Lafayetts Telstat 140 SSB now just low power

[Techno1]

Was using the radio this morning working fine then something happened now just about 2 watts on Am and about 2 watts on ssb both lower and upper.

Radio dead on frequency and receive is great
No burn marks on the bottom pc side.
I pulled bothe finals 2sc 1969 and 2sc2166 abd both are ok.

Seem like rf out power just dropped in radio.

Any suggestions Im going to get out the service manual later tonight and study it and see if i can figure this out

Forgot to add there is very little modulated audio going out on AM its now backwards modulation and ssb will get a 2 watt carrier this is with a turner hand power mic.

Radio was doing about 15 watts SSB and about 5 watts AM now all low rf out.

thanks for any help

 

[Techno1]

Well i searched the forum and found some post on low rf power for the telsat 140.

I replaced the balance modulator and I do have 8v on pin 6 with transmit.
I checked c78 for short and that is fine.

The radio is tuned to 5watts AM with very little swing and 6watts ssb.

When i talk in mic it will do 2 watts ssb and whistle in mic it will peak to 6 watts.
Am dead key 5 watts and peak to 6 watts forward .

Receive is fine good incoming signal and audio.

So im getting very little rf audio on the transmit carrier

Any help appreciated

 

[VMC]

What test equipment do you have? If you have a 40+ MHz oscilloscope with x10 probes, go through the TX line and see where your RF is falling off.

 

[Techno1]

My scope is out to lunch looking for another good used one.

the problem is the ssb power is only 5-6 watts out.

I have aligned the radio to the service manual and is on frequency but very low audio input to the rf carrier.

When i talk in mic it will do 2 watts ssb and whistle in mic it will peak to 6 watts.
Am dead key 5 watts and peak to 6 watts forward .

Radio was working well then bang low ssb power out

Receive signal is great and also audio but low ssb power

 

[hazelglen]

Try cleaning the trimmers and check the voltage on the TX 8V line.

 

[Techno1]

Try cleaning the trimmers and check the voltage on the TX 8V line.

The trimmers are working as I can adjust from 0-5 watts on am and also 6 watts on ssb so they are working.