Palomar 150watt bi-linear amplifier for c.b. radio-won't transmit
This RF amp. used to dead-key 3watts & swing to 150watts pep. Now, the unit is turning on,lights are working,pre-amp. is working. But when I key up my c.b., (dead-key set at 1watt) the relay inside of the amp. engages, But won't put out anymore than 1watt. I did find a snapped resistor(470 ohm) & replaced it,but didn't solve problem. Can you steer me in the right direction,to bring this ''SCREAMER'' back to life? Mark Hopkins
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The radio is either stuck in transmit or the RF power output section has a short in it. If there is no RECEIVE audio and the squelch is open, and the radio is not in transmit, the chances are pretty good that the audio power amplifier is shot.
There are any number of reasons for no sound. I will assume you're using new batteries or fully charged batteries. The simplest reason is that a wire has become disconnected from the speaker. This would make the radio sound the same on as off. To test this see if the radio has a way of turning the squelch off, sometimes a simple push button, sometimes a menu setting, sometimes a dial to adjust the squelch setting. If there is no hissing, sometime very loud so turn your volume down first, then either the audio output amp is dead or a wire to the speaker is broken or disconnected. I today's radios the audio amp is most likely a simple small IC but, it could be inside an all-in-one chip and if it's proprietary getting the chip could be a problem. If it's a simple audio chip you'll have to find a replacement or rig up another audio amp IC to work as a replacement. Let's hope for the simple broken or disconnected wire which should be easy enough to fix.
Now, if when you remove the squelch you hear the hissing but you still cannot hear transmitting from your other radio, it could be that the one transmitting is in fact NOT transmitting an not that the other radio cannot hear. You have checked that both radios can or can not hear someone else's radio right?
Assuming you do know that one radio cannot hear what the other can and make no sound other than hissing when the squelch is off the problem is either in the RF or IF sections of the radio's receiver. In general this used to be a more complex repair so let's go another easy fix by going to the very first place the RF comes in, the antenna.
Just like the audio section when a speaker wire is disconnected sometimes the wire or trace going to the bottom of the antenna can become disconnected or broken. To check this bring a good transmitting radio very close to the one that hisses but does not hear the transmitting radio and see if any place as close as you can get the two radios causes the non-hearing radio to hear the transmitting radio. If so, then look for a problem with the antenna connection.
If none of these easy things bring the problem to heel then there's probably something amiss in the RF or IF receiver sections. If the radio has one or two chips that do all the work here then see if you can get both and replace them. I haven't even taken apart my own small FRS radios to see how complex the receivers are in these so I won't go any further than that since I simply don't know your radio.
The reason for this is due to various possible conditions. The first being obstacles in the operation range of the unit. IE> hills buildings trees ect. This can greatly reduce the actual distance the unit will work in. The 18mile max is probably a rating that would apply in the best opt. scenario. You would have to be on a flat terrain with no hills or valleys,no trees or buildings for the unit to reach the max distance. In dense areas of trees,buildings or uneven terrian you wont even come close to these distances. Second: any unit RF unit that is held in your hand or close to your body does cause the antenna to detune to various degrees the amount that it does depends on how well the unit has been designed. The more it detunes the less resonated frequence is recieved and amplified making for a weaker signal. In conclusion for the best long range reception be clear of as much surronding interference as possible and as high a possible above any elevated terrian
The electronics in the transmit / recieve circuitry (RF = radio frequency) work very differntly from those in the display and control circuits, which prob ablyexplains why the display works, but not the rest.
The major problem with water in RF circuits is that even after it dries out, it leaves a residue, or worse still some corrosion, which adversly affects the tuning of the RF circuits.
It may be worth trying to dry it out a bit more - put it somewhere warm but not humid like near but not too close to a central heating boiler, for a few days. However, I suspect it is now beyond repair.
You may have a bad antenna. What happens is a lot of guys carry their radios around by the antenna, inside the connection to the antenna is weak and can crack at the solder joint, thus opening up the antenna circuit and prevent you from transmitting any power out. Our Motorola hand helds have this problem, they are weak at the antenna connector and guys swing them around by the antenna end up breaking them. Your next problem is that if the radios have been used often enough with a faulty antenna circuit, your final amplifiers are probably toast from transmitting into an open antenna circuit, causing all the power to be reflected back into the radio and burning out the final amplifiers
Nope, 6LQ6's are the tube used in most all Palomar CB linears. Most tube type linears of that class have one 6LQ6 driving two or three 6LQ6's. As far as the T/R relay keying as power is supplied, you have an electrolytic capacitor shorted in the Carrier Operated Relay. My advice: get a pro to fix it, as there is 800 to 900 volts DC at a quarter of an amp on the B+ circuit, which is more than enough to kill you if you make a mistake. Too many Hams and CBer's have died that way, I do not want you to have the same accident. Find a reputable repair guy, then pay the price. It's safer that way. Good Luck,