Mocom 70 Audio

[n3chu]

Hi all, Does anyone have any mods(audio) to make the lowband Mocom 70 transmitter have a little fuller audio?. have tried different mics and not much change . . Thank you. 73 Davie n3chu at atlanticbb.net

[1motoman]

You might try to replace the cap's in the transmitter audio chain.
They sometimes dry out after 30 + years.

[WB6NVH]

Presuming you have swapped mikes to make sure the trouble doesn't come from there, get an ESR meter and take a look at any electrolytics in the speech/modulator section. Some may be dried up. EVB makes an inexpensive ESR meter which you buy from their website.

[bernie]

My two bits worth:
I was a Motorola field tech when these were new.
There were no transmit audio problems that I am aware of.
As I recall the modulator circuit was very similar to the VHF/UHF main board.

Motorola was very particular how their radios sounded.
I do not recall any PSD (Product Service Department) or
SRN (Service Repair Notes), with the exception of somthing to do with the
operation of the new IDC circuit. The Mod scope trace in limiting is different than the earlier circuit.

There were some changes made when production was moved from Schaumburg to Austin, TX.

For $10 or so you can replace ALL of the electrolytics in the radio.
Electrolytics do not last forever.