I have a Mocom base cradle with a Mitrek radio.
The squelch is very erratic, and pops open ocasionally with no signal.
I have been told that there is a squelch circuit modification.
Could anyone help me with that information ?
Mitrek in Mocom cradle
Moderator: Queue Moderator
Mitrek in Mocom cradle
Reed Hurley
My two bits worth:
The Mitrek may be used with earlier control groups. This is no accident, Motorola planned it that way.
The Mitrek can be used on Motrac/Mocom 30/70 control groups with modifications.
The modifications are required because there are certain circuts that must not be grounded. The modifications isolate speaker low from chassis ground.
The audio PA is a Push-Pull IC amplifier, which can be damaged if one of the speaker leads get grounded.
In a mobile if the mike low gets grounded you will have alternator whine on TX.
Mike shield was grounded by the HUB in some applications as it was used as ground return for the PL hang up box in mobiles.
The HUB (Hang Up Box) must NOT ground the black wire.
The radio case MUST be grounded. It is not connected to the negative power lead because of the positive ground option.
The test sets also needed to be modified.
I do not think that the M70 Consolette chassis is the problem with squelch.
You could test the radio on the proper cable, but the squelch/volume control circuits are identical for all models.
I would suspect a problem in the IF.
Be sure the radio chassis is grounded .
This Consollette chassis is probably 30 years old. The Electrolytics may be failing.
The symptom would be if the output voltage drops under transmit, hum.
The Mitrek may be used with earlier control groups. This is no accident, Motorola planned it that way.
The Mitrek can be used on Motrac/Mocom 30/70 control groups with modifications.
The modifications are required because there are certain circuts that must not be grounded. The modifications isolate speaker low from chassis ground.
The audio PA is a Push-Pull IC amplifier, which can be damaged if one of the speaker leads get grounded.
In a mobile if the mike low gets grounded you will have alternator whine on TX.
Mike shield was grounded by the HUB in some applications as it was used as ground return for the PL hang up box in mobiles.
The HUB (Hang Up Box) must NOT ground the black wire.
The radio case MUST be grounded. It is not connected to the negative power lead because of the positive ground option.
The test sets also needed to be modified.
I do not think that the M70 Consolette chassis is the problem with squelch.
You could test the radio on the proper cable, but the squelch/volume control circuits are identical for all models.
I would suspect a problem in the IF.
Be sure the radio chassis is grounded .
This Consollette chassis is probably 30 years old. The Electrolytics may be failing.
The symptom would be if the output voltage drops under transmit, hum.
Aloha, Bernie
Also Mitreks would have squelch / audio problems when the interconnect board (vertical board in the very front of the radio) connection became poor - the stainless steel pins and sockett tarnish. Try cleaning them and hit it with some Staibilant 22A (Spelling?). To check you can pop open the lid and while the radio is on try wiggling the interconnect board directly above the connection to the mainboard. Good Luck.
MicorRT