SuperTiger 40A low modulation fix?

[Stapler]

I bought this old radio at a radio rally (ham fest) dirt cheap and it had a horrible howling on received signals and low modulation so I recapped it and that fixed the howling and it now RX good and 4w output but modulation is not good (quiet and slightly distorted) I have to use one of those cheap Altai single battery power mic on it with little wheel on 10 to make it usable, is there anyone here familiar with these old radios (PLL date code 22nd week of 1976) and is there something I can do to increase modulation?

TIA

 

[doffo]

I bought this old radio at a radio rally (ham fest) dirt cheap and it had a horrible howling on received signals and low modulation so I recapped it and that fixed the howling and it now RX good and 4w output but modulation is not good (quiet and slightly distorted) I have to use one of those cheap Altai single battery power mic on it with little wheel on 10 to make it usable, is there anyone here familiar with these old radios (PLL date code 22nd week of 1976) and is there something I can do to increase modulation?

TIA

from my experience, that is the world of the old Cybernet chassis radios. I thought something was wrong with my old 40 channel Midland SSB radio. Nope... Turns out you basically need to yell into the microphone to get any kind of modulation. Power mic is a must, and I forget which potentiometer inside you can adjust to get a bit more modulation (or whatever limiter to clip), but I didnt do any of that. I just went onto a better radio.

Though, the old General Electric radios with the power mic circuitry built in sound great. like the 3-5804D radios and a few others. I just avoid the other models that were not a cybernet board. 3-5804G was a completely different board inside.

 

[BayouRadioAmplifier]

playing "armchair technician"

just checked out the schematic to that radio.

so with a regular mic plugged in, does the PA work?
loud audio there? and receiver audio in the speaker?
If yes, then maybe a problem in the ALC circuit.

for TX modulation, and that audio ALC circuit.
turn RV102 to maximum resistance for less or no ALC.
and check negative limit diode VC6C.
the modulation audio passes through it.
check them capacitors C204 and C210.
maybe inject audio at the junction of R168 and C195
during TX. this is where receive audio is injected.

And to be able to maybe overmodulate,
bypass the neg limit diode VC6C.
cut out ALC clamp transistor Q121.

 

[Stapler]

from my experience, that is the world of the old Cybernet chassis radios. I thought something was wrong with my old 40 channel Midland SSB radio. Nope... Turns out you basically need to yell into the microphone to get any kind of modulation. Power mic is a must, and I forget which potentiometer inside you can adjust to get a bit more modulation (or whatever limiter to clip), but I didnt do any of that. I just went onto a better radio.

Though, the old General Electric radios with the power mic circuitry built in sound great. like the 3-5804D radios and a few others. I just avoid the other models that were not a cybernet board. 3-5804G was a completely different board inside.

This is definitely not Cybernet or atleast not the Cybernet I know, I’m fairly sure I had one many years ago that was Cybernet but maybe my memory is playing tricks on me, I know the super tiger 40 (no A) was Cybernet (PLLO2A) but that was the version with no channel LEDs

 

[Stapler]

playing "armchair technician"

just checked out the schematic to that radio.

so with a regular mic plugged in, does the PA work?
loud audio there? and receiver audio in the speaker?
If yes, then maybe a problem in the ALC circuit.

for TX modulation, and that audio ALC circuit.
turn RV102 to maximum resistance for less or no ALC.
and check negative limit diode VC6C.
the modulation audio passes through it.
check them capacitors C204 and C210.
maybe inject audio at the junction of R168 and C195
during TX. this is where receive audio is injected.

And to be able to maybe overmodulate,
bypass the neg limit diode VC6C.
cut out ALC clamp transistor Q121.

Thanks for the reply sorry I havnt responded sooner as I was away for a week

RX audio and PA audio appear to be good, You wouldn’t happen to know where Q121 would be located as in their wisdom no components are marked !!

 

[doffo]

This is definitely not Cybernet or atleast not the Cybernet I know, I’m fairly sure I had one many years ago that was Cybernet but maybe my memory is playing tricks on me, I know the super tiger 40 (no A) was Cybernet (PLLO2A) but that was the version with no channel LEDs

Bah! You are correct.

Board for sure isn't a Cybernet. The outside though looked like many of them that were made at the time.

The Tiger 40 is for sure a Cybernet chassis.