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Valiant Restoration K3MSB




 
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Author Topic: Valiant Restoration K3MSB  (Read 11006 times)
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Dave K6XYZ
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« Reply #25 on: January 14, 2018, 11:27:40 PM »

Mark....the first thing that caught my eye was over 210 watts output.
With the Ip at 400ma and 700v on the plate that's 280 watts input.
If that is really true....why is a fuse not blowing?
If there is no Ip dip...what frequency is the output on?
Sompin weird here.
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k3msb
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« Reply #26 on: January 15, 2018, 06:46:26 PM »

Gents

Thanks for your replies, both on this site and personal.     Saturday morning I rooted through the "pile-o-meters" and surprisingly found I have a 0-1 A DC meter.    I performed some tests and verified it was working.     Other things going on Saturday, including (unfortunately) me getting sicker.   Flu, cough etc.

I didn't think it the best idea to go mucking with the HV until I felt better.   So it may be a day or so before I disconnect the HV and verify the plate current reading.

Dave -- you're comments about why the 2 Amp fuse is not blowing is one of the reasons I'm wondering if it's the meter or shunt,  please see my previous post about this.   

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73 Mark K3MSB
York, PA
k3msb
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« Reply #27 on: January 18, 2018, 08:46:48 PM »

Good Evening.

Tonight I inserted a 1 A meter at the output end of L43.

I was able to dip the Ip as expected using the external meter, but the Valiant meter was pegged on Ip;  it was fine on the other settings.

Some tests into a dummy load;  this time I started with the recommended settings for Aux and Fine as per the manual chart.

160M:
180W Output @ 450 mA Ip  and 8 mA ig
Aux: 7     Fine 3
Exc 55     Final 78

80M:   Blew a lot of plate fuses…..   with only a single 2A fuse left  I moved on….. Grin

40M:
190W  Output @ 400 mA Ip and 4 mA Ig  (ig Maxed out)
Aux 6     Fine 0
Exc 48     Final 60

I guess I’ll need to remove the shunts and inspect them.    I may just order 0.2 and 0.4 ohms resistors anyway.

I will play with 80M and the other bands tomorrow or Saturday.

I’m thinking of just replacing all the caps in the Pi Network.   I haven’t priced that out yet.

73 Mark K3MSB
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73 Mark K3MSB
York, PA
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« Reply #28 on: January 18, 2018, 09:42:39 PM »

Tonight I inserted a 1 A meter at the output end of L43.

Any chance of placing your test meter in just the RF plate circuit? One possibility is to lift the jumper between pins 2 and 6 on P8, the 9 pin accessory plug on the back, which would give you a much more accurate reading. As it is now, you're seeing the total current of the AF and RF plates, screens, bleeder resistors, voltage regulators, and the surge current from the HV supply caps each time you key up. Yikes, actually.

Weird that 80M is blowing fuses and 160M is not. I say that because the latter uses all of the loading caps, so the low bands are usually the first to not dip. One thing to consider is that the oscillator runs at 160M with the 5763 (V4) driver acting as a doubler for 80M operation. Are you able to get 7-8mA of grid current on 80M?

 
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k3msb
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« Reply #29 on: January 19, 2018, 08:10:53 AM »

I put the meter where I did as I wanted to get a total picture of what was going on with the plate current.   I thought the plate component would far outweigh the others for what I was looking for.

I was thinking of putting the meter at the junction of L12 and R16,  but putting it in the jumper as you suggest looks to be the same.

One thing I've noticed is that with an initial drive of 8 mA you need to be fast on dipping the plate;   any particular reason the manual starts out at 8 mA instead of 2 or 4 mA for the initial dip?

I will revisit 80M tonight or tomorrow -- when I've restocked 2A fuses.

 
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73 Mark K3MSB
York, PA
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« Reply #30 on: January 19, 2018, 09:24:01 AM »

One thing I've noticed is that with an initial drive of 8 mA you need to be fast on dipping the plate; any particular reason the manual starts out at 8 mA instead of 2 or 4 mA for the initial dip?

Ah-HAH! 7.5mA is the target, not the starting, grid current...

The best way to tune up is to begin with the Drive control set somewhat low, then bring it up so that you get reasonable plate current, such as 300mA, then start dipping. The Drive control is no longer advanced when it gets to where it should be, verified by clicking the meter to Grid current. Use the Aux and Fine loading controls to further increase the loading until the dip is at the right current then double-check the grid.

