Nick said :
My 736 in its 3 rd decade has low audio on all modes. I have to turn the af gain to about 3 o'clock position.
I've not had that trouble w/736, but I do have the "Technical Supplement" for the FT-736R, which has block diagrams and schematics. The audio makes it way thru several boards and connectors on it's way around to the speaker. I can easily scan a few relevant pages and either email or post on my web site if you are so inclined to dig into it.
Might check the level at the front headphone jack (and exercise the switch contacts inside the jack) as well as the external speaker jack on the back. I've had output interruptus due to cracked solder joints on the external spkr jack before. Aged output blocking capacitors often result in lower sound levels as time goes by. I've fixed many a VHF scanner that way.
Reply direct email via amsat.org, and we can take this out-of-band... I didn't see your callsign handy, to reply direct. /;^)