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D104 Mic/Amp Transistors...Gone Bad?!?

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Old 03-02-2009, 08:17 PM
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Exclamation D104 Mic/Amp Transistors...Gone Bad?!?


So, I bought a D104 from eBay and wired it up for the standard Ranger/Magnum arrangement. Popped a new battery in it an plugged it in. Key it up and it is making noise and acts like the contacts on the leaf switch are dirty. Fine. So I get a thin, fine file and clean off the contacts a little bit. Presto; no more intermittent key-up. But now, there is another problem.

It appears that the mic can talk, but the modulation is way, way low - even when turned up all the way in the mic. And the radio mic gain is way up - too. I'm beginning to wonder if the transistors in this thing are gone - because there is no gain from the mic. Are the 2N2712 transistors known for failing - or is there another problem with this mic I haven't yet tracked down. Additionally, I also went over all of the solder joints on the amp board to make sure there weren't any bad joints. I'm wondering if I overlooked anything - or do these transistors in this mic have a history of going bad.

Anyone know?
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Old 03-02-2009, 08:52 PM
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very rare for the amp to go out .you probably have a bad head element.if you know someone with a working head ask to borrow it for a test.

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Old 03-02-2009, 10:22 PM
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You didn't mention what stand it is, Some of the TUG9 stands have a Choke on them, you may want to check it if it does. I also have an early Silver Eagle that has the same choke as well.

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Old 03-02-2009, 10:35 PM
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Quote:
Originally Posted by MisterFatty View Post
You didn't mention what stand it is, Some of the TUG9 stands have a Choke on them, you may want to check it if it does. I also have an early Silver Eagle that has the same choke as well.
Right.
It's a TUG9 stand w/6 conductor cable. It has the lazy key on it; the very reason that I bought it - sorta like a Silver Eagle in that respect. I don't have another mic head to see if the element has failed.
What is the significance of the choke? The schematic doesn't show one; although one part on the board itself looks like a choke. What's up with that?!?
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Old 03-03-2009, 01:07 AM
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Quote:
Originally Posted by Rob KI6USW View Post
Right.
It's a TUG9 stand w/6 conductor cable. It has the lazy key on it; the very reason that I bought it - sorta like a Silver Eagle in that respect. I don't have another mic head to see if the element has failed.
What is the significance of the choke? The schematic doesn't show one; although one part on the board itself looks like a choke. What's up with that?!?




My schematic does not show it either, this one originally had some yellow coating over the wire, it looks a bit messy, I hand wound it, I messed it up a bit taking the board out for the pic.. May not look great but it works fine, before I rewound it the audio was extremely low...

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Old 03-03-2009, 01:14 AM
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What was the specs on the rewind? Is there a microhenry equivalent?!?
I'm spent three hours working on this mic, and got it working - without the modulation like it should be. Why did Astatic leave it out of the schematic? SHould I just remove it and put a jumper in its place?!?
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Old 03-03-2009, 05:46 AM
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It was pretty common for people to bypass the amp circuit on the mic for use with radios that didnt need an amplified mic. Make sure that wasnt done on yours. it usually meant moving the white audio wire on the board directly to the mic plug wiring.

PR

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Old 03-03-2009, 07:50 AM
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rob,i wouldnt mess with anything until you try a new head.i rarely ever see the mic amps go bad .and i have had dozens of 104`s.if need be for a quick test take the head off,find an old mic element ,take the 2 wires from the element and put them in the holes in the top of the stand .the stand will amplify anything you can plug into the head jack,so if you can plug in an old stock mic element or something you can quickly find out if the stand is indeed amplifying.

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