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INTERMITTENT DROP-DOWN ON RECEIVE SONAR FS 2340

Discussion in 'General CB Services Discussion' started by Sonar, Jul 17, 2017.

  1. Sonar

    Sonar
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    The receive on my FS 2340 occasionally drops down about one s unit. This happens whether the transceiver is cold or hot.
    It immediately comes back up when I quickly key and un key the microphone.
    I don't recall which one of these crystals is what I believe to be a receive mixing Crystal. I have a NOS Y1 position crystal. Although I believe the Y1 to be the recive mixing crystal I'm not 100% sure. Is there anybody out there that knows if the Y1 is indeed the received mixing Crystal?
    If the Y1 position it is indeed the receive mixing Crystal I will drop in the nos one I've got. It can't hurt considering I have absolutely no clue as to why the receive is acting as I mentioned..
    I will also make sure the tubes are seated properly
    I will also remove and clean the contacts on the relay.
    Unfortunately I don't have a tube tester and although I suspect it might be a failing tube besides replacing each tube pertaining to the recive section one at a time looking for the possible culprit I'm out of options. My second guess is that a failing tube would not cause the receive to immediately come back up to its normal s unit reading of the station, once I tap on the mics key bar but I'm obviously guessing. This is happening often enough for it to need repairing.
    If you have any other ideas as to what might be causing this problem I would appreciate your input. 73 PS my knowledge is very limited. My goal is to not have to pack and ship it for a problem I might be able to rectify with someone's help. I'm fairly positive my tech will actually charge me less than the shipping cost to track down and fix the problem. I'm guessing it's not a major malfunction. Shipping always makes me nervous. I always imagine some UPS shipper kicking my parcel down a flight of steps and or throwing it into his or her truck. 20170716_230354.png


     

  2. nomadradio

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    I would be looking at the relay before I would blame a crystal for that. Or maybe a tube.

    If a crystal is losing its output level the frequency should shift in a noticeable way at the same time. A quick check of the fine-tune knob would reveal this. If it's still on frequency when the sensitivity drops down, the crystal is probably not the culprit.

    Simply tapping the side of each receiver tube with a steady signal in the receiver could zero in on a tube that's cutting in and out. A dirty tube socket is all it takes to do this, too. Same deal with the relay. A "thwack" with the back of a finger against the end of the relay nearest the contacts will typically cause a "pop" in the receiver audio, since you are shocking it in the direction the armature normally travels. A tap against the TOP of the relay should never get you any noise, unless a contact is oxidized or worn.

    73
     
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  3. Sonar

    Sonar
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    All very good advice for someone like myself with little to no knowledge.
    I replaced the original relay about a year ago.
    The reason I changed it out to a newer one was because of the incredibly loud pop that comes through the speaker of these Sonar's when the mic is keyed.
    The new relay actually lowered that popping sound tramendusly (the pop would bother the yl 2 rooms away.) The one I replaced it with has a red led inside of it.
    It lights up when the relay is activated.
    I will do everything you've suggested.
    I should get to it tomorrow.
    I'm optimistic about finding the problem using the methods you've listed. I don't know which tubes work the recive side, but I know certain ones don't. I'll just tap the one's I'm not sure about while the rig is receiving 100%. I have plenty of backup tubes. I'm really feeling good about finding the problem. Thanks nomad. 73.
    PS I'll post my results asap.
     
