You can replace your audio and receive transistors with a new one or a compatible one and be back on the road again. the transistors are available from all ham dealers and are normally not too expensive.
do not try to fix something that ain't broke. if it is working, leave it.
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Hi, I understand that your router's signal is weak and other connections drop because of that. To resolve this issue, I would suggest you to change the wireless channel to 1(one). Because, the frequency on Channel 1 will not interfere with other RF frequencies. Thanks,
The FT-840 uses a die-cast RF power amp
with thermally switched fan to ensure full power output (up to 100
watts). The digitally synthesized local signals ensure clean, low-noise
transmitter output on all HF amateur band. There might be no AC line interference. it has strong Rf output. any AC line intersect does not affect its radio performance. Check and adjust RF power so to maintain proper output. some times more RF power generated at the output may cause interference. adjust Rf power..Even some unfiltered Noise getting the other end of the end may calso cause interference. Check for any Ripple voltages present at the output. Contact authorised service station for further Rectification. thank you shanth
You've replaced the pre driver, the drivers and finals. Set bias and still low output. The pre driver is the same transistor used as the tx exciter transistor on other pcb chassis on bottom of radio. Follow the gray coaxial wire from the pre driver on the RF circuit board back to the tx/rx i.f. Circuit board. The gray coax cable plugs right next to the tx exciter transistor on this pcb. Again it's on a different pcb all together and on the bottom of the radio and also. Replace it! And check for open bias or emitter to ground chip resistor next to it. You will get your drive back. Very few rigs have I seen the actual Finals blown in the mosfet or the bipolar version. Just the driver stage with a week pre driver and the SMT "pre" pre driver on the same RF pcb. And the tx exciter on the other pcb.
you can find it easy with google, but here is how it works...the incomeing rf signal is mixed with a signal of another frequency from the local oscillator and then passes through a non linear device (semiconductor). after passing through the nonlinear device the output will contain the original frequency,the local oscillator frequency, and frequencies equal to those added together and subtracted from each other,these signals are then passed through filters to obtain only one which will be either the rf frequency plus the local oscillator frequency or the rf frequency minus the local oscillator frequency. This new frequency is then coupled to the intermediate frequency amplifier stages where most of the amplification takes place before the audio is removed and passed to the audio stages.
sir ... i have to construct a model bridge in which i have to give a mechanism for the passing bridge.the problem is arrival of the ship should be detected by mechanism employed on bridge and ship should have a way to cross through. plz give detail mechanism of the signalling system which should be used on the bridge which detect the coming of the ship
73s I have heard of similar problems and some were heating related. the best is to check if your rig is heating up causing it to switch off and lose memory when switched back on. I have a buddy who had an unusual experience where he actually dropped frequencies so low that he could pick up ordinary radio frequency and also go into bands like 27mhz and 25mhz. But once switched off, the rig worked normal again. If you are experiencing heat problems then i suggest you put in a fan and remove all dust from inside the rig. You could probably also be having problems with power supply either internal or external. If all else fails, refer to a good repair shop this type of radios are very sensitive.
Looking at the end of
the plug that goes into the 290 the pins are labeled, with the notch
at the top, the connection to the right is pin 1 , counting clockwise
connection 2 thru 6 (6 is to the left of the notch.) 7 centre
1mic earth and common
return for up/down button via lock switch and ptt, 2mic, 3ptt, 4 +5V,
5 spkr, 6 up button, 7down button
Hope this helps regards, Colin