BTW, at zero drive, the clamper will/should limit plate current which will gradually increase with drive.

Yep, sounds like a hassle, but this is what separates the "appliance operators" from those with "The Right Stuff" as Chuck Yeager would say.
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k3msb
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« Reply #31 on: January 19, 2018, 10:03:20 AM »

Ah-HAH! 7.5mA is the target, not the starting, grid current...

Well, not according to the page 14 of the manual!

     Turn METER switch to "grid", tune EXCITER dial for maximum grid current.
     Adjust grid current to 8 mA by turning DRIVE control.
     Turn METER to "plate"

     Immediately after throwing SW8 to "man" position (on) tune final dial for minimum current (resonance).

After blowing enough fuses,  I modified that to an initial grid current of about 2 mA or so then upped it afterwards.
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73 Mark K3MSB
York, PA
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« Reply #32 on: January 19, 2018, 10:17:42 AM »

Makes me curious what the E.F. Johnson engineers considered "immediately". I would have used the term "At the speed of light".

My Valiant didn't work right because the original builder followed the assembly instructions to the letter.  In fact, I spent -four months- puzzling over why I had anemic grid current on 20M only to find out that a later revision of the manual included a modified driver tank circuit.

Love these rigs, but sometimes....

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KB2WIG
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« Reply #33 on: January 19, 2018, 01:14:29 PM »



I have absolutely no experience, rpt no experience with the  Valiant, but that won't stop me from commenting....

The Johnson Viking du,  Manuel has one do all the Osc and buffer peaking and then dropping the drive ( grid current on da meter) to zero, before switching on the HV. Then throw the hv switch and watching the plate meter, advance drive to around 100 mA, then dip. Then recheck the grid current. Maybe a nicer way of loading the thing up.


klc
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k3msb
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« Reply #34 on: January 19, 2018, 06:52:29 PM »

Well, unexpected results.

With the 1A meter between pins 2 and 6,  the difference between that reading and the one taken before (after L43) is about 1 needle's width.    That's seems too small. Huh
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73 Mark K3MSB
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« Reply #35 on: January 19, 2018, 07:24:17 PM »

That *is* odd given how many other current drawing devices are no longer being measured.. At least your meter isn't getting slammed when you key up. On the other hand, a 1A meter isn't going to indicate much difference if you lose the 60mA of modulator resting current.
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k3msb
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« Reply #36 on: January 20, 2018, 09:57:46 AM »

Tried a 500 mA meter.     Results a bit more realistic.

Meter between J6-8:
400 mA.
50 mA Resting current
 
Meter at the output end of L43:
430 mA
80 mA Resting current.

That seems more reasonable.

I'll be hopefully working on the Valiant on and off this weekend;  stay tuned.....
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73 Mark K3MSB
York, PA
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« Reply #37 on: January 20, 2018, 03:31:41 PM »

Getting output on all bands and didn't blow any fuses today, but I'm concerned about some readings on the higher bands.

Band  OSC(ma)    Grid(ma)   Ip(ma)   Pout(W)   Exc  Final  Aux  Fine

160       25               8          450       180         55    78      7       3
80        25             1.5-2        430       200         58    70     3        7
40        25                4           400       190         48    60     6        0
20        27              .5-1         420       125         51    62     9        2
15        27                1           420       160         25    32    10       5
10        30               2            420       180         42    22   10        3

The grid current is maxed out on 80, 40, and 20M               
               
The grid current can be increased a bit on 15M and 10M but no further output               
               
On 10M, VFO set to 28.0,  my frequency counter showed output on 27.5.   Verified on Icom RX;  VFO needs aligned.
               
The plate current is measured with external 500 mA meter between J8 pins 2 and 6.   

The drive on 15 and 10 seems very low for the power output;  is this typical for a Valiant?            
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73 Mark K3MSB
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« Reply #38 on: January 20, 2018, 04:50:41 PM »

Getting output on all bands and didn't blow any fuses today...

That's a milestone for Valiant owners. You should be picking out a bottle of bubbly...

The grid current readings suggest a weak 5763 driver/multiplier tube and you should be able to get 8mA on all bands. The Drive control varies the 5763 screen grid voltage, so if you get to a point where no further advancement of the control increases grid current then the tube is weak.

