The AM Forum

Hello again - I am almost ready to put the refurbished Valiant I have posted about on my variac.

I have 2 multi-meters, basic $50 dollar types from Home Depot rated 600Vac. My question:
What if any measurements should I hook these up to as I slowly turn up the juice on the transmitter?

without blowing 2 perfectly good meters of course.

Any thoughts appreciated..
73
John-N2LK

  Hey John,


        There are 3 power supplies in the Val.
Bias, LV and HV.  I would pull the HV Rectifiers
out as well as the LV rect. and check to make
sure you have bias voltage. Once you find -300VDC
in there you could add in the LV rect. If all
that is good (Meaning, the rig should do everything
it should) see if you can hear the VFO in the
shack RX, PTT should work, Dial lamps, EVERY
thing except make RF power. VR tubes should Strike.


        Then I would pull the Modulator tubes
and add in the HV rectifiers. If HV comes up
add back in the Mod tubes, and be ready to set the
Modulator bias. Put the meter switch in MOD
position and adjust the side panel pot for
correct resting current.


        This process should get you "out of the
woods" with minimum excitement...

GL

/Dan

Dan, thank you..!!  this is great...was just going to power it all up slowing with all tubes inside...

Keep you posted
73
John-N2LK

If you have removed the 866 or 866A tubes from the transmitter, you may want to read the document at this link before turning on the high voltage power supply:

https://www.die-wuestens.de/iz/RECT.pdf

After handling, mercury vapor rectifiers MUST be operated with filament voltage only (no plate voltage) until the mercury is heated so that it returns to a pool at the bottom of the tube.  This takes a lot longer time than the normal warm-up period required between operating sessions when the tubes have not been disturbed, while they remain in an upright position in their sockets.  

When removing tubes from their sockets and moving them about, it is likely that the mercury becomes displaced and adheres to the plate, or other parts of the tube.  The documented pre-heating process is essential to avoiding damage to the tubes, transformer, and other components in the high voltage power supply.  Hope this information is helpful to you.

GL OM.  

Thanks, I have gotten 3B28 tubes as replacements...right now we are at 117Vac, all the tubes (minus HV Rectifiers and LV Rectiier) which are pulled , are lite up.
No sparks yet...bulbs light up...still waiting to finish the warmup...

then will check Bian voltage and go from there...
Keep ya posted.
73
John-N2LK

WOW!!
I feel like a Novice again, very excited....put in the LV rectifier tube and powered up...hear the VFO in my reciever on all bands but 80m...needs calibration but still, wow...to bring this old beast back to some life is quite a thrill....no smoke either!

The VR tubes are not "striking" as of yet, nada....no 3B28 tubes in there yet, that is next step...

73
John-N2LK

So exciting!  Is there no 80M spot signal/final grid current or is the dial way off?

  Gud Job John,


      I can't recall if the Val does 160 or not
but the VFO does. Should be able to hear the
low band VFO sig 1.75mc to 2.0 mc. Maybe the Band
Switch is "Goofy". The VFO is doubled for 80m.
But you should prolly see why the VR tubes aren't
glowing first.

      I would make Solid State rectifiers for all
the power supplies, I've found that the line
"E" from the variac needs to be quite high just
to get the Fil. hot.   Higher than you prolly
want to test with..


      A work around would be to use the 3B28's
and leaving the PLATE Sw off let the rig cook
till well warmed up. Lower the variac to about
60 VAC and hit the plate Sw. I'd still leave the
mod tubes out. This step needs to be done
rather quickly as the tubes will cool fast.

GL

/Dan



     

  Just another thought,


       You could also disconnect the HV
Xfmr PRIMARY from the rigs wiring and hook
a line cord to it and just use the Variac
to tame the HV for testing. Of course you
should investigate the VR tube thing first.

       So at this point you should be able
to run the bias and LV supplies off the
your standard line voltage and the HV off
the Variac.

        This setup will keep the fils hot
and hopefully all will be normal. You will
also need to hook a dummy load to the
RF output at this point.

Again,

GL

/Dan

Here is the latest, I measured -274Vdc on the bias so left that alone. Put in the 2 HV rectifiers and all the other tubes and powered up.

