New use for 6300

  • 3
  • Praise
  • Updated 4 years ago

I had a Heathkit VFO VF-1 that clearly was way off frequency, and I do mean way off. Could not find it with my KX-3 so I turned on my 6300 set it for a 5 Mhz view around 40 meters and saw a peak at 6 Mhz which was the VFO. Thus the 6300 is great to find where old boat anchors have gone off to.

The rest of the story:

Symptoms:
1. Light behind the disk about 1/3 brilliance.
2. Frequency way off, 80 meters about 3.3 Mhz, 40 meters about 6 Mhz

I did fix this, what do you think it was?

After that the frequency was at least in the 80 meter band but after I set in on the right frequency 3.8 with the readout and the output the same when I went to increase the frequency as I turned the dial up, the frequency actually decreased!

I did fix this, what do you think it was?

Photo of Burt Fisher

Burt Fisher

  • 1105 Posts
  • 383 Reply Likes

Posted 4 years ago

  • 3
Photo of Jim Gilliam

Jim Gilliam

  • 462 Posts
  • 71 Reply Likes

I would change EVERY capacitor with type and value, except for the variable capacitor, they don't degrade with age. Wouldn't hurt to check/replace all vacuum tubes including the voltage regulator.


Jim, K6QE

Photo of Ken - NM9P

Ken - NM9P, Elmer

  • 4025 Posts
  • 1248 Reply Likes
Possibilities...
1) Dial cord slippage and VFO tuning capacitor alignment reversed.
2) Bad capacitors in the oscillator circuit
3) mouse nest in the coil?
4) voltage regulator gone bad
5) somebody "diddle sticked" it, hoping to use it as a CB "slider" in the 70's.

Just a few of my guesses...there could be more...<grin>

Ken - NM9P
Photo of Ken - NM9P

Ken - NM9P, Elmer

  • 4025 Posts
  • 1248 Reply Likes
Just remembered the other clue.... Light behind the dial at 1/3 brilliance. This indicates a power problem, either bad votage regulator, power supply rectifiers gone bad, or perhaps even a center tapped transformer operating on half the windings....? It has been years, so I don't remember the total circuitry of the VF-1. BTW, I used mine with a Globe Scout 65 back in 1974.
Photo of James Kirk

James Kirk

  • 79 Posts
  • 12 Reply Likes
It was upside down
Photo of Steve W6SDM

Steve W6SDM

  • 622 Posts
  • 280 Reply Likes
Old age?   Alzheimers?  Not you, Burt, the VFO  :)

Seriously though, I am with Jim on a capacitor or two failing and throwing a circuit out of resonance.Just about any out of tolerance component could do that but capacitors are more likely to degrade with time.
Photo of Dave - W6OVP

Dave - W6OVP

  • 221 Posts
  • 69 Reply Likes
First: We don't know if was ever correctly assembled and working properly. If not, it's then wide open.

Fix the voltage problem first. Then, if still a problem:

Was the variable capacitor installed 180 degrees out? (Or upside down?)

Last time I looked inside and fixed a friends VF-1 was 1958! I subsequently bought it along with his DX-35 and worked the world with it. Including 11 Meters.)
(Edited)
Photo of Ken - NM9P

Ken - NM9P, Elmer

  • 4025 Posts
  • 1248 Reply Likes
I actually have a manual for a vf1 somewhere in my shack, if you need a copy.
Photo of Roy - W5TKZ

Roy - W5TKZ

  • 124 Posts
  • 13 Reply Likes
I give up!  What did you do?
Photo of Burt Fisher

Burt Fisher

  • 1105 Posts
  • 383 Reply Likes

Here was the solution. The light is in series with the filament of the 6AU6 which was cool to the touch. I checked the voltage rating of the bulb and it matched the required voltage but the bulb required was a #47, it was not a #47 so I found another bulb that went to close to full brilliance, the 6au6 was now warm, the frequency was much closer.

As far as the frequency going up when it should have gone down the dial should have been on the index line when the capacitor was meshed, it was way out, after fixing that adjusting the trimmer capacitors fixed it all.

(Edited)