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Johnson Viking II Stuff




 
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WBear2GCR
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« Reply #25 on: November 25, 2007, 09:13:52 PM »

Bear,  My camera is a cheapo pinhole type digital that I'm not sure has the "close-in function". I'll check  The two 30 ohm, 30W ceramic resisitors each have one lead cut.  They are wired in parallel. So, in effect they are floating.  Almost all of the old paper capacitors have been removed BTW.

73,
Ellen - AF9J

Ellen, maximize the light in that case! Soak it in light!! Too much you can't have!
Use outside light and artificial light or any combination you can manage.

Warp Factor 9 lighting!

If you have software like photoshop you can take the final image and adjust the brightness and contrast. Then use the sharpen filter, then reduce the image size down to ~800 pixels wide for something that really needs detail or 640wide for regular posts, reapply the sharpen filter save as jpeg, pick a medium quality save.

30 ohm, eh? Sure it's not 30kohm? But what do the connected ends connect to? That will tell you something about where it is in the circuit.

The filter cap with the lead cut off, needs attention... btw. Unless you did that already.

You'll want to change some things in the speech amp after you get it mostly settled and mostly operational...

                   _-_-bear

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AF9J
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« Reply #26 on: December 28, 2007, 10:37:55 AM »

Hi Everybody,

Sorry this took so long, but here's what's been going on with the Viker II:

1.  Further examination revealed that my Viking II dos have the PTT mod.

2  I had absoloutly no Plate Current at all.  Circuit checks showed no voltage from the SS rectifiers.  These were replaced with a single SS rectifier that was beefy enough to handle the current load (thanks Rodger!).

3.  With the new SS rectifier in,  Plate Current was way too high (over 420 mA, even with the crystal switch setting in a position where there was no crystal).  This indicated a several possibilities: not enough bias voltage, a bad set of finals; or a bad clamper tube. 

4.  The bias was checked on both the finals (with and without the finals in [a major difference in bais voltage with finals out could indicate the finals are bad) and the modulator tubes.  In both cases (with and without the finals in) the bias was too low.  There was no significant change in the readings, with the finals removed  So the finals weren't the problem.  Bias voltages as measured on the finals - I only got about -55V (it should be at least -75V).  On the modulator tubes - I only got about -21V (it should be -30V).  So it looked like the bias capacitors C12 & C13 (that goofy dual 15 mFd paper capacitor), were bad.  I replaced the dual paper biasing capacitor with 2, 200V rated 22 mFd.  Biases on the finals and mudulator tubes were rechecked.  This time I got -77V on the finals, and -28V on the modulator tubes.  Much better.

5.  The Plate Current was rechecked.  It's still way too high (on the order of 390 mA).  Since biasing has been eliminated as an issue with regards to the high plate current, it looks like the 6AQ5 clamper tube is bad.  I ordered 2, 6AQ5s this morning (since the buffer tube is also a 6AQ5, I figured I might as well also replace it at this time).  Until the 6AQ5s arrive, I can't do much more with my Viking II.

6.  I also ordered some other capacitors from Mouser to replace the remaining paper capacitors in my Viking II. 

73,
Ellen - AF9J 
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WA1GFZ
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« Reply #27 on: December 28, 2007, 11:44:39 AM »

sounds like the bias voltage is low. the modulators should be around -35 volts. Heck I converted to AB2 and run 29 volts. AB1 the plate mod current will be quite high having high voltage on the mod screens. Check the filter caps on the bias.
Better yet yank the tube and install a couple 1N4007s to solid state it.
You can down load the manual on bama.
You might remove the tubes and see if it comes back to normal. I think the output of the rectifier should  be about -90 volts.
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KX5KW
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« Reply #28 on: December 28, 2007, 02:45:52 PM »

> Since biasing has been eliminated as an issue with regards to the high plate current, it looks like the 6AQ5 clamper tube is bad.

Not sure about the V2 specifically, but I wouldn't think the clamp tube would come into play unless there was no drive.  I wonder if the crystal or vfo frequency may be doubling or tuned to a harmonic in some stage that is far removed from the final tank frequency.  If you have a frequency counter, you could check and if it's way off, you could probe back through the driver/buffer/etc to see where the problem starts.

