The AM Forum

Another lesson was learned from my little more than a year fighting this Valiant transmitter. As you know, I took on this project with zero experience and I've literally worn you folks out bringing me up to speed. The lesson is a simple one...

Whenever one is clipping leads, trimming wires, soldering, etc., make sure the conductive fragments (I call them "sniglets") are all accounted after the fact. Surgeons use this principle before closing up a patient by counting sponges, tools, candy wrappers, etc. Of course the stakes are LOTS higher for surgeons.

Anyway, back to my situation....the Valiant exhibited yet again the dreaded zooming plate current issue. My first thought was that one of my loading caps had went south again. So, I tried the "clip lead a spare doorknob to ground" trick. That trick didn't work this time. Another hint was that the rig loaded up fine on some bands but the plate current meter would PING on others.

Yesterday, I poked around the bandswitch and loading wafers and whaddya know, there was a sniglet hiding on the backside of the wafer. I removed said sniglet from wafer and VOILA! Operation is back to normal and the Valiant is again repaired (never say "fixed") for a few days, weeks, months, etc.

In other news, the epoxy repair of the cracked bandswitch wafer appears to be holding up, at least for the time being.

Now, if we can have an afternoon without these popup thunderstorms along the coast, I'll try to light up the antenna instead of the dummy load.

Thanks as always.

Philip

Glad you got it going again Philip, congratulations!

Would you be upset if I start a betting pool for how many hours it will be until your Valiant blows up again???  :)

I've lost sniglets, solder blobs, lockwashers, etc. in the works.  If a chassis is too big or heavy to shake - like your Valiant or my DX-100 - poking around with a blast of compressed air often brings these troublemakers into view, or maybe I can hear something rattling around in there!

Rodger....

Not at all, if the moderators don't object. My preference would be for the winner to donate funds to the upkeep of this site. Since I've eaten up so much bandwidth here, it would sorta even out the karma all around.

I'm not a betting man....however, since the Fates have apparently picked me as one of their favorite folks, my gut feeling is I've got about a week of operating time. Also, the size of the 330 PF doorknobs is significantly smaller than the 680's, so I worry about their current carrying capability.

P

"  I'll try to light up the antenna "

NO NO NO NO  Poor choice of words.!!!!!



klc

I see a capacitor that I would change.

Big greenie on far left and others of its ilk, I presume.

I can see how that coarse loading switch would/could crack the way the caps are wired to the switch and then wrapping/looping that solid wire around the screws on the caps rather than using wire lugs.

Al VE3AJM

There is zero tension on the switch wafer. Wafer was broken prior to installation of new caps. Prebent wires before hooking to caps and contacts. Good, heavy, #12 buswire.

Yes they are older than the radio.  While not indicative of poor performance or trouble, you should at least check the insulation resistance.  If you don't have a way to test them then replace them.

Jim,

Good catch on the capacitor and in the Valiant I would just replace it and not even bother testing it.  I am not sure the plastic encapsulated paper capacitors of that era are any more reliable than the older style wax coated types.  Most of the plastic designs had end seals that failed readily and I remember reading a report in one of the old electronics journals in which the author estimated 25% or more of the end seals were damaged during installation and unlike the older dipped wax types the end seals didn't heal themselves when they were soldered.

Philip I hope this will finally start a good long run for your Valiant without further failures.  You have stuck with it and kept a great attitude while dealing with these issues and you seem to have a good sense of humor about these things.  I hope your sense of humor is intact because I have to admit when I was browsing ebay I immediately thought this is just what Philip needs for quick shutdown of power when something bad happens :)

http://www.ebay.com/itm/LARGE-RED-EMERGENCY-OFF-Button-IDEC-ABD311N-RWith-BST-001-NC-010-NO-Contacts-/171343962716?pt=LH_DefaultDomain_0&hash=item27e4e5625c

In all seriousness having a well marked power shutoff system is a good idea for all of us, especially those of us involved with vintage gear.  There may come a time when your life depends upon a family member being able to quickly and safely shut things down and it is also a very convenient way to kill power to the gear when not in use rather than hoping some 60 year old power switch doesn't fail and start a fire during your absence.  Most of my radio gear is in a 1,000 sq. foot basement room and I have a separate breaker panel fed by a clearly marked 100 amp shutoff switch arranged so that only the lighting and two marked outlets are on the main house panel.  When not in use the switch is pulled.  I installed a similar setup for the upstairs radio room (Desk KW, Johnson 500, BC-610, S line, Drake 7 line, etc.) which is a littler simpler but has the same style master shutoff.

Big red mushroom switch with a shunt trip coil on the downstairs breaker feeding this MLO shack panel...AND a proper fire extinguisher/respirator.......

Maybe even hang a rosary over the doorway to the shack????

Loading up on 40m at the moment...no problems. If only the static wasn't so bad. Can't get on in early evenings due to popup thunderstorms we've been having this week. Similar to an amateur astronomer buying a new scope....guaranteed 3 weeks of solid cloud cover.

OK, it was YOU calling me on 7295! Sorry, I just wasn't able to pull you out of the QRN. I did hear you make another contact before I shut down, though, so I assume all is well. Despite the hassles, I love my Valiant. Next project is to cure the Valiant "thump" when the mic is keyed. I think there is a cure for that in a post somewhere on here.

Good luck!

Doug, WB5IRI

Doug,

An inrush limiter for the plate supply cures the thump.  All of my Valiant transmitters have NTC inrush limiters.

I think the "thump" gives it character. I believe someone said its eddy currents setting up in the steel case when the big iron energizes and causes flexure. Now I need to wire up this Herald M24A crystal mic I obtained cheap and see how it does.

