The AM Forum

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.

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.

   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

Don't give up now.....

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

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

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

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

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 :)

Red chicken knobs, too cool.

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

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

Philip

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.

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.

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

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.

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.

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...

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.

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

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.

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

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

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

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

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

You're right, something that I forgot to mention, connect the hot line cord lead directly to the rear terminal of the fuse holder.  So, like you say, when you remove the blown fuse you not handling the hot lead since it's on the far end of the blown fuse.

Of course, all bets are off, if the blown fuse is not blown ;D

Fred

I have an internally mounted inline holder. I didn't cut any holes in the chassis.

Short in the PTT relay line to ground. Plate iron okay!

Glad to hear it!!! On to the next problem!
Terry  N3GTE

    Glad to Hear that Phil, I hope you have a bunch of
fresh doorknobs in waiting. I was wondering how you
made out with that.

     BTW I was a Harbor Fright today for some heat shrink
and actually picked up one of their "Good" DMM's, it was
on sale for 19.99 and I had a %20 coupon so it was like
$15. It has a freq counter and "uF" meter as well.  The
freq counter only goes to 20KC and the capacitance reading
takes a while but it does work. Their model #P37772. Also
has a temp range with internal sensor and came with a remote
sensor as well... Of course the "Harbor Fright Kludge" is
it only displays temps in centigrade.

/Dan

Not blowing fuses, screen voltage on transmit is around 205 volts. Loading is screwy on 80/40. Everywhere else is fine. Looks like the band switch and coarse loading are likely the causes again.

P

Philip,

Just think of all the money you're now saving on fuses.  Glad you found the problem, never thought it was the plate iron.

That screen voltage looks about right,  6146s will run around 200 volts.  RCA manual says 150 volts but my 6146 always ran about 200 volts on the screen.

Keep us posted on the next problem.

Fred

....next problem.....

That has an ominous sound to it. Anyway, looks like I am going to have to reexamine the coarse loading and bandswitch networks again. Not doing its job on 80/40. The rest seem fine (10 is persnickety), with good current level and power outpoot (around 140W).

P

   Sounds like that 1200pf section of the loading cap
"Stepped out for a Smoke". That's the way they do ya'.
If all is "Normal" above a "Course" loading position of
3 or 4 (where it is no longer used) assuming the switch
is good that's it.

    Still got those "Snubbers" in there?

/Dan

Yes I do. Replaced them all with snubbers, rated 1000V.

At the outpoot coupling, I paralleled 2-600s for the 1200, 2-450s for the 900, 2-300s for the 600, and 2-150s for the 300, to reduce heating. HOWEVER, knowing what I do now, this approach does nothing for the voltage rating. No visible scorching, but wonder if the top two could've been fried as they're only good to 1 KV. These are the CDV snubbers. Continuity across the contacts seems good, with around 1 ohm or less.

At the bandswitch, have 2 sets of 350s paralleled that are in series with each other, for a total of 350 at 2000V rating. At the next position, have a 6 KV 150pF doorknob (Commie-Cap brand).

Getting close. No screws in the back this time. The time for boldness is over.

Well the only way you will see anywhere close to 1KV on those output coarse coupling capacitors is if you have a nearby lightning strike.  Assuming the Valiant manages 600 watt PEP output at 100% modulation (that is a very healthy Valiant loaded to the gills) then with a 50 ohm antenna you will have a mere 174 peak volts appearing on the output side of the coupling network.    Lets say you try to load a badly mismatched antenna providing around 1000 ohms, this is not a smart thing to do but even with this ridiculous load you are still under 800 peak volts.  Take a look at the variable capacitor in the loading circuit, it clearly isn't designed for high voltage.  Legal limit amplifiers run into 50 ohm loads can use "receiver" spaced variables for the loading capacitor.

   Right on Rodger, Low voltage and relatively high
peak current. Thats why I question "Snubbers". Just
what the H*ll is a Snubber, It's a network of either
R/C or L/C, heck some even have diodes in em. I think
there intended purpose (Transient suppression) would
make them Iffy for all but the lowest  continuous
RF currents.

    The "C" may be the predominant component but
he's not alone, from what I read.

   Anything can take 500A for a cycle or 2.

   Maybe Phill can provide the part number of these "Snubbers"?

/Dan

Dan,

I am with you on RF current rating.  I believe some of the "snubber caps" were aimed at wide market and may carry a decent RF current rating but I doubt if that goes for all of them.

I nearly got figuratively AND literally burned by some Ceramite doorknob caps.  Although they look like a regular RF doorknob they certainly don't act like one in terms of current capability.

Anytime I have used snubbers that were either in switch mode power supply design in the primary of the switched converter stage or networks to suppress arcing on relays. 

From an RF standpoint, especially in the loading circuit you want the lowest possible series inductance along with low ESR.  As mentioned, its not a voltage rating issue but with the technology of the cap, how well it can handle the RF current.

