Realistic TRC 55 No Sound

[TRIPPLE NICKEL]

Passed to me from a close friend, a really nice vintage type radio. It has not been used in about 10 years, closet kept no moisture.
Plugged in and all seems well, Mic keyed, ON AIR lamp comes on, least bit of noise MODULATION lamp comes on as well. Meter shows good SWR, there is no noise except a HUUM. Antenna connection is good, tried on different Antennas, still no noise. Squelch seems to efferct needle operation, just no receive. Is it something simple, PO said when last used was working good, who knows. Any help would be appreciated, it's just to nice of a base station to discard.
555

[doctor]

Well if I remember right a microphone has to be plugged for the receive to work, but if the swr is OK you must have the microphone in, try plugging in a separate speaker on the extra spkr plug, a relay might be stuck a few times in/out should get it to work<hopefully>
DOCTOR

[TRIPPLE NICKEL]

Thanks Doctor, I will give it a try. OP have suggested spraying all the button controls, but that's a lot of wirk just to get too. I will check the external spkr. plug real good. I hope you don't mind if I call on you if it doesn't work ? OK. 3's to you and yours.
555

[Sandbagger]

Sept 16, 2013 17:10:46 GMT -5 TRIPPLE NICKEL said:

Passed to me from a close friend, a really nice vintage type radio. It has not been used in about 10 years, closet kept no moisture.
Plugged in and all seems well, Mic keyed, ON AIR lamp comes on, least bit of noise MODULATION lamp comes on as well. Meter shows good SWR, there is no noise except a HUUM. Antenna connection is good, tried on different Antennas, still no noise. Squelch seems to efferct needle operation, just no receive. Is it something simple, PO said when last used was working good, who knows. Any help would be appreciated, it's just to nice of a base station to discard.
555

It could be a number of things. The fact that you seem to have transmit modulation means that the audio amp is good. Do you see signals on the meter (just can't hear 'em)? PA switch dirty? Channel selector dirty? broken mic wire? Volume pot dirty?

[TRIPPLE NICKEL]

Sandbagger, thanks for the reply. This is the latest I've found today.

The HUUUUM is coming from the clock, on the left side there is a micro switch that is activated by the clock and the clock is not running. The clock seems pretty easy to take out and see if I can clean and get it running again. The Mic has never been tampered with on the plug, it has a push type pin to release it, it's a Virgin also, wiggling the wires close to the plug makes no difference. Any suggestions, or what do you guys think ?
555

[TRIPPLE NICKEL]

here's the last thing I found.

Here is what I found. Removed clock,laid to side. Ant/ext spkr all hooked up. SWR is just over 1.1. When you push in the PA button, you get a motorboat sound until you key the Mic, then you hear yourself through the ext spkr. as should. Release the PA button all is quite, push it back in, motorboat until Mic is keyed. When you try to adjust squelch, there is a lot of ststic and the meters show erratic. Is it the squelch is bad ? I'm kinda lost, I've never been inside of a radio, this is the 1st.
555

[Sandbagger]

Sept 17, 2013 12:55:21 GMT -5 TRIPPLE NICKEL said:

here's the last thing I found.

Here is what I found. Removed clock,laid to side. Ant/ext spkr all hooked up. SWR is just over 1.1. When you push in the PA button, you get a motorboat sound until you key the Mic, then you hear yourself through the ext spkr. as should. Release the PA button all is quite, push it back in, motorboat until Mic is keyed. When you try to adjust squelch, there is a lot of ststic and the meters show erratic. Is it the squelch is bad ? I'm kinda lost, I've never been inside of a radio, this is the 1st.
555

It's difficult to troubleshoot a radio through postings. I'd actually have to see it to track down these issues. But if what you said about the radio working ok when it was put away, and now it's not, suggests to me that some part (likely an electrolytic capacitor) has failed due to age. Finding it will be the tricky part, and it'll be tough without some good test equipment.

