Hi all. I have an original equipment Delco AM/FM Stereo Radio from a 1994 Chevrolet Full Size Blazer (I bought it new) that has recently started to give me intermittent problems. About a month ago, the issues were sporadic and tolerable and would solve themselves with a power off and back on of the radio power button. That isn't working anymore like it used to.
The radio system has two main parts. The control head, with the display and control buttons, which is mounted in the dash, and the CDM (the brain of the system, model number 16169561) mounted under the dash and hidden from view. The CDM has plug-in connections for the upper control unit, an equalizer, a cassette deck, and the four speaker outputs.
The initial problems started out with the display not changing with the input buttons. The volume level indicator (small downward pointing triangles in a row-see pic) used to raise up and down (move left or right on the display) with the push button volume control; the clock used to work but now it stays at 1:00; the radio station frequencies used to show up on the display when the stations were changed but now it stays on 98.1; the clock used to be able to be set, etc. Additionally, the power button used to turn the radio on and off and it is getting increasingly difficult for that to work now as well.
Here is what I have done so far: I have read that the issue is with the Radio CDM that is under the dash. I have seen where repair facilities identify this as the problem component in the system with the issues I am having and it does not look like it is a rare problem. Many others have had the same issues as I am having. I have removed and inspected the CDM for bad solder connections. I have re-flowed most of the solder connections that would typically cause solder joint issues. I have removed and replaced the nine Electrolytic Capacitors with new. I have looked at all of the other components on the PCB and have not found anything that would visually indicate a problem component...no burns, leakage, or other visible damage to anything on either side of the board. The plug-in connections are not corroded or rusted and look to be in good condition. I have tested each pin connection and followed it to the first component location the pin would contact and I have continuity from each pin. I do not have a schematic of the board and do not know if one is available. I have looked for one.
I do not have sophisticated testing equipment and am simply a novice when it comes to these things, but I have gotten lucky several times before and that is why I am here now and that is to seek your advice as to what to test or look for next. I would rather keep the system original, although I do know there are used replacement CDM's available, and I can send this one in for repair, if I can't figure this out with your help.
Additionally, there is a small blue box component I am not able to identify. The markings show "SFH 450 F3 Cm C." A pic is attached. Is that possibly a relay of some sort? The other larger black box is a relay and I have removed and tested it for proper operation. It works as it should. I have not removed the blue one. The reason I am curious about the blue one is in the case of a failing/failed relay, it may not be allowing the proper signals to get to the control head to utilize the power and control buttons??? Just guessing here.
Sorry this is so long, but I figured I would give you as much info as I had from the beginning. There are pics attached too. I can take better ones, or more specific ones of the board, if needed. Thanks, in advance for any helpful replies. I am hoping someone out there has experience with this particular unit and can point me in the right direction for component replacement.
The radio system has two main parts. The control head, with the display and control buttons, which is mounted in the dash, and the CDM (the brain of the system, model number 16169561) mounted under the dash and hidden from view. The CDM has plug-in connections for the upper control unit, an equalizer, a cassette deck, and the four speaker outputs.
The initial problems started out with the display not changing with the input buttons. The volume level indicator (small downward pointing triangles in a row-see pic) used to raise up and down (move left or right on the display) with the push button volume control; the clock used to work but now it stays at 1:00; the radio station frequencies used to show up on the display when the stations were changed but now it stays on 98.1; the clock used to be able to be set, etc. Additionally, the power button used to turn the radio on and off and it is getting increasingly difficult for that to work now as well.
Here is what I have done so far: I have read that the issue is with the Radio CDM that is under the dash. I have seen where repair facilities identify this as the problem component in the system with the issues I am having and it does not look like it is a rare problem. Many others have had the same issues as I am having. I have removed and inspected the CDM for bad solder connections. I have re-flowed most of the solder connections that would typically cause solder joint issues. I have removed and replaced the nine Electrolytic Capacitors with new. I have looked at all of the other components on the PCB and have not found anything that would visually indicate a problem component...no burns, leakage, or other visible damage to anything on either side of the board. The plug-in connections are not corroded or rusted and look to be in good condition. I have tested each pin connection and followed it to the first component location the pin would contact and I have continuity from each pin. I do not have a schematic of the board and do not know if one is available. I have looked for one.
I do not have sophisticated testing equipment and am simply a novice when it comes to these things, but I have gotten lucky several times before and that is why I am here now and that is to seek your advice as to what to test or look for next. I would rather keep the system original, although I do know there are used replacement CDM's available, and I can send this one in for repair, if I can't figure this out with your help.
Additionally, there is a small blue box component I am not able to identify. The markings show "SFH 450 F3 Cm C." A pic is attached. Is that possibly a relay of some sort? The other larger black box is a relay and I have removed and tested it for proper operation. It works as it should. I have not removed the blue one. The reason I am curious about the blue one is in the case of a failing/failed relay, it may not be allowing the proper signals to get to the control head to utilize the power and control buttons??? Just guessing here.
Sorry this is so long, but I figured I would give you as much info as I had from the beginning. There are pics attached too. I can take better ones, or more specific ones of the board, if needed. Thanks, in advance for any helpful replies. I am hoping someone out there has experience with this particular unit and can point me in the right direction for component replacement.