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. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Yeah, we all see that. Actually, the values are critical when it comes to dielectric type and rating. The OP doesn’t know about this stuff and he wants to repair that amp safely, so you could be constructive and explain to him what kind of capacitor to get and how to install it.

    I’m on cell phone this weekend so it’s a pita to go through that or I would.
     
    Last edited: Sep 28, 2019
    N6UH likes this.
  2. KC5DFP

    KC5DFP Ham Member QRZ Page

    All,Thanks for all the replies!

    After looking at the tuned input board one of the two caps on the 10M portion was burnt as shown in the photo. I pulled the two out and plan to replace them while I’m I there along with c11 door knob type.

    One of the caps is a 5 pf but the other I’m not sure. I’ve attached a pic of them both and hope you can let me know the values and voltage needed.

    Thanks again for the great posts.

    Joe
     

    Attached Files:

  3. AI3V

    AI3V Ham Member QRZ Page

    Yeah, well nobody mentioned it.

    And from the op's last post he hasn't actually checked either part, he "thinks" they are ok.

    But he doesn't KNOW.

    It's his funeral.

    And here is a quote of my advice a few posts ago.

    "I would replace it with a exact factory replacement"

    What part of "exact factory replacement" is confusing you?

    Rege
     
  4. WA7PRC

    WA7PRC Ham Member QRZ Page

    "12J" = 12 pF ±5%. Typically, M = ±20%, K = ±10%, J = ±5%. Generally, values at & above 10 picofarads have a tolerance in percent of marked value. Below 10 pF, the tolerance is absolute (the other capacitor is marked 5 pF ±0.5 pF). :)

    Bryan WA7PRC
     
  5. AI3V

    AI3V Ham Member QRZ Page

    Yeah, well nobody mentioned it.

    And from the op's last post he hasn't actually checked either part, he "thinks" they are ok.

    But he doesn't KNOW they are ok.

    It's his funeral.





    12pf 5% 500volt

    Rege
     
  6. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Nothing Rege. I’m one of those guys who knows his own strengths and weaknesses and is comfortable with them.

    I saw that cap a couple days ago and was driving to a gig to fix a multi hundred thousand dollar system for grateful clients so I thought someone else here would pick that point up.... and you did.

    Dentron stuff was a bit willy nilly. That “exact factory replacement” may be hard to determine. Perhaps you could use your expertise to give the OP an idea of what to look for and an RF Parts part number to look up online and perhaps order.

    That and a couple tips would go a lot further than wasting thread space with posts stipulating that Steve doesn’t know what he’s talking about, which is obviously BS.

    As I’ve posted before over the years about your posts, you could be more pleasant, forgiving of mistakes, and constructive.

    Cheers,
     
  7. AI3V

    AI3V Ham Member QRZ Page

    The factory service manual calls for a 1000pf 6000v "doorknob"

    That's what he needs to install.

    And he needs to verify rfc7 is installed (correctly) and is in working order.

    Rege
     
    KD2ACO likes this.
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    This isn't a very high powered amplifier so things aren't as critical as they would be with a legal-limit amp; but that output coupling/blocking cap needs to handle fairly high current with minimal dissipation and also block the B+.

    There are disc ceramic caps that can do this, but the one shown in the picture isn't well identified and may be insufficient; Dentron used a doorknob most likely because that's what they also used in their bigger amps, so they had a lot of them. The doorknobs used in similar amps (and bigger ones) are usually N750 ceramic and rated for current handling at a few RF frequencies (1 MHz, 10 MHz, etc.). RF Parts has some, so does Surplus Sales and lots of other places. They're not very common in general electronics anymore.

    When Dentron was in business manufacturing stuff (70s-mid 80s) Denny also ran "Amp Supply" which sold all the parts used in Dentron amps as individual components for very good prices. I built two large amplifiers buying parts almost entirely from Amp Supply. One is shown on the cover of CQ magazine, July 1985. That was a great source! Too bad they're long gone.:(
     
    KD2ACO likes this.
  9. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    I can see in my mind’s eye the perfect cap for the job in the RF Parts catalogue but can’t easily dig around for the number right now. Gonna take the kids out sailing around Martha’s Vineyard in a few. It’s gorgeous out today!

    Cheers, lads!
     
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    MV is gorgeous! I love it.

    Lived in Boston for a while and visited MV and Nantucket at Christmastime...they're both amazing that time of year.

    Back here in California, if you ask for a "bucket of steamers" they look at you like you're from another planet.:p
     

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