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Valiant Restoration K3MSB




 
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k3msb
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« on: January 01, 2018, 07:04:32 PM »

I finished electrical work on my Valiant yesterday and did initial power up tests today – absolutely dead.

Prior to starting restoration I verified the transformers were good etc.    I solid-stated all 3 supplies.   I used socketed diodes / dropping resistors for the bias and LV supplies.   Those units, as well as all other tubes, were out of the radio when I powered up today using a variac and low amperage fuse.  My AC current meter showed no current draw at all, and no bulbs came on.    J8 had the plug in.

I replaced the internal plate supply fuse holder with one on the chassis,  and of course the plug mounted fuses with one on the chassis.   I was very careful doing this work,  but obviously I got something wrong.   

Here's a diagram of what I currently have:

I'm really wondering if the wire from T2 to RY1-2 should go instead to the Filament ON/OFF switch;  I'm pretty sure it didn't before I started, but now I'm now sure.

The two wires labeled “unknown” go the wiring harness near the modulators and I've been as yet unable to trace them.

Any help appreciated.


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73 Mark K3MSB
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« Reply #1 on: January 01, 2018, 08:26:49 PM »

First, you need a good schematic...

Grab one here: http://www.mbzponton.org/n2awa/radio_Johnson_Viking_Valiant_schematic.jpg

Second, your schematic shows that T2, the low voltage power supply transformer, will never see 117vac. There are several discrepancies between what you have drawn and the schematic, so it would be good to do a comparison and be sure that things are wired as they should be.

Assuming that the power supply hasn't been rewired and you still have the original plug, check that the two fuses in the actual power plug are good. Johnson fused both leads of the A.C. plug with internal fuses.

Did the Valiant work fine before you began the modifications?


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k3msb
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« Reply #2 on: January 01, 2018, 09:34:54 PM »

Yes, I have a schematic (excellent manual & schematic from Pete ("manualman") .

I have no idea if the radio worked.   As I said,  before starting work I verified transformer secondary AC voltages with all tubes removed.    To that extent,  the radio at least powered up and the Filament ON/OFF and Plate ON/OFF switches worked as expected.

I've stared at that schematic for a number of hours (the power input circuit isn't that hard.... Roll Eyes ).

I agree that T2 will never see 117 VAC so I had to have rewired something incorrectly.    Removing the wire that now goes to RY1-2 to the hot 117 should solve the problem.   However,  I don't think it was there when I started my work,  and I'm concerned that moving it may induce other issues.   

I was hoping someone had a construction manual that shows what's connected to those three coils and can confirm moving that wire is the correct solution.

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73 Mark K3MSB
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« Reply #3 on: January 01, 2018, 09:41:05 PM »

Check this out; it wont load for me all the way

http://hammadeparts.jivetones.com/Amateur_Radio_Manuals_Schematics/JOHNSON/Johnson%20Viking%20Valiant%20Transmitter%20(construction%20instructions)%20WW.pdf


I ended up using Firefox to view the file

klc
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k3msb
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« Reply #4 on: January 02, 2018, 08:39:58 AM »

Thank you;   that's exactly what I was looking for!
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73 Mark K3MSB
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« Reply #5 on: January 03, 2018, 10:59:12 AM »

Good luck with the restoration and all the challenges you are likely to encounter...be patient, this rig will test you but it is rewarding to get them going.
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k3msb
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« Reply #6 on: January 07, 2018, 07:26:11 PM »

Found the problem -- after finding it, I thought of the saying “if it was a snake it would have bitten me!”.

I did the preliminary VFO tests as per the construction manual.

80M (VFO Full CCW):
OSC                      22 mA
Buffer (1/3)      10 mA
Grid (Exciter)       6 mA peak

40M (VFO Full CCW)
OSC                      25 mA
Buff (1/3)              25 mA
Grid (Exciter)       7 mA peak

With my solid state rectifiers and 120VAC input:
Bias is -250 VDC   (pin 5 of SS plug in)
LV  is +372 VDC  (pin 8 of SS plug in)

Note I have not yet adjusted the bias pots as per the manual.    

