My Valiant may be down for the count

[ka4koe]

I think the plate HV transformer has developed a primary short to ground. This may explain the higher power output of almost 200w loaded to 330mA I was experiencing. Pulled the rectifiers and still blowing fuses. Showing low R going from phase to ground. Will pull both wires off their termination points and check again. The only other way this could be blowing fuses by the schematic is a short in the transmit lamp socket or something amiss in the TR relay. I can't identify any single event leading to this, other than just the usual wear and tear over the years.

The ohmmeter readings on the secondary are pretty close to what is specified in the manual, in circuit.

Checked for interelectrode shorts on the 6146s out of circuit with an ohmmeter and seemed okay. My reasoning is that the primary winding shorted a few turns leading to a increased P-S ratio/higher plate voltage/higher plate current and then shorted after that to the grounded bell casing. Does this sound reasonable?

Not sure if its worthwhile to get the transformer rewound or just throw in the towel on this one.

[W3RSW]

If you haven't already and highly suspect the primary, disconnect the transformer leads from everything and then measure resistance between pri. leads, leads to shell, etc.  it might be a short in power switch to chassis or similar. Improbable but worth a try.

Clip lead 110 vac to the leads via a  series 100 watt light bulb and then check for shorts.

If really shorted, Pull the transformer bells and look for obvious flash overs and maybe reparable windings close to outside.  May be repairable.  I don't have one but if primary is buried under secondary it's a tough cookie.

[N8ETQ]

   Make sure those "Stupid" enamel coils aren't touching each
other or chassis.  Disconnect all 5 wires of T2 and hit the primaries
with 5.0 or 6.3 and verify secondary voltage.  Also measure the
resistance from the input to the coke to ground. (Shorted load)

   T2 is usually the weak link in a Valiant.

GL

/Dan

http://www.ebay.com/itm/Pair-Stancor-Plate-Transformer-1800-Vct-400mA-high-power-tube-amp-6550-811A-/141209189688?pt=Vintage_Electronics_R2&hash=item20e0b93d38

[KL7OF]

Don't give up now.....

[WD5JKO]

Phillip, I know you have been increasingly frustrated over this rig. Then again when it works well you have been quite proud of it. I recall a night when you were top dog on a Monday night 20M AM gathering with that Valiant.

If the tranny or big choke are toast:

If you are up to some surgery, consider replacing that plate transformer and filter choke with a control transformer. Look on Ebay for 300va transformers with 120V in and either 550V or 600V output. The idea would be to use a full wave bridge, and capacitor input along with a relay step-start for PTT. A 550V transformer would probably give you about 650V key down, and 750 key up.

There are a lot of 300va control transformers right now on Ebay for $29.99 Buy It now. Here is the description of one of them:

NORTHERN H-550-11A CONTROL TRANSFORMER 300VA 550V PRIMARY 115V SECONDARY 85415

Jim
Wd5JKO

[KA2DZT]

If the primary had a short to ground it would read very low resistance to ground, a few ohms.  Check everything connected to the primary circuit after the fuse.  Unlikely the primary is shorted to ground,  look for something else.

Fred

[W2VW]

I'm with Fred. Primary to ground failure would be unlikely.

Also this has nothing to do with the output loading problem.

[WQ9E]

I agree with the others that this type of failure in the Valiant plate transformer is very unlikely.  There are many places where a short to ground in the feed to the primary can occur including several "TVI" coils and capacitors, the goofy antenna relay connector, and the plate relay itself along with all of the associated wiring.  One solder blob in the wrong place is enough.  Disconnect the transformer primary leads themselves (both of them) and recheck resistance.  Take a look at the leads where they enter the transformer shell to check for damage.

