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

2510 Again

Discussion in 'CB Radio Modifications' started by kopcicle, May 2, 2018.

  1. kopcicle

    kopcicle Well-Known Member

    Joined:
    Feb 17, 2016
    Messages:
    327
    Likes Received:
    234
    Cross posted to start my own ...

    #2

    ...all mode operational and 500 milliwatt. :-/ As is it would make a decent QRP or driver for a high gain MosFet input. The output is as clean as the desigh sheet intended.
    Now to figure out if it's 2166, 477, or further up in the 1973 or the 2086. Could even be some passive component. As usual I look in the back and both bias potentiometers are maxed...

    ...output varies according to bias setting for both driver and final but still no more than 500Mw . Also looks like someone disturbed all the potted toroids and several of the disc ceramics.



    I don't seem to have the sensitivity to see beyond the DC component off the buffer and pre-driver atm. Need to futz with the probes and a possible low level broadband amp.

    Before anyone goes off on shotgun repair and "just replace the driver and final" the 2166 is getting as rare as the 477/497 and the 2312/1307/1969. The failure mode is well understood be it a clueless butter knife monkey or reverse polarity (the driver and final are always connected to B+) . This exercise is because I need near assembly line proficiency. I may have mentioned that I have (had) 8 of these in house. I now have 12. I swear they multiply when I'm not looking. At least 3 of the 12 will be parts radios for the others and again, what is left is already spoken for. At least one hulk will go to a member here for cosmetic reasons and one stays here for the same reason. I hope to have small parts available and will post when that happens. In the mean time I'll keep this updated with what little progress and humor I have to offer.
     

  2. ExitThirteen

    ExitThirteen Grumpy and Cranky

    Joined:
    Apr 18, 2008
    Messages:
    1,669
    Likes Received:
    935
    If the bias pots were both cranked, there's a good chance it may have damaged the driver and final. But it sounds like it's also a possibility that someone was playing with the TX chain cans as well. Do you have any C2166's or C1306's laying around at all? You can replace the MRF477 final with a C1969 final, you have to cross emitter/collector legs, but a C1969 will work fine (even though output will be reduced to that of a CB, about 18~20W PEP on SSB).


    ~Cheers~
     
    rabbiporkchop likes this.
  3. kopcicle

    kopcicle Well-Known Member

    Joined:
    Feb 17, 2016
    Messages:
    327
    Likes Received:
    234
    13,
    wouldn't be the first time :)
     
  4. ExitThirteen

    ExitThirteen Grumpy and Cranky

    Joined:
    Apr 18, 2008
    Messages:
    1,669
    Likes Received:
    935
    How true indeed. If I had a dime for every time a radio came across my bench that had failed driver/final because of the bias pots cranked..... well. I could at least buy another radio. :LOL:


    ~Cheers~
     
    Robb likes this.
  5. kopcicle

    kopcicle Well-Known Member

    Joined:
    Feb 17, 2016
    Messages:
    327
    Likes Received:
    234
    Screenshot at 2018-05-03 15:29:26.png
    Anyone have the rest of this image ? It's looking from the bottom of the main board with the components drawn on it ...
     
  6. sp5it

    sp5it Master of puppets

    Joined:
    Jul 9, 2009
    Messages:
    891
    Likes Received:
    405
    Cbtricks have it
     
  7. kopcicle

    kopcicle Well-Known Member

    Joined:
    Feb 17, 2016
    Messages:
    327
    Likes Received:
    234
    Main PCB Parts Layout Bottom View is what I need ,
    Not there :-/
     
  8. Low_Boy

    Low_Boy Well-Known Member

    Joined:
    Jan 21, 2010
    Messages:
    501
    Likes Received:
    103
    I will have to look I think it is in my factory service manual.
     
  9. kopcicle

    kopcicle Well-Known Member

    Joined:
    Feb 17, 2016
    Messages:
    327
    Likes Received:
    234
    Okay I'll try to update in some kind of order.

    Handy Andy,
    I knew K7ES and spoke about fishing more than RF but because of this '477 / 497 construction is no mystery. I may have eliminated the active region of driver and final from the problem. (more below) .

    Low_Boy,
    Did the routine inspection of the toroids.and examined /diagnosed the settings as well as verified voltage charts.

    Nomad,
    Electrons they doth vex me ... :)

    So in the course of verifying dc voltage across the 9 pins of the the TA7320P I touch on pin 9 (the output) and the watt meter jumps to 40 watts from 500mw ?!

    I had previously done the alignment of FT104 getting no more than 500mw with AM pwr maxed (yes both) and signal on the scope down near two orders of magnitude.

    So placing the scope probe on pin 9 in either 1x or 10x produces 40 watts + at 32MHZ with vco indicated 28MHz and is unresponsive to vco input. (essentially an unlocked condition).

    I think I can safely eliminate the active components from the problem save for the Balanced Modulator .

    Now on to FT104 and BM output to it . I suppose I can temporarily mod the 2086 buffer for "some" gain and check results.
    http://www.cbtricks.com/rogerbird/2510/hp2510_dia.htm

    I'm still more than a little stumped as to why everything else dc wise is correct (and compares to my working radio) and I still loose a good deal of signal on the way to buffer/pre/drive/final.

    I won't get to do anything today but ...
     