Joe, GMS     

Search CDV on Mouser, 1000V, Cornell Dublier. Can't seem to find affordable doorknobs in the right values. Grabbing at straws here. Any suggestions for these caps? Don't want to buy anything that is going to fry.

Data sheet here for CDV series: http://www.cde.com/catalogs/5.024-5.027.pdf

Side note:  used "DuckDuckGo" search engine to get away from Google adding all of their garbage to the HTML when copying address.  Another reason I despise google :(

The Class E guys get away with chip caps at plenty of I @ 50 ohms.

I have always used silver mica caps as loading caps up to 100W or so.  Over 20 years with them without any problems.  I try and get the 1KV parts. 

Joe, GMS

As they say, $20 and a handful of chip caps will build ya an e-rig.... ;D

Looks like those snubbers didn't make it. Paralleled a good doorknob via jumpers and it works fine. Loading switch is fine.

Tried some 3 KV Ceramite ceramics. Also, used a temperature probe. I paralleled three 470 pF at the 1200 pF coarse loading position. Needless to say, they heat up fast. I think they are rated 85 degrees C. Back to the drawing board. But hey, it loads up pretty as you please!!

Philip

Phillip,

   You won't blow these guys:

https://www.atceramics.com/UserFiles/trans_cap_equiv.pdf

Explore their web sight, they have all sorts of stuff.

The ATC stuff is the Cadillac in RF capacitors. We use various ATC's in a SMT package at the 3KW level at work. They never fail. They won't be inexpensive though.

Why your caps get hot:
http://www.atceramics.com/Userfiles/esrlosses_appnote.pdf


Jim
WD5JKO

Dern, Jim, you made me laugh.

I warned you about those Ceramite caps which behave more like thermite when in the presence of RF :)  I remember one of the commercial manufacturers tried to use similar caps for awhile in one of their amps as padders on 160 and the power would drop during an extended dash as the capacitor rapidly changed value from heat.

I think you warned someone else but I read your post ex post facto. It was fun, however, watching that digital thermometer climb and climb and how FAST it did so! Anyway, they were cheap as dirt so no biggie.

However, I did note that you liked the CDV snubbers. Mine went, so I'm wondering if I needed to reconfigure them differently. Did you parallel some of lower value to split up current and therefore reduce heating? The CDVs come in 1 KV, I think, so would you also need to do a series/parallel setup to reduce heating and reduce voltage across each????

Which series did you use?  The CD/CDV series from CD are traditional dipped mica caps and some of the "larger" series are specifically designated for "snubber" service since they will handle high peak current.  They  aren't like some of the caps purpose built for snubber service which may not work so well at RF.

I used to have a RF current guide for the 19 series but I can't  find it anymore.  But you can take a look at the data sheet for the next series smaller which has good RF current capability.  RF current capability generally increases with capacitance value and frequency.  What this means in practice for the Valiant is although RF current capability goes down for 160 meters this is also the band where you will typically have several of the large value coarse capacitors in circuit.  For the higher bands you will have smaller/less of the coarse loading caps in play but the current capability of the capacitor is also higher at these higher frequencies.

The 19 series in the 1KV (or greater) rating should be fine for the Valiant unless you are trying to load some very odd extremely high (voltage issue) or low (current issue) impedance load.  If you are  looking at very low impedance loads on 160 then use 1/2 or 1/3 value capacitors with two or three in parallel respectively.  If you are looking at really high impedance then get a tuner :)

The original valiant coarse loading caps carry a 1.2KV rating but that allowed for matching some pretty bizarre loads without using an antenna tuner.

Even the next smaller series should have no current issue except on 160.

I originally used the CDV16 series, but did not parallel the caps. So that may explain the failures on 80/40m.

Phil Said:
" Any suggestions for these caps? Don't want to buy anything that is going to fry."


   Hey Phil,

        Thought I had suggested this before but...

  "Have your credit card ready and call Ameritron at 1-662-323-8211.
Ask for "Parts Department" and order 1 of each."  You won't need the
first few values but there handy for "Trimming".  They will be on your
porch by early next week and cost less than $30.

   These are what they use for loading padders in their AL-800 Amps.
You'll be set for life unless you do something foolish!

http://www.ameritron.com/Product.php?productid=AL-811

Are the Ameritron caps made by Cornell Dubilier?  The numbering scheme seems to fit.  If so their DM15 parts would not be suitable for use in the Valiant since the fixed coarse loading capacitors carry the lion's share of the current in many situations.  The CD 15 series has even less current carrying capability than the 16 series he tried earlier.