A large number of Valiants were kit built and a solder blob or poorly placed connection can show up at any time.  I recently restored a Meissner Analyst which is a cool looking piece of 1940s test gear.  Everything worked except the section which measures radio current draw.  When I dug into it I found the builder had moved both leads of the current transformer secondary to the same terminal so I was afraid that was done because of a bad transformer but it was fine and the problem was when the builder had soldered a resistor to the center contact of the calibrating pot he created a bridge to the grounded pot case.  Once I cleared the short my properly repaired Analyst seen below is fully operational and ready for 1940s radios

[KA2DZT]

Red chicken knobs, too cool.

[K1JJ]

Phil,

Yes, the Johnson gear can be a challenge to keep running.

Back in the late 80's I had two Rangers. My troubles started after solid stating the power supplies. After that I had crap out after crap out. Sometimes the terminal strips, other times different parts. I remember wondering how the average technical ham was able to  maintain this gear.

I eventually gave one Ranger to the Tron and he got it running for some purpose.  I then built all my own gear and after that could only blame myself for crap-outs.

So, stay confident knowing that it is not an easy task to keep some of this old stuff running. You really are a good technician if you are successful at it.

T

[ka4koe]

Issues at the house right now….got to get back into the troubleshooting mode.

Philip

[ka4koe]

I'm a bricks n' mortar double E….not a technician. As such, I have two strikes against me. Lots of book knowledge, zilch experience in troubleshooting other than this radio.

[Jim, W5JO]

If you want 100 watts, get it going, if possible at a reasonable price, then sell it.  Hopefully, you will get enough money, then go find a good DX 100.  Heath used much higher quality parts provided you find one that does not have the turnstile cap.  If it does, there is enough room for doorknobs. 

Johnson Valiant and Valiant II are fragile transmitters.  You spend almost 2 hours repair time for 1 hour transmit.

[n1ps]

I disagree as to the Valiant being fragile.  Nothing wrong with the design. 

Now to your issues.  Which fuse is blowing?  I assume it is the 1.5A.  Check to make sure you did not pinch a wire. Look at the lamp wires.  Pull the shorting plug. Remove the lamps.   If you have to, pull all the tubes until the short goes away.  It could be a tube also with a filament to cathode short.  Do your testing with a meter movement ohmmeter (Simpson 260 for example) and not a digital type. 

Like others above I doubt you have a transformer problem.  You have to eliminate the variables one at a time until you exhaust all possibilities.

After you solve the short problem, we can look into your output power concerns. 

Hope this helps,

Peter

[N3GTE]

I'm with Jim on this one. I had a valiant but spent more time fixing that darn thing than it was on the air. Any company that uses 4 series / parallel 350pf 500v postage stamp caps where there is the possibility of having 3kv across them is just plain poor engineering. Heck I figured that out and I'm no engineer. Plate voltage+ audio voltage+ rf voltage

From a reliability standpoint the Viking II is good. I've serviced a few over the years and have very little issues with them.  And as the a for mention Benton Harbor KW DX-100 is another good reliable transmitter.
Soap box mode off.
Terry
ps. am sorry you are have troubles with the valiant.

[Pete, WA2CWA]

I told you they should have named it Valiant SS. It's also probably why my Valiant has been sitting at the end of the workbench waiting for repair for the last ten years.

[w3jn]

I've had a Valiant II for almost 15 years and never had a problem.  Haven't had it on the air in about 5 years though...

[WQ9E]

I had a Valiant as a novice and I own both a Valiant and Valiant II now, a Valiant was my first acquisition when I got involved with vintage gear in 1995.  Outside of the usual capacitor updates and a few tube replacements the only failure was a plate relay.  I run them both at rated power on AM and CW but I don't switch the coarse loading while in transmit mode.  Neither has been modified outside of replacing the MV rectifiers with SS plus dropping resistor and an added inrush limiter.  Audio is stock.  I regularly talk to several stations using them on AM who also have had good service from their Valiant.

The Valiant was very popular with the higher power CB folks in the 1970s so I wouldn't be surprised if some of those now in circulation suffered abuse in that service leading to some current problems.  I wish my Collins 32V-1 was as trouble free as my Valiants, I have operated it less and spent more time curing problems.  My B&W 5100B has also spent far more time on the bench than either Valiant.

