• 1st RF stage ?

    From philo@21:1/5 to All on Sun Jul 14 11:21:38 2019
    After not having done any radio repairs in years, I now have five radios
    in my workshop.

    The first one belongs to a friend so I have begun to look at it.


    It's a Lyric Model S-7


    Though I have not found a schematic it's a typical 1930's superhet
    employing

    2 ) 24A

    2) 35/51

    1) 27


    With a type 80 rectifier and 47 audio output.


    After I re-capped it I at first thought it needed no other work as it
    had decent audio output.

    After about five minutes, the volume dropped to near zero.


    If I removed the antenna and placed it on the grid cap of the second RF
    stage, it works fairly decently.


    This left me with the conclusion that the first RF stage tube 35/51 was
    low emission, but flipping the two tubes around made no difference.


    I decided to bring my Hickock 533a tester down from the attic and all
    the tubes check OK

    Before I go further, just wondering if anyone here has some ideas.

    Thanks

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  • From retiredinprescott@21:1/5 to philo on Sun Jul 14 14:37:45 2019
    On Sunday, July 14, 2019 at 9:21:40 AM UTC-7, philo wrote:
    After not having done any radio repairs in years, I now have five radios
    in my workshop.

    The first one belongs to a friend so I have begun to look at it.


    It's a Lyric Model S-7


    Though I have not found a schematic it's a typical 1930's superhet
    employing

    2 ) 24A

    2) 35/51

    1) 27


    With a type 80 rectifier and 47 audio output.


    After I re-capped it I at first thought it needed no other work as it
    had decent audio output.

    After about five minutes, the volume dropped to near zero.


    If I removed the antenna and placed it on the grid cap of the second RF stage, it works fairly decently.


    This left me with the conclusion that the first RF stage tube 35/51 was
    low emission, but flipping the two tubes around made no difference.


    I decided to bring my Hickock 533a tester down from the attic and all
    the tubes check OK

    Before I go further, just wondering if anyone here has some ideas.

    Thanks

    I believe this link has the Schematic for the Lyric S7 set: http://www.nostalgiaair.org/pagesbymodel/817/M0028817.pdf
    Mark

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  • From retiredinprescott@21:1/5 to philo on Sun Jul 14 14:21:19 2019
    On Sunday, July 14, 2019 at 9:21:40 AM UTC-7, philo wrote:
    After not having done any radio repairs in years, I now have five radios
    in my workshop.

    The first one belongs to a friend so I have begun to look at it.


    It's a Lyric Model S-7


    Though I have not found a schematic it's a typical 1930's superhet
    employing

    2 ) 24A

    2) 35/51

    1) 27


    With a type 80 rectifier and 47 audio output.


    After I re-capped it I at first thought it needed no other work as it
    had decent audio output.

    After about five minutes, the volume dropped to near zero.


    If I removed the antenna and placed it on the grid cap of the second RF stage, it works fairly decently.


    This left me with the conclusion that the first RF stage tube 35/51 was
    low emission, but flipping the two tubes around made no difference.


    I decided to bring my Hickock 533a tester down from the attic and all
    the tubes check OK

    Before I go further, just wondering if anyone here has some ideas.

    Thanks

    I would check to see if B+ is dropping after a few minutes. Does this set have it's filter capacitors in a can full of tar? Have they been replaced? If the filter caps are going bad and leaking I have seen this sort of problem
    Mark

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  • From philo@21:1/5 to retiredinprescott on Sun Jul 14 20:58:08 2019
    On 7/14/19 4:21 PM, retiredinprescott wrote:
    On Sunday, July 14, 2019 at 9:21:40 AM UTC-7, philo wrote:
    After not having done any radio repairs in years, I now have five radios
    in my workshop.

    The first one belongs to a friend so I have begun to look at it.


    It's a Lyric Model S-7


    Though I have not found a schematic it's a typical 1930's superhet
    employing

    2 ) 24A

    2) 35/51

    1) 27


    With a type 80 rectifier and 47 audio output.


