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I recently was able to pick up a nice Kenwood ts-940 and it was working great until.......
At a recent contest a few of the guys decided to hook up a amp to the rig now as soon as I turn the rig on it goes into transmit and doesnt come out of it
Anyone else ever have this problem and if so were you able to fix it?
For clarification, does it do this even when it's no longer hooked up to the amp?
Yes no amp hooked up and as soon as it powers it goes into transimit
Not having a schematic handy, my first guess would be to look for a problem in the T/R switching circuitry. If it's switched by a relay see if the relay driver is shorted or just biased on all the time. That should get you traveling in the right direction. Use the block diagram to get a general idea of how the switching is done, and then use the schematic to take you to component level.
Thankyou will start looking in that direction
Which model of amplifier was hooked to the '940, and how was this done - directly, via an isolation device such as an ARB-704?
And the most obvious question: Has the "Send" pushbutton on the leftmost side of the rig somehow become engaged?
Not familiar with that radio but maybe there's a jumper on a connector that needs to either be removed or added?
A quick Google search suggests maybe a defective Q29.
If the amp was an older one, it's possible that the T/R switching ran at too high a voltage for a solid state rig. For instance, on an SB-220 amp, the no-load voltage at the T/R relay jack is well over 100VDC. That could easily fry a transistor on your rig, which was probably designed for around 25V max on the T/R circuit.
Yes I believe it was a old amp and I have started to look at the TR circuitry it definitely shorted something to ground to bring it into tx mode