73',
Kent/KX5KW
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WA1GFZ
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« Reply #29 on: December 28, 2007, 03:05:22 PM »

a clamper tube pulls the screen down a bad tube will not push it up. yank it out the rig will run fine without it. A shorted tube could mess with the bias again yank it if it is a suspect.
First before the rig is keyed does it have final grid current. If it does not then find out why before you key the final. You should be able to easily get 10 ma on 75 meters.
No grid drive check the drive pot. Put the function switch in CW and tune up the osc and driver for max final grid current then reduce it to around 8 ma with the final un keyed. Make sure your driver stages function properly before turning on the final or modulators.
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WBear2GCR
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« Reply #30 on: December 28, 2007, 05:37:27 PM »

Ellen,

Try dipping the plate??

Without the plate being dipped, the current will be VERY high.

On my Viker II the thing pins the meter before it gets dipped!

Surprised the heck out of me! I thought I had a shorted tube!
Take the plate cap OFF one tube or two tubes for testing, if you want to keep the plate meter inside its range. I removed one (check for B+ first), it stayed inside the range, did not pin.

Put the rig into "grid" meter, put the switch for vfo to "zero" and peak the "exciter" knob for max. Then set the drive control for 8ma. That' something between 5 and 10, nothing too fine. Next, set the AUX Coupling control down to the first or second click  from full CCW position. (Assuming a dummy load here) Put the meter into plate, turn the switch on and key it. Dip the plate by swinging the FINAL control. If you don't see much dip, key off, and change the AUX Coupling control, try, repeat until you find a range that gives some dip. I think you'll get dip pretty quick. The variable control "fine" can be varied key down for optimizing the loading you want. I load to about 230ma max.

Sounds to me like the rig is working...  Grin

             _-_-bear

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AF9J
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« Reply #31 on: December 28, 2007, 08:15:56 PM »

Here';s a little more info people (I wrote my last post at work, so it was a little hurried):

1.  I have been unable to dip the finals (which is frustrating for somebody who's done the peak and dip routine for 25 plus years).
2.  I did replace the bias capacitors.  After replacement - the biase voltages were: -77V for the 6146 finals and -33V for the 807 modulator tubes.
3.  My grid current is very low (less than 1 mA).
4.  My excessive plate current even occurs, when no crystal (or VFO) is in the oscillator circuit.
5.  All readings were done in CW mode, and keydown had no effect on them.

BTW - I'm finding the Viking II manual I downloaded from BAMA, to be much better than the manual I have for my Scout.

73,
Ellen - AF9J
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WBear2GCR
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« Reply #32 on: December 28, 2007, 09:03:59 PM »

Here';s a little more info people (I wrote my last post at work, so it was a little hurried):

1.  I have been unable to dip the finals (which is frustrating for somebody who's done the peak and dip routine for 25 plus years).
2.  I did replace the bias capacitors.  After replacement - the biase voltages were: -77V for the 6146 finals and -33V for the 807 modulator tubes.
3.  My grid current is very low (less than 1 mA).
On the rig's meter? In the Grid mode?
Should peak up, as I wrote in the previous post.
To use the VFO, place the function switch into "Zero" - then peak the grid current.

Oh - the position of the "kicker" arm below the chassis seems to often be changed and set wrong - that will cause the rig to run very funny and not be on 80m when you dial it up. On the Viker Duece I got, it was wrong, and it took me about 3-4 hours to figure out that the VFO was ok, it was just being switched wrong!! I had to undo the set screws on the kicker and reset it to the proper position.

Try 40m, if 80m and 160 do not work... the kicker arm is usually not a factor on 40m!

Quote
4.  My excessive plate current even occurs, when no crystal (or VFO) is in the oscillator circuit.

Makes sense... no dip... try the trick I mentioned above first, remove one or two plate caps and see what the plate meter does when you can see it not being pinned.

Sounds like you have a drive problem - no grid current on the meter = no drive?


Quote
5.  All readings were done in CW mode, and keydown had no effect on them.

Ok, but is there B+ being applied on the plates of the finals when it is keyed?
Keydown = apply B+

In the CW position, the xtals will fire, and you can peak the grid using the exciter control and set the grid drive mA using the front panel control... using the VFO you have to dump it into the "zero" position to see grid excitation...

You ought to be able to hear your xtals fire in the CW position on your receiver, no keydown!

