Kenwood TS-2000 K201

[W6GQ]

I have been trying to find out why my radio cuts out on TX and RX. The radio
will work just fine then all of a sudden, no TX/RX. I power the radio on or off
a few times and it comes back to life. The display and lights are always working
during the cut out.

I was pressing on different sections inside the radio when the failure occurred
and pressed the K201 Relay on the FINAL UNIT (X45-360X-XX).

When the failure occurs, this K201 relay "chatters" and I can tap it and
everything is back to normal. I did notice that this relay and the general area
near it gets quite hot. I was thinking I should replace the relay but have read
a few things on here about the pre-drivers in this area possibly being bad?

I have asked on the Yahoo Groups but not much traffic there lately

Any guidance?

[G4COE]

Sounds as if you located the problem, bad contacts perhaps but if it chatters more probably bad soldered connections.

There was a spate of 2SC1971 single ended and 2SC1972 pp drivers giving problems, the result is no output on HF and VHF.... but OK on 70Cms, the take off point for the VHF PA is the HF drivers. This wouldn't cause the relay to chatter though.... and certainly wouldn't affect the RX side.

Edit:
Without looking not too sure where this relay is... but you need be careful should you remove the main pcb... very careful!

With the set facing you looking in the back right corner theres a wire link concealed under some wires.... this wire link links the main board to the filter board (I think it is), it needs to be unsoldered before lifting the main board away.

Another point to watch is the driver transistors, the middle tab is the emitter.... these are grounded by a 10 ohm resistor, thus very important you don't loose the mica insulators and the plastic bush.... if you take the emitters direct to ground you are likely to have instability and blown drivers!

Dave

[KH2G]

Need to check for full B+ on anode of D201 and see that it is still good on the hi side of K201. If all is good then note that K201 is driven by Q207 which may not be getting driven hard enough. You may also have some poor solder joints in the area.I would however, suspect the relay is failing as it is fairly common and CN10 neds to be checked to ensure good mating/ no corrosion. BTW D205 is suspect because often thos little suckers fail on one side and your in trouble. being intermittent, I'd probably go for check solder first.
Enjoy
Dick

[KA5IPF]

Sounds as if you located the problem, bad contacts perhaps but if it chatters more probably bad soldered connections.



With the set facing you looking in the back right corner theres a wire link concealed under some wires.... this wire link links the main board to the filter board (I think it is), it needs to be unsoldered before lifting the main board away.

Another point to watch is the driver transistors, the middle tab is the emitter.... these are grounded by a 10 ohm resistor, thus very important you don't loose the mica insulators and the plastic bush.... if you take the emitters direct to ground you are likely to have instability and blown drivers!

Dave

The wires are on the back left corner and connect output of the VHF finals to the filter board.

The drivers have the emitter (tab) tied directly to ground. Do not use insulators or bushings on the screws.

[KA5IPF]

A thought but if you have an ammeter inline with the power cord you could tell if the no rx/tx problem is a relay problem or a digital control problem. Check the current draw in rx and tx SSB with no signal for reference points. When it quits check the same 2 points. If it's a relay problem the current draw in both rx and tx will be the same as when it was working. If a digital problem the current draw will be less. That will help point to where to look for a fix.

[G4COE]

Must be the single ended driver that has the resistor in the emitter, think that would be the 2SC1971, thanks Clif for the reminder.

Dave

[KA1MDA]

Before doing any more trouble shooting, I would reflow all the connections for the relay. At least 70% of the electronics repairs I've done in the last few years involve cold solder joints on components with larger thermal mass. This usually includes Molex connectors, relays, and transformers. My guess is that the wave soldering process doesn't apply enough heat to the components with larger thermal mass.