Project VIking II, another brother, but BETTER !

[Detroit47]

I would stay away from a voltage doubler. The L input full wave rectifier provides a much cleaner DC output and better regulation. If you must go with a capacitive input filter system at least use a full wave bridge. Having ripple on your DC don't make for beautiful audio.

John N8QPC

[KI4THX]

Got a final good bill of health on the Ranger I bought last weekend, I went ahead and replaced all the wax paper caps, so other than the micas...she should be good. Now Ill turn my attention back to the Viking II.

First things first, before I even worry about the transformer with a smoking habit, Ill be replacing the rest of the caps. Thanks for all the advice from all.

The lightbulb trick Ive seen in many a handbook but have yet to take the time to slap a board together. Bought a crate of 100 watters when there was talk of banning them.

 I managed to build a neat little TX/RX ant switch box yesterday too, no 120 VAC outside any cabinets now. Built it out of an old Wawwassee antenna switch box, threw in some neon bulbs, with jeweled lenses in a woodgrain case with the picture of a cat on the front. Only way it could get any more swaggier would be shag carpet on the top...

[WBear2GCR]

DOH!  There is no chernobyl resistor in the VFO, it's a Valiant II not a Viking Valiant II!!

 Sorry...


             dofus has left the building...

[Pete, WA2CWA]

DOH!  There is no chernobyl resistor in the VFO, it's a Valiant II not a Viking Valiant II!!

 Sorry...


             dofus has left the building...

This must be a trick statement.



EF Johnson Viking Valiant II

[KI4THX]

That's a handsome rig ^^^^ I really like the white/grey colors on the Ranger II's.


Well, pulled the offending transformer out in the course of removing weight from the chassis to make it easier to work with. An odor emanates for sure in side the endbells. I might try it one more time with the light bulb and variac trick. Check out the pics.







Ive dug out a slightly larger unit (it has filament, bias and control voltage windings) but it has NO center tap. Is there a way to use this transformer, I think I recall reading somewhere about working around that problem ?  

Heres a pic with the original transformer (sans endbell caps) and another dug out from the pit of despair.

[KI4THX]

Yes, Something about a 100 ohm wirewound slider tapped resistor across the secondaries and using the center slider as a center tap......

Anywhoo-doo da doo,

Found a slightly smaller transformer that will get me by for the time being. Installed it yesterday and finished wiring it up today. Also, stripped all the extra crap from the chassis and put it back to somewhat stock configuration on the speech amp sections. Also removed the half-butt attempt at a PTT setup, it was done fairly crappy.....so it had to go.


Now, it tunes to about 15 watts (Low indeed) and when in phone I have NO MOD current. Shouldn't I have current 50-60ma with the plate on ?

[W6MQI]

Now, it tunes to about 15 watts (Low indeed) and when in phone I have NO MOD current. Shouldn't I have current 50-60ma with the plate on ?

Do you have screen voltage on the modulator tubes? No screen no current.
Did you adjust R13? is R13 good? mine was found to have an open luckily I had an extra left over from a previous Ranger repair.
After adjusting R13 adjust the clamper.

73,Dave

[flintstone mop]

DOH!  There is no chernobyl resistor in the VFO, it's a Valiant II not a Viking Valiant II!!

 Sorry...


             dofus has left the building...

This must be a trick statement.



EF Johnson Viking Valiant II

That's a nice clean TX  Pete

[KI4THX]

Fixing to throw it back on the bench, spent the weekend over in Eastern KY with my son and ALOT of gunpowder...ALOT of gunpowder......

In the hopes of saving time and troubleshooting, the previous speech amp mods were gutted. The unit arrived in non-working condition with many "aftermarket" parts added by other owners, so the slate was really dirty when received. I turned back the clock in that section back to the original (?) radical-schematical (new word?).... so there has been a lot of tinkering with unknown results up to this point.

Saying this, just to see some activity from it is refreshing and a clue that I am at least heading in the right direction, HA.

Im really unfamiliar with this whole "modulator" setup, this be virgin grounds for this dummy, and I have yet to totally find all the voodoo stashed away in this thing. Wish me luck, Im reading the chicken bones on the bench right now !


They say "take another Advil, and rub your temples".... I comply.

