Kenwood Basic C2 help?

I picked up this Kenwood pre-amp, hoping for the best. Well, not quite. Something seems to be affecting the right channels of all the inputs, or, somewhere between the inputs and output. Here's what it does...

I'll plug in good RCA's to any input (aux, tuner, etc) and run good RCA's from the output to an amp/speakers. I'll only get sound from the left channel. Yes, I did all the channel swapping on all the RCA's to make sure it wasn't them, the amp, or the speakers. I can switch the unit to mono, and I get sound from both channels in mono, so it makes sense that "something" is coming out of the left AND right pre output. I can move the rca's to the tape outs and get sound out of both channels, too. This would tell me that the RCA inputs must be getting a signal from both sides, right? So, something somewhere in the middle of the electronics is failing me for stereo operation. What's a good way to diagnose it? Where do I look now? Nothing inside looked clearly burned, leaking, etc...

here's a stock pic for reference:

For reference on a possible cause:

http://www.audiokarma.org/forums/showthread.php?t=165374

Work the Balance control. There's a pretty well documented issue with it and that could be your problem. If the right channel comes and goes, it's your culprit.

Unfortunately, due to the uniqueness of the control, the solution seems to be removing it from the circuit via a couple resistors and jumpers.

Yeah, I'm researching those options right now...

One test you can do (carefully) is to:

• take the front panel off (remove the top panel, unscrew the three screws on top and on the bottom of the front panel, pull front panel off)
• unscrew the two screws holding the loudness switch and remove the nut around the balance pot (requires removing the balance knob first)
• carefully pull the loudness/balance board out and place it face down (circuit board side up) on something non-conductive with the balance pot shaft pointing at you
• find the contacts for the balance pot - it will be two rows (parallel to the leading edge of the board) of three pins each
• with headphones plugged in, the preamp powered on and a source playing at low-ish volume, very carefully bridge the left hand and center pins on the row of potentiometer pins closest to the edge of the board and see if you get output in the missing channel. Repeat with the right-hand and center pins on the second row of pins. If your balance pot is bad you should get audio out of the missing channel when you bridge the appropriate channel pins

For reference, bridge the pins in light blue in the image:



(sorry I can't be more specific, but I can't rightly recall which row corresponds to which channel - I want to say that the front row is right, but I could be mistaken)

-D

Andyman said:

Work the Balance control. There's a pretty well documented issue with it and that could be your problem. If the right channel comes and goes, it's your culprit.

Unfortunately, due to the uniqueness of the control, the solution seems to be removing it from the circuit via a couple resistors and jumpers.

Click to expand...

Resistors aren't necessary (and even if they were, 180k is the wrong value - it should be 42k) - only the jumpers are really necessary.

-D