Panasonic stereo volume is "crackling"

[tommybitt]

Hello,
I own a Panasonic SE-P5 stereo system (circa 1982). When I turn the volume knob the sound get all "crackling/hissing".
Is it a knob repair/replacement/cleaning?
Befroe I start taking it apart I wanted an idea of what it might be.
Any info is greatly appreciated.

TBitt

[Guest]

*Note: I would recommend either a VOM or DMM before you start this, since the rest of the troubleshooting will probably need Volt and Amp readings.

*Note 2: I don't mean to write this in a condescending tone, I just mean to write it in an easily understandable way for non-technicians, hobbyists just getting started, or people that just want to fix it without knowing what they're doing.

The stereo's being overdriven either by the Variable resistor (Volume knob) or something internal. Some manufacturers choose Variable Resistors that aren't fit for the stereo's full potential in order to cut costs on production, which is why I start here. The easiest way to see if it's just the variable resistor requires an Ohmmeter, which can be found as just an Ohmmeter, a VOM (Volt-Ohm Meter, I think), or a DMM (Digital Multi-Meter). Depending on the model of the stereo, you may need to take the plastic casing (what technicians call "the box") off of the stereo, or you may have enough room once removing the knob's cover to touch the leads, assuming the knob's cover is meant to be detached for servicing, repair, and cleaning (some are, some aren't).

If you're going to test the Variable Resistor, you need to have the power OFF before taking readings, or else you'll get wonky readings, or blow the meter, both of which are bad. There should be little rounded circles attached to the Resistor once the box is off, and those are what you take measurements from. You'll be checking for any jumps/drops in reading when you touch the leads of the Ohmmeter to the leads of the Resistor. There should either be 2 or 3 little circle things (sorry, can't remember which for this application).

Turn the knob as you're reading with the meter and it should generally increase in resistance one way, and decrease in resistance the other way. If there's a spike or drop somewhere in there that doesn't follow the pattern, take the same readings over the same area to make sure it wasn't human error. If it's the same after the 2nd or 3rd time (I'd go for at least 3 to be sure), then there's a problem with the resistor.

If you don't care much about aesthetics, you can just replace the knob with any Variable resistor of the same rating (should be marked on the flat side opposite the turning part of the knob), making sure the Resistance, Voltage, and Amp values are the same (the Amp being the most crucial to stop the problem from happening again, the Resistance and Voltage also being important).

If the resistor isn't the problem, e.g: it reads relatively smoothly, then you should look at the schematic. There should be an internal amplifier circuit in the schematic, or attached to the schematic, and that's what you'll need to troubleshoot if the resistor isn't the problem.

[Xpender]

My experience with the volume knob or any knobs found on a component, is that it will need to be replaced. You can try to use contact cleaner, while spraying you turn the knob from left to right and it will "fix" it for a while, but the noise will come back.