Quote
BTW - I'm finding the Viking II manual I downloaded from BAMA, to be much better than the manual I have for my Scout.

73,
Ellen - AF9J

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AF9J
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« Reply #33 on: December 28, 2007, 09:32:42 PM »

HI Bear,

I can't get much grid current at all, when I try to peak it per the Viking II manual.  BTW, my B+ to the oscillator is 285V.  I'm a bit leery about testing the B+ on the finals, until I get the Plate Current to come down.  I don't want to nuke the finals.  To clarify things, following the tuneup procedure, with just the filaments on, I get little to no grid current, when I try to peak grid current.  When I flip on the HV, Plate Current is extremely high, and I cannot get it to dip down to where it belongs.    Plate current is also extremely high, even when I have the cryastal slector in a postion, where i have no crystal plugged in.  BTW, I can get decent drive/buffer current.  I will check the kicker arm.  Maybe it is funky.

73,
Ellen - AF9J
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WQ9E
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« Reply #34 on: December 28, 2007, 10:28:25 PM »

Just a quick heads up concerning an earlier post I read, I would NOT recommend removing the plate connectors on the final on any rig using tetrode or pentode finals unless you also pull the screen voltage feed-otherwise you are probably going to damage the final tube since the screen current draw will be excessive when there is no plate voltage. 

Rodger WQ9E
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WA1GFZ
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« Reply #35 on: December 28, 2007, 11:19:17 PM »

DO NOT WASTE YOUR TIME KEYING THE FINALS UNTIL YOU FIX THE GRID DRIVE PROBLEM. GRID DRIVE HOLDS THE FINAL IN CLASS C. LOW GRID DRIVE WITHOUT A FUNCTIONAL CLAMP NUKES THE 6146s

My V2-CDC mod of the day. Put a 3 conductor line cord on the rig. I found a nice shielded cord from an old monitor headed to the scrap heap. Added the 5R4 heater winding in series with the LV transformer primary dropping the heater voltage from 6.7 to 6.4 volts with the unit cold. Should drop a bit as the transformer heats up. Result cooler LV transformer and better heater voltage on all the tubes.
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N3DRB The Derb
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« Reply #36 on: December 29, 2007, 08:42:24 AM »

let me help with one part.

Put a 3 conductor line cord on the rig.

Every transformer run rig you have needs a 3 wire AC power mains ground and a earth ground. And you need to make sure there's very little difference between the two grounds. Paranoid? you bet, and you should be too.



 
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WA1GFZ
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« Reply #37 on: December 29, 2007, 08:47:08 AM »

YUPPER caps to chassis from the line put voltage on the chassis. Every time I connected the antenna there was a spark. Did mine yesterday. Also filed the hole to accept a nice strai relief for the new cord.
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AF9J
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« Reply #38 on: December 29, 2007, 10:53:10 AM »

Hi Guys,

I'm luck in one regards - the 3 conductor mains cord is already installed on the Viking II.  I'll do some more checking of things today. 

I just got done finding out that my Scout has a power supply problem.  The 6146 voltages are almost 200V over what they're supposed to be.  Voltages from the 5U4 rectifier are off by as much as 140V!  The worst part about it, is that I put in a new rectifier tube when I got it, due to the old one being smashed up in shipping (the guy I bought ti from, only packed the Scout in a single walled box with a few crumpled up newspapers in it, ugh!). Now I'm not sure if the Russian 5U4G is junk, or if I have a bad power transformer in it (the transformer's mounting tabs are bent, so it leans a little bit to one side - in other words it may have suffered shipping damage too).  So much for easy fixes!  The thing worked fine for the first two months I had it.

73,
Ellen - AF9J
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WBear2GCR
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« Reply #39 on: December 29, 2007, 09:05:46 PM »

Awright - pull one of the 6146s, that will put the plate current within the range of the plate meter when it is way out of resonance.

I pulled the plate cap on mine, and the 6146 did not fry... but then again I keyed it fairly quickly and dropped it quickly too...  Roll Eyes
(and I have a small box of 'em to fry...)  Wink

Ok, do you have a scope Ellen?
That will help with troubleshooting the oscillator/buffer/drive circus...

Once you get the clowns out of there, and the elephants in line, it should fly straight!? Shocked

Doesn't that pot on the front panel that does the drive level fry?
Isn't that the "Chernobyl pot"??
maybe that's the problem...?