Haven’t turned the HV on yet either…. Tired now, so best not to play with HV…..

Getting excited about maybe having the Valiant on for the AM Rally!
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73 Mark K3MSB
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« Reply #7 on: January 07, 2018, 09:04:06 PM »

Congratulations on the progress!

You could use a variac or series 150W bulb to limit the current draw if you're concerned about the first HV test. In any case, start with the Drive level low for first test to prevent slamming current while the final tuning and loading are adjusted. If the plate current pins with the drive down then the Clamper Tube adjustment will need to be made first.

Looking forward to hearing it on the air!
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k3msb
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« Reply #8 on: January 08, 2018, 07:25:28 PM »

Greetings from central PA where we're having a heat wave -- 25F !!

The HV turned on with mostly no ill effects.  I switched to AM and the two VR tubes lit up.

As I was staring at the schematics with the radio on (HV off) I heard a small "pop".   I removed power but could find no zorched components etc.   I applied power and did the same VFO testing I did last night on 80 and 40M,  and they were fine, the bias, LV, and HV looked fine.   I'll have another look tomorrow.

I performed the RF Bias adjust as per the manual.

Since I have not yet tuned up the radio,  I left the AM Bias pot mid range.

I adjusted the clamp level as per the manual.

I was rather concerned about the LV and bias values as I built solid state rectifers with dropping resistors.

Here's some measurements:

V11-6 (manual):  330V
      (120 VAC): 358V
      (115 VAC): 326V

V11-9 (manual): 5.8 VAC
      (125 VAC): 6.2 VAC
      (115 VAC): 5.6 VAC

HV    (Manual):  600V
      (125 VAC): 716V
      (115 VAC): 652V

Since I didn't use a dropping resistor for the HV solid state rectifers, I figure that's good for about 15 to 20V more....

Bias Rectifier (R50 side not connected to SS rectifer):
      (125 VAC):  -216V
      (115 VAC):  -194V

After doing the clamping adjustment,  I find when I turn the HV on the Ip spikes to around 400 mA.  When I turn the HV off the Ip spikes to aroud 200 mA.  Is this normal on the Valiant?

I think it's time to squirt some RF tomorrow!


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73 Mark K3MSB
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« Reply #9 on: January 08, 2018, 07:55:54 PM »

As I was staring at the schematics with the radio on (HV off) I heard a small "pop".   I removed power but could find no zorched components etc.   I applied power and did the same VFO testing I did last night on 80 and 40M,  and they were fine, the bias, LV, and HV looked fine.   I'll have another look tomorrow.

Welcome to the "El Valiente Club". You'll get used to this kind of thing after a while...

I performed the RF Bias adjust as per the manual. Since I have not yet tuned up the radio,  I left the AM Bias pot mid range.

AM bias?

Having the RF bias properly set to -70 Volts prior to tuning up is important. I use the non-grid end of L7 as a test point.

The modulator bias is also important to be sure that those 6146 tubes aren't in full conduction. I adjusted the bias for about 60mA of modulator resting current.

After doing the clamping adjustment,  I find when I turn the HV on the Ip spikes to around 400 mA.  When I turn the HV off the Ip spikes to aroud 200 mA.  Is this normal on the Valiant?

Not that I've experienced. The 6AQ5 is supposed to conduct enough to sufficiently pull down the screen supply to the 6146 RF tubes whenever RF excitation isn't present. The clamper adjustment can be tricky and may need some fine tuning -or- this could be due to insufficient bias voltage.

I think it's time to squirt some RF tomorrow!

That would be fantastic!
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k3msb
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« Reply #10 on: January 09, 2018, 08:54:31 PM »

There be RF here!  Cheesy Cheesy Cheesy

I turned on the Valiant and after warmup checked the oscillator current -- nothing.  On any band.   Nuts.   Poked around and couldn't find anything.    I then remembered that I had plugged in my straight key into J2.   I wondered if J2 was a shorting type jack, so hit the key and the Oscillator current was fine.   Whew.....

The good news is I'm getting about 200W out on 80 and 40M.   The bad news the Ip is pegged and will not dip.