    After I re-capped it I at first thought it needed no other work as it
    had decent audio output.

    After about five minutes, the volume dropped to near zero.


    If I removed the antenna and placed it on the grid cap of the second RF
    stage, it works fairly decently.


    This left me with the conclusion that the first RF stage tube 35/51 was
    low emission, but flipping the two tubes around made no difference.


    I decided to bring my Hickock 533a tester down from the attic and all
    the tubes check OK

    Before I go further, just wondering if anyone here has some ideas.

    Thanks

    I would check to see if B+ is dropping after a few minutes. Does this set have it's filter capacitors in a can full of tar? Have they been replaced? If the filter caps are going bad and leaking I have seen this sort of problem
    Mark




    I did replace the filter caps but I guess I better get my meter out and
    start taking readings.

    Thanks for the link to the schematic, that should help.

    Will start working on this tomorrow

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  • From JWil@21:1/5 to philo on Sun Jul 14 19:42:25 2019
    On 7/14/2019 9:21 AM, philo wrote:
    After not having done any radio repairs in years, I now have five radios
    in my workshop.

    The first one belongs to a friend so I have begun to look at it.


    It's a Lyric Model S-7


    Though I have not found a schematic it's a typical 1930's superhet
    employing

    2 ) 24A

    2) 35/51

    1) 27


    With a type 80 rectifier and 47 audio output.


    After I re-capped it I at first thought it needed no other work as it
    had decent audio output.

    After about five minutes, the volume dropped to near zero.


    If I removed the antenna and placed it on the grid cap of the second RF stage, it works fairly decently.


    This left me with the conclusion that the first RF stage tube 35/51 was
    low emission, but flipping the two tubes around made no difference.


    I decided to  bring my Hickock 533a tester down from the attic and all
    the tubes check OK

    Before I go further, just wondering if anyone here has some ideas.

    Thanks

    AGC problem? I had a RF tube fade causing a similar problem. Checked it
    on two testers, tested OK. Replaced with a known good tube and the radio worked.

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  • From Peter Wieck@21:1/5 to JWil on Mon Jul 15 08:38:24 2019
    On Sunday, July 14, 2019 at 10:42:27 PM UTC-4, JWil wrote:

    AGC problem? I had a RF tube fade causing a similar problem. Checked it
    on two testers, tested OK. Replaced with a known good tube and the radio worked.


    AMEN! To this.

    I have a couple of tubes I keep as "demonstrators" that I use to let people know that tube-testers are momentary devices as typically used. Leave these demo tubes on the tester for 5 minutes, and they gradually go from Good to Not so Good to Fail (Hickok
    539B).

    Peter Wieck
    Melrose Park, PA

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  • From philo@21:1/5 to Peter Wieck on Mon Jul 15 18:59:13 2019
    On 7/15/19 10:38 AM, Peter Wieck wrote:
    On Sunday, July 14, 2019 at 10:42:27 PM UTC-4, JWil wrote:

    AGC problem? I had a RF tube fade causing a similar problem. Checked it
    on two testers, tested OK. Replaced with a known good tube and the radio
    worked.


    AMEN! To this.

    I have a couple of tubes I keep as "demonstrators" that I use to let people know that tube-testers are momentary devices as typically used. Leave these demo tubes on the tester for 5 minutes, and they gradually go from Good to Not so Good to Fail (
    Hickok 539B).

    Peter Wieck
    Melrose Park, PA




    I generally do not use a tube tester but I was trying to determine if I
    had a low emission tube.

    Looks like that is not the case.

    Have tried other tubes but thus far no difference.

    Due to the hot weather I did not feel like doing any troubleshooting
    today but will eventually dig deeper.

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  • From philo@21:1/5 to JWil on Mon Jul 15 18:57:02 2019
    On 7/14/19 9:42 PM, JWil wrote:
    On 7/14/2019 9:21 AM, philo wrote:


    <snip>
    If I removed the antenna and placed it on the grid cap of the second
    RF stage, it works fairly decently.


