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eHam Forums => Elmers => Topic started by: AA4PB on March 22, 2023, 11:13:13 AM

Title: IC-756PRO low audio during warm-up
Post by: AA4PB on March 22, 2023, 11:13:13 AM

My IC-756PRO has low audio levels (speaker, ACC1 output, ACC1 tx input, microphone) which gradually increase until warm-up of about 30 minutes. After that period of time everything seems to be normal. Because it is all audio in/out I'm suspecting perhaps a reference voltage regulator feeding the D/A converters on the DSP board. Has anyone else experienced this? What was your solution?

Title: Re: IC-756PRO low audio during warm-up
Post by: N0GV on March 22, 2023, 11:58:47 AM

I have not ever dealt with the unit myself but on general principles I would look at the reference voltage circuit. Either a resistor is way out of spec or a capacitor is leaking....

Good luck!

Grover

Title: Re: IC-756PRO low audio during warm-up
Post by: W9IQ on March 22, 2023, 12:49:03 PM

Quote from: AA4PB on March 22, 2023, 11:13:13 AM

My IC-756PRO has low audio levels (speaker, ACC1 output, ACC1 tx input, microphone) which gradually increase until warm-up of about 30 minutes. After that period of time everything seems to be normal. Because it is all audio in/out I'm suspecting perhaps a reference voltage regulator feeding the D/A converters on the DSP board. Has anyone else experienced this? What was your solution?

Scope the input to the audio amplifier section (DRAF out of the DSP board) to isolate the source of the problem. I would be skeptical of a V_ref problem.

- Glenn W9IQ