Radio headphones

Thread Starter

Kevinmatth

Joined Jul 4, 2021
30
I have a pair of earphones that have the radio built-in. I have watched a few videos on PCB's and some guy repairing a pair of honywells that like mine but beyond that I don't know much about boards and troubleshooting. I have a multimeter and have verified that the batteries are good and now I am trying to determine if the power from the batteries is making it to the wires and I can't figure out which wires the power should be going to. Does anything jump out at anyone about this?
 

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Thread Starter

Kevinmatth

Joined Jul 4, 2021
30
I have had these for many years but the radio stopped working several years ago. I have just been using them as ear protection ever since with no radio but recently I started becoming interested in repairing them. I took both sides of the earmuffs apart and checked the continuity between the six different colored wires from one side to the other. I believe two of the wires did not have continuity but I cannot remember which colors did not. After watching the video of this guy repairing a similar pair, I figured I better check the power supply first to see if power is even getting out I just don't know how to distinguish where the power is going. I set my multimeter to DC and checked the batteries then I tried to check different points on the board pictured above to see if I could get the total 3 volts from the 1.5 volt batteries somewhere on the board. I see the only one that I recognize is the ground but past that I don't know what those markings mean if someone could teach me about it I am very interested to learn about it. Thank you.
 

LesJones

Joined Jan 8, 2017
4,174
look at the other side of the board where the batteries are mounted. Follow the tracks from the battery connections to where the wires are connected. The two wires that connect to these two tracks are the power wires. Check the voltage between these two wires first at the battery end then at the other end. There is a good chance that some of the 8 pin ICs are audio amplifiers. Google the part numbers of these ICs to find the datasheets for these ICs The datasheets will tell you which are the power supply pins of these ICs so you cna then check if there is power getting to these ICs..
Have you noticed that the LCD display seems to be cracked ?

Les.
 

Thread Starter

Kevinmatth

Joined Jul 4, 2021
30
The LCD looks cracked on the picture but in person you can't feel any breaks or cracks in it it almost looks like stress marks or maybe just markings from being knocked around. Correct me here but is this kind of where it looks like the wire is going from the battery? If that trace is correct and it is the positive, which one of those points would you check for the neutral?
 

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LesJones

Joined Jan 8, 2017
4,174
Scrape some of the solder resist from the large are of copper to the right of Q108 so you can make contact between you meter negative probe and the copper. Measure the voltage between this point and the top right connection on Q108. I would expect a reading of 3 volts. Are there any controls such as the on/off switch on the side containing the battery ?
What does the left hand end of the flat grey cable connect to ?

Les
 

Thread Starter

Kevinmatth

Joined Jul 4, 2021
30
I will try what you are saying on the one that I see that says Q100 when I get home tonight at 7:00. Also I don't know what IC's are.

I will also let you know what that flat gray cable goes to.
 

Thread Starter

Kevinmatth

Joined Jul 4, 2021
30
There is right about 3V coming in right where you said and the flat grey wire doesn't plug into anything. Where would the power be coming into on the other headphone.
 

Thread Starter

Kevinmatth

Joined Jul 4, 2021
30
I take that back on the LCD screen, I can feel the cracks in it so it is cracked. Which I don't need the screen if I can just search stations on it still. Unless that would be repairable too I would like to try to fix it.
 

Thread Starter

Kevinmatth

Joined Jul 4, 2021
30
The on/off switch and other controls are on the opposite side of the battery. How does the power get over to that on/off switch?
 

Thread Starter

Kevinmatth

Joined Jul 4, 2021
30
I am probably making this extra difficult to get a full picture of how this thing is setup. Here are maybe some better pictures so you can see an overview. These are in order.
 

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LesJones

Joined Jan 8, 2017
4,174
Now we know that there is no physical switch on the battery side of the headphones (I suspect this is the left side. Am I correct ?) there must be a conductor from each side of the battery in the 6 core cable to the other side of the headphones. So do as BobTPH suggests in post #14 to confirm that the battery connections get to two conductors in the cable on the battery side of the headphones.
I am now guessing that the board on the end of the flat grey cable is a step up converter to provide the higher voltage required for the varicap diodes in the front end of the receiver section. (This is from the +VCC_tune label on the brown wire.)
Telling us what the labels are on the PCB under the black, white and yellow wires would be VERY helpful to try identify which one connects to the battery positive. I THINK the blue is probably connected to the battery negative. (Am I correct ?)
Is the on/off switch a physical switch or is the microcontroller left is sleep mode and woken up by pressing some sequence of buttons ?

Les
 

LesJones

Joined Jan 8, 2017
4,174
You have the advantage over us in that you can move the wires to read the text. We can only work from the pictures. I can see a + at the end of the text under the yellow wire, What is the complete text. You have not told us what the text under the white wire says. You say that the blue wire connects to the battery terminal but you do not say which terminal. ( + or -)
If we had the had the item in front of us it would only take seconds to get this information but getting the FULL information from you is taking days.

Les.
 
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