Dentron GLA-1000B... a few things I need help with

Discussion in 'Amateur Radio Amplifiers' started by KC5DFP, Sep 26, 2019.

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  1. KC5DFP

    KC5DFP Ham Member QRZ Page

    All,

    Thanks for all the replies!

    Reviewing the 10M mod instructions I think I might have found the issue. Looks like the filter cap isn’t disconnected as shown in the image below, built let me know if I’m correct.

    Also, is there any disadvantage leaving the glitch protection in?

    Thanks again.
     

    Attached Files:

  2. W1QJ

    W1QJ Ham Member QRZ Page

    Resistor was intended (incorrectly) as a glitch resistor, and the "hair" of a wire is supposed to be a "fuse link", also incorrect.
     
  3. W1QJ

    W1QJ Ham Member QRZ Page

    These amps had a 10/11 meter filter or at least the non input circuit model did. That needed to be removed or bypassed to work on 10. Your 10 input circuit might be grounded somewhere as it would have to have been inoperable on 10/11 meters.
     
  4. KC5DFP

    KC5DFP Ham Member QRZ Page

    All,

    I think my previous post was incorrect. After reviewing the 10M mod instructions the door knob cap between the two variable caps is actually reinstalled. Glad I didn’t try to remove and try it.

    Anyway the search continues.
     
  5. AI3V

    AI3V Ham Member QRZ Page

    Since the output "coupling capacitor" has been replaced,

    And it's function is not to couple the output power,

    BUT TO PREVENT DEADLY HIGH VOLTAGE FROM APPEARING AT THE RF OUTPUT JACK.

    I would replace it with a exact factory replacement,

    And I would make sure, absolutely sure, the "dc safety choke" (RFC7) that should be somewhere on the antenna side of that cap, and shorts the power supply to ground in the event the capacitor fails, is in fact there, and the correct one.

    Before I ever turned the amp on again.

    Rege
     
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That would be "its" (not it's) and sure it is; it serves both purposes: output coupling and DC blocking. If DC blocking was the important thing, it could be 1 pF at 10kV.

    Using the correct component is a good thing.

    Unfortunately, when it comes to Dentron amps, sometimes the right components actually weren't used. The worst example of that was the Clipperton-V for the 2m band: Holy cow.
     
  7. W1QJ

    W1QJ Ham Member QRZ Page

    In the photo with the doorknob cap apparently grounded and connected to the band switch I would say it is padding for the lower bands and that isn't your DC blocking cap. To answer your question, I would simply remove that crazy excuse for a glitch resistor and the "hair" of a wire as a fuse link and just connect the PS B+ to the base of the plate choke with a couple of .oo1 caps to ground rated 3KV or higher. I can't see the input circuit as your photo was from behind, how about a photo from the front of that?
     
  8. AI3V

    AI3V Ham Member QRZ Page

    No Steve, it could not be 1 pf.

    You probably cant :) do the math, but what do you suppose the reactance of a 1pf cap wood bee at 3.5 mhz, and what would that doo two the signal,

    Hint: what doo ewe suppose the output impedance of the toob is.

    Rege
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    You missed the point entirely.

    If it was only for DC blocking, it wouldn't matter what the value is.

    It's not.

    It's a DC block, but more importantly it's an RF coupling capacitor which is why proper selection is important with respect to not only capacitance but dielectric material and construction.
     
  10. AI3V

    AI3V Ham Member QRZ Page

    And you are once again wrong.

    Its PRIMARY JOB is to keep you from being electrocuted if you touch the aerial.

    You could, if you were so inclined, replace it with a length of wire with absolutely no difference in power output.

    And turn the amplifier into a death trap.

    As a rf coupling capacitor it is a quite uncritical value.

    As the part that will save your life....

    Same with rfc7.

    That part will bleed "static charge" off of your antenna during rx.

    That's NOT what it's there for.

    Rege
    [​IMG]


    I can SEE that its broken.

    Rege
     

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