[doctor]

If it has eratic meter movement, it could be dust has gathered on the controls and circuit board.
I see where you live, if there is an electronic shop near you, you will want to get a can of contact cleaner, this involves taking the radio out of the cabinet and spraying all controls, and the circuit board, or if you are not sure of taking it apart, remove the plastic knobs on each control and spray the shaft after all has been sprayed turn the set on, and turn each control to see if it comes alive or the meter for example is less erratic, again spray.
You can pick up the contact cleaner at a wally world. and sometimes at a RADIO SHACK, but DO NOT use anything but the contact cleaner....
If you have no place to get it, post that and I will get an address where you can but the postage is high...
DOCTOR

[cbrown]

Sept 17, 2013 16:35:36 GMT -5 Sandbagger said:

It's difficult to troubleshoot a radio through postings. I'd actually have to see it to track down these issues. But if what you said about the radio working ok when it was put away, and now it's not, suggests to me that some part (likely an electrolytic capacitor) has failed due to age. Finding it will be the tricky part, and it'll be tough without some good test equipment.

Agreed. Usually 'motorboating' is caused by a bad capacitor in the audio IC circuit. Do you have a schematic?

[TRIPPLE NICKEL]

What's so weird with the PA button pushed in, I get the MOTORBOAT sound, as soon as you key the mic it goes away, release the PA button and no MOTORBOAT sound is not there. Push the PA button back in and the sound re-appears but goes away when the Mic is keyed. I have tried to describe as best I could, the radio will Transmit with the ext spkr connected and the PA button IN. I have bench tested between both radios and it will Transmit as well as receive from other radio, just cannot hear as a normal radio does. Could it be the SQUELCH POT is blocking receive? like I mentioned before, the needle goes crazy when you turn the knob back & forth. OP asked did I have a schematic, I downloaded on line. I just got a feeling this is something simple, I sure hope so.
555

[2600]

Quick test when receiver audio is missing: Take a small screwdriver, lay one finger along the shaft and touch the tip to the center lug of the volume control with the volume turned up. Your body will pick up enough stray 60 Hz energy from the building wiring to hear in the speaker if the audio system is working from that point downstream to the speaker.

If it passes this test, the road is blocked upstream from this spot in the radio. If you hear nothing, the problem is downstream from this point.

Just don't ground yourself to the radio's chassis while doing it. This tends to reduce the level of your "digital test signal".

And if you have ever heard an electric-guitar amplifier when the plug is pulled only halfway out of the guitar, you'll recognize your 60-Hz test signal when you hear it.

All the advice you hear about blaming one or more bad electrolytic capacitors is true. All of it. Frequently the first of these parts to fail will have the lowest voltage rating, 10 Volts or less. Not a prediction, just a statistical reality. But a statistical reality doesn't tell you WHICH of all these parts are causing a fault like this. The chemistry inside this family of components has a limited life. A rubber plug in one end of the component seals in the water-based chemistry that makes it work. Sooner or later the rubber plug deteriorates from age and exposure to heat.

They are not meant to last 15 years, let alone 35 or more. Replacing them all only makes sense if your desire is to "restore" the radio. If you only want to fix what's broke, zeroing in on the cause is a divide-and-conquer process.

Fill us in on what you find, and we can take it from there.

73

[TRIPPLE NICKEL]

Thanks 2600, know where you are, been to Freedom Hall several times for the Saddlebred Horse show over the years.
I will try the screwdriver test you described and hope I don't get shocked, I will be carefull and not touch the chassis when I do it. Repairing CB's is not my specialty, but I like to tinker. I just can't make myself throw away a really nice radio(@ no cost to me) for something simple, I hope. They don't make these anymore, all the more reason to hear it talk again after so long. Thanks for your interest and look forward to hear from you. Will update soon. For now, 3's to you and yours, good evening.
555

[BBB]

Here is a site with the Factory Service manual.

www.cbtricks.com/radios/realistic/trc_55/index.htm

Much more useful than just a schematic as it has test points and voltages pointed out among other helpful things.

[TRIPPLE NICKEL]

BBB, thank's for the website, I had already found it, but being a stranger to the inside of a radio, and especially schematics, I'm lost. I was just hoping it would be simple. 3's to you and yours.
555