Many amplifier designs use a large variable loading cap supplemented by fairly small padding caps for the lower  bands.  The Valiant uses a fairly small "fine tuning" variable for loading with the fixed capacitors providing most of the needed capacitance on the lower bands.  With a typical antenna on 80 meter AM the variable is providing around 300pf of loading capacitance while the fixed capacitors are providing from 2,100 to  2,7000 pf  causing most of the current to flow through the fixed capacitors.

Heath ran into similar issues with the fixed loading caps in the  DX-100 when owners tried to match unusual antennas and the DX-100B version moved from the fixed coarse plus fine loading combination to a mutli-section variable with all sections in parallel. A modification kit was also made for the earlier transmitter and many DX-100 transmitters were converted.  It lost some of the matching range but got away from the problem with fixed capacitors.  There really isn't room to do this in the Valiant without major modifications.

I can't help but wonder what is happening in the case being discussed.

  LOL   It is provocative isn't it?

  Jim said:

"I can't help but wonder what is happening in the case being discussed."

   Right Rodger,

      The Load cap is about 800pf in the Amps.  He needs
to use the website to choose an Amp. They have doorknobs too
and  for about $65 he could re-create the Johnson "In House"
job with doorknobs.  I'm not sure who they get the caps
from.

      I haven't gone back and read this whole thread but
I thought he just lost the 1200pf chunk. A 1000pf DK and
a couple of silver mica's will bring that back. 

      I know Phil enjoys taking all those screws out
every couple of months anyway.

/Dan

P,

Your friendly ePay has the following listing

Two  1000pF 6kV 40kVAR Doorknob K15Y-1

for

US $8.76
+$12.00 shipping


klc

Okay, make it easy for us lazy guys and publish the
ePay item number... That way we can "cut & paste"
right to the search line on eBay, thank you...

http://www.ebay.com/itm/2x-1000pF-6kV-40kVAR-Doorknob-Tesla-Capacitor-K15Y-1-/201046317152?pt=Vintage_Electronics_R2&hash=item2ecf4b5860

This thread is hilarious....

Al VE3AJM

"I know Phil(ip) enjoys taking all those screws out every couple of months anyway."

I consider it very bad luck to install more than one or two in the back.


We all have to start at the beginning. Everyone who loves old radios and works on them has a "first" that requires repair and restoration. I've just had more problems than most. My particular Valiant (The Beast) came to me after looking like it had been ridden hard and put up wet and was sort of working when I got it.

I started out with zero troubleshooting experience. But, I have learned so much! And, everyone has been so helpful and patient here.

I brag on the AM folks to my ham friends who don't do the mode. And, I still contend that AM folks are perhaps some of the nicer folks on the bands. We have our bad apples, but then again, who doesn't???


"This thread is hilarious...."

Let us all in on the joke so we can enjoy it!
 

Again, thanks!

Philip KA4KOE

Just read some of the replies posted earlier. You may or may not get it. Good luck with all of it. ;D

Al VE3AJM

"  I consider it very bad luck to install more than one or two in the back. "

There is a story of an AA in WW2 in GB.

It seems the RAF wanted to beef up bombers to increase the survival rate. So they had their boffins count holes and assess damage on the returning aircraft. Where there was the most damage, they were going to increase, or add armor to these areas.  One of the more senior designers took a drawing of the bomber improvements, and circled the areas that were not to be armored. He said something like "these aircraft came back shot up so we know the plane can fly with this damage. The planes shot down were probably hit in the other areas."

So, P is in good company not wanting to put the screws back in. I for one, utilize the same Ozona Bob methods with my VK2. I don't have any of the case attached ' caus I know things are gonna crap out......   ( I just got some Ruskie door knobs, and now its off the Ace Hardware  for some ' metric screws and then fingure out how to replace the fixed caps in the coupling.)

klc

Well, here we go again. Installed new snubbers, 1 KV, with three CDV16s paralleled at each position this time! Works fine as before .... UNTIL....

Are we excited yet?

Plate current need slams the right side of the meter.

Looked underneath. One of the jumper wires between the two rotary switches had come off one of its anchor points. Resoldered. Works fine again. I swear, is everything in this radio going to break before we're done??

Getting about 130 watts carrier, Coarse at 3, Fine at 10, 300 mA, 3.9 MHz.

OK, perhaps this will hold a couple of weeks. This time out, I learned the significance of ESR and what happens to caps when they get a leedle too hot.

PAN

Philip,

Sorry you keep having so many problems with your Valiant.  But, looking at the other side, just think about all that you have learned working on the rig.  How much would a college course or courses cost you to learn this stuff?  Now add in all that all the readers of you posts have learned.

Don't give up,  you're finding every weak point in that xmtr.

Someday, as time permits, you'll be able to build up your own rig using your own design from everything you're learning.  You'll know what features to use and what methods  and circuits to not use, like fixed caps for loading, bad idea.

