Viking 2 CDC capacitor wiring

[Pete, WA2CWA]

Page 26 of the CDC manual shows you the pin connections for each tube. Regardless of who says what or when, you should always confirm when a reference is made to connect this to pin X, connect this to pin y, etc. Take the info from page 26 and mark the pin numbers on your schematic. You should also review pages 21 and 22 which have some very useful voltage, current, and resistance measurements under various operating conditions.

[Pete, WA2CWA]

The wiring seems right. I am wondering if I misunderstand how to tune this. I have a 7.200 crystal in position 1. This isn't tuning on 40 but on a different band using that crystal. I need to figure out the proper settings and what band a 40 meter crystal would be used for.

A 7.200 MHz crystal at the very least is used for 40 meters. If it's an overtone type crystal, it can also: 7.2 X 2 =14.4; 7.2 x 3 = 21.6; 7.2 X 4 = 28.8. Obviously, X2 and X3 are out of the amateur band but if it's an overtone-type crystal, you could set the bandswitch to 10 meters and tune up on 28.8.

Also read the tuning details starting on page 9. Very useful information.

[N9axl]

Thanks. I'm getting a 20 amp variac. I hated to spend $109 but I'm at the point it's a necessity.

I have the Viking 2 assembly manual so plan to simply work through that. Pages 34 and 35 are the instructions for when it is fully assembled. Turn on LV with no tubes, turn on HV with no tubes, ok that didn't blow up, put in the rectifier tube, etc etc. I also ordered a new 6au6 tube.  Actually 4 since that got me free shipping.  I have a tube tester so I will run everything through that also.



I think I can work through that and find out where the issue is.  Working with this at 20 percent power on a variac will make it somewhat easier I think - I won't worry about clobbering myself with 700 volts.  I feel sure this is a fixable issue given enough time and patience.

[Pete, WA2CWA]

If you run it on a Variac, there may be circuits that won't run properly or not at all. Plus, you can't get accurate voltage and/or current measurements unless you run it at the rated AC voltage. If this transmitter is a Viking II CDC, I would use that manual. If I remember correctly, I thought the CDC was only sold as a factory wired unit so having an assembly manual for the plain Viking II may not accurately provide the correct and necessary information for all the circuits in the CDC. As they say, use the right tool.

When diddling around voltages, wear a long sleeve shirt, keep one hand in your pocket, and have some insulation under your feet if you're standing on concrete or a grounded surface.

[N9axl]

Good advice which I follow. I started checking resistors this morning and found that r29 had drifted up from 470kohm to almost 800kohm. I will keep plugging away at this and I greatly appreciate everyones advice.

[DMOD]

Today i fired this up and see get no oscillation current, no buffer, no voltage between pin 3 and ground on the VFO plug. A low b+ issue since there should be 300 volts. Now on the 5v4 there was 380 volts between pin 3 and ground so t2 is working.

In earlier discussion pin3 was seem as correct.

However,the pin out diagram for the 5v4 shows the plate is on pin 4 not 3. It would seem that pin 4 is the correct tie point for the positive of the 450 volt cap. Pin 3 is not used in a 5v4.


Am I thinking about this correctly?

Did you not receive the CDC manual I sent via private email?

It has the schematic as well as tube pin outs.

The Viking II-CDC is a factory wired unit.

Recall that I suggested you check the junction of C11 and L2 and trace from there to the junction of C10 and the other wire from L2. I also stated that some pins on the rectifier tubes are not internal tube connections but interconnection points.

Pins 2 and 8 on the 5V4 should have over +350V DC on them and connect to both C11 and L2. Pins 4 and 6 on the 5V4 have HVAC on them. Pins 3, 5 and 7 on the 5V4 may be used for interconnection points.

Trace them out.

Phil - AC0OB

[N9axl]

Oh yes I see that now. Thanks. I'm following through that.  I do see about 380 on those pins as you suggest. I also checked the positive end of r13 and got 780 volts. There is about 270 at the tap. I will just continue to trace through this as suggested and see why there is no oscillation, no meter indications of any kind. It seems to me that the power supply circuits are doing what they bare supposed to. I just have to figure out why that voltage isn't actually doing what it is supposed to.

