KENWOOD TS-430S WON'T TRANSMIT

[KD2DBM]

Hi
I have a Kenwood ts430s that won't transmit. It receives fine just won't transnit in any mode. No carrier, nada...."on air" light does not come on, send button doesn't go into transmit, VOX with CW does nothing.....I have traced the transmit circuit to 8,9,10 connectors on th IF board per the Service Manual. When I pull the 9 connector the radio DOES go into transmit in all modes. I am stuck as to what could be the problem other than a possible transistor, I'm thinking Q28 or Q29. but since when I disconnect the number 9 connector it goes into transmit...is there something I can do to get transmit back other then sending it out. I am disbable and live on Social Security...any help would be appreciated.

Bill,
KD2DBM formerly N2AZN

[KA4POL]

My first idea was bad ground connection of a PCB. I'll have to see what the pulled connector inhibits.

[KA4POL]

What I found so far is that the microprocessor gives out a TX inhibit signal under certain conditions. This could be a reason.
The #9 connector has just two pins if we are talking about the same one on the IF board. It has signals TXB and RXB. It is connected to #10 connector on the same board as well. If you pull it you interrupt the voltages RXB/TXB. I would measure those and see where they might have an influence.
But still keep in mind the grounding problems. So also measure not to chassis ground but rather PCB ground.

[KD2DBM]

I have looked and see no grinding problem. Could the problem be a transistor on the IF Board? Has anyone had this problem with the 430s? Any suggestions on what I can do to get the rig to go into transmit? A mod or something? Any ideas would be appreciated.

[KE3WD]

I have looked and see no grinding problem. Could the problem be a transistor on the IF Board? Has anyone had this problem with the 430s? Any suggestions on what I can do to get the rig to go into transmit? A mod or something? Any ideas would be appreciated.

MODS are not repairs. 

At this point, the rig likely could stand being placed on the test bench and, with Service Manual in hand, follow voltage test points, then signal path, in an effort to find out what has stopped the show. 

73

[KA4POL]

Did you measure the voltage changes when pulling the connector?

[KD2DBM]

After following the all TX paths according to the schematic and testing all the transistors in that path I can tell you that all transistors are operational, and not open. I am TOTALLY stumped as to what could be causing this radio to just STOP transmitting in all modes and the no carrier when when the tx button next to the VOX button is toggled. Anyone have ANY further Idea of what I can do or should I just consider the radio DOA and use it for a reciever only radio. That'll suck as I don't have the money to buy new(er) radio to get on the air.

[KA5IPF]

Where is this connector 9 you are unplugging. There is one on about every board??

Clif

[KD2DBM]

Cliff, Connector 9 is in the middle of the IF Board near Q29. There are 3, 2 pin connectors, 2 vertical and one horizontal. Number 9 conector is next to the horizontal one. On the IF Board component view that I downloaded it is just to the left of the "Y K - 88C" Filter. When I pull it it sends the rig into transmit mode. I am wondering one thing, I am using an AT-250 Tuner that is connected into the back of the rig in the ACC connector PIN 1 I believe it is. I have read online somewhere that plugging in and unplugging the connector sometimes corrects the no transmit problem....I do not want to try this in case I make things worse....What do you think my next course of action should be??

Bill

[KA5IPF]

CN9 on the IF unit is Rx bias and Tx bias to the RF unit. Unplugging it should keep it from rx or tx.

Look at the RF unit Cn9-10-11 and compare the voltages to the schematic. If TXI (TX inhibit) is high it will not put out power.

The AT250 should be disconnected as should everything else except power supply and dummy load until you get the radio working. Then you can reconnect things one at a time.

Clif

[KD2DBM]

Well after finally finding someone local who could work on the radio it is fixed and back on the air. The problem was Transistor Q21 which was open and the IF board had allot of bad solder so Q21 was replaced and the IF board re-soldered and YIPPY!! Back on the air!!!! Thanks to everyone who helped me try to figure out the problem.

P.S. I read somewhere in the forums that someone else had the same problem with Q21 opening....is this a common occurrence with the TS-430 does anyone know?