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
Dismiss Notice
This forum does not allow a single user to have more than one username. If anyone wants to change their username contact an admin and it will be done. Multiple accounts belonging to the same member will be deleted without warning.

Golden Falcon 400 tube amp

Discussion in 'Amplifiers' started by Toltec, Jul 6, 2017.

  1. nomadradio

    nomadradio Analog Retentive

    Joined:
    Apr 3, 2005
    Messages:
    3,587
    Likes Received:
    4,041
    Never has been a diagram that I have ever heard about.

    Every one I ever saw was different from the one before. Seems like the design was being worked out with changes to the circuitry as they were built one by one.

    The Golden Falcon amplifiers with one, two, four or six of the ceramic 4CX250 tubes are nothing like the one diagram that has made the rounds for years. There is a diagram for a four-tube version on CB Tricks, but it's nothing like what was inside every one of those I ever saw. Completely different.

    Whenever I would estimate the cost to fix one of these, it would include the labor to draw up a schemo. Made the price I quoted really high.

    Stupidly high.

    But that's the starting point I learned for any repair job, a schematic.



    Every customer turned me down.

    Sure don't blame them.

    You wouldn't want to hire an engineer to write the shop manual for your daily driver.

    73
     

  2. John Spahn

    John Spahn New Member

    Joined:
    Aug 30, 2019
    Messages:
    26
    Likes Received:
    0
    Why did he make them all different or were they over the years I hope one of the local people here won't charge me to much I paid 79 dollars for it I dont think I can pay to much in to it
     
  3. nomadradio

    nomadradio Analog Retentive

    Joined:
    Apr 3, 2005
    Messages:
    3,587
    Likes Received:
    4,041
    I really don't know why they kept revising the design.

    Every brand of CB linear that built a decent quantity of their product would make engineering improvements year by year. D&A and Varmint would do that. Maco would change something in the design of their amplifiers each batch they made. And changes were not always for the better.

    But the GF amplifiers would have serious differences in the setup from one amplifier to the next.

    Makes me think they never built enough of one model to get the design perfected. The basis of mass production is to get the kinks ironed out of your first batch of manufactured widgets and then copy it in mass quantities. I don't think the Golden Falcon folks ever made it to "mass quantities".

    The GF ceramic-tube amplifiers we rebuilt were not a problem because we removed most of the original power-supply, bias and control circuits. Installed circuits I like better. The factory's way of doing things just caused problems. And the higher price of this kind of "repair" would get approved for boxes this size. Not so much for the smaller sweep-tube models.

    But that's the dilemma. Anyone qualified to design and build an amplifier like that won't have trouble making sense of this one.

    Just not a lot of those to choose from.

    73
     
    wavrider and John Spahn like this.
  4. John Spahn

    John Spahn New Member

    Joined:
    Aug 30, 2019
    Messages:
    26
    Likes Received:
    0
    What are these called
     

    Attached Files:

  5. nomadradio

    nomadradio Analog Retentive

    Joined:
    Apr 3, 2005
    Messages:
    3,587
    Likes Received:
    4,041
    Those are PNP germanium power transistors.

    The physical package is called "TO-36", if memory serves. The "TO" designation is assigned by the industry-standards outfit called "JEDEC". Pretty sure it means "transistor outline". Back in the day, that big round metal transistor style was called the "doorknob" package.

    These transistors act as what's called a chopper. They "chop" the 12-Volt DC power into AC. This feeds into the big transformer which steps the voltage up to get rectified for the 800 Volts DC needed for the tubes.

    They are obsolete and this makes them really pricey. They are not really protected from overloads or from overheating. It's built as two sets of three parallel transistors. If those three parts don't match each other well enough, they won't share the load equally three ways. When that happens, one of them will run hotter than the other two and fail prematurely. Just make sure you're sitting down when checking prices for types 2N1522 or 2N4048.

    To make a matched set of three parts might take a half-dozen or more of them to get three that test nearly the same. If you needed all six, no telling how many you would need to buy so that you can put together two sets of three that match.

    When the amplifier is keyed, you'll hear the AC frequency as it vibrates the transformer. Pretty sure this one produces a fairly low pitch, around 200 Hz.

    A tube-type mobile linear will typically require twice as much DC current to operate as a solid-state model with the same RF power rating.

    The low efficiency of converting DC to AC, and then back to high-voltage DC has a lot to do with this.

    73
     
  6. John Spahn

    John Spahn New Member

    Joined:
    Aug 30, 2019
    Messages:
    26
    Likes Received:
    0
    I'm getting no transmit out of it
     
  7. nomadradio

    nomadradio Analog Retentive

    Joined:
    Apr 3, 2005
    Messages:
    3,587
    Likes Received:
    4,041
    If you don't hear any kind of buzz or growl sounds from it when the big relay in the back goes "CLICK!" this suggests that the high-voltage power supply is not running.

    And if that big relay doesn't close when you key the radio, there is some trouble with the keying circuit. That big relay should activate when the amplifier keys up.

    73
     
  8. John Spahn

    John Spahn New Member

    Joined:
    Aug 30, 2019
    Messages:
    26
    Likes Received:
    0
    I have three relays all three work
     

    Attached Files:

  9. nomadradio

    nomadradio Analog Retentive

    Joined:
    Apr 3, 2005
    Messages:
    3,587
    Likes Received:
    4,041
    Then the reason you have no RF power is that you don't have high voltage on the tubes.

    You should hear some activity from the transformer, a buzz, growl or tone.

    If not, you probably need a set of six of those doorknob transistors.

    Or, more correctly two matched sets of three.

    Maybe. Other things can shut down the high voltage.

    But blown power transistors was the most-common cause back when we were still willing to fix these.

    A long time ago.

    73
     
    John Spahn likes this.
  10. John Spahn

    John Spahn New Member

    Joined:
    Aug 30, 2019
    Messages:
    26
    Likes Received:
    0
    How do you check them
     
  11. nomadradio

    nomadradio Analog Retentive

    Joined:
    Apr 3, 2005
    Messages:
    3,587
    Likes Received:
    4,041
    I would check transistors with a transistor tester.

    There are YT videos out there showing how to test a transistor using a simple multimeter. I found those methods only let me identify if a part was catastrophically shorted inside. Won't tell me if the part works, only tells me if it's blown completely to the devil.

    But to see that a part actually works and has current gain like it should calls for a transistor tester.

    Same tool you would use to match sets of three.

    73
     
    John Spahn likes this.
  12. nomadradio

    nomadradio Analog Retentive

    Joined:
    Apr 3, 2005
    Messages:
    3,587
    Likes Received:
    4,041
    John Spahn likes this.
  13. John Spahn

    John Spahn New Member

    Joined:
    Aug 30, 2019
    Messages:
    26
    Likes Received:
    0
    Thank you for the help
     
  14. John Spahn

    John Spahn New Member

    Joined:
    Aug 30, 2019
    Messages:
    26
    Likes Received:
    0
    What would cause these caps to blow like this they are 450v 47 uf
     

    Attached Files:

  15. John Spahn

    John Spahn New Member

    Joined:
    Aug 30, 2019
    Messages:
    26
    Likes Received:
    0
    I bought one of these at a ham electronic fleamarket at frys this weekend it works now i need to figure out how to reed it
     

    Attached Files:

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!