I truly appeciate everyone's assistance. I realize my questions are, for those who know what they are doing, somewhat boring and simple, but I'm learning so please bear with me. 

[DMOD]

Let's take one step at a time.

1) How much voltage do you have on the terminal strip up in the audio section where the red wire meets the terminal lugs? That's LV (325V+) for the audio section.

2) How much voltage do you measure at the bottom of R20, the 100 ohm resistor? That's LV (325V+) for the OSC and Buffer-Driver section.

If you don't have LV (325V+) at these points, then you may have a LV wiring problem.

If you do have LV (325V+) at these points, then you may have a metering problem or a different problem.

Also check the Key circuit at the cathode of the OSC, pin 7, and see if it is getting grounded when the CW/Phone switch is in the CW position. In the CW position, you should get some grid current on the meter when the Meter Switch is in the GRID position.

When there is no key in the Key Jack, the cathode of the OSC gets grounded in the CW position, assuming you have a good crystal. And check to see if the crystal position and the Crystal Switch match.

Disregard the HV and anything else until you clear the LV situation. The LV is on all the time when the Main Power (Fil.) Switch is up. So you should NOT have to key anything to get LV.



Phil - AC0OB



 

[N9axl]

Thanks. Checked both of these.  My eyes aren't great but the red wire looked like it was the third from the end going from the center of the radio.  I saw 775 volts there. I checked r20 and saw 375. I will check the other item this weekend.  I do notice that the meter glass is broken so it's possible that there is a problem in that it hasn't been a sealed unit.

Perhaps I should replace this? I ask because I see a Johnson Viking 1 meter on fleabay right now, but I don't know if that will work. I'm not sure how I would test a meter.

[KA2DZT]

Checking a meter movement can be a bit tricky, so don't do anything before telling us what way you plan to test the meter.

Fred

[N9axl]

I intend to do nothing to the meter until I have checked out everything and eliminated everything but the meter. I agree its a tricky job I want to avoid if possible. I would have o learn how to do it anyway.

Like the man says - one step at a time. It appears,based on limited testing, that this is producing LV and HV which is something.

[DMOD]

Thanks. Checked both of these.  My eyes aren't great but the red wire looked like it was the third from the end going from the center of the radio.

I saw 775 volts there. I checked r20 and saw 375. I will check the other item this weekend.

Put the transmitter on the bench and Remove BOTH 5R4's.

Do not attempt to key or flip the transmit switch. It just isn't necessary so keep it "off."

With the wiring (bottom) side facing you, orient the chassis so the 807 Modulator tubes are on top (or 6146's down). The Front Panel with the knobs and controls will be to your left. The audio terminal strip is in the upper left area. This terminal strip lug with the red wire on it should have LV on it, no more. This is with just the filament switch on.

There is no way you should see 775Volts on that terminal lug with the red wire. Please recheck your voltage here.

The voltage on the bottom of the 100 ohm R20 resistor is high but that may be your resting LV voltage without a load. The same voltage you saw here should be the same voltage you should be seeing on the red wire in the audio section.

Even though I have good eyesight, I still use a bright flashlight and a 4" magnifying glass.

Phil - AC0OB

[N9axl]

It is 375 volts in both locations.  My mistake. I measured to the other red wire to the terminal strip to the right next to the 807s the first time.

This time I measured to the terminal strip in the upper left with the bright red plastic wire in the wiring bundle coming along the front bottom of the radio.

[DMOD]

It is 375 volts in both locations.  My mistake. I measured to the other red wire to the terminal strip to the right next to the 807s the first time.

This time I measured to the terminal strip in the upper left with the bright red plastic wire in the wiring bundle coming along the front bottom of the radio.

OK, whew, that's better.

Now put the oscillator tube and buffer-driver tube in, and with the CW/Phone switch in CW, turn the Crystal Switch to the second position with a crystal in the first crystal socket.