[w1vtp]

Gary WZ1M enjoys a good reputation:

http://members.tripod.com/tubes_tubes_tubes/transformerrewindingservice/id28.html

Unless you are going to have this transmitter as a parts, I'd recommend investing in fixing the transformer.  It would be a shame to jury rig something else that might not do the trick

Al

[KI4THX]

Thanks for the link again AL, But it still is not feasible. I have ALOT of priorities (young father in a crap economy) ahead of this gal. Besides, I found a suitable transformer, I realize now that update never made it to print. 600VAC CT at almost the same physical size... slighty smaller (IE about 10 plates less thickness). Don't know the current rating, but this should be sufficient to bide my time to line everything else out until I can find a OE replacement.

Just measured the screen voltage, its reading almost 300V with the plate switch flipped and does not change in either phone or CW. This voltage should be ALOT lower correct ?

[Pete, WA2CWA]

DOH!  There is no chernobyl resistor in the VFO, it's a Valiant II not a Viking Valiant II!!

 Sorry...


             dofus has left the building...

This must be a trick statement.



EF Johnson Viking Valiant II

That's a nice clean TX  Pete

Not mine. I got rid of my Valiant II years ago at Dayton for around $90. Didn't look as good; probably didn't work as good; and was a constant annoying piece of equipment. Don't miss it at all.

[Tim WA1HnyLR]

OOOOOla,  After following the threads about the Viking II i felt I must interject.
 The HV plate transformer in the Viking1&II is a piece of crap. It has porr voltage regulation and runs hot. I have a number of Viking II plate transformers that I will never use. If you are interested I could part with one. There are better pieces.
            -----------------Overview--Viking I & II -----------------

