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Hy-Gain 8 SSB low wattage

Discussion in 'General CB Services Discussion' started by slidetbone, Oct 24, 2018.

  1. slidetbone

    slidetbone Member

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    I got my hands on a very clean Hy-Gain 8, not the VIII version. It is a Cybernet, of course. PTBM059COX. I opened it up and it is not modded, but looks to have had the finals replaced at one point. Other than that, rig is super clean.
    I hooked up a wattmeter and see that AM deadkeys around 5 watts. But on SSB, I can barely pass 5 watts and this is speaking loudly into the mic.



    I have the schematic and trying to figure out where to look first.

    Any ideas where to start looking? I am familiar with the AM Cybernets, not the SSB models. I figured out the ceramic VR will adjust AM power, not SSB.

    Any help would be appreciated. In the Tampa Bay FL area, no one will service or align old classics. The techs here only deal with "Ranger" types. So I am on my own to try and bring this rig back up to par.

    Same radio as shown on this thread:
    https://www.worldwidedx.com/threads/hygain-8-not-viii-40-ch-ssb.221350/

    Thanks in advance!
     

  2. nomadradio

    nomadradio Analog Retentive

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    5 Watts?

    On what kind of wattmeter? Average-reading or peak-reading?

    The radio's typical 12 Watts PEP on sideband would show about 5 Watts on an average-reading wattmeter.

    A peak-reading wattmeter should show more than 5 Watts.

    73
     
    slidetbone and L2 like this.
  3. Redbeard U812

    Redbeard U812 Active Member

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    That sound similar to my situation with a 148. We found there was not enough useable power for the SSB to operate. It was garbled. Check out : 148GTL SSB Strange Drift

    Kopcicle was able to put the math to what I had suspected, my power supply was not adequate. Swapped to the 50 amp 13.8 DC on my camper and the AM dead key went up slightly, from 4w to 4.75w. AM PEP swing went to about 23w. SSB jumped from 21w to about 30w swing modulation. There is information from Handy Andy in there that may help you.

    Good luck.
     
    slidetbone likes this.
  4. slidetbone

    slidetbone Member

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    Interestingly enough, my audio on AM transmits with a hum and I was thinking about checking that power supply. When I get to the bench, I am going to swap internal power to 13.8V external and recheck. Using an MFJ-815 for my measuments.

    Using an MFJ-815
     
  5. slidetbone

    slidetbone Member

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    Well, rule out the power although I have not opened the unit yet to check voltages at circuit level. I switched from internal to power from my 40W bench power supply. I definitely have less ripple from that PS, so I will see about later beefing up that internal PS. Measuring output power from both, I still have an underpower issue on SSB. Switched out the mics and same result. This unit has a modulation gain and that did not make a difference. Since I do not have a lot of test equipment, I switched my MFJ to my TRC-490 and I can definitely see the meter swing up to close to 10 watts using normal voice. So the meter is good. I do not have an o'scope but is there anything I can do with the fluke meter to find the issue?
     
  6. nomadradio

    nomadradio Analog Retentive

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    The one thing that comes to mind is the setting of the SSB ALC trimpot.

    Could be set too low. Can't find a diagram for the PTBM059, but the PTBM058 has this adjustment marked "RV2". It's usually somewhere near the final transistor, more or less.

    No pics or placement diagram here for that board.

    73
     
    slidetbone likes this.
  7. slidetbone

    slidetbone Member

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    Nomadradio, I will give it a shot. As soon as I open the radio, I will post what I find. I cannot locate this units service manual, but I have to assume it is the base equivalent of the Hy-Gain 2705 mobile and I located that service manual online with alignment procedures. Cybernet SSB chassis are so different that what I am used to with the AM ones. And this rig is in near mint condition, no scratches or anything. I can tell it has a great receive. Thanks!
     
  8. slidetbone

    slidetbone Member

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    An update. For those that cannot locate the service manual for the Hy-Gain 3108 AKA Hy-Gain 8, use the Hy-Gain 2705 service manual available online. The alignment procedure worked for the HG8.

    The radio is pristine and I wanted to be sure it was working good, but checking for power, found SSB was weak compared to AM. I could tell the finals were replaced by the crappy solder job, so a simple alignment corrected the issue. I was able to get around 8.5W PEP. Alignment says to obtain between 9W to 11W PEP, so I will take this for now.

    After probing deeper, I see that Q10 is a 2SC2312. Schematic calls for a 2SC1969. I cannot tell what is in Q9 as it too was replaced. Hard to see between the heat sink. Should be a 2SC2166, but I am not sure what was put there unless I desolder it off the board and pull the heat sink. I did a search here and found a few posts on the 2312, so I will keep it as is.

    Now it is time to re-wire a Turner M+2/U to use on this radio!
     
    Shadetree Mechanic likes this.

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