  4. Sonar

    Sonar
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    I did as you suggested. I even decided to reinstall the original relay. The original relay has the rig acting just as it did with the replacement one. I made sure all the tubes were nicely set into their sockets. I looked as best as I could with the lights off to see if any tubes were not lit or close to being out. I know that's not a good way to decide if a tube is either good or not but I really don't have anything to lose at this point.
    I just noticed something interesting that might help you figure out what could possibly be causing this receive to drop out an s unit and then immediately return upon keying then un keying the microphone.
    I have been listening to the sonar for about an hour now. The receive stayed solid and did not drop out until about after 50 minutes of it being on. I did not key up from the time I turned it on until the recive dropped out.
    I have the amplifier (300a) on but in standby.
    The receive did not come back up after quickly tapping the microphone bar while the amplifier was in standby.
    As soon as I flipped the switch from Stand by to operate then quickly keyed and un keyed the mic, the receive quickly came back up. Could it be the amp?
    The only items I have inline after the amp is a Dawia 2 position switch Wich switches me between the sonar/palomar 300a and the uniden Madison/phantom, and an Autek wm1 meter.
    The Madison's recive is not acting up as the Sonar's.
    I'd think if the wm1 could/was causing the issue it would be happening to the Madison also.
    Could it be the Dawia 2 position switch?
    The fact is that the recive won't come back up with the Sonars 2 watt DK and only comes back with the 300a's 125 watt dead key.
    If I had hair I'd pull it all out.
    I'm tempted to hook up the backup 2340 but this particular rig has special meaning and I enjoy operating it more than the other.
    HELP ME!!!
    I hope the amp HAVING to be in the operating position gives you the proverbial light bulb over the head idea. Thanks Nomad. I do appreciate your time. 73
    PS. If you do come up with another idea for me to try I will follow it to the T.
    If that doesn't work I guess I'm going to have no choice but to box it up and send it out. Or might I be having to box up the 300a? God only knows how much I hate having to ship this stuff. UPS has never fucked up anything but it's only a matter of time. The odds are moving against me with each shipment. Granted I haven't had to ship anything in quite a while but I know with each shipment my luck is running out. Help me through this and I'll buy you a case of whatever it is you drink. Thanks again nomad. Two case's!
     
    #4 Sonar, Jul 20, 2017 at 3:50 AM
    Last edited: Jul 20, 2017 at 4:15 AM
  5. nomadradio

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    My first bet would be on the 300A's preamp relay, especially if it's one of the square white plastic "R50-E2-Y2" relays. They are a failure waiting to happen.

    Second bet would be on the 300A's antenna relay. If yours has the three identical relays on a plug-in circuit board behind the Load control, you'll find it a challenge to obtain replacements. The "R10-E3604" relay is a custom version with a RF shield inside it next to the relay's coil. The pin pattern is different from the stock relay this size, so you end up drilling holes in the pc board and/or wire-jumpering foil traces to use readily-available replacement relays.

    Good news is that if it's the other version, with the relays on the deck BELOW the Load control, you can simply bypass the preamp relay with a single wire jumper once you remove it from the pc board. The antenna relay on this one is in a socket. Far less effort to swap out.

    Has it ever done this nasty trick with the amplifier taken out of line?

    If so, that points to a fault in the radio, not the amplifier.

    OR, there may be a separate fault in each one. Not such a far-fetched idea for a 40 year-old amplifier and radio.

    73
     
  6. Sonar

    Sonar
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    I'm guessing it doesn't matter if the 300a's preamp hasn't worked in ages.
    The preamp relay could still cause this issue?
    I couldn't do the repairs myself even if it's the one that could be repaired.
    I'm going to take the amp out of line. If the issue ceases It's obviously the amp causeing the recive drop problem.
    Would you mind helping me to know for sure which one of two 300a's this is?
    I can take and post photos.
    Do you need photos of the tops tube side or under side?
    Both? Let me know. I'll take them and I'll take it from there.
    I might retire it. To bad. I do enjoy it. It makes an excellent match for the 2340.
    Let me know if you'll need to see top and bottom side of the amp. I'll take plenty detailed photos. Thanks again nomad. 73
     
  7. nomadradio

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    The preamp relay's "off" side carries both your barefoot transmit power and the receiver's connection to the antenna. That side of the relay is prone to dropouts. The gap that develops between the contact points is incredibly thin, and keying the mike will cause a tiny arc across the gap. This restores the broken circuit across the contact points.

    For a while.

    Only.