The HV Rectifiers (3B28's) get warm but do  not glow at all.
VR tubes do not strike, the dont light up at all.

For a lark, I put rig in recommended cw settings from manual on 160M and 40M, fiddled with it and got up to 90 watts output to my dummy load.
I hear the OCS on 80 meters but Very weak, low OSC current on the rigs meter for 80M.

And R51 gets REAL Hot! like you cant touch this at all HOT....felt the warmth thru the radios panel...

I have to go and now learn how to set this radio up but it does work, not sure what the deal is on the VR tubes but will see.

Any suggestions appreciated as I now go from parts replacement to setting up..have construction manual and ops manual.

73
John-N2LK

 Hey John,


          What is your AC line voltage? What is the
LV coming in at? R51 (The Drive control) is a 4 W
wire wound pot that controls screen voltage to the
driver tube. Not sure bout the Val, but on the Ranger
it is the LV Bleeder as well.

          If your AC mains are real high like 125VAC
your LV supply will also be real high. 

   300/25000=12ma.

        300 X 0.012=3.6 watts

   It was barely heavy enough to do the job
when new. Even if your LV supply is 350 VDC that is
4.2 Watts..  I'll bet you will be surprised how
high your LV supply is.

        Hook your meter across one of the filament
lines and set your variac to 6.1 to 6.3VAC as measured
at a socket.  Then measure your LV...


GL

Your almost there!!


/Dan

This tip is a bit late considering the great progress you have made....

Whenever I get ready for the first application of power, after repairing the obvious (parts with zero remaining smoke), checking the safety things (AC wiring, proper fuses, and grounding) and yanking the tubes as is described above,  I wire an appropriately sized light bulb in series with the AC line.

Appropriately sized:  start small (40W for your tonnage assuming all the big tubes are out and all you are looking for is filaments and bias).  Power up, you'll likely see something around half brightness on the bulb.  Full brightness is a short circuit somewhere.  The good news is even a dead short on the primary of the LV transformer will only draw 40W.

As you engage more of the rig (LV tubes then HV tubes) jump to a 100W bulb for the initial trial.  Once again the bulb should be relatively dull with just application of power (no TXing yet). 

Obviously full brightness at any stage of early bring up is a problem, usually an issue in the AC side of things, shorted transformer, naked wire someplace.  You've got a bug to work out but the good news the bulb trick can save you from a disastrous fail.

Next step is remove the series bulb load completely, check the status of the fire extinguisher - you should probably do that FIRST in this process, and full speed ahead to getting the rig to to work after decades of door stop duty.

Have fun and be careful in there.

Best 73,  Bill   N2BC

Incredibly, R51 does get very hot. The VR tubes regulate the screen voltage for the modulators so they will only light when the MODE switch is set to AM and transmitting.

Did you adjust the PA bias to -70 VDC at L7 / C73 junction per the manual? The modulator bias should probably be set to max for initial testing. It can be set later when the RF section is under control.

Interesting about the low 80M drive. I had a Valiant come through that had sufficient drive on all but 80 after the "L6C modification" that evened out the drive levels on the upper bands.

OK, measured as Dan thought 125Vac at input, dropped it to 117Vac from variac.

Tonite went by the book and have following data:

80 Meter CW Mode:  OSC current 17ma cw mode, (goes to 0 in AM mode)
                            Adjusted R62 to -70Vdc (grid amp voltage)
                            Measure 357.2Vdc at pin 6 of XV3
                            Measure 255.4vdc on pin 5 of XV21
Followed manual, went to AM mode, Meter on Grid...meter went to 0, tuned the Exciter control and did nothing to this reading, 0. Adjusted Drive control pot and nothing on the rigs meter, dead as a doornail.  Did not go onto Clamper Adjustment as not sure I should, R13 is fully clockwise as manual states.

Went to 160 meters, CW mode:  OSC current 28ma (cw mode, goes to almost 0 in AM mode)
                                             Measure 261Vdc on pin 5, XV21
                                             Measure 376vdc on pin 6 XV3
                                             Amp grid voltage went to 074.9vdc
Went to AM mode, meter on Grid, same result as 160m, meter goes to zip and no adjustments to Exciter control or Drive made any difference.