After playing around with this a bit I put the Meter into the Grid position and proceeded to adjust the "Final" control and the power did indeed peak.   Adjusting the Coupling controls got me to about 210W out on 80M and about 190W out on 40M.    I'm wondering if the problem is the meter shunt?  I replaced both the original plate and modulator current shunts so they should be good.   

Here's my front panel readings:

80M:
Osc:  25 mA
Buffer:  18 mA
Grid 8 mA    (6.5 max key down)

40M:
Osc:  25 mA
Buffer:  15 mA
Grid 7.5 mA    (6 max key down)

Since everything looks to be in the ballpark, and the power peaks with the Pi Network controls, I really don't think there's a problem with the Ip not dipping - I think it's the meter shunt.  Another thing that leads me to this conclusion is that I put the dummy load into J5 initially -- I was seeing some dipping around 300 mA -- which I think is wrong for no RF load.   Not seeing any power on the wattmeter and 300 mA on the Ip was pretty much a turn the radio off now situation and take a look. As I said, I did replace both meter shunts and they tested OK.

I tried to adjust the Modulator resting current (of course I could not load to 330 mA so I went for max power out).   I could only adjust down to 75 mA, not 50 mA as per the manual, and that's at the extreme end of R61.   For the RF Bias adjustment, I added a 1K (I think...) resistor in series with the R62 wiper; I read that this helped in the adjustment process due after solid stating.    I may do this for the R61 wiper arm as well.

I'm also a bit concerned that I can't get 8 mA drive during key down conditions.

Comments welcome from you Valiant gurus.....
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73 Mark K3MSB
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« Reply #11 on: January 09, 2018, 09:22:02 PM »

It's pretty important to get the plate current meter to read accurately, or, get the dip where it should be. Have you tried 20M? Failures of the output loading caps will prevent low enough current dips at lower frequencies. Also, turning the drive down should reduce the plate current. Does it?

Do you have access to an antenna analyzer? There's a way to use that to check the output tuning network.

As for the modulator current, that should easily be able to be lowered if the bias supply is solid stated since it's producing too high a voltage. Not being able to get the static current down to the normal level suggests something else is going on.

Did the current spike issue get resolved?

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k3msb
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« Reply #12 on: January 10, 2018, 07:38:45 AM »

It's pretty important to get the plate current meter to read accurately, or, get the dip where it should be. Have you tried 20M? Failures of the output loading caps will prevent low enough current dips at lower frequencies. Also, turning the drive down should reduce the plate current. Does it?

Good morning.    The same for 20M.    Yes, turning the drive down reduces the Ip;   to get 300 mA of Ip the drive does not register on the meter and power output, on both 80 and 20M, is around 25W or so.

Quote
Do you have access to an antenna analyzer? There's a way to use that to check the output tuning network.

Yes, I have an MFJ-259 analyzer.   No, I don't know how to use it to check.

Quote
As for the modulator current, that should easily be able to be lowered if the bias supply is solid stated since it's producing too high a voltage. Not being able to get the static current down to the normal level suggests something else is going on.

Can't disagree with you;  the common item for both currents though is the new meter shunts.   Maybe I'm fixating on those to much?

Quote
Did the current spike issue get resolved?

No, still there.
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73 Mark K3MSB
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« Reply #13 on: January 10, 2018, 09:22:03 AM »

Output tuning networks are basically impedance matching circuits and they work both ways so it's easy and safe to troubleshoot component issues using the following method.

First, the transmitter should be unplugged and all power supply caps checked for full discharge (that's the safe part).

Next, a non-inductive resistor with a value that matches the RF section is connected between the plate leads and chassis. For the Valiant, a 1.8k or 2.2k resistor will work fine. 1/4 Watt is more than sufficient. Leads should be as short as practical.

An antenna analyzer or impedance bridge is then connected to the antenna jack and set for the frequency to test. The most rigorous test would be on 160M as that utilizes all of the tuning components.

The Final, Aux, and Fine controls are then adjusted to get a 50Z reading with +/- 0 reactance. The settings should match what you use for that frequency during normal operation. If you can't get a match or if the controls are at their maximum ranges then it's likely that a loading cap has failed, which is common, particularly for the turnstile cap.