Remember, the first position of the Crystal Switch selects the VFO, so the second clockwise "click" of the Crystal Switch selects crystal number 1.

Make sure you have the FREQ SW in the 5.8, 8.4 position for your 40 meter crystal.
Set the Meter Switch to GRID and turn on the Main Power (Fil.) switch. After warm-up, turn the crystal and buffer tune knobs to get a reading on the GRID, as per the manual.

Phil - AC0OB

[N9axl]

Getting no joy on this. I checked the voltages on the 6au6 and found
Pin 1-0
Pin 2-0
Pin 3-0
Pin 4-0
Pin 5- 383.5
Pin 6 - 379
Pin 7-29.24

I did check the tube in my tube tester and it tested good.  Admittedly, it's an old Jackson 648 which I haven't calibrated, but it checks for shorts and it seems all good

[Ralph W3GL]

Getting no joy on this. I checked the voltages on the 6au6 and found
Pin 1-0
Pin 2-0
Pin 3-0
Pin 4-0
Pin 5- 383.5
Pin 6 - 379
Pin 7-29.24

I did check the tube in my tube tester and it tested good.  Admittedly, it's an old Jackson 648 which I haven't calibrated, but it checks for shorts and it seems all good

These are DC meter readings at the tube socket ?

What is the voltage on the filament at the socket (AC) ?

Is the tube WARM to the touch?

Looks to me like you might have a problem in the filament wiring...
,

[WD8KDG]

N9axi & others:

The force is strong to bring the new puppy home and plug it in. Lets see how much magic smoke pours out! Unless the seller can prove all is well on all bands and you are there to watch for said "magic smoke"; don't plug it in.

First: Get a skizmatic of said magic smoke producer.
Second: Enlarge said skiz to at least a 3 foot X 3 foot skiz.
Third: Tack/Tape said skiz above lobotomy work area.
Fourth: Check every wire, passive component, tube socket, all additional  extra great ideas, etc. Is it all there, wired correctly?
Fifth: Throw all old electrolytic caps into the dumpster, replace crap caps with new. Include BBOD's to cap list.....dumpster item.
Sixth: Mark up skiz with notes, repairs, crappy great ideas.

At this point you might be ready/safe to plug in said smoke producer. Ready oneself for anxiety attack, turn on power..........
Seventh: READ MANUAL......there might be some good information as how to tune/load/operate said smoke producer.
YMMV...........

Craig,  

[DMOD]

Getting no joy on this. I checked the voltages on the 6au6 and found
Pin 1-0
Pin 2-0
Pin 3-0
Pin 4-0
Pin 5- 383.5
Pin 6 - 379
Pin 7-29.24

I did check the tube in my tube tester and it tested good.  Admittedly, it's an old Jackson 648 which I haven't calibrated, but it checks for shorts and it seems all good

Which 6AU6, the OSC or the first audio amp?

http://frank.pocnet.net/sheets/049/6/6AU6A.pdf

Like Pete said:

Page 26 of the CDC manual shows you the pin connections for each tube. Regardless of who says what or when, you should always confirm when a reference is made to connect this to pin X, connect this to pin y, etc. Take the info from page 26 and mark the pin numbers on your schematic. You should also review pages 21 and 22 which have some very useful voltage, current, and resistance measurements under various operating conditions.

Keep 5R4's outta here until we get grid current.

Put your meter on AC and check ACROSS pins 3 and 4 for about 6.5VAC.

If you have AC, ground pin 8 of the Auxillary Jack momentarily and see if you get grid current.

And make sure the Drive pot is not above 2.5.

Take one aspirin and report back.

Phil - AC0OB

[N9axl]

Pins 3 and 4 had 6.5 volts AC. This is the 6au6 oscillator v6 directly in front of the Crystal sockets.  If by auxiliary Jack you mean the VFO octal socket - a jumper from pin 8 to ground did nothing but trip the GCFI socket in my shack. I should not have it on this GCFI but it's how the room is wired. 