So, that is where I am at...seems voltage on XV3 is above the Norm no??

Now I have gone from replace parts mode to troubleshoot mode. This is where I really learn. Will do resistance checks now per manual and see what I get...

Any advise appreciated, thanks guys.

73
John-N2LK

So the OSC position only shows a reading when the MODE switch is on CW and it shows nothing when on AM?

This is normal unless you're keying or if you have the Oscillator switch in ZERO, which turns on those circuits.

Switch the Mode to AM and the Oscillator to Zero. This turns on all the low level RF circuits and should show grid current when the Meter switch is set to Grid. Use the Drive control to keep it at 7.5 mA. Use the Exciter knob to peak it for that frequency.

I tried what you just recommended, Meter switch at 0, AM mode, PTT, ..no meter readings at all, a slight bumps up when I flip thru OSC to Grid but Grid is nada....eciter adjust and drive adjust do nada.

Should I turn on HV in AM mode to do this check? Forgive me for some probably dumb questions...

Did measure on Modulator tubes at pin 5 a -53.3vdc, manual says -46v...not sure if that leads to any suggestions?

Thanks
73
John-N2lk

Hey John,

       I'm confused..



     Knowing whats not broke is as helpful as knowing what is...

/Dan

At this point it would be best not to transmit until you can verify that you're getting grid current.

The transmitter does not need to be keyed/PTTed to see grid current on the finals as indicated on the meter set to Grid although the Oscillator switch needs to be set to Zero in order to activate all the low level RF circuits.

Also, try several bands. The Oscillator runs straight through on 160 and 40. All other bands use doubling, etc. There could be a poor switch connection since the rotary switch contacts can get badly tarnished. I use a pencil tip eraser to clean the rotating metal surfaces. Follow that with isopropyl alcohol applied with cotton swabs.

Good Morning Dan and everyone-
I realized I goofed a little on understanding some terms, so here is a refresher of data:

1. Checked on Pin 2 of one of the PA filaments, read 6.0Vac and left that alone.

2. R62 is one of the adjustment pots on side of chassis. 5K Pot...for bias voltage for final amplifier, page 8 of manual
I Set Pot to -70 volts amplifier grid voltage as measured at either end of L7 and ground (direct wording from manual)..

3. 357.2Vdc at Pin 6 of XV3 and rig was NOT KEYED....

4. Pin 5 of XV21 is - 255.4Vdc.

I just re-did (correctly) now your recommendation, Switched MODE to AM, OSC switch to ZERO and was able to adjust DRIVE to get 7.5mA. I then adjusted Exciter and could peak up to 300ma and then just fiddled a second to between the 2 to get 7.5ma  and peak to 12.5mA. What is best way to make these adjustments (160 meter band by the way).

Now, some questionable resistance measurements:

2 large Modulator Bias 7W resistors R63 (15K, 7W) is reading in circuit, across each lead, 7.49K, (Radio not powered of course)
                                                 R62 (9K, 7W) is reading in circuit, across each lead, 5.75K

Could these be the reason my Voltage on XV3 so high???

Thank you very much, I feel I am real close now.
73
John-N2LK

You *are* getting close!  The resistors are probably reading low because both the modulator and RF final bias dividers are in parallel, so they affect the measurements of each other. Unless the bias settings seem way off or you can't set them to the right voltages, then you're fine.

The voltage at V3, pin 6 is the LVB+, which is always present even when not keyed.

I agree on the parallel resistor being low in reading, but figured worth mentioning.

One of my problems is trying to follow the tips here and the manual, the manual is a bit limited in my humble opinion for someone not used to 16 or so tube radios. Here is what I have done and get so far:

Have measured 6.0V on pin 2 of one of the PA filaments
Have -70V for Bias voltage to amplifier grid
Measure 357 or more depending on band for Pin 6, XV3. Not keyed
Measure -255.4vdc on Pin 5 of XV21
Messure -53.3Vdc on pins 5 of the modulator tubes, V16 and V17

If I power up unit and switch to AM Mode, Oscillator to ZERO, Meter switch on GRID, I put DRIVE to about 3, I get Grid Current and can peak with Exciter. This works as recommended. When I turn Oscillator back to VFO, Grid current drops to 0 with all other settings kept same.