What are the "Buffer" readings for each band? That measurement is the cathode current of the 5763 and can indicate tube condition. As the manual says, the Buffer current should be around 22mA when the Drive control is at "3", which is read as two times the bottom meter scale reading (11mA).
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k3msb
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« Reply #39 on: January 20, 2018, 09:51:08 PM »

Just checked the buffer current on 10M since the radio was already tuned up there from this afternoon -- about 16 mA with the drive on 3;  my measurements on 10 were made with the drive on 5 and it was 22 mA.
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73 Mark K3MSB
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« Reply #40 on: January 20, 2018, 10:15:25 PM »

Do you have a small coil on your bandswitch where the wires connect from the driver tank? It might be time to revisit a post I made just about a year ago (reprinted with my own permission)...


Suffering from low drive?

Several Valiants have come across the workbench with this issue, so I decided to share the secret to restoring that Valiant libido to where it should be and with only minor invasive surgery!

"Valiant A", as we'll call it, had nearly no drive on 20M. "Valiant B" had widely varying drive on the upper bands. In both cases, the 5763 would not be able to create the specified 7.5 mA of PA grid current, and high settings of the DRIVE pot would cause saturation.

As it turns out, later factory wired Valiants and all Valiant IIs have an additional coil "L6C" mounted to the SW3A band selector switch which increases the inductance and Q of the driver tank circuit.

L6C can be easily made with 12 turns of insulated solid conductor hookup wire tightly wound on a 3/8" diameter (I used a drill bit). Installation is simple:

1) Red wire from driver tank coil removed from terminal #4 on SW3A. Insulate the end as it will not be used.
2) Green wire from driver tank coil moved from terminal #5 to terminal #4 on SW3A.
3) L6C installed between terminals #4 and #5 on SW3A.

The attached schematic shows the change of heart the E.F. Johnson engineers had late in the original Valiant production run that became the norm for the Valiant IIs.

You should see an improvement in drive for 20M and up or your money back. Not recommended for 11 meter operation. Use as directed.



* L6C_New.jpg (253.04 KB, 644x785 - viewed 93 times.)
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k3msb
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« Reply #41 on: January 23, 2018, 08:12:11 PM »

Hi Clark

Thanks for the mod for the drive issue;  that seems straightforward to implement.

Before looking into the shunt issue (which will require some surgery) I decided to try the Valiant on AM just to make sure there were no big issues lurking there.   

I did not run at the full 330 mA Ip as I'm still leery of the plate current issue,  but the AM sounded OK on the ICOM with the the audio up to the recommended modulator current.   The clipper worked, but I don't think I desire to use that too much.....

OK, so I need to get the shunt issue solved, which is what I'll start on tomorrow.

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73 Mark K3MSB
York, PA
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« Reply #42 on: January 23, 2018, 08:58:07 PM »

It would be great to hear it on the air and we're a reasonable distance apart. Drop me a note if you like to set up a sched. 40M is good in the early afternoons and 75M is good until about 5:30pm.

I load my Valiant to 300mA for AM. Plenty of power and much easier on the modulator, particularly with today's higher voltages.
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k3msb
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« Reply #43 on: January 26, 2018, 09:26:27 PM »

Good Evening All

I thought I had the plate current problem identified, but alas that was not the case.

I found a cold solder joint at the ground end of shunt resistor.   My meter read about 0.8 to 1 ohm from before the solder lug joint to ground, and 0 afterwards.   

The screw it's attached to secures a terminal strip, and the user didn't even use a lock or star washer.   The top is blocked by a transformer so the screw can't be removed as I wanted to put a toothed solder lug next to the chassis.    I decided instead to attach a solder lug to the screw nearby securing the transformer itself;  it comes with a nice star washer and I added a regular washer.    My meter now reads a solid 0.2 ohms from the hot end of the shunt to ground.     Interestingly, when I was re-attaching the nut to secure that terminal strip,  the bolt sheared off.    Sometimes you just can't win.

Anyway,  the Ip is still high.    Using my external meter connected across the plug on the back,  I'm finding the Johnson meter reads about 175 mA high.     I don't know if that was true before or not.

I also cleaned the meter switch contacts.

