1. You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
    Dismiss Notice

Robyn T-240D Executive

Discussion in 'CB and Export Equipment and Accessories' started by Shadetree Mechanic, Sep 7, 2018.

  1. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

    Joined:
    Oct 23, 2017
    Messages:
    921
    Likes Received:
    647
    Hey guys,
    I just got a Robyn T-240D from eBay. It came with a D104 and it works well except for one strange thing. When I took the coax off of the Sonar and hooked it up to the Robyn, I didn't get any noise in the receive. I found that unscrewing the coax connector and pulling it out a little it would receive. My station and all the equipment is grounded to a ground rod by the antenna. If I unhook the antenna coax from the station and hook it directly to the Robyn then it works like normal. Any ideas why it doesn't like the station ground? Bad capacitor in the power supply on the Robyn maybe? Any help is appreciated.
    Chris
    IMG_20180906_135142810.jpg


     

  2. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

    Joined:
    Apr 23, 2018
    Messages:
    1,385
    Likes Received:
    1,032
    Eww...yeah...make sure the chassis is not live ground...check it to ground and coax ACROSS itself - it may have an output network problem - especially if you find a voltage on it...
     
    Shadetree Mechanic likes this.
  3. nomadradio

    nomadradio Analog Retentive

    Joined:
    Apr 3, 2005
    Messages:
    1,911
    Likes Received:
    1,339
    Failed coax jumper in line?

    73
     
    Shadetree Mechanic likes this.
  4. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

    Joined:
    Oct 23, 2017
    Messages:
    921
    Likes Received:
    647
    Everything works fine with the Sonar that is tied to station ground. Maybe I will connect the Robyn to station ground. I will measure the case and see if there is any voltage to ground first.
     
  5. jon666

    jon666 Sr. Member

    Joined:
    Jan 24, 2006
    Messages:
    1,469
    Likes Received:
    590
    sounds like a short in a jumper or ground take your pick
     
    Shadetree Mechanic likes this.
  6. Dmans

    Dmans Well-Known Member

    Joined:
    Jan 22, 2017
    Messages:
    343
    Likes Received:
    215
    Possibly a "spread" center pin connector (SO239) on the not so new (but looks great Robyn!)? Could be that your "main coax" PL259 center pin is a bit fatter from not getting swapped out very often? (A bit easier to swap the coax jumper-More cycles on that PL259?)

    Looks Great Shadetree! I'm sure a station ground for the Robyn is imminent as well.

    73's
    David
     
    Shadetree Mechanic likes this.
  7. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

    Joined:
    Oct 23, 2017
    Messages:
    921
    Likes Received:
    647
    Holy cow, I just put the volt meter on it and the radio case to ground has 54vac on it! I thought I felt a little tingle when I laid my arm across it to play with the coax.... I am not sure that I want to tie it to station ground yet. I also noticed that the transformer in the radio hums when I plug it in and its turned off. The cord has no ground and the plug is not polarized. I unplugged it and turned the plug over and now there is 60vac to ground.... with the antenna by itself it works but I got a report that there is a hum in the broadcast audio. 60 HZ? I am looking through the schematic for some clues.
     

    Attached Files:

  8. Dmans

    Dmans Well-Known Member

    Joined:
    Jan 22, 2017
    Messages:
    343
    Likes Received:
    215
    I believe you will find that with the power switch "Off" that the tube filaments are still powered up.(Turn lights off in the room to confirm) This is the "Stand-By" mode for this unit. Turning the power switch to the "On" position should make the unit ready to go with no tube warm up time as is the case with most other tube rigs. Hence, the "tingle" across the arm. It is drawing current even with the switch off.

    Teaberry and Gemtronic's radios (Same Panasonic chassis) do not have this feature. They have a switchable "Stand-By" (full clockwise/detent of the Squelch control) and separate "Power" switch (full clockwise/detent of the Volume control).

    Regardless, sounds like you have a leaking capacitor. As to isolating it, I would start with the power input bypass disc caps-C31 & C32. You can hook Pin 1 of your Octal socket to ground per the schematic.

    Still a great looking classic! Good luck and BE SAFE!!

