These are the mods I applied to the
Donated basic unmodified GE BASE.
I started by Performing the Mods documented in the repeater
builders web site for
BASE
conversion..
I also needed to follow the power wires from the front door to an
external AMP connector that was not connected to anything. I fused and
ran that to the power supply as well as powering the amplifier.
Audio and Squelch problem.
It took me
a long time to figure this one out.. You need to add a jumper between
pins 2 & 5 of J213C on the mother board. For some reason
without this the VOL/SQ HI is not tied to anything! This was to obvious
of a thing for me to even check. Without this there was no audio to the
RAB (Repeater audio Board). The RAB does the de-emphasas and filters
the PL tone on receive.
Also had to remove Jumper from the 10v power supply. H16 & H17 on
the 10 v near pin A6 on the board are seperated to remove RX MUTE
during transmit feature.
I then applied the mods from SCOM
7k
interfacing .
This was another hard one.
The BASE conversion doc cut the jumper between RC MUTE on the CG board
and the IFAS board so you can have both PL and regular COR outputs
independant of each other. That breaks a CG filter becase now it is not
biased high.
I had to add a 10k
resistor
between J908 Pin 4 & 5 to bias the CG's REC MUTE pin(5)
high. This
was done to half duplex CG board # 19D432500G1 or the COMSPEC TS-64
board which has full duplex encode/decode modes.
Pre receiver mods the
relative receive ability ( a rough measurement)
using a HP 8640B sig gen was about -80dbm.
I removed all the unused wire for the external control head. Then
removed all 6 of the AMP connectors and direct soldered them.
Before:
http://www.ke3ht.org/mods/PB200006.JPG
You can see the unused bundle of wire in the back. All gone now.
Cleaned and kryloned the
heilacals.
Re-tuned the receiver and got -107dbm relative receive ability on the
same HP 8640B sig gen. Final tuning we got 0.6uv @ 20db sinad.
There is a tuneable cap that appears to be broken. So I will make up
another LO board with mods to replace the origional. Goal: .5uv @20db
sinad (.35uv@12db sinad).
Brought the Local Osc into the ham band per Rebeater
builder mods and the GE LBI for
this radio..
Pulled apart the PA and replaced all the heat sink grease. I also
disconnected the T/R relay and bypassed it.
Mod to improve Squelch like the Micor.
here