The Viking I and II is the best thought out in the RF department. It is almost general coverage as it is. Yep! 17 and 12 meters on AM . The rest of the transmitter is in great need of fixing:
    Power supplies. Solid stating of ALL supplies is a must. Why screw with lossy heat producing vacuuuuuuum tube rectifiers. Biass supply: Get rid of the 6AL5. Use two 1kv PIV diodes . Go choke inpoot filter. ( Eliminate the first cap at rectifier anodes. Use existing filter reactor. Use at least a 100Mfd 150 volt cap for filtering the Biass. The outpoot voltage will be in the order of -80 -90 volts or so.This is fine. Next, the LV supply; Solid state this one as well. Use 3Kv worth of diode per leg. Set this one up for choke inpoot as well. If left cap inpoot ,the B+ will end up being about 370 volts,A bit much! Going choke inpoot will drop the voltage to the order of 250 volts. This will be a lot easier on various components and circuit considerations. A low drive issue may be on 10 and 15 meters if operation there is contemplated. I used a 6BF5 instead of a 6AQ5. The pin out is the same. It is a drop in. The filter cap should be at least 200Mfd@450 volts used in the low voltage supply. The HV supply must be solid stated as well a pair of K2AW type diodes ,at least 6-8Kv PIV rating to be used or two strings of 1Kv diodes mounted on a terminal board works well too. With the stock plate transformer the outpoot voltage will be about 700VDC. The 8MFD oil cap is barely sufficient for the job . Jim WD5JKOs suggestion to use a pair of 330 Mfd caps in series is the best way to go. In terms of plate voltage anything from 500-800 volts will work. Obviously the 800 volt level will make about 125 watts outpoot. Whereas 500 volts will make about 75-80 watts out. In the grand scheme of things the difference in outpoot power will be hard to notice at the other end. A machine tool transformer as suggested will work well . A 480 volt secondary with a bridge rectifier and cap inpoot filter will deliver about 625-650 volts under load. I noticed a discussion of a transformer that was rated @ 575 volts. This would deliver 500 volts under load choke inpoot bridge rectified.
You have many options here. ---------------AUDIO--------------------
Probably the weakest part of the Viking I & II is the modulator. The speech amp has barely enough gain when using a  good D-10-4 microphonium. The audio quality is like that of two dixie cups and a string. There are many modification articles to fix the problems more or less. Problem is they all involve drilling and blasting and replacement of at least the driver transformer.
The mod transformer can be a weak link as well. The existing circuit can be improved by doing the following : K.i.s.s. mod.( Keep It Simple Stupid) If you are using a preamp /EQ and good microphonium . Low gain of the system is not an issue. Replace the carbon resistors used on first stage of audio,6AU6, After 60 years or so the values can change radically. Use at least a .2Mfd screen bypass cap. Use at least a .01 cap for the coupling cap to microphonium gain pot. The cathode bypass cap should be at least 25 Mfd@ 10 volts or so . Don't forget the plate de-coupling cap. A.1 mfd cap is used. This should be changed to at least a 10 MFD 450 volt cap. Change the second 6AU6 to a 6AQ5. The pinout is very similar. The cathode pin of the 6AQ5 is what was the suppressor grid pin on the 6AU6. The cathode pin of the 6AU6 is one of the two pins used for the grid of the 6AQ5. This makes it simple. The cathode resistor can be of the same value but a two watt rating for safety. Use at least a 50Mfd 25 volt bypass cap. The 6AQ5 is triode connected by connecting the screen to the plate through a 4.7K resistor,value very non critical.  This will at least open up the audio response of the speech amp without getting too carried away.
Not so K.i.s.s.  mod. If more gain is needed to use a D-10-4 microphonium do the following: Follow instructions for the upgrade of the first 6AU6 but change the 1Meg grid resistor to at least a 10 meg resistor. This change should be done to ANY transmitter when a D-10-4 or other peizo-electric microphonium is used. Relocate the goose tube(6AQ5) from where it is located to the tube socket vacated by the 6AL5. Place another 6AQ5 in the socket and wire it according to the K.I.S.S mod. The second 6AU6 becomes a resistance coupled stage. Simply use a 47K 1watt resistor from the LV B+ to the plate of the 6AU6. The 22K screen resistor is connected to the plate. A .01-.05 cap connects the plate of the second 6AU6  to the grid of the 6AQ5 audio driver. A 100K resistor is connected from the plate of the 6AQ5 to the plate of the second 6AU6. This is a loop of negative feedback around the audio driver. The cathode resistor of the second 6AU6 should be 1K unbypassed. This can be a point to wrap a loop of negative feedback around the modulator. This mod with negative feedback around the modulator still has plenty of gain with a D10-4 microphonium. --- Modulator addendum---
It is important to place a 10-15K 1 watt resistor in parallel with the secondary of the driver transformer. This provides a much steadier load impedance presented to the audio driver. When the grid voltage swing does not drive the mod tubes into grid current the driver transformer is looking into an infinite impedance. Some audio clipping distortion will be noticeable as one leans into to audio. There are also phase shifts that take place near the ultrasonic audio range that will cause the modulator go into parasitic oscillation when negative feedback is placed around the modulator. I introduced negative feedback with two 470K 2 watt resistors directly from the secondary of the mod transformer to the cathode of the second 6AU6. Adding negative feedback is the very last step to be considered before calling it done. If the modulator takes off reverse the modulator tube plate caps. This is what happens with positive feedback.  The biass and screen voltages are very poorly regulated in the Viking I & II. This must be fixed. First of all deal with the screen voltage. In one Viking II I did up 20 years ago I used the choke inpooted low voltage supply(250 volts) through a set of relay contacts as part of the  PTT circuit I installed. This voltage also feeds the screen of the goose tube. This required a biass voltage of about -24 volts or so. I used a string of 6 Volt radio shack zener diodes. I also placed a 100 Mfd or so 50 volt cap across the zener string. The only disconcerting thing to someone that does this mod it will be noticed that the PA plate current indication will take a negative swing. THIS IS NOT REALLY HAPPENING. Being that the modulator cathode return is tied to the HV B- rail and the meter shunt for the PA stage is from chassis ground to the B- rail. The screen current drawn from the modulator tubes is referenced to chassis ground . This varying current is in opposition to the current flow through the PA plate shunt and there fore causes the meter to swing in a negative direction. To anally retentive people this is a problem. For those that understand it is a non-issue. The usual 20K 50 watt bleeder with the slider tap has always been a failure point in the Viking I & II transmitters. A good stiff voltage source for the screens of the modulators is just as important as a stiff biass supply. There is an alternative. In my collection of gear I have a practically mint Viking II CDC . I was very hesitant to do any rip tear mods. The 20K bleeder was in perfect shape. I simply placed a pair of VR150s in the sockets vacated by the 5R4s I did not even have to reset the tap, It worked perfectly. One thing though. A 10 MFD 450 volt cap must be place across the VR tubes.A 500 ohm 2 watt resistor is placed in series with the VR tubes to prevent the possibility of any relaxation oscillation effect that can occur with gaseous regulator tubes. Zener diodes are free from this effect. See AM Window- Valiant mods I authored.
 In the case of your Viking II ,you are free to make some bigger changes. Move the modulator tubes to the socket holes used by the 5R4s This opens up space for a much larger and better modulation transformer, IE Stancor A 3894 etc. -------------------------PA Stage---------------------------
The  6146s are not neccessarily operating in class C.  The biass voltage from the biass divider string goes through a low value resistor to the grid RF choke The value should be 4.7-5.6K to provide more grid leak biass. This improves modulation linearity. The screen dropping resistance is 20K .This should be 30-35K depending on plate voltage. If the replacement plate transformer delivers 500 volts,20 K is OK. If a DX 100 plate transformer is used.(800+volts) 35-40K is needed. The disc ceramic bypass caps used at the base of the plate FR choke are .01. This really impacts high audio frequency response. They should be pared down to 1000-3000Pf 3Kv units.
---------------------------Addendum-------------PTT----------------
 A PTT circuit is very useful. There are a number of different schemes.  4 poles of relay should be contemplated. One pole to key the exciter, another for the plate transformer and Keyed AC for antenna changeover relay. Another pole for modulator screen voltage and the last pole for auxillary equipment control. RX muting etc. With the solid stating of the power supplies this leave two 5 v philament windings. Seriesing up of these windings  and use of a bride rectifier with 4700MFD filter cap will give you 12-14 volts DC for 12V relays. If a higher voltage keying system is contemplated. The biass supply will work well. A 240 AC coil relay should pull in @ 70-90 volts DC . A pair of 120 DC coil relays with the coils in series should work. If somewhat more voltage is needed simply hang two more 1Kv diodes off of the Biass taps on the LV xfmr and 100 or so 200 volt cap will provide 130-150 volts or so.
In most locations the AC line voltage is around120--125 volts. This results in higer than 6.3V philamnet voltage. This causes the transformer to run hotter than usual along with reduced life expectancy of the tubes. The LV transformer is wound for 115 VAC. I wired the two unused seriesed 5 volt philament windings in series with the primary of the LV transformer. This dropped the philament voltage to 6.1 or so. In the end ,you will have a reliable transmitter that will have respectable audio with full modulation and minimal distortion. The Viking II will give many hours of pleasurable operation in it's modified state.
I realize I made a real old buzzard transmission here but when I see someone in a sand trap I thought I would help out. To others who have a Viking I or II who are contemplating modification please consider what is said here. Hmmmmm I smell another Henrynellar modification article Unless Steve HX edits it and put it up on AMFONE -----------------------------------FINI-
Tim WA1HnyLR