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AF9J
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« Reply #40 on: December 29, 2007, 10:05:19 PM »

Hi Bear,

Yes I have a scope (I got it for free from the same neighbor who gave me the ICOM IC-740).  As for the front panel Drive pot, I'm able to adjust it down to the level the manual suggests for buffer current.  Buffer current tune up seems to go OK.  Things go bad, when I get to Grid Current (basically zip, as read in the Grid Current meter function), and Plate Current (almost 400 mA, as read in the Plate Current meter function).  Tonight I'm trying to work some of the heavy metal stations.  I got the Scout working again (everything pointed to power supply issues, and it turned out that the Chinese 6146W I put in was junk; I put in another 6146W, and it works fine <sigh!>).  I have a long weekend, so I'll get to the Viking tomorrow.

73,
Ellen - AF9J
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WA1GFZ
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« Reply #41 on: December 30, 2007, 10:31:30 AM »

Well why not fire up that scope and see what is going on at the driver tuning cap. If you have a signal there check the 6146 grids
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WA1GFZ
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« Reply #42 on: December 30, 2007, 09:54:22 PM »

Today's V2 CDC modification.
Connect the LV rectifier heater winding in series with the LV transformer primary and 5R4 heater winding. This dropped the filament voltage to around 6.1 volts.
The temperature rise of the transformer dropped to just barely warm after an hour of operation. So with the 5R4 winding I got down to just under 6.4 from 6.7 and now with all three in series just under 6.3. The voltage is still in spec and everything functions fine. Slightly lower heater voltage should be good for tube life.
I noticed the only wire left on the 6AL5 socket was the green 6.3 volt heater lead. I cut it and fed it back up the harness to the terminal strip at the VFO power socket. Then I removed the socket and installed a second fuse holder so I could fuse the LV transformer. It sits right next to the final RF plate choke so really can't put any parts there.
 
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K1DEU
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« Reply #43 on: January 01, 2008, 08:16:15 AM »

Tim's WA1HLR's modification of compensating for the Old Design of 115 VAC Mains now run on 120 VAC, where we use an unused 5 V filament winding to buck the Low Voltage, bias, filament transformer primary is Excellent.

This works well in many older receivers and transmitters lowering especially higher than normal filament and bulb voltage extending their life!

I initially did this along with protecting the primary's with a 1 picosecond Transorb and slow MOV http://hamelectronics.com/k1deu/pages/ham/general/pages/surge_suppression.htm . But now prefer a different method. This method is strongly condemned by Many who believe in Constant, Stiff voltages for all things. For example in my DX-100 I added a 20 Ohm 20 Watt resistor in series with the LV, bias and Filament transformer primary. Yes my Filament voltage is now within range using 120 Volt Mains and when I snap the power switch on my Dial and meter light bulbs and filaments in the tubes flicker on gently instead of an initial bright flash on. Yes this mod requires much more time to locate a spot above the chassis to mount the Big resistor (or small in a receiver) with some Teflon wire but my dial lights and tubes are much happier. 73  John K1DEU 
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WA1GFZ
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« Reply #44 on: January 06, 2008, 08:30:46 PM »

This weekend I cleaned up the JS around the LV transformer primary with a little terminal strip in place of the TVI filter. I found a nice shielded line cord off an old monitor and installed it with a nice strain relief.

Then I looked at the low voltage output sitting at 340 volts. We were talking about the drive pot on 75 today and Tim suggested changing to choke input on the LV supply would reduce the dissipation in the pot and make the transformer even cooler.
A quick cycle of power and a moving of a filter cap wire dropped the voltage to 250 volts. I had to raise the pot setting from 2 to 4 to get back to the right final grid current. 6AQ5 audio driver current dropped to about just under 30 ma from 40. Still had plenty of monkey swing to the 807s. The rig stayed on all day and at 6:00 the transformer core would barely warm a finger. Now that I only need 1 cap in the LV supply the LV tube socket area looks like a good spot to mount a 680 uf / 500 V beer can.
The negative lead of the drive pot goes to the bottom of the chassis. The pot dissipation could be reduced even more if a resistor is added in series with it.
I looked at the plate voltage at the 807s plate caps I have plenty of drive to swing them quite close to zero volts.....guess they are healthy.
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