RX Loss?

[steved]

A friend has a no-name 4-pill in a bright blue case...Class AB, 4x1446s...has a printed circuit board. Hooked up to a Uniden 78, running mini-8 coax into a roof-mounted Wilson 1000.

When he flips the amp on (just turns it on) the RX signal drops and sometimes slowly builds back up (like something in the amp is charging?) sometime it doesn't come back. If we turn the radio off for a few seconds, then back on; the RX levels return to normal. If you toggle the amp on/off a few times, you can literally eliminate ALL the background noise to zero. Turn the radio off/on, and things return to normal (regardless if the amp is on or off).

We've tried toying with the ANL/NB switch, looked everything over, switched antennas (used my W5000 in place of his W1000). We even went as far as swapping in my 2-pill and the 2-pill doesn't do it (class C). The only thing that works is to turn the radio off for a few seconds...

Is this characteristic of a Class AB amp? Or should we have it looked at? I don't know what make it is...looks fairly clean inside. Other than this annoyance, the amp works well...I was almost wondering if it was the relay??

 

[Beetle]

Sounds like there may be misaligned/dirty relay contacts somewhere in the receive line through the amplifier. If you take the amplifier completely out of the system, how does the radio act all by itself?

An amplifier's "class" applies only on transmit. Some CB amplifiers have built-in preamps which theoretically improve your reception (but in practice they generally aren't worth it).

Assuming the radio by itself works correctly in all respects, try using the amplifier with a different radio. You won't have to transmit since the problems you describe are all about the receive side. This will help isolate the problem. If it's a new amplifier, and things point to the amplifier as being defective, I'd take it back.

 

[steved]

Thanks Beetle...

The radio acts fine without the amp in the system...I'll try my radio in his truck tonight and see if that makes a difference.

 

[Switch Kit]

Thanks Beetle...

The radio acts fine without the amp in the system...I'll try my radio in his truck tonight and see if that makes a difference.

You answered your own question , and it does sound like dirty relays in the amp either not opening or closing correctly or the dirt on them is causing the problem , Shockwave once helped me out with kind of the same problem I had on a small amp , on mine it just turned out to be a cold solder joint on the bottom of the relay....easy fix which IM sure your buddies will be as well. good luck to you and let us know how it all turns out .

 

[Beetle]

Oops! I went back and reread Steve's first post. You're on the right track, Steve. Let us know how your radio acts with the mysterious no-namo amplifier.

 

[steved]

We hooked up the radio directly to the antenna...issue gone, lots of receive. Hooked up a different radio through the amp (receive only) and same deal...low or no receive. He said it actually quit receiving today, and toggling the on/off did nothing.

Sitting in my driveway, with the amp in line, we had 1# of noise (sitting under electrical lines within a mile of a major interstate). Take the amp out of the picture and his radio has lots of receive, including truck traffic from the interstate.

One thing to note, my amps all make two clicks...one when you turn them on, the second when you key. His only makes a click when you key (but the fan and everything seems to come on with the switch).

This is leading me to believe the relay is the problem...does my logic make sense?

 

[steved]

Let us know how your radio acts with the mysterious no-namo amplifier.

He said the amp was built by a local guy that's been gone for a while...

 

[mackmobile43]

Sounds like the transistor in the key circuit which is usually a 2n222a or a tip 3055 is not switching and assuming there is a electrolytic capacitor in that key circuit it may not allow the cap to bleed off while not in tx which would hold the relay in tx even when it's not being fed rf.

Blown pills have been known to case similar symptoms.

 

[steved]

Thanks Mack...

At least I can have an idea of what to tell the local guy...instead of walking into it blind...he's a pretty good guy, knows FatBoy inside and out.

I looked through it (visually), looked for anything touching that shouldn't be and anything physically broken (that's about the limit of my expertise...); nothing looked out of place.

I'll probably drop it off tomorrow since this guy drives all day, during the shop's hours.

 

[mackmobile43]

Thanks Mack...

At least I can have an idea of what to tell the local guy...instead of walking into it blind...he's a pretty good guy, knows FatBoy inside and out.

I looked through it (visually), looked for anything touching that shouldn't be and anything physically broken (that's about the limit of my expertise...); nothing looked out of place.

I'll probably drop it off tomorrow since this guy drives all day, during the shop's hours.

Most likely something simple and as far as fatboy keyups go they are very typical and are subject to blowing that small transistor with large deadkeys from the radio, it happens.

 

[steved]

Found it was the relay...all fixed now, works perfectly!