[1000mp] New Owner - Help Sought

[Mark G0MGX]

Hi Group

New here, Mark G0MGX and I am in central England in the UK.

I've recently acquired an MP Mk5 (200W version) with a missing (or 
thrown away) PSU. I have homebrewed a PSU and am now finding I have a 
fully functional SUB RX, but the main RX is extremely deaf - there are 
some signals audible, but they are very weak on the main RX, switching 
to the SUB RX for the same signal and they are 59+++. I also note that 
the attenuator function seems fine, there is a clear click when 
switching to the RX antenna, the VRF function seems to be working also. 
I also see that the S-Meter for the main RX is permanently at about S5.

I can find quite a few references to deaf RX generally in this group and 
other places on the internet, however I think the SUB RX being OK 
eliminates a lot of the RF Board where the most common faults seem to be 
in PIN diodes et cetera. It seems from reading the circuit description 
that my fault is downstream from the 1st IF as the signal split to the 
sub RX happens just prior to this stage.

Is there anyone on the group able to provide any pointers or help with 
diagnosis of this fault?

Many thanks for any assistance.

Mark
G0MGX