I am lost on next step in manual, page 9 for Adjusting Static Modulator Current. I follow the manual with settings exactly as:
VFO-         3.5
Mode        AM
Oscillator   VFO
Meter        Grid
SW7           ON
SW8         OFF (PTT)
Audio        0
Coupling     0
Drive          2

Says TURN EXCITER CONTROL FOR MAXIUM GRID DRIVE ----- I get nothing, no meter movement, nada
Says Adjust Drive control for 8 ma. of grid drive           ------ I get nothing, no meter movement, nada
Turn METER SWITCH to MOD position.                        ------- I get nothing, no meter movement, nada
I cant adjust R61 for static modulator current, I tried and I get nothing on the meter obviousely

I have done some resistance measurements per Table 2 in manual, pg. 33...not done yet but some figures that are way off:

XV3, pin 1 is suppoed to be 0, I read 2.7
VX4, pin 8 is supposed to be 70K....I read 14.58K
XV8, pin 7 is supposed to be 200k...I read 313K

TS6 terminal strip for XV1 and XV2, terminal 2 supposed to be .1, I read double at .20

That is as far on resisitances as I have gotten.

My 2 things right now are how to get modulator bias to work and what to do on that high voltage on XV3 of 357 V

Must admit this is fun...

73
John-N2LK

Connect a dummy load, key up, and tune up so that you have:

7.5 mA of grid current and 300 mA of plate current (conservative setting). Use the Drive control to keep these from going too high as you make the adjustments.

That should get you some decent output power.

With that established, switch the Meter control to MOD, key up, and adjust the modulator bias pot for 65 mA of resting (no mod) current.

That should do it!

Tonights update- finally figured it out and got tuned up on 20M AM with 100 watts....quite amazed I have not electrocuted myself yet !! ;D
Finally got Modulator Bias set as advised so that is done, set keyer adjustment, set clamper adjustment.

Now for VFO calibration, its way off...like 100khz off...so started that process tonite and of course, the 160m dumb clip to the little VFO cap slipped off so now I have to pull the VFO case off and get it...the upside is I have been into that VFO now more than I care to so I know what I am facing.
Think I will tape those wire clips in this time to not have to that again.

I have a signal gen, freq. counter and receiververs but me and the manual are still fighting for understanding on VFO calibration/

Any tips on VFO calibration is well appreciated..

Have to hunt ebay now for a D-104!  and build a little TR relay box.

73
John-N2LK

    dial pointer???? 

Dial calibration is performed for 160, 40, and 11 (although that's more for thoroughness than practicality).

First, identify the trimmers on the top of the VFO assembly. With the front panel facing you, starting with the closest trimmer on the left and moving clockwise, they are:

1) 40 high
2) 40 low
3) 160 low
4) 160 hi
5) 11 meters

This can be done in Zero (spot) mode:

Switch the band to 160m and set the VFO pointer to 1.8 mc.
Adjust 160 low until the Oscillator is on 1.8 mc

Set the VFO pointer to 2.0 mc
Adjust 160 high until the Oscillator is on 2.0 mc

These may need to be repeated a few times until they both line up.

40 is calibrated the same way by using 7.0 and 7.3 mc and the 40 low/40 high trimmers

11 meters, well, ethically I can't detail that but you get the idea...

     Actually you need to turn the tuning dial
Fully CCW with the dial pointer removed to feel
the "Bump" when the cap inside the VFO stops.
may not be noticeable depending on wear/adjustment
of the reduction drive.

    Then reinstall the dial pointer Parrallel with
the bottom edge of the front panel. That will get
the "Mechanical" synchronization complete.

    Then follow the manual or N1BCG posts..
let the rig warm up a while first.


GL

/Dan

Dan brings up a *very* good point, particularly since the dial is off by that amount. Def check the mechanical alignment first!