Cool, eh?

The RF shunt is R58 (0.202 Ohms) and the modulator shunt is R59 (0.404 Ohms), but since the modulator current sample also flows through R58 then an issue there could cause high readings for both MOD and Plate. Check that the R58 resistor wire connections are tight. To be absolutely sure, you could lift one end and use a current meter of known accuracy in its place. For calculations, I believe the Valiant's meter is 5mA full scale.
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k3msb
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« Reply #14 on: January 11, 2018, 08:30:00 PM »

Hi Clark

Sorry for the delay in response;  everyone in the family is catching the bug that's going around and I'm no exception.    I went downstairs today and ran tests on 40M and that was about it for me.

I placed a 2.2K resistor from the final plate cap (junction) to ground and then tuned up via the Analyzer.   Here's what I got:

R= 51.5 ohms      X = 10.0 ohms

Final:  78
Coupling Aux: 0    Fine: 7

Max power output was 130W with 7 mA drive.   

Ip still way off the scale, but would come in range with decreased drive.

I then tuned up via the manual, removed power etc, then put in the 2.2K resistor and hooked up the analyzer:

R= 90 ohms   X = 38.8 ohms

Final:  90
Coupling Aux: 3  Fine: 0

Max power output was 200W with 2.5 mA drive.    I did start out with the Coupling and Fine controls both at 0.

Increasing the drive in both situations did not yield increased power output.

Both cases show a lack of C to cancel out the L,  but is 10 ohms that critical?    Not sure what's causing the 38.8 in the second case.
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73 Mark K3MSB
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« Reply #15 on: January 11, 2018, 10:29:24 PM »

The resistor value should be the same as the impedance of the RF tubes. Your B+ is significantly higher due to the solid state rectifiers and that nominal line voltage is higher today than it was in 1957 and the actual current is unknown without a working Plate current meter. That said, I can understand the discrepancy.

A more significant issue is the high amount of loading capacitance needed for 40M. You might find it difficult to tune on 80 and 160M. This suggests a loading cap failure.

I think it's pretty important to get the current meter working since the Valiant wasn't designed to operate at these voltages. You might see rated output, but that could mean that energy is getting dissipated in the components.

Check the lug connections for the meter shunt resistors, particularly R58 (0.202 Ohms). Soldering nichrome wire isn't an option so the lugs are clamped onto the ends of the resistance wire. Sometimes the lugs become loose. Be sure the chassis is clean at the contact point.

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k3msb
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« Reply #16 on: January 12, 2018, 08:37:50 AM »

Hi Clark

Thanks for you comments!

Both the plate and modulator current shunts were replaced during the restoration.  The 0.404 ohm modulator shunt was replaced with two 0.82 ohm resistors in parallel and the 0.202 plate ohm shunt was replaced with four 0.82 ohm resistors in parallel.  Not the best solution but I used what I had on hand.

I tested the meter during restoration.   I measured 16 ohms internal resistance and 5 mA full scale deflection.    I asked Rodger NQ9E to confirm the resistance as 16 ohms was a bit odd, and he said the nominal resistance is 20 ohms.   So, I think the meter itself is working OK.   I put a pair of 1N4004 diodes across it for protection,  although that's not near the best solution with 0.7 volts forward drop and the meter dropping 100 mA full scale, but again it's what I have on hand.

To show 500 mA on the meter,  the shunt will need to drop 495 mA.

The plate tranny T1 output is 720V and the input is about 120.  So  Ns/Np = Vs/Vp.
Ns/Np = 720/120 = 6.

Ip/Is =Ns/Np  Ip = Is(Ns/Np)

For 300 mA plate current,  Ip = 0.33(6) = 1.98A which is within specs of the tranny. (and Ip in this context is primary current)

But, the meter is being pegged rather hard.  If the meter is seeing even 7.5 mA though it,  the total current would need to be about 740 mA.

Primary T1 current = 0.740*6 = 4.4A and that would most certainly blow the 2A fuse in the plate primary circuit.   While I've blown one or two,  if the current was that high I'd be blowing it every time I tuned up.