[KA0HCP]

Reminds me of George Washington's hatchet.  The handle has been replaced five times and the head twice! 

[KI4THX]

Wowzer ! That's a wonderfully informative post Tim !!!!

To start, Ive read  more than a handful of your writings already and especially enjoyed the Plate Xformer to Mod Xformer article.....just up my ally with all the junk laying around here. Researching around, I found an article somewhere in a internets-spacewarp about your mountain and was intrigued. To shorten the story here, I am enjoying the archives of your Broadcashhhh . Its nice to find something I can listen to, sit back and be truly entertained for the evening ....with a few cold ones of course.


Thanks for pitching it back to me Tim, Id bet your a busy fella and it too some time to write all that.

It was an Ebay buy, and had quite the layer of funk amongst it. There has been an extra hole punched in the audio section, and many odd-ball resistor (gonna-get-me-by) combos. I guess from what Im gathering is my fine specimen is not really that fine and I should just cut loose on it.


I did find the big tapped resistor in the bottom open due to rust forming under the slider. That's the stopping point of current progress right now. I found it going through the voltage charts in the manual.

I will re-read your post a few more times to fully grasp ahold, otherwise Im liable to say something completely stupid.


I really appreciate the extra gust of wind in my sails, its going to be a good challenge for me.

[KI4THX]

replacement tapped resistor ordered ! MAN ! Some of this stuff is getting harder to find !

In the meantime I am in step one of Tims advice....SS the power supplies.

Im not a fool to disregard good reading for sure.