  10. kopcicle

    kopcicle Well-Known Member

    Joined:
    Feb 17, 2016
    Messages:
    327
    Likes Received:
    234
    bench.jpeg bench.jpg
    Not like it used to be but it's a start . I'm a little cramped for space and time but the essentials are there.
    VTVM, Audio VTVM, V-7A, 1805A HP (old reliable), Trygon supply (bullet proof) , WD-755 that can count better than I can, Tek 2213, the genny is under the bench, the Drake mn2700b and the TS830-S .

    oh...

    Yup that is the beer fridge to the right.

    ./
     
  11. Handy Andy

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

    Joined:
    Apr 23, 2018
    Messages:
    677
    Likes Received:
    409
    You're closer than most, wanted to warn you if any mods were done to the 7320P - pin 9 is showing you have artifacts, you're missing one of the two signals. So the mixer products are "accumulated" as noise from your probe tip.

    So I'm thinking they may have tweaks done to the audio path to the 7320 because you have one side, not the other, to make the mixing product. (Downmix)

    How's FT102's condition?

    Regards!
    :+> Andy <+:
     
  12. kopcicle

    kopcicle Well-Known Member

    Joined:
    Feb 17, 2016
    Messages:
    327
    Likes Received:
    234
    Time to update this mess.

    This particular mess is courtesy of a brain dead mental midget of extraordinary capacity to do harm.

    CPU pins 34-35 were pulled up from the board from the upper side and tied to +5V power through a 4.7M resistor. Couldn't have taken the time to remove the CPU board and done the mod on the back side like everyone else.

    Mounting screws had been driven into the mainboard from both sides, one disconnecting the 38.695 from the mixer and the other shorting and burning up a trace.

    The power plug has been ripped out of the radio and wires have been installed w/o strain relief and the connections are tearing at the board.

    The accessory plug was wires twisted and hot melt glue gun.

    There was a relay connected to the back of the radio that was supposedly there to take the B+ off the final and driver when the radio was off. It may have worked , once. The coil is 5V and the contacts are rated at 2A. Relay is melted and contacts are welded.

    AMC and ALC have been defeated.

    Both AM PWR and VR107 have been jumpered.

    Backlight was a burned out GE #47 bulb

    There wasn't one screw in the radio that was tight.

    None of the locating knobs had their retention inserts, instead they were stuffed with what looks like and smells like news paper and Permatex.

    The covers have multiple hole from multiple mountings . The covers weren't removed for the drilling , there are drill marks in the mainboard and metal shavings throughout .

    The epoxy around pins 34-35 CPU was removed with a dull, rusty, paint scraper

    NOT ONE adjustment was left untouched. Every adjustment that could be made was made , incorrectly. I have never seen such a tortured radio.

    Remaining is the receive. The rest of the radio is working now and all but the power and accessory plug have been fixed leaving me with the world's second worst receive audio. What I'm hearing is severely distorted scratchy , kazoo sounding audio. All indications so far point to a receive only audio problem.

    There are other issues to come but this so far is the one that has me temporarily stumped .
     
  13. kopcicle

    kopcicle Well-Known Member

    Joined:
    Feb 17, 2016
    Messages:
    327
    Likes Received:
    234
    "What I'm hearing is severely distorted scratchy , kazoo sounding audio. All indications so far point to a receive only audio problem."

    Negative only audio peaks.

    "DO THE NAME RUBY BEGONIA STRIKE A FAMILIAR NOTE?"

    TDA1905...

    Next
     
  14. Handy Andy

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

    Joined:
    Apr 23, 2018
    Messages:
    677
    Likes Received:
    409
    Oh I'm sorry thought you meant your microphone in TX!

    Oh geez! Sorry 'bout that!

    :+> Andy <+:
     
  15. kopcicle

    kopcicle Well-Known Member

    Joined:
    Feb 17, 2016
    Messages:
    327
    Likes Received:
    234
    Scrapin the bottom of the barrel with this one . What a mess .
    I haven't let the smoke out of any of them , yet. In all cases someone did that for me :-/
    I'm not as completely clueless as I was when I parted out the original radio only to find out 20 years later it was a comparatively easy fix.

    To Do ...
    TDA1905, a rare failure I'm told but there is no question in one case , it's missing completely having been donated so that another might live. In the other case only the positive audio peaks are missing leading one to believe that one half of the output is dead or missing.

    TA7320P , again just not enough output to drive the emitter follower to any degree . On the other hand it would make an ideal QRP radio @ all of 250mw

    I think this one was left in reverse polarity for , a while?
    there was a crater in the 2SC2166
    So the whole RF chain from the 2086 to a MRF455 substitute board

    And one is totally deaf on AM so back up to L315, L317 and see what I can do .

    Noise blanker(s) , Why in the world would anyone twist anything in the noise blanker area ? Change the SynGen around again and go through all of them.

    Finally one is making me a bit crazy. I can't even get close to 10.6975 in USB before L116 makes the oscillator drop out. Tuning up as far as '69701 and watch the oscillator shrink P to P then drop out. All the basics, not loading the circuit, all components intact, swapped 470uh inductors to make sure, found a destroyed trace repaired with a piece of fine buss wire leading from one leg of the USB inductor but ????
    Just a puzzle that one ...

    And so it goes
     

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!