[DMOD]

Pins 3 and 4 had 6.5 volts AC. This is the 6au6 oscillator v6 directly in front of the Crystal sockets.  If by auxiliary Jack you mean the VFO octal socket - a jumper from pin 8 to ground did nothing but trip the GCFI socket in my shack. I should not have it on this GCFI but it's how the room is wired.  

Pin 8 of the X12 jack is the Key line for the OSC and also keys the VFO.

Were you counting the pins from inside the chassis or outside the chassis? You have to count from inside the chassis starting with the index tang and count clockwise. Trace the wiring on pin 8 of X12. A gray or slate-colored wire should be on the left side of the coil that connects to pin 8.

If you have nothing plugged into the Key Jack the cathode, pin 7 of V6 the 6AU6, should be grounded when in CW mode and oscillate.

Turn off power and do an Ohmmeter check from chassis to pin 7 of V6. It should be close to 5 ohms when in CW mode.

Phil - AC0OB

[N9axl]

Yes. I saw around seven ohms between chassis and pin 7 in both cw and phone positions with power off and plate switch in the on position.  I checked the resistance of the shunt resistor and saw it as infinite.

Now, the other day, per your earlier message, I did put in the oscillator tube, etc. etc. while leaving the 5r4s out - they are safe in a drawer - and , for a few seconds, did see grid current to about quarter scale on the meter. It then dropped to zero and stayed there.  The shunt resistor did measure about 5.1 ohms before.  I was told I should replace these already by a knowledgeable person but hadn't gotten to it. 

I truly appreciate your help with this.  It seems I may need to order some parts and, at any rate, work calls me so it may be a week until I get back to this.

[DMOD]

Before you order parts make sure the Key Jack is shorting to ground when there is no plug in it.

The SH3 shunt IS 5.1 ohms.

You got somefin flaky going on there that you're going to have to patiently track down with the manual I sent you.

I was told I should replace these already by a knowledgeable person but hadn't gotten to it. 

You can do what you want but in my years of rebuilding and upgrading, I have never replaced these low value shunt resistors in the OSC and Buff because they are usually 1 Watt types that just don't carry enough current to get hot.

Now, as a matter of maintaining meter accuracy, I do replace those nichrome wire SH1 and SH2 with 1% 0.2 ohm ceramic coated resistors because those Nichrome wire shunts have been found to be outa whack.


Phil - AC0OB



 

[N9axl]

Yes I will check. I realized I didn't clean the Jack so it may be dirty. I did the switches and forgot that. Thanks.

[DMOD]

Recall that  previously this is what I sent you in regards to potential OSC and Buffer-Driver problems:

In the oscillator section one may find the oscillator cathode current to be too low resulting in low buffer and final grid current. This can be traced to screen grid resistor R19 changing value, so replacement is warranted. A 1 Watt carbon composition resistor or carbon film is necessary since this resistor is part of RF feedback to the crystals. Another problem child is the C29 silver mica which can be replaced with a single 47 pF 1kV ceramic unit. Replacing the medium gain 6AU6 with a higher gain 6AH6 results in more drive at the higher frequencies and I found no need to re-bias the oscillator stage.

Another silver mica that will deteriorate is C25, the buffer-to-final grid coupling capacitor. A single 68 pF 1kv ceramic cap helps here as well. If you are not getting enough final grid current or buffer drive, check R23 for value change. R23 should be replaced with a 47k-51k ½ Watt carbon composition as well.

Another drive related problem can be found with R25. Notice that in stock Vikings, the Drive pot R25 is the only load for the LV power supply when in the AM mode and not transmitting. I added a new 200K resistor in the LV supply to shunt some current away from R25 so that it does not dissipate as much power.  Make sure the replacement pot R25 is a true 5 Watt WW resistor.

However, one should only do testing and initial checkout with the 6AU6 Osc tube.

Good Luck.

Phil - AC0OB

[N9axl]

yes.all  suggested parts are on order and will be installed per your comments. I am carefully checking everything over again. your help is greatefully appreciated and is being followed.