[ka4koe]

The rig is blowing the 8 amp fuse in series with the line cord. The 1.5A is okay. I just think this particular radio was rode hard and put up wet prior to my getting it. Glad I wasn't in the middle of the Timtron audio work when it broke. I had JUST received the parts in the mail the day before. No kidding.

It has worked since last October when I got bold and inserted four, count 'em, FOUR screws in the back. I have used it a LOT. I have worked almost NIL SSB since them, so the last set of repairs had a lot of hours on them.

Just got to get back into troubleshooting mode. I have a lot of other distractions that popped up about the time the Beast burped again. These things come in threes.

Anyone hear of soaking the windings in marine spar varnish and baking for 4 hours at 250F to repair transformers?

PAN

[WQ9E]

Anyone hear of soaking the windings in marine spar varnish and baking for 4 hours at 250F to repair transformers?

PAN

If it truly has a hard short to the core/case that isn't going to help.  But until you actually disconnect the primary leads and test I wouldn't condemn the transformer.

I had a friend in high school whose car started puking water out of the overflow and he immediately ordered a set of head gaskets.  The cure was a new radiator cap and at least he finally listened to us before he jerked the heads off.  The moral of the story is when a symptom appears don't immediately jump to the worst possible root cause.

[KA2DZT]

I had a number of xfmrs that were completely under water.  After a long dry out (number of years) every xfmr survived and I'm using some of them in my xmtr, working fine.

Philip,

You have a short on the AC line somewhere.  It should not be that hard to fine.  Remove the MV rectifiers,  check those sockets for shorts.  Work onward from there.  Look at any line filter components, coils-caps.  Could be a line cap is shorting.

Let us know what you're finding.

Keep in mind, MV rectifiers need to be kept in an upright position or they will keep shorting when first turned on.

If the Valiant was my rig, I would replace all the tube rectifiers with SS,  also I would get rid of all those useless filter networks on all the incoming and outgoing lines, you don't need all that clutter.

Fred

[K1JJ]

It has worked since last October when I got bold and inserted four, count 'em, FOUR screws in the back. PAN

Funny, you reminded me of a hair-pulling event back when I owned my first Ranger in 1965.  On this particular unit, someone had substituted a cabinet screw that was longer than the others. Whenever I put the rig back in the cabinet, it blew fuses. Worked FB out of the cabinet.  How could this be

After a long time I finally realized the longer screw was shorting out a terminal strip when in place.  I found the problem by pulling out one screw at a time and firing up the rig.

I never fell for that trick again afterwards... and it happened again in various rigs. We need to watch those screw lengths when we first pull the rig apart. People lose screws and cob in bogus ones sometimes.

T

[n1ps]

Fred is right on.  There is a dead short BEFORE the xformer.  Possibly one of the line caps.  If you measure the inductance  across the line plug, it will read the transformer pri L.  In your case it probably is zero....

Could also be a screw?  You mentioned some screws.  Tom pointed that out.

Did you sh$$-can the Johnson fuse plug?  That thing is dangerous....if the neutral fuse blows...well...heaven awaits. Replace with a single fuse on the hot side thru the switch using a fuse holder.

you almost have it...

The trouible with the Valiants is they only last 60 years.  Worthless.

Peter

[KA2DZT]

On all my power supplies or anything plugged into AC has a fuse.  I have the fuse wired first, right off the line cord, then the switch.  As mentioned, only fuse the hot leg.  The switch should also be on the hot leg.  In old equipment, it was common to have the switch open the neutral leg.  What were they thinking??

Fred

[K1JJ]

Speaking of fuses.... a safety thang all youse old timers know; Be sure to connect the line cord directly to the END lug on the fuse holder.  This way if you space out and change the bad fuse with the plug still in, the hot end of the fuse is not touching your finger when you pull it out.   (maybe we should use a pair needle noze  just in case)

T