Golden Falcon 400 tube amp

[nomadradio]

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

 

[John Spahn]

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

 

[nomadradio]

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

 

[John Spahn]

What are these called

 

[nomadradio]

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

 

[John Spahn]

I'm getting no transmit out of it

 

[nomadradio]

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

 

[John Spahn]

I have three relays all three work

 

[nomadradio]

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]

How do you check them

 

[nomadradio]

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

 

[nomadradio]

Here's a cheap one. The same and similar testers are all over Fleabay.

https://www.ebay.com/itm/Pocketable...239045&hash=item5218a45ae1:g:U1YAAOSwpPNcpbb9

73

 

[John Spahn]

Thank you for the help

 

[John Spahn]

What would cause these caps to blow like this they are 450v 47 uf

 

[John Spahn]

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