    This left me with the conclusion that the first RF stage tube 35/51
    was low emission, but flipping the two tubes around made no difference.


    I decided to  bring my Hickock 533a tester down from the attic and all
    the tubes check OK

    Before I go further, just wondering if anyone here has some ideas.

    Thanks

    AGC problem? I had a RF tube fade causing a similar problem. Checked it
    on two testers, tested OK. Replaced with a known good tube and the radio worked.



    Thanks for the reply.

    Good point except this radio is from 1931 or so and AFAIK no AGC

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  • From philo@21:1/5 to All on Tue Jul 16 12:33:42 2019
    <snip>

    After I re-capped it I at first thought it needed no other work as it
    had decent audio output.

    After about five minutes, the volume dropped to near zero.


    If I removed the antenna and placed it on the grid cap of the second RF stage, it works fairly decently.


    This left me with the conclusion that the first RF stage tube 35/51 was
    low emission, but flipping the two tubes around made no difference.


    I decided to  bring my Hickock 533a tester down from the attic and all
    the tubes check OK

    Before I go further, just wondering if anyone here has some ideas.

    Thanks




    The tuning capacitor is insulated from the chassis by rubber grommets.
    One was worn out and the capacitor was simply at least partially shorted
    to ground,

    Though I major PITA to replace, a shot of RTV in there should do the trick.

    The other radios I have are very low priority but may poke around with
    at least one of them someday.

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  • From JWil@21:1/5 to philo on Tue Jul 16 15:58:09 2019
    On 7/16/2019 10:33 AM, philo wrote:


    <snip>

    After I re-capped it I at first thought it needed no other work as it
    had decent audio output.

    After about five minutes, the volume dropped to near zero.


    If I removed the antenna and placed it on the grid cap of the second
    RF stage, it works fairly decently.


    This left me with the conclusion that the first RF stage tube 35/51
    was low emission, but flipping the two tubes around made no difference.


    I decided to  bring my Hickock 533a tester down from the attic and all
    the tubes check OK

    Before I go further, just wondering if anyone here has some ideas.

    Thanks




    The tuning capacitor is insulated from the chassis by rubber grommets.
    One was worn out and the capacitor was simply at least partially shorted
    to ground,

    Though I major PITA to replace, a shot of RTV in there should do the trick.

    The other radios I have are very low priority but may poke around with
    at least one of them someday.
    Some of those old radios had rubber grommets on the tuning caps but they
    long ago rotted away. So you don't know they were ever there in the
    first place. The schematic doesn't show the insulated feet of the cap,
    so if it wiggles, I put some grommets on. Radios Daze has grommets from
    time to time.

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  • From philo@21:1/5 to JWil on Tue Jul 16 21:33:41 2019
    On 7/16/19 5:58 PM, JWil wrote:


    <snip>


    <snip>

    After I re-capped it I at first thought it needed no other work as it
    had decent


    The tuning capacitor is insulated from the chassis by rubber grommets.
    One was worn out and the capacitor was simply at least partially
    shorted to ground,

    Though I major PITA to replace, a shot of RTV in there should do the
    trick.

    The other radios I have are very low priority but may poke around with
    at least one of them someday.
    Some of those old radios had rubber grommets on the tuning caps but they
    long ago rotted away. So you don't know they were ever there in the
    first place. The schematic doesn't show the insulated feet of the cap,
    so if it wiggles, I put some grommets on. Radios Daze has grommets from
    time to time.



    I have some plumbing washers that probably would have worked but it
    would really have been a major job to replace them.

    But speaking of plumbing


    Actually did a 2nd repair job today.


    I'm the only person in the world who can repair a radio and need a
    plumber when I'm done!


    The second radio just needed a filter cap replaced and the pilot lamp.

    When I went into my small storage area in the basement to get the bulb,
    I noticed a small water leak from a shit off valve.

    Had it not been for the radio repair it might have been a long time
    before I would have noticed.

    Minor leak, no major problem.


    When I told my wife she got a good laugh...but not when I said it had
    nothing to do with a grid-leak circuit.

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