Kenwood TS-440S 20 meter transmit problem

[WA4GOU]

I have a TS-440S with the antenna tuner that exhibits the following problem:

Using a dummy load in CW mode the unit will not transmit within the frequency range of
10.500 to 14.500 MHz. Transmit on 1.6MHz to 10.499 and above 14.500 to 30.000 MHz is okay.

After pressing the send switch the on the air light will come on for about 1/2 second then go off and will  go back on for 1/2 second when the frequency is changed only to drop off 1/2 second later. There is no RF power output at any time during this sequence. The CW indicator is on when selecting the CW mode.

Also if you place the unit in the FM mode and press the PTT no RF power is generated. However if you hold the PTT down and then press the FM mode button again the unit goes ito transmit mode and then works okay. If you drop the PTT you will have to press the FM mode button again with PTT depressed to get the unit to transmit again.

During all of this the display appears normal and the FM mode indicator lamp is on.

I did check the path though the 7.5 to 14.5 MHz filters and the relay path appears to be cut though. This would make sense since operation from 7.5 to 10 Mhz  works okay.

I just picked up this "perfectly working" transceiver at Dayton an would like to put it on the air on 20 meters.

Has anyone seen this before?

Thanks for your help !

73's

Sam

WA4GOU

[K8OM]

Hi Sam,

I had a TS-440 (have upgraded to a TS-2000) and only had one problem with the rig. The ROM (Read Only Memory) chip is in a socket and not soldered to the board. Over time a small amount of oxidation forms between some of the pins and the socket and can cause all kinds of weird and intermittent problems.

I'm not sure if this is your problem but I would suggest looking there first. I just removed the ROM and cleaned the pins with an eraser. Kenwood suggests removing the socket and soldering the ROM to the board. I wasn't brave enough to try that.

Kenwood has a Service Bulletin on their web site on how to fix this and several other problems.

Good luck.

Joe  K8OM

[SKIPPER300]

KC9MFL Bruce , I have the same problem with a 440 only i loose trans on more bands let me know if you find anything .thank you .

[KC8CDZ]

This is a very old post but has anyone solved the key up problem on some bands where the transmit light comes on for about 1/2 second then goes out in cw, ssb, am you name it. mine is doing it on every band above 10 mhz but has been intermittent on 28 mhz at times.

[KE3WD]

Did you try adressing the IC in the socket with corroding contacts as described above? 

[KA5IPF]

This is a very old post but has anyone solved the key up problem on some bands where the transmit light comes on for about 1/2 second then goes out in cw, ssb, am you name it. mine is doing it on every band above 10 mhz but has been intermittent on 28 mhz at times.

You have one or more leaking diodes in the RX BPF, most likely D4 and/or D6.

Clif