Results 1 to 6 of 6

Thread: Colecovision - suspected bad Rf modulator- no video, slight hum.

  1. #1
    Insert Coin (Level 0)
    Join Date
    Mar 2016
    Posts
    6
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Default Colecovision - suspected bad Rf modulator- no video, slight hum.

    I picked up a colecovision, but when I hook it up I get no video, and a slight audio hum. The video doesn't change at all, I just get the fuzz from channel 4. The audio slightly changes when powered on.

    I have basic soldering skill, but not sure what to tackle. I checked the power supply with another coleco and it works fine.

    My question is, would the composite mod bypass this and fix the issue? If so, that might be easier than trying to desolder the Rf board and find the issue.

    Any other thoughts on what to check?

    Thanks

  2. #2
    Great Puma (Level 12) Steve W's Avatar
    Join Date
    Jun 2006
    Location
    DFW Metroplex, Texas
    Posts
    4,385
    Thanks Thanks Given 
    42
    Thanks Thanks Received 
    30
    Thanked in
    27 Posts

    Default

    I'm not an expert on Colecovisions, but it could be a number of issues. I don't often hear about RF modulators going out, I mostly hear about chips going bad (have one with that problem, it has lots of graphics glitches) or sometimes the power switch needs work.

  3. #3
    Insert Coin (Level 0)
    Join Date
    Mar 2016
    Posts
    6
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Default

    Quote Originally Posted by Steve W View Post
    I'm not an expert on Colecovisions, but it could be a number of issues. I don't often hear about RF modulators going out, I mostly hear about chips going bad (have one with that problem, it has lots of graphics glitches) or sometimes the power switch needs work.
    I've tested the voltage coming off the switch in the on position and I get a consistent 12v and 5v off each side. As far as I'm concerned the power source and switch are ok.

    I figured I'd try the composite mod first, then failing that replace the Ram chips.

    Anything else to check other than broken traces?

    I thought I'd try hook up audio direct from the sound chip and see if my TV detects it, that tells me if the issue is just Output, or maybe something else.

  4. #4
    FPGA arm-based system Custom rank graphic
    bb_hood's Avatar
    Join Date
    Aug 2003
    Location
    Rhode Island
    Posts
    2,091
    Thanks Thanks Given 
    46
    Thanks Thanks Received 
    23
    Thanked in
    21 Posts
    PSN
    bb_hood99

    Default

    Quote Originally Posted by amace View Post
    As far as I'm concerned the power source and switch are ok.
    .
    Check the power-on/off switch. Thats the problem with 95% of colecos... it happens to all of them at some point.

    Ive owned at least 10 colecos, only one was working when I got it. The rest had broken power switches.

  5. #5
    Pretzel (Level 4) APE992's Avatar
    Join Date
    Jun 2007
    Location
    Chico, CA
    Posts
    999
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts
    Xbox LIVE
    APE992

    Default

    There are more voltages than 12v and 5v, I believe there is a -12v rail as well you should check.
    I fix things. You name it, I'll work on it. Want something modded? Recapped?

  6. #6
    Insert Coin (Level 0)
    Join Date
    Mar 2016
    Posts
    6
    Thanks Thanks Given 
    0
    Thanks Thanks Received 
    0
    Thanked in
    0 Posts

    Default

    Following up on this (quite a while later, but oh well).

    Turns out it was the channel selector switch in the RF Board. Something wasn't right, I reflowed all the connections and I started getting crappy video. Sometimes B&W, sometimes not. I realized then it cleared up when I took the case off and was able to apply pressure to the RF cable itself, so that told me there was a loose connection of some type. Went back and made sure every single connection was well soldered, with nothing grounding itself that shouldn't be grounded, and voila! It works.

    While I was at it, I installed a composite mod, so I'm getting decent (as decent as the CV can output) video and audio now.

Similar Threads

  1. Suspected/Confirmed GCD Reprints
    By backguard in forum Classic Gaming
    Replies: 25
    Last Post: 05-02-2006, 06:19 PM
  2. My wonderswan collection (slight bragging)
    By djbeatmongrel in forum Classic Gaming
    Replies: 15
    Last Post: 03-23-2005, 09:57 AM
  3. Suspected Pirate MegaDrive, Confirmation please?
    By Epicenter in forum Classic Gaming
    Replies: 42
    Last Post: 05-30-2004, 04:25 AM
  4. Suspected DP Forum Criminals. WANTED! Read Inside.
    By digitalpress in forum Classic Gaming
    Replies: 42
    Last Post: 01-03-2003, 02:28 PM

Posting Permissions

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