Copper Talk » Ask The Tech » Microphone Wiring » Wiring a Workman DM502B Desk Microphone for the President Lincoln 2+ « Previous Next »

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Sandman7
New member
Username: Sandman7

Post Number: 1
Registered: 3-2022
Posted on Sunday, March 27, 2022 - 8:46 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I have a Workman DM502B Desk Microphone that I am trying to wire for use with a President Lincoln 2+ radio.

I cannot seem to get it right though. The down channel button will work but not the up and sometimes when I let off the key it will just start scrolling channels down, I also cannot access the menu function of the radio with it plugged in. I could sure use some help.

I bought the Workman DM502B Desk Microphone new from Copper’s when they first started carrying them and it came with the echo board installed.

This is what I had found on-line:
DM502B Desk Microphone
- Factory Microphone Cord Wiring Information:
- (Shield = Mic Ground)
- (White = Mic)
- (Red = PTT Transmit)
- (Blue = PTT Receive)
- (Green = Up)
- (Yellow = Down)
- (Black = Up/Down Common)
- (Orange = B+ (NONE)

For the six pin mic on the President Lincoln 2+ I found this:
1 = Modulation
2 = RX
3 = TX – Up/Down
4 = _
5 = Ground
6 = Power Supply

I wired the mic as follows with the results/problems I posted above:
1 = White
2 = Blue
3 = Red & Black
4 = (Unused)
5 = Yellow & Shield
6 = Green

I obviously do not have it right, but I am also lost.
Any help you can offer would be GREATLY APPRECIATED.

Thank you so much,
Sandman7
MicWiring.JPG
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Sandman7
New member
Username: Sandman7

Post Number: 2
Registered: 3-2022
Posted on Monday, April 11, 2022 - 9:11 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

Well, looks like no one knows. Even gave up and sent it off to a CB Shop, they tried everyway they knew or thought and still no joy.

OK, so how about wiring to a 4-pin for a Stryker 955 HPC? I guess I can read and figure this stuff out, not with this microphone anyway.

I had bought this from Copper Electronics when they first came out and it came with the echo board installed in it. Not sure if that is why this thing is giving me such problems or not.
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Ke0koy
Member
Username: Ke0koy

Post Number: 53
Registered: 12-2018
Posted on Wednesday, April 13, 2022 - 6:34 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

I glanced at the schematic for the Lincoln 2 and I think I know why nobody has answered this... You have a stock mic with channel up and ch down buttons. The schematic shows six mic socket pins: 5 and 2 are tied to ground, 1 is mic audio, 6 is a filtered voltage source, 4 is RX audio and 3 is the PTT line. Interestingly, there is no wire marked "Ch UP" or 'Ch DN" from the mic socket. What is even more interesting is that the PTT line goes straight into the PLL chip. And that doesn't look like any ordinary PLL chip either, its a tiny MCU with ADC inputs! The STC15S204EA datasheet (which the lincoln schematic, I believe, is wrongly labeled as a STC15F204EA, which is a 28 pin device) says that the pin the PTT line is connected to is one of the ADC inputs... Now, why would a PTT signal need to be on an ADC input? If I had to guess without looking, I'd bet the stock mic uses a resistor divider network to assign each button, including the PTT button, a voltage level and the MCU (the one doing the PLL work) interprets it. This also explains the necessity of a filtered power supply at the mic socket (probably also powering an electret mic preamp). You should hook up the stock mic and get a voltage reading on the PTT line while pressing each of the buttons and see what is going on there.
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Ke0koy
Member
Username: Ke0koy

Post Number: 54
Registered: 12-2018
Posted on Wednesday, April 13, 2022 - 7:36 am:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

...I didn't even see the schematic on the bottom of the post, it would help if I finished reading things before diving in lol. That makes sense. Are you using the resistors like in the drawing? What are the values of the resistors and the zener? Can you compare the voltages on pin 3 between the stock mic and the DM502B while pressing buttons? Whatever the problem is, I would bet it is on pin 3. Scope or probe that pin and see what the difference between the two is.
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Dale
Senior Member
Username: Dale

Post Number: 2426
Registered: 12-2002
Posted on Friday, April 15, 2022 - 10:30 pm:   Edit Post Delete Post    Move Post (Moderator/Admin Only)

i was reading somewhere to leave pins 3,4,6 empty ..dont use them
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb

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