Kenwood MC60A schematic error???

[N1508J]

Greetings!!

Was doing a pin out diagram for the MC60A mic and noticed what apparently is a schematic error in the mic manual. When looking at the amp board the runs for the mic amp in and out switch don't agree with the schematic. Since the mic works fine apparently the schematic is in error.

Specifically, the emitter of the regulator 2SC1815(GR) is physically connected through the connector to the normally open side of the mic amp switch ('IN' position) whereas the schematic shows it connected to the common terminal. Also, the cathode of the 1N60 isolation diode is NOT connected to the source for the amp chip on the schematic whereas it IS on the actual board.

In addition, since the manual calls for alkaline cells it appears that the regulator is attempting to charge the cells when the switch is on!
Although the mic works in either configuration (the schematic being the desired method) the actual board connection keeps the amp powered all the time.

Has anybody else noticed this apparent discrepancy or am I going nuts?

 

[John_S]

Yes, there are some anomalies in Kenwood's schematic. There are also grounding issues in the circuitry. And to make things worse, the problems aren't consistent through the whole MC60A line. Went through this a couple of years ago. There's a Yahoo group just for this mic. I solved my issue by not using the preamp at all. Just plugged it right in the rig and used a foot switch. Of course, I was using a TS-450SAT for the rig, and it just needed the mic gain adjusted a bit from using the hand mic. In the end, I just went back to the hand mic that came with the radio... used to get reports with that mic too. But I've always had flaky luck with desk mics anyway.

 

[N1508J]

Thanks for the reply!

Greetings!

Thus far no problems with rf or other weird happenings. Was very surprised that the switch board was not wired as the schematic. Was doing a pinout of the interconnecting cables since they are not identified in the schematic. Thants when I noticed the switch board was not IAW the schematic. Can't imagin why they want to keep the preamp fired up all the time. I find that when I push the send button on the ts-2000 audio is transmitted when I am trying to load up. Seems like they would keep the audio switched out until you key the mic. Real strange!!!

Thanks for you imput!!!!

Yes, there are some anomalies in Kenwood's schematic. There are also grounding issues in the circuitry. And to make things worse, the problems aren't consistent through the whole MC60A line. Went through this a couple of years ago. There's a Yahoo group just for this mic. I solved my issue by not using the preamp at all. Just plugged it right in the rig and used a foot switch. Of course, I was using a TS-450SAT for the rig, and it just needed the mic gain adjusted a bit from using the hand mic. In the end, I just went back to the hand mic that came with the radio... used to get reports with that mic too. But I've always had flaky luck with desk mics anyway.

 

[John_S]

Is it possible that someone did some rewiring in there, maybe to run on a different brand of rig? This guy had some good info... http://raymoeller.com/kenwoodmic.htm

 

[N1508J]

Possible rewire??

Is it possible that someone did some rewiring in there, maybe to run on a different brand of rig? This guy had some good info... http://raymoeller.com/kenwoodmic.htm

Does not appear to be a rewire since the switch board has pristine runs.
Was able to attain a "factory schematic" from Kenwood which actually shows all wiring which the manual schematic doesn’t. It too has the preamp in out switch wired differently from the actual board. The board does indeed keep the preamp energized all the time regardless of which position the switch is in.

Incidentally, I find it peculiar that the mic assembly does not disable the audio through the PTT switch. When keying my TS-2000 with the "send' button for tune-up I find the audio is transmitted. Ain't never seen that before!:roll: