Einzelherz

I've only had my 98 for a week now and while I've got a lot of things to ask, right now I'm mostly curious about this. The volume **** on the stereo goes from off to 'too loud to listen to' within like 20° of rotation. It's a standard pioneer system. Is this how they normally work? I had hoped that there would be more graduation in the amplification power.

I've read there's a way to adjust characteristics of the sound system through secret menus, but I thought that was just for bass increase and other EQ tuning like that.

Thanks in advance.

Yamae

Sorry for your trouble. It is not normal to go from off to too loud within 20 degrees of rotation. It usually needs to rotate more than 360 degrees or more from off to the comfortable level. Something must be wrong but I can't say what is wrong without analyzing the unit myself. I am an electronics guy and if I were you, I would check the DSP part of the board shown below. There are two separate volume control ICs and I would check those output levels of IC401 and 421 first turning the volume ***.

mcomer

Might someone have installed an amplifier that is driven by the speaker outputs?

philmstar

I think mcomer's idea makes a lot of sense. If an aftermarket head unit has been installed and front "speaker out" from head unit connected to Lexus Amp "Front Audio in" under passenger seat. Would give similar result.

Einzelherz

It's the factory stereo. I can't say if it's the factory amp, but the two previous owners were elderly so I assume it's not be messed with (nothing seems to have been.)

My guess was that the potentiometer for the dial was messed up and giving the wrong resistance for any given position. I'll dig into it and report back anything I find.

Yamae

Things are a bit more complicated than you think. The Pioneer stereo system does not use an old potentiometer. Instead it uses a digital pulse encorder and decorder. The number of pulses controls the sound level using a directional pulse detector and the level control ICs. In order to troubleshoot, an oscilloscope is useful to find the exact failed part. Without it, it would not be easy and quick. It needs some skills and measuring equipments to troubleshoot.

Einzelherz

The image you posted above looked like the amp. I assume that means all of the volume control is there, correct? If so, would replacing the amp with a junkyard part be an acceptable first step in troubleshooting before I pull mine apart and get out the meters and scopes? I have them, it's just a lot of work, as you said.

mcomer

Why not just get some highly accurate speakers with 16 Ohm ratings and suck down the excess power...