Sonar FS-23

[479tx]

I just picked up a Sonar FS-23 w/ matching BR-21 amp and Turner Plus Three mic. The FS-23 is very dusty inside, bought some compressed air today to clean it out really good tonight before proceeding further.

Turned the radio on last night just to see if it would receive (didn't intend to transmit until I cleaned the radio/checked it out further). Well, bummer, I don't get any receive. (connected to dipole antenna, verified RF-gain was cranked wide open, squelch off, volume up, mic plugged in (but no battery installed, shouldn't matter right?) checked all channels).

I have a 40 channel CB walkie talkie, brought it over right next to the FS-23 and tried transmitting once on each of the 23 channels (rotated through each once on the FS-23) and it didn't receive anything, S meter wouldn't swing like it was receiving my test transmission from the walkie talkie)

S meter is about a 3 on all channels (doesn't move around like it should if it was receiving and it was just the speaker that wasn't putting out), and when I back the RF gain down the S meter goes to zero.

The guy I got the radio from had a big box of spare tubes and said I could have any that went to the FS-23. The only two I took were new/in box RCA 6HS6 tubes.

I checked the service manual and saw that the 6HS6 is a direct replacement for the two 6BA6 in the 1st IF amp and the 2nd IF amp. Could either of these tubes being bad kill my receive? I guess since I have two brand new tubes I could try replacing them but I'm kind of shooting in the dark without a tube tester. I realize there could be any number of things wrong with this 40+ year old radio (caps, crystals, tubes, resisters gone high, etc.)

Can you safely pull tubes out of a radio like this without discharging everything or am I going to get shocked just pulling tubes and staying away from capacitors? <ignorant hat on>

Would really love to get it up and working though, always wanted a tube rig and love the audio these things are known to produce.

 

[Marconi]

479TX, I have a model FS-3023, and if it sits around for a long time, as it does, and I turn it on, it act similar to what you describe. I switch the channel selector and the other knobs back and forth or around until it starts to respond. Try that.

 

[479tx]

Thanks Marconi,

I've rolled the channel selector through all 23 channels 4-5 times now. I turned it on today and it's doing the following:

no static like you'd expect from a receiver, just a hum that becomes louder and louder as the volume setting increases. Then at about 75% turned up on the volume, a squeel becomes apparent, almost sounds like feedback.

the speaker definitely works, I hear split-second/loud bursts of scratching when I mess with the volume knob (turn it back and fourth quickly, as if the VR is dirty).

It seems like I'm not receiving anything since the S meter isn't jumping around when I key/talk into my CB walkie talkie right next to the Sonar.

I popped the top, cleaned out the dust bunnies as best as I could with canned air. I do see all tubes glowing, for what that is worth (I don't know anything about tube rigs).

Any advice would be greatly appreciated.

 

[wd586]

Sonar

This may help: http://www.cbtricks.com/radios/sonar/fs23/graphics/sonar_fs23_manual.pdf

 

[Shockwave]

Here are some tips on tube related failures in the FS-23. If the radio transmits but only the receive is dead, chances are your V-3 6EA8 is weak. If you have lost both transmit and receive, suspect tubes V-7, V-8, or V-9. These tubes operate critical oscillator and mixer stages with relatively tight tolerances. As the tubes weaken here, we approach a condition where the crystal oscillators will not self start.

For testing purposes you may notice that these same tube types are used in other places in the radio. You could swap them in an attempt to locate the troubled tube. However, I would then return the working tube to its original location and buy a replacement for the bad one.

Sonar's were great radios but they have also been noted for having defective crystals with their old age. Many are off frequency today as a result of this. It is possible that you could have a bad crystal causing this problem too. If only the receive is dead, suspect the 5.545 MHz crystal. If both RX and TX are dead on all channels, suspect the 6 MHz crystal. As I recall these crystals are mounted under the chassis and not on the channel selector.

One interesting thing about this radio is that it plate modulates the final with a push-pull class B audio amp. One of the very few CB radios that used push-pull rather then a single ended audio amp. I've noticed this makes it run cooler with less distortion and more output then many other rigs. The tone quality of the transmitter is exceptional for a stock rig too.

 

[479tx]

Know where I can get a replacement set of crystals?

I see most of the tubes in this radio are available on ebay.

I ordered a replacement relay already.

Can someone tell me (with this particular radio in mind) the best way to discharge all the lethal HV inside before working on it? I have no previous experience with tube radios that store a charge and I want to be as safe as possible.