So, my thoughts are the plate current really is in range but is being displayed incorrectly -- yet I've replaced the shunts.   Maybe I'm fixating on this?

Maybe I'll disconnect the T1 CT where it connects to C92 and stick a meter in there.....




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73 Mark K3MSB
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« Reply #17 on: January 12, 2018, 12:01:40 PM »

It's better to put a pair of diodes in series, then back to back across a meter.  Otherwise, as the diodes come into conduction, you end up with bad values being shown on your meter. You don't want any current flowing through the diodes until a fault.

This somewhat hinders the diodes protecting the meter, but.....

W6WRT (Bill Turner) showed this effect on the amps reflector years ago.

--Shane
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« Reply #18 on: January 12, 2018, 01:44:22 PM »

Both the plate and modulator current shunts were replaced during the restoration.  The 0.404 ohm modulator shunt was replaced with two 0.82 ohm resistors in parallel and the 0.202 plate ohm shunt was replaced with four 0.82 ohm resistors in parallel.  Not the best solution but I used what I had on hand.

That would seem to get things close as long as the resistors have close tolerances so at this point you've got the arduous task of troubleshooting numerous components, ie, meter, shunts, power supply (assuming the off-scale readings are correct...yikes).

Did the original shunts have to be replaced? That's not something to do unless it's absolutely necessary. It may be worthwhile to put the original shunts back in unless they are known to be bad.

To show 500 mA on the meter, the shunt will need to drop 495 mA.

Kind of...

I tested the meter on my Valiant and determined that it showed 0.1 Volts across the terminals at full deflection. In series with a ammeter of known accuracy, it showed 5 mA, confirming that the internal resistance is 20 Ohms.

*** These tests were done with the meter in the "Off" position to remove any circuitry.

In theory, the shunt will deliver 0.06 Volts across the meter at 300mA of plate current. If you're seeing a meter resistance of 16 Ohms then that voltage would produce a reading of 375 mA on your meter.

Yep. Get out your magnifying glass and begin searching for clues to lead to the suspect!
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« Reply #19 on: January 12, 2018, 01:55:51 PM »

Yes, I have a schematic (excellent manual & schematic from Pete ("manualman") .

hear hear for those good manuals!
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k3msb
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« Reply #20 on: January 12, 2018, 02:39:16 PM »

I was told to replace the meter shunts as they were usually not as accurate as modern components, so I did.   They were thrown out long ago.

I've a question on "SW6", the Output Coupling switch, on the schematics.  What does the "rear" section do?   There's only 2 capacitors,  but nothing is connected to them!! 

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73 Mark K3MSB
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« Reply #21 on: January 12, 2018, 02:59:59 PM »

SW6, the "Aux Coupling" switch, connects various combinations of 300pF, 600pF, 900pF, and 1200pF in the "turnstile" capacitor to the output circuit for loading. The variable capacitor shown (C9) is the "Fine Coupling" adjustment. You can test this by putting an Ohmmeter between the output lead and each of the turnstile cap tabs and observing the continuity as the "Aux Coupling" control is rotated. On 160M, all the caps should be connected.

Send pix!



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« Reply #22 on: January 12, 2018, 03:13:24 PM »

Could the front and rear rotor sections be connected integrally? Could there be one wire connecting the two sections' common contacts? One of those would make sense for adding capacitance in steps.
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« Reply #23 on: January 12, 2018, 05:01:08 PM »

I should have clarified my post;  I know what SW6 does,  I just don't see how the rear wafer does anything as the two caps C42B and C42C are not connected to anything.

There has to be some common contact between wafers.   I'll take a look.

61F When I left the office and we have a winter storm watch for tomorrow morning -- ice and snow mix.... Tongue Sad
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73 Mark K3MSB
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« Reply #24 on: January 12, 2018, 05:23:50 PM »

You think the two caps are not connected to anything.  Take a close look at the rotating wipers.  Most likely the rear one is connected to the front rotating wiper by way of the taps that hold the wipers in place on the rotating insulating material.

Fred
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