TS850modifications

VCTXCO upgraded, for higher PLL-reference stability. This small PCB can work in many synthesized Kenwoods, in addition to my '850

Kenwood TS-850 Noise Blanker Modification - stiffens the bias-voltage, raises the threshold, alters time-constants

TS-850 volatile-memory backup battery relocation (mine's under the DRU-2 top-cover hatch, for easy replacement - I have no DRU-2)

Make the CW sidetone level adjustable, via the front-panel MONI control (just like SSB)

Stablize the Transmit-ALC reference-voltage, by broadening the operating range of the multivibrator/invertor

TS-850 Low Band (MF: 0.5MHz to 1.6MHz) Sensitivity Improvement, by disabling/bypassing the broadcast-band attenuator

I have also replaced all my carrier-board aluminum electrolytics with 25V-rated solid tantalum caps. No leakage was present in my '850, but while it was open I thought it best to ensure continuing operation. These solid tantalums have no liquid to leak, and maintain their capacitance to well-below freezing. They were physically a bit larger than the aluminum cap carriers, so I had to gently scrape solder-mask from nearby traces, to accommodate the negative contact of the larger tantalums.

There are reports that C18 on the display-PCB can also leak. I replaced this 470uF with a higher-voltage-rated tantalum capacitor also. This bulk/filter cap is not present in the schematics, but is present on the display board nonetheless. When it leaks, it can etch and open-circuit one of the supply-traces to the display (resulting in no display).

Installing my #528 Inrad filter (500Hz / 455kHz IF)