Denon PMA-737... What would be the cause of this volume issue?

[tiefbassuebertr]

No it's permanent. Unfortunately adjusting the volume control way up and back down doesn't have an effect. If I go back to 0, it again favors the left side as it diminishes in volume.

In the whole signal path (from the input selection to the speaker selector switch or speaker protect relay), contact resistances can occur, giving the impression that only the volume control is affected.
Bad caps in front of and behind the volume control often give this impression (crackling while rotating), and after replacing these elcaps by foil caps this disappears completely - provided the volume control is already in perfect condition.
Strip down the switches as show in post #18 is an effortful option - my favorite approach is the bypassing of the whole input selector unit and introduce an outdoor top quality rotary switch for source select like e. g. ELMA 04. This unit is equipped with such an ELMA:
https://web.archive.org/web/20070206191733/http://www.redwineaudio.com:80/Signature_3S.html
An overview of source selector units are to find in post #22 under

F

Thread 'Rotary source selector for audio'

2011-12-15 5:55 pm

Hi,

I'm building a gainclone amp, and I need a rotary selector to switch between sources. I have three inputs to the amp, and I bought one of these:

Rotary Switches : Rotary Switches : Maplin Electronics

I got the 4-pole 3-way one and that's fine, but will this switch do for audio?

Can you recommend something else I can use for this purpose? This is my first attempt at something like this and I'm not sure if this switch will work or not, I'd like to be sure before I solder everything up.

Thanks,

• franke
• Replies: 28
• Forum: Parts

 

[madis64]

Nice pic... Yes, still on the agenda but I need to get a better de-soldering tool. I've been using de-soldering wick and it's very time consuming.

Ca 45 minutes from starting desoldering (using wick) to final placement back per switch, after that a coffee break.

To clean switches once they're opened, would you recommend 91% alcohol, Deoxit or something else?

Once they are opened I have used physical cleaning methods - starting from erasure rubbers of various softness.
After finishing with the physical treatment I have flushed the switches either with a contact cleaner or with isopropanol.

 

[Jonwb1]

UPDATE: Well I de-soldered, opened and cleaned the blue cable switch. Afterwards I quickly tested the amp and the Denon is operating like new again. Even volume balance and good functionality. For the heck of it, I started on the white switches but when I opened those, I was greeted with 6 small copper 1/8" rail pieces that were ready to fall out. I decided that since they looked good, I didn't want to continue. Too much of a chance I'd screw things up. It took me an hour to get them back into the right configuration and closed. Like I said, I'm still a novice.

I wanna thank you all for leading me to a solution for this. The Denon should outlive me now. Glad I found the group... have a great New Year!