    73's
    David
     
  9. Rwb

    Rwb Well-Known Member

    Joined:
    Jun 30, 2018
    Messages:
    571
    Likes Received:
    367
    ahh hah now i know who outbided me.haha just kidding but i eyed it couple times . Looked pristine in photos
     
    Shadetree Mechanic likes this.
  10. Dmans

    Dmans Well-Known Member

    Joined:
    Jan 22, 2017
    Messages:
    343
    Likes Received:
    215
    Correction to the above. That should have said "Full Counter-Clockwise" for the Stand-BY and Power-On. Not "Clockwise"
     
    Shadetree Mechanic likes this.
  11. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

    Joined:
    Apr 23, 2018
    Messages:
    1,385
    Likes Received:
    1,032
    Man! Glad you're still here to Tell us that ShadeTree...

    Live Chassis can kill - glad to know your body resistance was enough for you to feel the tingle.

    The chassis, yes, check the output network too - there are several areas in there that can take the final tubes plate voltage into the chassis - that's how my ex-XYL was able to get hers' from the original owner - he got tired of it and sold it off - we sent it to a local tech whom fixed several issues - including a network problem - as he put it, but I can see, how, where and why you got "poked" by it.
     
    Rwb, Shadetree Mechanic and Dmans like this.
  12. BJ radionut

    BJ radionut Supporting Member and 6m addict

    Joined:
    May 9, 2008
    Messages:
    1,797
    Likes Received:
    952
    These Highlighted Chris...could give you the issue...Those tied to ground in PS and or tied to Audio T-windings...
    All look to be easy find, common values and should be easy access under chassis. I am thinking Hum in RX and or TX the 350vdc caps...but TX also could be the ones hooked to audio xformer...
    I would change these anyway...look at the diodes hooked to these for cracks or damage also.
    Those are all 30++ yrs old.
    GL
    All the Best
    Gary
     

    Attached Files:

    Dmans and Shadetree Mechanic like this.
  13. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

    Joined:
    Oct 23, 2017
    Messages:
    921
    Likes Received:
    647
    I found the problem with hooking it to the station coax. I hate to say it but I had it on the station that was disconnected. I had the wrong coax hooked up and stupid me did not realize it until the next day. I took the bottom cover off and started checking the diodes with my DVM. There were some components in one section that looked like the leads might have been touching so I separated them a little.
    IMG_20180911_083008348.jpg
     
  14. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

    Joined:
    Apr 23, 2018
    Messages:
    1,385
    Likes Received:
    1,032
    Otherwise, how's the new arrival doing?

    Receive?

    Transmit?

    That rear plug that kinda looks like a tube socket, any issues since the "live chassis" incident?
     
  15. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

    Joined:
    Oct 23, 2017
    Messages:
    921
    Likes Received:
    647
    I took apart the tube socket plug on the cord and the connections looked correct against the schematic. I measured the chassis voltage with it plugged into the antenna and it was 0v. After I plugged the correct coax into my station, I tried it connected to the station and again 0v. Maybe it is normal to have a floating voltage on the chassis if it is not grounded because there is no ground in the power cord and without coax connected? I will have to disconnect some of my other equipment and check it the same way.

    I was able to use it for about a half hour with good reports until the transmit audio quit. It became intermittent then nothing. When I key up I get the carrier but no modulation. Maybe a bad capacitor? I hooked up a speaker to the PA and no audio there either. I cleaned the relay, PA switch and speaker switch with Deoxit. I pulled out the tubes one at a time and wiped them off and cleaned the pins with Deoxit. Still nothing. Maybe a bad audio tube? Like V5a? The tubes V5b and V6 I assume are ok because I get receive audio. Maybe I could swap V5a with V5b just to see if the problem moves? I am open to suggestions.
    Chris
     

    Attached Files:


Share This Page

  • About Us

    The WorldwideDX Radio Forum was originally established in 2001. We pride ourselves on welcoming Radio Hobby enthusiasts of all types, while offering unbiased, informative, and friendly discussion among the members. We are working every day to make sure our community is the best Radio Hobbyist's site.
  • Like us on Facebook

  • Premium VIP Member

    The management works very hard to make sure the community is running the best software, best designs, and all the other bells and whistles. Care to buy us a beer? We'd really appreciate it!

    Donate to us!