Viking II 40 Meter No Output

[w9bea]

Good Evening All:

I decided to move my Viking II off of 160 onto 40 meters today to get on the noontime group.

I normally get 90-100 watts carrier, today, I got nothing.

160 and 80 all work fine.  100 plus watts out.  Radio tuned up fine.  The Oscillator and Buffer seem to make their mark.  Yet on 40, The PA seems to be under load and producing power, yet I see no power out on the Bird Wattmeter.

Looking at the schematic for stuff that should be concentric to 40 meters, I see a small 22 ohm resistor on SW4A and a 4.7K resistor between 80 and 160 (?) hard to tell on the schematic.  Is this a part known for failure?  I put an ohm meter across it, and when the bandswitch is tuned off of 40 meters I see 23 or so ohms.  When the band switch goes to the 40 position, it "appears" to short it out.  Is this expected?

Neither the 40 meter XTAL in the transmitter (cut to 7.290) or the 122 VFO seem to work on 40.  The other crystals all are fine on other bands.

Any ideas?

73--Wally W9BEA

[Pete, WA2CWA]

160 and 80 all work fine.  100 plus watts out.  Radio tuned up fine.  The Oscillator and Buffer seem to make their mark.  Yet on 40, The PA seems to be under load and producing power, yet I see no power out on the Bird Wattmeter.
<cut>
Neither the 40 meter XTAL in the transmitter (cut to 7.290) or the 122 VFO seem to work on 40.  The other crystals all are fine on other bands.

You say the Xtal and VFO don't seem to work on 40. Do they work on the higher bands?

You say:  "on 40, The PA seems to be under load and producing power, yet I see no power out on the Bird Wattmeter."

What does this mean, "under load and producing power"?

[w9bea]

When I increase the drive control, the Plate Current increases.  Takes a great deal of drive to do this (like 4-5 on the control).

The wattmeter registers a few watts, like 3-4 watts.

I did not check the higher frequencies as I never operated the radio there.  I have a tuning chart for the controls to preset them for my usual haunts at 1985, 3885, 7290, 7040, etc.  Never had one for 20-10.

I will check it out tonight after work to see if I can make power there.

I was getting close to 120 watts on 80 Phone.  Wither either the 122 VFO or a Crystal that I bought from AF4K long ago.  I never drive it that hard..... Keeping it around 85-90 watts seems to keep the radio happy.

73--Wally W9BEA

[WD5JKO]

Any chance that the "160 in/out" knob is still in the "in" position?

Jim
Wd5JKO

[DMOD]

Hi Wally,

I have a Viking II-CDC and the 40m positions are as follows:

FREQ - 5.8 - 8.4
Coupling Switch 3.5 - 30.

Phil - AC0OB

[w4bfs]

this is where an indicating wavemeter comes in handy .... if not need some way to see if generating/amplifying 40 mtr energy .... the low power generated indicates this may be the problem ... clean bandswitches and variable cap wipers ...gl

[w9bea]

@ WD5JKO Jim... No, it is out.  Had the 160 switch in for the additional capacity for 160 though.

After another hour of fiddling around.... I think it is fixed now.  Kind of.  Not sure.  I loosened and tightened the connections on the variables.  One connection screw was an 1/8 turn short of totally snugged up.

I took some deoxit on a Qtip, rung it out and gently cleaned the bandswitch as best as I could without dismounting it.

I ran it up on 40, and played with the plate tuning.  It was supposed to make full smoke with the knob at 64.  Now it makes full power at 54.

Repeaked the buffer and the oscillator, got over 105 watts.  dropped the drive down to 90 watts with 240 mils of plate current.  I repeaked the oscillator and buffer again, and got no addl power like I did the first time.  So I think it is fully loaded.

Let it cook on the bench, periodically keying into a dummy load and the bird.  Still holding at 90 watts.  No snap crackle or pop.

Went up to 20 meters.  My 122 VFO does not seem to drive the transmitter well if at all.  This will be a project for another day.

Thinking of replacing the wax papers in the audio stage.

There is still the matter of the resistors on the band switch  SW4A and B.  I see a big older style 10K, the tiny 22 ohm and a 47K.  I do not think I can accurately check them in-circuit with a DVM as the resistance measurement will be corrupted by whatever the resistor is connected or grounded to.  I was able to sneak a pair of spring clip test leads on the 22 ohm job and as long as the bandswitch is not set to 40 meters I get something like 23 ohms which I guess is within the 10% tolerance.  R36 which is the 10K looks like it took some heat.  It appears to connect between the 20 meter and 160 meter tap.  I assume that this is for the buffer stage..?

Also, ever since I owned the radio, the grid metering never worked.  The grid metering shunt is M3 or SH4 as I can tell; a 5.1 ohm resistor  I will check this out before bedtime tonight since I have the bottom cover off the set.

Making progress.

73--Wally W9BEA

[w9bea]

160 and 80 all work fine.  100 plus watts out.  Radio tuned up fine.  The Oscillator and Buffer seem to make their mark.  Yet on 40, The PA seems to be under load and producing power, yet I see no power out on the Bird Wattmeter.
<cut>
Neither the 40 meter XTAL in the transmitter (cut to 7.290) or the 122 VFO seem to work on 40.  The other crystals all are fine on other bands.

You say the Xtal and VFO don't seem to work on 40. Do they work on the higher bands?

You say:  "on 40, The PA seems to be under load and producing power, yet I see no power out on the Bird Wattmeter."

What does this mean, "under load and producing power"?

You know, I forgot I can take the 40 meter XTAL and get it to load on 20.  My 7.040 times 2 would land me on 14.080 MHz.  I will do that later.  I just shut the radio off to play with the grid shunt.

73--Wally W9BEA