The AM Forum

THE AM BULLETIN BOARD => Technical Forum => Topic started by: W1ZFB on January 20, 2023, 06:23:18 AM

Title: ART 13 no audio cw-mcw
Post by: W1ZFB on January 20, 2023, 06:23:18 AM
I'm rather new here so hopefully I'm in right place. I'm homing to get some ideas, help with this problem.
I just got a ART-13 with the AC supplies. After repairing the HV PS I started testing the transmitter and found very low sidetone in the Calibrate mode. Then I found there is low audio from Sidetone jack with the microphone and no audio tone from the CW or MCW using the CW Jack. I checked both jacks and clean them. I do get audio hum when I'm plug into the sidetone jack and as I said in the Calibrate mode I can hear the beat tone but very low. Also I have RF out and no modulation in voice or CW-MCW.
So my suspicion is there is something wrong in the speech amp. input side maybe as I'm getting something out of the output through the sidetone jack. I think the oscillator is working too as I'm hearing it at sidetone jack but very low when calibrate mode. The manual says you could use a speaker to hear the beat so I know I have a problem in the audio side of things. I know the microphone is working and the switch is correct to use the carbon mic.
I've have a spare 6v6 that I swap in both of the 6v6's on the speech amp and no difference. One thing I did see and clean was there was tar like substance on the bottom of the two transformers on the left side of the speech amp looking at it when its in the transmitter. Maybe one or both the transformers are bad causing my issue?
Hopefully someone has some ideas. I'm also wondering how I could trace the audio through the amp since you can't operate the speech amp while its out of the transmitter.
Thank you

Title: Re: ART 13 no audio cw-mcw
Post by: WU2D on January 21, 2023, 09:22:37 PM
You can operate the speech amplifier outside of the transmitter if you make an adapter cable. This is an essential if you plan on keeping the ART13 for a while. I have used my cable several times. My other suggestion is getting hold of a spare speech amp module. You do find them at flea markets.

Title: Re: ART 13 no audio cw-mcw
Post by: W1ZFB on January 22, 2023, 06:23:41 AM
Thank you! I thinking about doing that too but I until read it in the maintenance manual I was little hesitant.  I just found the right connectors to do so. I suppose you can do the same for the oscillator section too? I haven't read that far ahead to see although I don't suspect that's my problem right now. 
AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands