Bi Polar vs Polarized Caps and DC noise

[scott2000]

I'm working on cleaning up an old Tapco 6200B mixer..... Have a garage sale coming up and am trying to work through some noise on the pots or somewhere . I can tell it's not a scratchy sound from the pot itself so, I'm thinking it's DC getting into something it isn't supposed to........

I've replace a bunch of caps already and everything is going good but I still have some noises when turning all of my channel volume pots and one one of the master volume pots...

One thing I noticed was that, on the schematic, c36 & c37 are listed in the parts list as non polar but are polar caps in the mixer and on the schematic. The parts list also has a voltage rating of 10v....so, parts list 22uf 10v NP.....schem and mixer 22uf 16v...
I have some new 22uf 10v NP, will these work here? Would it affect anything in a positive or negative way?


Also, c22 & c27 are 47uf NP on the parts list,schematic,and inside mixer . I have some new polarized 47uf caps. Can I use these here or is there going to be a problem with DC noise? Obviously the orientations need to be right here but, do the NP caps serve a purpose in this section and shouldn't be made polar? Something to check????

I've tried making sense of the concept of the polar vs NP but, I get mixed information (like you can use NP anywhere and you can use Polar if it's the right orientation...etc) and just wanted to know if my caps on hand will work...Also, .My new 22uf NP caps are only 10v but, not sure that's a problem here even though it's on parts list as 10v....



Any extra info is appreciated too. I'm trying to learn.... Like where to probe the pots etc.. for common dc problem areas.....is this a static reading or can it vary with rotation...etc... no worries either way...I'll keep trying to figure it out.... I did find this page so I have some reading to do.......http://el34world.com/charts/fenderservice6.htm

I feel bad starting a thread just for a  question but wasn't sure where to slide this in.  If someone could tell me if I should move it or whatever, that's fine.....

Thanks!!! I appreciate any direction.....

 

[PRR]

> new 22uf NP caps are only 10v ...... on parts list as 10v....

So what is your problem?

Measure the in-circuit voltage across each cap. If nothing else has failed, those voltages will be "zero" (<0.1V). A polar electrolytic will stand <1V of wrong-polarity DC pretty OK. And I will not obsess about a 1976 design-- clever, but incredibly crude by later standards.

 

[JohnRoberts]

You should be able to determine which pot(s) is/are scratchy and replace the capacitors immediately feeding them.

In old designs I would generally replace all similar (same capacitance and voltage) caps when one is found faulty because they are likely from the same production batch and all are suspect after one is found bad.

JR