I'm getting kind of stumped.   There's not much else to try.   If the meter resistance (which I measured a while back at 16 ohms) is indeed accurate,  then the 0.2 ohm shunt will no longer work, nor will the modulator shunt.    I was thinking of didling with the shunt to try to bring the meter back in line using my external meter as a reference.
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73 Mark K3MSB
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« Reply #44 on: January 27, 2018, 10:07:18 AM »

If the meter is not reading correctly then that's where the correction should be whether it means obtaining a new meter or adding a resistor in series with the meter to calibrate it. What happens if you put your known good meter in series with the Valiant meter? They should read the same current with 5mA full scale. You could also try putting a meter in place of the Valiant meter.
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k3msb
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« Reply #45 on: January 28, 2018, 07:28:20 PM »

Good Evening

The beating of the head against the wall continues. Tongue

I decided to put a 0.9 ohm resistor in parallel with the 0.2 ohm Ip shunt.   This dropped the Johnson current meter reading by about 30 mA.      I then put a 0.2 ohm resistor in parallel with the 0.2 ohm Ip shunt and this dropped the Johnson current reading by 50 mA.    Putting in a lower parallel resistance did nothing more;  I even tried using resistance wire with the length such that it was almost negligible.  There must be something else in the circuit that has a low enough resistance that is taking over as the lowest resistance;  not sure what.    In any event,  using a lower value shunt does not look to be the answer. 

I then read Clark's post.

I set the Ip to full scale and then inserted my 500 mA external meter in series with the Johnson meter.   The Johnson meter dropped to less than half scale.   Hmmmm.     Well, if the internal resistances of the two meters was about the same that might be expected.

I then put my Fluke DMM in series with the Johnson meter.    The Johnson meter read full scale and the Fluke read 4.99 mA.   Great!    I then used the Fluke to measure the voltage across the Johnson meter and it was about 103 mA.   Great.    That shows an internal meter resistance of about 20 ohms, as it should be.

But then it started getting “not so great”......

I decided to verify my readings and put the Fluke back in series with the Johnson meter.   Now the Johnson meter will NOT go full scale.   Removed the Fluke and the meter goes full scale.   I repeated this with my Simpson 260 as well as my Military ME-29U Ammeter.   

I've no idea why I got good readings once then not again.   

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73 Mark K3MSB
York, PA
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« Reply #46 on: January 28, 2018, 07:36:05 PM »

Here's some photos of the HV rectifier board and the LV and Bias solid state plug-ins.


* 20180107_193453.jpg (3125.69 KB, 4160x2340 - viewed 65 times.)

* 20171228_183311.jpg (3896.95 KB, 4160x2340 - viewed 73 times.)
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73 Mark K3MSB
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« Reply #47 on: January 28, 2018, 08:09:34 PM »

If you put your Fluke meter in series with the Valiant meter, do they agree on other meter switch settings? It's possible that the Valiant meter windings or movement is damaged. Isolating the meter readings issue to the meter or sample points will determine the next step. You're looking to see if they either basically agree on the various switch settings.
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KA2DZT
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« Reply #48 on: January 28, 2018, 09:38:07 PM »

Studying the schematic, the shunt for the modulators is 0.404ohms.  The shunt for the PAs is 0.202ohms.  You can not insert another meter just anywhere to put in series with PA current metering circuit.  Doing this will disturb the metering circuit and you will get false readings.

There is one location in the circuit where you can do this.  The connection point where the PA current shunt connects to the plate xfmr CT.  Keeping the meter circuit connection on the 0.202 shunt, open the connection between that connection point and the plate xfmr CT.  You can put another current meter between those two points without disturbing the metering circuit.  The inserted test current meter will read the same current that the plate current circuit is reading.  You can compare current readings to see how far off the plate current metering circuit is.

Depending on how all these components are located and wire in the circuit, doing the above may not be that easy.  You may have to remove connections from one connection point and separate the one circuit point into two separate connection points.

Study the schematic that is posted on the first page of this thread and you will see what I am talking about.

Fred
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k3msb
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« Reply #49 on: January 28, 2018, 09:42:10 PM »

Good Evening Clark

Yes,  I looked at that and the meter seems to read fine:

             Fluke      Johnson
Grid        1 mA         5
Buffer     1 mA         5
OSC       1.7 mA       8.5

I'm using just the bottom scale in this case for all 3 settings.
5 corresponds to 1 mA
25 corresponds to 5 mA etc

"5" corresponds to 1 mA.
5/25 = 0.2
0.2 * 5 mA full scale = 1 mA

"8.5  corresponds to 1.7 mA  
8.5/25 = 0.34
0.35* 5 mA full scale = 1.7 mA
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73 Mark K3MSB
York, PA
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