Zenith K731

[YamahaFreak]

Originally Posted by Tube Radio

I have had three K-731 radios. I have yet to find a fix for the electrostatic tweeter. Your best bet is to find a small high impedance horn tweeter and put that in there. I've been inside one of those electrostatic tweeters and there's no real fixing to them as what's not riveted is glued and the plastic is quite fragile also. If you havn't already replaced the selenium rectifier do so. Take a voltage measurement where the 22 ohm resistor from the rectifier connects to the first filter cap. Then replace the selenium with a diode and note the increase in voltage. Now comes the fun part. Try different resistors until the voltage at the first filter cap is close (+/- 2-3 volts) to what you measured with the selenium rectifier in place. Don't replace any components in the shielded box where the FM tuning slugs are unless you have a problem with FM operation as parts placement is critical in that area. Even using the radio without that cover soldered in place affects the operation of the FM circuitry. What chassis do you have? The ceramic capacitors will be ok. All resistors, paper caps and electrolytic caps should also be replaced.

I was worried about dropping in a regular type speaker because of the difference in impedance for the ES panel. What would be a good rating for the new driver?