By studying the basic circuits you see in the vintage Handbooks, studying the circuits of the project xmtrs in these Handbooks and even the circuits in your Valiant you'll begin to learn that most of these xmtrs are just variations of the same circuits.

In time you'll be able to piece together your own xmtr design from parts you have or able to obtain.  It takes time, a lot of work and patience.  You've already proved that you have patience.

What I described above is probably the way most all of us OTs learned how to build xmtrs.  I doubt any of us went to xmtr building school.  I think I can speak for most of us OTs and say that we're eager to help.  We want to pass on to the next generation or even folks a decade younger whatever we think we know so it doesn't pass into history when we do.

Fred

I haven't given up, Fred, and I appreciate the patience and encouragement. I've "buttoned" the Valiant up for now, with no screws inserted in the back.

Philip KA4KOE

In my particular case, the biggest weak points were the accessory plug (removed mine) and the band-loading switches and their associated caps.

Additionally, but not the biggest problem, the microphone jack was worn out as well.  When I say this TX was rode hard and put up wet, I meant it!

Here is a repair summary:

1. Removed/jumpered accessory jack.
2. Replaced microphone jack.
3. Replaced 866s with 866A RF Parts solid state equals.
4. Replaced modulator tubes and associated resistors after audio stage oscillated.
5. Replaced all electrolytics.....twice.
6. Replaced coarse loading caps three times.
7. Provided new tubes in the VFO compartment.
8. Replaced Chernobyl resistor in the VFO compartment.
9. Troubleshot multiple instances of fuse blowing.
10. Replaced power cord with 3 conductor type.
11. Provide line fuse on hot conductor (see item 10).
12. Cleaned topside of chassis and coils.
13. Put spaghetti over conductors where the pass thru holes to the various transformers.
14. Installed higher R shunt resistor at first audio stage.
15. Installed new clamper tube.
16. Installed new MV rectum-fryer tube twice.
17. Troubleshot overheating in MV circuit. Turned out to be a short underneath the internal metal shield over the band switch area.
18. Went through one can of Deoxit cleaning tube pins, sockets, and band switches.
19. Removed all tartar from rotary switches with toothbrush.
20. Provided new lamps throughout.
21. Cleaned big coils with Nevr-Dull.
22. Replaced 500 PF doorknob in loading circuit with 1000 PF doorknob.
23. Replaced HV bypass caps at B+ choke.
24. Repaired B+ choke.
25. Wired in a short cord for TR switching of Dow Key.
26. Set grid bias and modulator bias a couple times.
27. Troubleshot audio issues with oscilloscope.
28. Repaired lack of grid current on 40m and higher....this was a toughie.
29. Troubleshot excessive plate current at least three times.
30. Removed and thoroughly cleaned front panel, VFO eschutcheon, and knobs.

I'm sure I'm forgetting something.

      Hey Phil,

          Did I miss it or did you not strap a pair of 1N4007's Back
to Back across that beautiful teardrop Meter?

/Dan

Didn't hear about this one. Meter protection similar to that in Heathkit amplifiers in case the finals melt down, eg. grid to cathode short?

   Yes, Any anomaly that would endanger the meter coil.

/Dan

You are learning a lot.
Just think of the value in knowing how to keep 50 year old radios working!

All these radios are very old now, and most have had a lot of abuse or neglect.
The trick is to fix problems in advance with better then original parts, then a rig can be reliable.
Frequent use often keeps them that way, letting something sit unused is often bad for reliability.

My idea of fixing up a vintage ham rig is to remove all the parts inside and replace them all with ones twice as big, and you are good to go.

I dislike operating a bunch of old marginal parts in a bad design built to a price point, so went home brew a long time ago.
Its lots of fun trying to get the most/best out of the old radios though...and many looked very cool.

Two radios I had really good luck with are the 32V series, and the Gonset G76, both of which put up with a lot of abuse over a long time with no problems at all.
I think the 32v I have left has all its original parts in it except the rectifier tubes were changed to solid state and the modulator has been changed.

Yes, you are learning a lot. And while these old rigs can be frustrating, there is a reason why so many are still being worked on and are still on the air. There's just something about these big old monsters that just won't die. Perfect, no. Good, yes. Improvable, most definitely.

Don't want to get too far off topic, but anyone know why the modulator resting current in my Valiant is too high (150 ma) when I first fire it up but drops to normal value (50-70 ma) after 15 minutes or so of casual transmitting? Modulator pot is backed all the way down. Leaky cap?

Also, anyone know of a source for the jeweled power and plate indicators on the Valiant?

Doug, WB5IRI

WWW.tubesandmore sells some jewels.

Modulator resting current changes, look at the bias voltage (is it steady?) or the current through the modulator tubes is causing a cathode resistor to heat up.

Plate voltage will be steady, as will filiment voltage, but bias, screen and cathode resistance can change.

When I swapped out the D104 element for an original, the change in audio quality was staggering.