    The area below and behind the Load control is where the relays will be. Either three identical clear-plastic enclosed relays in a row, mounted on a vertical plug-in circuit board. -OR- two smaller white-plastic relays about an inch square, with a third clear-plastic enclosed plug-in relay. All of them on a circuit board bolted to the horizontal chassis deck.

    And there are more than "two" 300A amplifiers. But only two arrangements of the relays on the top side.

    73
     
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  8. tecnicoloco

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    The area below and behind the Load control is where the relays will be. Either three identical clear-plastic enclosed relays in a row, mounted on a vertical plug-in circuit board. -OR- two smaller white-plastic relays about an inch square, with a third clear-plastic enclosed plug-in relay. All of them on a circuit board bolted to the horizontal chassis deck.

    And there are more than "two" 300A amplifiers. But only two arrangements of the relays on the top side.

    2 Relays.jpg 3 Relays.jpg

    Hope this helps
     
  9. Sonar

    Sonar
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    Great help. I will now know which one of the two preamp circuts I've got.
    Thanks for taking the time. 73
     
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  10. Sonar

    Sonar
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    I won't get around to removing the cover and taking pictures until later next week.
    I have a very strong suspicion that you are absolutely correct in assuming the issue is being caused by the preamplifier section in the 300a
    A curious thing happened
    As I mentioned in my previous post, the preamplifier on this 300al hasn't worked in years. I'm sure you know what happens when the preamps in these amplifiers goes south. They actually D amplifier when switched in the pre amplification mode.
    I decided to put the switch in the pre amplification position. Lo and behold the preamplifier actually works! I didn't have enough time to run the radio and amplifier with the switch for the preamp in that position for a long. so I don't know what exactly will happen when I do use it for an hour or so. I did get a chance to have a couple of short qso's with a few locals and during those conversations the preamp did exactly as it's supposed to. The odd thing about it is when I switched the preamp into the off position it did as if I switched it in the on position when it wasn't operational and D Amplified everyone signal. I flipped it up and down a few times rapidly thinking I'd possibly do something positive by doing so. Shows you how much I know! Anyway, the deal with it now is if I leave the preamplifier switch in the on position it works and amplifies everyone signal as if it was never busted. Believe me when I tell you this preamplifier hasn't worked since 1980. I haven't opened the cover or done anything to the amplifier that would change the way it was working or in this case not working. I guess I will wait until next week when I remove the cover and take some photos. Depending on which configuration of relays this particular 300 a has depends on (I guess) whether it can be repaired or even if it's worth it. As of last evening with the pre amplification switch in the on position the receive did not drop out and the amp just seemed as if it was working properly as far as the preamplifier goes. I am fairly positive that this is not going to last. There is obviously an issue with the preamplifier on this 300a, and it's an issue that makes it annoying enough to either have it repaired or to boxing it up and relegate it to the closet with the rest of the retired equipment. I do have other choices. there's one reason why I like using this amplifier with the sonar 2340. The 2340 with the Demco modulator turned up to approximately 3 gives me nice loud yet clear audio with little to no background noise from the amplifiers fan. It is truly one of the quietest fans of any amplifier I own. I once was using the Phantom with the 2340 but with that fan noise I could only turn the Demco modulator up to approximately 11. It still sounded nice with the modulator at 11 but I get much louder reports with the Demco at 3 o'clock. It's impossible to leave the Demco at 3 while using the Phantom. At 3 o'clock on the Demco with the Phantom my dead key reeds 300 watts (150 watts of fan noise). Compared to the 300 a which theres practically no background noise and dead keys a solid quiet 150 watts. With the Demco at zero (no audio) I get 145 DK. That's 5 watts of fan noise. No one I've asked says they hear any fan on a quiet Dead cake while I use the 300 a. The Phantom sounds like a jet engine taking off. The difference between the fan noise is night and day. This is really the only reason why I use the 300a with the sonar and Demco modulator. I would love to fix the 300a but considering it's something I wouldn't be able to do on my own and would have to pay to have it done sadly means it most likely will become a closet case. It's going to cost me $60 to ship it round trip. Then probably around 60 to $100 to repair. It's really not a lot of money but it's not worth it considering I do have other options. I hope that you (nomad) can possibly guide me through the repair. And even though I'm skeptical of being able to fix it on my own, I am willing to give it a try. The choices are fairly simple. Trying to fix it myself or put it in the closet where it will most likely stay until I can find a use for it. I do appreciate all the help. 73
     
