Help needed repairing a Workman or Valco DM-452-4RB Mic

[North_star]

Hello, I've got a nice old Valco DM-452-4RB Mobil mic. It was made and sold under other names like Workman. The DM-452 is still made, but the mic I've got is a DM-452-4RB It is a power mic, with echo, with the addition of a switchable roger beep.

Anyway, One of the wires came loose, and it appears to have damaged the power mic circuit.

When I hit the transmit button, It keys up, but unless I yell into the mic, it does not transmit any sound. BUT if the roger beep is on, it keys it up loud and clear. So I assume that the mic pickup circuitry is the issue.

The problem is, I can't find any diagrams for this mic, and I have inspected the board and see no obvious issue.

Does anyone have any experience with this mic? Any help would be great! If I can't fix it, does anyone know where I can pick up another one? I tried **Non Sponsor**, but he never responded.

Thanks in advance!

(edited by MDY, removed **Non Sponsor**)

[Bombero]

Hey North Star...

A few places have decided not to carry this mic any longer due to excessive issues.

I found a few for sale on the auction sites...check it out.

Good Luck

Bombero

[MDYoungblood]

One problem I have found with the DM-452 models are the 9v battery sometimes comes in contact with the mic cord solder points on the PCB, a short piece of electrical tape on the battery is a quick fix. I have a "Road Pro" version with "Talkback" that kills the battery in a couple days, this has me puzzled too.

3's

Greg

[Deleted User 14541]

One problem I have found with the DM-452 models are the 9v battery sometimes comes in contact with the mic cord solder points on the PCB, a short piece of electrical tape on the battery is a quick fix. I have a "Road Pro" version with "Talkback" that kills the battery in a couple days, this has me puzzled too.

3's

Greg

I used to use one of these in my early cb days and had the same issue. Wrapping the battery in electric tape did the trick. That was the most bulky, ackward mic I've ever used but people liked the sound.

[North_star]

Yup, Its an ugly looking thing, but I have been using the two that I have since I bought then new in 1996. They do sound great, and I have always loved the roger beep function.

I can only find the DM-452 online now. It looks the same, but only has the echo function, and not the roger beep. Hopefully someone will chime in with some repair ideas, or maybe a link to someone that still has the DM-452-4RB for sale.

Money is tight, so I'm hoping to be able to repair it, but it has 3 IC chips inside of it and I'm guessing that the shorted wire took out one of them.