I have taken the bottom cover off to get at the dip switches without having a schematic.
The main problem with the new RMN5068A Desk microphone that replaced the HMN3000 is that it works with the Motorola mobiles but doesn't work with dispatch solutions such as the MC series desksets and the Commandstar lite console all of which are manufactured by CML. What we discovered is the mic DC voltage supplied by the mobiles is around 5 to 7 volts. The mic dc that the CML products supplies is almost 12 volts. The HMN3000 tolerated the higher voltage without affecting the mike audio. The new RMN5068A can't tolerate that higher voltage and causes the mic amplifier circuit to go into distortion.
We have modified the new mic by bridging a 680 ohm resistor across mic high to mic low in the mic. The resistor drops the mic DC voltage allowing the RMN5068A to work with the CML products with great success. We presently have about 20 RMN5068a working on MC series desksets. This modification is not from Motorola so it is not sanctioned by them but works every time.
As some additional information on this microphone, you will notice that there is a multi position switch located inside the mic to allow the mic to be configured for different radios. (Monitor before transmit, separate grounds for PTT and mic low, etc.) You will find this info in no manual. If you call the System Support Center they will read you the functions of the various switch positions but they can not fax or email any documentation. I have included the switch functions in this email so you don't have to go through the same problem.
What is the function of each dip switch in the mic?
How do you separate the front and rear covers on the mic?
New Motorola Desk Microphone
RMN5068 replaces HMN3000B
Internal Switch S-5
S5-1 Off Microphone hot all the time
On Microphone switched w/ PTT
S5-2 Off PTT doesn't change state of Monitor
On PTT changes state of Monitor
S5-3 Off PTT and Monitor Buttons Function
Separately
On PTT and Monitor Buttons both act as PTT
S5-4 Off Must Monitor before PTT
On Monitor has no effect on PTT
S5-5 Off PTT Ground and Audio Ground are separate
On PTT Ground and Audio Ground are common
S5-6 and S5-7 work in conjunction For Monitor Polarity
S5-6 Off On
Monitor Low Monitor
High
S5-7 On Off
S5-8 On Microphone AGC on
Off Microphone Level adjusted by pot
accessed
Through hole in rear of
microphone only
I have also connected a foot switch to accessory connector pin 3 and pin 7 on the M1225. PTT works but there is no transmit audio using the RMN5068A desk mic. The dip switch controls the audio path.
S5-1 Off Microphone hot all the time
On Microphone switched w/ PTT
We hope this may help others.
Andre VE3WZW
http://www.ve3wzw.net/
Good work!
ReplyDeletede VK3TU