436
    Feedback
    50 (100%)

    Default

    Its a mk1. Where should I check for cold solder ?
    A4000D '040@33mhz 16MB OS3.9 Picasso II - A2000'030@25Mhz 8Mb KS3.1 - A1200 '030@50Mhz 64Mb OS3.9 - A600 2Mb Chip + 4Mb fast ,2gb CF HD KS/WB 3.1 - A500 Plus 2mb chip + 2mb A590 + Gotek - CD32 + Analogic FDD - CDTV With joy/mouse ports

  5. #5
    Beavis's Avatar
    Join Date
    Nov 2013
    Country
    Netherlands
    Region:
    South
    Posts
    551
    Feedback
    57 (97%)

    Default

    Quote Originally Posted by dougal View Post
    Where should I check for cold solder ?
    That's easy, everywhere.
    But check the flyback circuitry first, when there's a bad joint, it will start arcing, and cause more damage.
    You didn't answer my question though, is there any HV present?

    Oh, and I assume that you already knew that the HV in a monitor can be lethal, but I'm telling you anyway.
    And what Marmes said, if you're not sure, or lack some skills, better take it to a repair shop.

  6. #6
    resistance is futile! Amibayer! roy_bates's Avatar
    Join Date
    Dec 2011
    Country
    england
    Region:
    birmingham
    Age
    49
    Posts
    8,308
    Feedback
    98 (100%)

    Default

    did you ever fix this?

    can you take the back off and take a picture of the main board from the rear with the tube neck pcb also in shot,if its the same as mine i can take a look at it for you if you send me all the pcb's in the monitor,itll save on shipping.

    it can be the mk1 or mk2,it wont matter to me...

    give it a few weeks though im recovering from surgery...
    Last edited by roy_bates; 12th June 2015 at 08:06.
    i have got too much hardware,it would only hurt your eyes to look at it here

  7. #7
    Amibayer! dougal's Avatar
    Join Date
    Nov 2009
    Country
    Malta
    Age
    38
    Posts
    2,436
    Feedback
    50 (100%)

    Default

    Never really continued on this. I'll try and take a look this weekend and post back
    A4000D '040@33mhz 16MB OS3.9 Picasso II - A2000'030@25Mhz 8Mb KS3.1 - A1200 '030@50Mhz 64Mb OS3.9 - A600 2Mb Chip + 4Mb fast ,2gb CF HD KS/WB 3.1 - A500 Plus 2mb chip + 2mb A590 + Gotek - CD32 + Analogic FDD - CDTV With joy/mouse ports

  8. #8
    GKJetpack's Avatar
    Join Date
    Aug 2017
    Country
    Denmark
    Region:
    South
    Age
    39
    Posts
    1
    Feedback
    0

    Default

    I have the exact same problem... black screen and a whistling noise from the main PCB near the flyback.


    I checked the BU508 transistor for short, but it was all good. Then I ordered a replacement of the flyback, got the HR 7506 and after mounting this I got the HV back on.


    But, the screen is getting all white and there is a sound of something is getting saturated. ( The tube warm up time is like normal, but the screen is getting all white )


    Videosignal is not be shown on the screen. ( can't remember if the sound is good, but I thinks so )


    PSU voltages are measured and they are only a little of nominal values.


    What am I missing ?

  9. #9
    Only Amiga..... fordav1's Avatar
    Join Date
    Aug 2014
    Country
    Australia
    Region:
    WA
    Posts
    148
    Feedback
    0

    Default

    I have bought many replacement flybacks over the years and every one has been shipped with the screen control turned up full. That basically over-volts the neck board and tube RGB guns by 2 to 3 times and can blow up the neck board or tube or both. With it up full you'll get a very bright white screen and some HV noise and arcing on the neck board. Turn the screen control pot (on the flyback) all the way down (maximum turn counter-clockwise) then adjust it as required slowly. Usually it only needs a very small turn clockwise and it is enough.
    It that doesn't help then you simply have some other issue. You should start by changing all the caps because dry shorted caps can cause many problems. Plus, they are all 30 years old so should be changed anyway. Or pull each one and test it in a cheap chinese cap tester available on the other bay for a few bucks. if changing the caps still doesn't fix it then start looking closer and testing parts (transistors/resistors/pots etc). All those Amiga monitors can be fixed no matter how bad the problem, it just takes time to go through it.
    A4000,A3660,IndAGA4k,AriadneII,BIGRAM256,DenebUSB A3000,A3640,PicassoIV,XSurf100+RRoad,A2386,A1011 A2000,AdSCSI2080/8MB,A2286,A1010 A2000,A2630,A2091,GoldnGate A1000 A1200,eMatrix 030/50+32M,8G CF,Gotek A500(x9) A500+,Kipper2k 8MB+8GB CF A600 C64+1541(x5) C128D+1541U2 SX64(x3) ColecoVision A2600 N64 Saturn(x3) MasterSystemII MegaDriveII Dreamcast(x2) XBox PS1 PS2(x3) C= Monitors=13

Similar Threads

  1. Black screen breadbin 64
    By Aysel in forum AmiOracle
    Replies: 20
    Last Post: 22nd May 2014, 22:04
  2. Philips CM8833-II Banding on Black Screen
    By Simon_G in forum AmiOracle
    Replies: 7
    Last Post: 24th May 2012, 10:27
  3. C64 Black screen on power on
    By Wolfy in forum AmiOracle
    Replies: 5
    Last Post: 3rd May 2012, 05:02
  4. cd32 black screen
    By Justin in forum AmiOracle
    Replies: 11
    Last Post: 19th November 2010, 14:36

Tags for this Thread

Posting Permissions

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