  11. tecnicoloco

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    Hi Sonar:

    FYI the quote is from Nomadradio,credit and thanks to him

    I posted his quote along with the pictures that I been gathering from the net for clarification and show you the differences in the relay boards

    I own 3 of these amplifiers and his comments been helping me to fix the issues with my own amps

    Kudos and thanks to Nomadradio for sharing his knowledge
     
  12. Sonar

    Sonar
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    Y
    Yes I noticed the quote was from nomad. I appreciate the photos. From what I've been reading over the past few years nomad is definitely someone who understands amplifiers. I get the feeling and he could correct me if I'm wrong but he either just was fortunate some might say unfortunate enough to work on enough palomars amp to know them inside and out. He's also helped me with my DNA Phantom. It's unfortunate but the chances are the 300a will be retired and replaced with the 350 Z. I would really prefer two have the 300 a repaired but I don't know if it's financially feasible. It has been rebuilt and when I say rebuilt upgraded capacitors and whatever one could do to that amp to improve the original design of it was performed about a year-and-a-half ago. I don't think it's a major problem. I do know that he is absolutely right and it is the preamp on the 300 a causing the drop-down on my sonars receive. My knowledge and dexterity are about equal. Both being basically non-existent so the chances of me being able to repair it on my own is not likely. I'll change that to a not going to happen. Do you want to repair it for me? After I take the photos and Nomad gives advice on how to if it's possible to repair if u would you be willing to take it on as a job? I have a tech who is very good but is also fairly backed up. I will be sending my tech some other equipment but I wouldn't mind spreading it around. It's always good to know more than one qualified person and considering you've worked on three of them I don't think this should be something too difficult. But then again I don't know that myself. I will take the photos and then wait for Nomads reply. if you're interested after he lets me know what needs to be done I'll pack it up and send it to you. Until then I'm basically using it the way it is. As I mentioned the preamp miraculously works in the on position after 20 something years of not working. As a matter of fact if it's not in the preamp position it affects the receive adversely. The last time I used it I used it with the preamp in the on and it brought everyone signal and the noise of course about 3s units but did not drop out like it did when it was in the off position. Very strange. I doubt it will last long in the problem needs to be addressed. If I get it fixed I will put the 350 Z back in the closet. I enjoy the 300 a very much and so does my FS 2340. Thanks for your interest and replies. 73
     
  13. nomadradio

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    A 350Z !?!

    Brings to mind the old phrase "Out of the frying pan and into the fire".

    73
     
  14. Sonar

    Sonar
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    I know where you're coming from. The 350 z had more issues than an HIV, crack addicted prostitute.
    Ever issue the one I have it left the factory with has been addresed.
    I don't have the receipt handy but when I locate it ill list the upgrades.
    If the 350 Z I own would've left palomar with the corrections this one has it would've been as popular than the 300a. It truly has been refurbished and upgraded to the highest standard. I'll list everything and take some pics.
    I won't use it until I give up on the 300a.
    Two days ago the 300 a fixed itself. Lol. It was working fine with the preamp on. How long that'll last I don't know. Probably not long at all. 73
     
  15. nomadradio

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    Yeah!

    Brings to mind the old phrase "More issues than National Geographic".

    'Bout fell over the first time I heard that one.

    I'll see if the picture showing where to put the jumper wire in place of the R50 preamp relay goes. Had it, but haven't seen it in a while. Never made a list of which pics fell into the data drain over the years.

    73
     

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