Johnson Viking II sending carrier with plate off

[KC3GMQ]

I can get 6 terminal,  So that would be and on off on then am I correct?

[KC4VWU]

Just use one side of it. There are also DPDT's without a center off.

Phil

[KC3GMQ]

Thanks

[KC3GMQ]

Well I replaced the plate switch. All mods removed, turned it on and it loaded the finals fine, no issues there. Now the audio section is crap lol. CW no tone when transmitting but it does break the carrier. Phone works if I max out modulation but highly distorted. I wonder if I fried some other items when the relay fried. I'm currently checking components in the audio section. I get to use my signal tracer again yeah!!!

[Pete, WA2CWA]

Well I replaced the plate switch. All mods removed, turned it on and it loaded the finals fine, no issues there. Now the audio section is crap lol. CW no tone when transmitting but it does break the carrier. Phone works if I max out modulation but highly distorted. I wonder if I fried some other items when the relay fried. I'm currently checking components in the audio section. I get to use my signal tracer again yeah!!!

Turn the BFO on in your receiver. You can't hear CW tone in the transmitter.

[KC3GMQ]

LOL  Doh,  I got it, so I guess im putting out modulation, just not readable,  back to looking at things

[N1BCG]

Low distorted audio could be a few things. The easiest place to start is checking tubes. I've always thought that anyone with tube equipment should also have a tube tester (very handy!). The next step is to test socket voltages. The manual should list the expected voltages for each pin of each tube. Be sure to set everything the way the manual suggests for this test.

Check the value of all resistors for our-of-tolerance readings. Coupling caps from plates to grids should *not* show a resistance! Check them using a high resistance scale (100k Ohms).

[KC3GMQ]

  I found two resistors out, and the wax caps were totally shot.  Ordered caps for the entire transmitter, Already replaced resisters.  I will update once I get the area freshened up.  I do have a tube tester, all tested very good.  Thanks

[KC3GMQ]

Hello all, Well I have the Viking II re capped, audio resisters replaced and I tested the transmitter.  Everything looks good no as far as the extra carrier is gone, finals load nicely, but now I have very distorted audio.  I have tested to the first audio tube 6AU6.  My question...My Apache the audio circuits are operating with the plate off, is this true of the Viking II?  I have safety in mind here, so if I have to turn the plate on, I guess I would make my test hookup with power off, then power on to get a reading, then power off to connect the next tube pin?  I want to check voltages and also use my signal tracer, just want to know the safest way to do this.

Thanks
Dave KC3GMQ

[N1BCG]

Do you have an audio oscillator and an oscilloscope? A good way to check audio circuits is to insert a tone at the input and check the waveform amplitude and quality at each grid in succession.

There are free audio oscillator apps available. No free oscilloscope apps as far as I know.

What are you seeing for bias voltage at the grids of the modulator tubes?

[KC3GMQ]

I do have a scope and a signal generator,  just not real good using them hi hi.  I will figure it out

[N1BCG]

Well, set the signal generator for 1khz and a -40dB output level. Feed that into the mic jack and monitor the waveform at each grid. In theory, it should be a clean sinewave with increasing amplitude at each grid as you go from V1 to V2 to V3 and V4. Be SURE your oscilloscope is set for AC input!

Try connecting the oscilloscope probe to the signal generator first to get the hang of it.

[KC3GMQ]

voltages are off on the first two 6AU6,  I need to find that first I think

[N1BCG]

voltages are off on the first two 6AU6,  I need to find that first I think

V1 and V2 should have B+ without the need for the Plate switch to be on. What's the DC voltage at the grids of V3 and V4?

[KC3GMQ]

On V2, the voltages are way out of whack. Screen is supposed to be +180 and its +370 lol

[N1BCG]

That could also mean you have a bad V2. What's the Plate voltage? That's going to be your LVB+ for the transmitter.

[KC3GMQ]

Plate is +370 vdc One resister going to pin 7 (cathode) was wrong, suppose to be 470Ω and it had 470K installed,  I have it replaced, rechecking things

[N1BCG]

Plate is +370 vdc One resister going to pin 7 (cathode) was wrong, suppose to be 470Ω and it had 470K installed,  I have it replaced, rechecking things

Brown band, orange band, they can look similar. I sense a major improvement coming...

[KC3GMQ]

Tube tester said tube was real good,  but I have a lot of 6AU6's, I will replace with a new one.  Remember, V2 had the wire from the relay to the plate switch to this tube!!,  audio was crystal clear before I removed the relay that fried lol.

[N1BCG]

You replaced the resistor? Which tube connection did the relay go to?

[KA2DZT]

Would be a yellow band instead of brown.  470K would have a yellow multiplier.  47K would have an orange multiplier.  The screen voltage is way up because the tube is nearly cut off due to the very high cathode resistor.

[KC3GMQ]

it was going to the heater , changing the tube made things a lot more responsive, but still sounds muffled and distorted, Ill check more parts.  Pin 7 cathode of V2 is at +5 vdc.  Pin 6 Screen Grid is over +300 vdc (should be aprox 180), Pin 5 Plateod V2 is +325 vdc which is close to what it should be (+300).

[N1BCG]

Would be a yellow band instead of brown.  470K would have a yellow multiplier.  47K would have an orange multiplier.  The screen voltage is way up because the tube is nearly cut off due to the very high cathode resistor.

Absolutely. Yellow, not orange for 470k...

[KC3GMQ]

Also, I did verify the mic up to V1 was clear and strong.

[N1BCG]

it was going to the heater , changing the tube made things a lot more responsive, but still sounds muffled and distorted, Ill check more parts.  Pin 7 cathode of V2 is at +5 vdc.  Pin 6 Screen Grid is over +300 vdc (should be aprox 180), Pin 5 Plateod V2 is +325 vdc which is close to what it should be (+300).

The wire to the heater was to supply the relay with a coil voltage, I suspect. Are you getting 6 VAC on that terminal? Any improvement in the audio with the proper resistor installed? Also, there should be an electrolytic cap in parallel with the resistor.

R37 from plate to screen is 22k (red, red, orange) right?