Are the 3 big capacitors in the radio the only thing I'm worried about discharging before safely touching/replacing parts (relay, tubes, crystals, etc.)

 

[Shockwave]

I think these radios only used about 250 volts of B+ and the bleeder resistors should pull this down to nothing in under a minuet of turning the power off. You could always use the third prong of the power cord to short the terminals on the larger electrolytic cap mounted to the chassis. I think you can confirm with your volt meter that there is nothing there after power off in these cases. Crystals for the entire radio may not be worth doing since I think companies like Jan Crystals now charges over $20.00 each. I think there are some other companies that are more economical but I haven't ordered any in years.

 

[479tx]

Here are some tips on tube related failures in the FS-23. If the radio transmits but only the receive is dead, chances are your V-3 6EA8 is weak. If you have lost both transmit and receive, suspect tubes V-7, V-8, or V-9. These tubes operate critical oscillator and mixer stages with relatively tight tolerances. As the tubes weaken here, we approach a condition where the crystal oscillators will not self start.

For testing purposes you may notice that these same tube types are used in other places in the radio. You could swap them in an attempt to locate the troubled tube. However, I would then return the working tube to its original location and buy a replacement for the bad one.

Sonar's were great radios but they have also been noted for having defective crystals with their old age. Many are off frequency today as a result of this. It is possible that you could have a bad crystal causing this problem too. If only the receive is dead, suspect the 5.545 MHz crystal. If both RX and TX are dead on all channels, suspect the 6 MHz crystal. As I recall these crystals are mounted under the chassis and not on the channel selector.

One interesting thing about this radio is that it plate modulates the final with a push-pull class B audio amp. One of the very few CB radios that used push-pull rather then a single ended audio amp. I've noticed this makes it run cooler with less distortion and more output then many other rigs. The tone quality of the transmitter is exceptional for a stock rig too.

Had a little more time to tinker around with it today. Receive is dead on all 23 channels. Radio transmits (connected to load/watt meter) strong modulation with the Turner plus three. Keys a few watts and swings almost 10 (PEP).

I don't have a freq counter or any special test equipment but I have a 40 channel CB walkie talkie that works fine, when I was on the same channel as the Sonar (within ft. of the antenna connected to it) I could only hear my transmission just barely, like it was way off frequency and I was hearing some splattering station many channels over.

I suspect the TX is WAY off freq. So that'd be crystals and or tubes. Does Jans or Kens carry crystals for this radio?

 

[479tx]

Just tried replacing V6 and V7 (6BA6's) with two NOS RCA 6HS6 tubes since I had them laying around. I let the radio warm up, connected an antenna and I actually get a "little" bit of static/noise floor when the receiver is powered on now. My CB walkie talkie pegs the needle on the Sonar now and I can hear a very faint/distorted transmission from the walkie talkie through the Sonar speaker.

I still have a very strong hum coming through the speaker and a feedback like squeal that happens when I turn the radio up very loud.

 

[479tx]

Some progress...

Found a shop to test all of the tubes.

1. V4 - 6EA8 (service manual labels it 1st Synth Mixer - 4MC Osc.) is shorted
2. V12 - 6AU6 (server manual labels it "Buffer") was giving kind of erratic readings on the tube tester.

Every other tube tested excellent.

He also pulled the bottom side radio cover off and we both immediately noticed C2 (biggest cap, 450V 40 MF) was had a big dried glop of something that had oozed out the positive end and the cap. He replaced it with a 100 MF 450V cap electrolytic for me. The other caps visually look OK ...

I had hoped the cap on the bottom was the cause of the loud hum I get when the radio is in receive mode, but the hum is still there. I guess I should replace the 3 big silver "canister" caps on the top side of the radio since they could have gone south too.


Found a 6EA8 (ebay) for V4 and 6AU6 for V12. Will replace them when they get here.

 

[479tx]

Old cap:

New cap:

 

[Needle Bender]

Interested to know how it finally turned out?

Also, Shockwave, do you know of any other old tube CBs which were Plate Modulated?

What about the Pearce Simpson Guardian 23?

 

[Shockwave]

I think just about all tube CB radios were plate modulated. Many also modulated the screen voltage to the final.

 

[Eastside]

My FS-23 works good accept it does not have much forward swing...is there any way of turning up the modulation to get more forward swing on my meter?

 

[Charles hemmings]

I have fs23 and I can't get no modulation just a dead key I replaced all audio tubes everything else seem fine dead key no modulation please help