P

Yeah, it does add a certain characteristic flair to things, but it also shakes the table and wakes up the dog sleeping under the table. Plus I didn't put screws back in the cabinet, so the whole thing rattles and whangs when I key the mic. But not putting the screws back in is a good thing, because now I gotta pull it out of the cabinet again. Never put the screws back in because that's just asking the gods to strike you down for your impudence and over confidence -- unless you are going to sell the rig, that is.

As to inrush limiters, any advice on what device to use with the Valiant? Some say put it in the AC line, some say in the primary of the HV transformer -- which is best? One leg or both? Any other precautions?

Doug, WB5IRI

Doug,

I use a CL-40 (6 amp 5 ohm cold resistance) in one lead of the plate transformer and I also use a CL-120 (1.7 amp 10 ohm cold resistance) in one lead of the low voltage transformer.  This gets rid of the "bong" and reduces inrush stress to transformers, switches, tubes, etc.    Available from Mouser for less than $3 plus shipping.

Any reason not to use the CL-40 in both the high and low voltage primaries?
Doug

Ahh, I have the same busted Valiant VFO coupling.  What did you use for the repair material?  Nice work.

Rich

You don't want too big of a mismatch between rated current for the NTC inrush limiter and actual current draw.  I try to shoot for 60-80% of expected and the 6 amp is way too high for the LV transformer.  Going from memory I think the LV transformer draws about 1.25A, less if the 866A tubes are replaced with SS. 

If you are asking about putting just one device inline for both transformers it will offer no protection for the plate transformer since it will already be close to minimum resistance from the current drawn by the LV transformer before the plate relay is activated.

   Right on Rodger,

       The LV xfmr is fused at 1.5A with an In-accessible POS
in a fuse holder inside of the rear apron. the LV Xfmr IS the "Weak Link"
in a valiant.  Much to the dismay of my customers, I have no
problem Blowing a 7/16" hole fore an accessible fuse holder. Better
that than letting it "cook" away with the 10-30 A fuse I often find
in that position... It should be a 1.5A SB...  When you can find em'
a Valiant LV XFMR is going for around $70.

/Dan

Thanks, Rodger. I'll follow your advice!

I must apologize for the photos uploaded into this thread by mistake. I was trying to upload them to a topic in Restoration, when I had a computer crash at work. Don't know how they ended up here, and the message I was trying to send never made it anywhere. But, since it's done, I'll just post it here anyway, and the moderator can move it if he wants.

Did the foolish thing, set the Valiant on its face to remove the cabinet, which was being stubborn, and broke the coupling. Lesson learned the hard way. However, ER Magazine, issue 300, just came out with a fix, which involves drilling out the rivets in the old coupling and replacing the insulator with a nylon washer. A pack of 4 at Lowe's cost me $0.92 plus tax. They are Lowe's part number 881539, 1x13/32x1/16 nylon washers, and you only need one. So, I have 3 extras, if anyone wants one. Drill holes for the coupling and secure with 1/4" 4-40 machine screws and capture nuts. I've got extras of those if you need them, too, since it seems you can't just buy 4 of this type hardware.

Interestingly enough, I bought a box of old Johnson parts at an auction, and as the pics below show, found in the box one of the original couplings that works. The original Valiant part is Johnson 264-3, and it has a smaller diameter shaft hole on one side and a larger one on the other. The part I found is Johnson 264-1, with the same diameter hole on both sides, but it works just fine. The smaller shaft is clamped tight by the set screws and there is no binding at all. The slight misalignment is not noticeable, and the VFO tunes smoothly. I have an extra one of those, if anyone wants one.

Found lots of other Johnson NIB goodies in the auction lot I got, including a NIP bandswitch with long shaft, and the elusive green jewel for the power light on the Johnson, which it turns out was standard on the Valiant II, while red was standard on the Valiant I. Always thought a green jewel would be better for power-on indicator than the red one, and now I have one. It's not as long as the original, so it doesn't go all the way through the front panel, just the VFO dial plate, but the light bulb behind the cabinet shines through just fine. Got an extra one of those, as well, if anyone wants it.

Also found an original Johnson relay plug, the one that goes in the crystal socket on the back of the transmitter to key the TR relay. Anyone wants it, let me know, as I just make my own from old crystals and have no need for this plug. Pic attached.

All this stuff is free to anyone who wants it, first come, first serve. Email me off list at douglas.rowlett@gmail.com.

Doug, WB5IRI

Thanks, Dan. I will indeed go with the lower current thermistor for the low voltage transformer.

Oh, in my  previous post that's not a Japanese bandswitch but a "new in the box" bandswitch which looks to be the one for the Valiant. Have to check the part numbers against the manual, which I haven't done yet.

Doug

Dan,

The first Valiant I restored had a cooked LV transformer due to the wiring to the 866A filaments, it was regular hookup wire and couldn't withstand the HV imposed on it.  I think Johnson changed the wiring fairly early in production but I have seen two more parts chassis at hamfests with this same broken down insulation.

Doug,

Thanks for posting the picture of the relay plug, I have never seen one before.  Like you I make mine from old crystals but now at least I know what the real thing looks like.

In Texas they call them solder "spurs."  :D

In Iowa we call them solder "tits."   ;D

Phil - AC0OB

Betting Pool Results:

Anyone thinking the repairs would last less than one week is a winner (I'm in that category).

Either the band switch or plate blocking cap is acting up......and as noted on many occasions by many others, the switch is a piece of junk. As happened previously, I was operating on a higher band with no problems (in this case, 15m). Went down to 80m last night and heard the familiar WHAM of the plate current meter pegging with zero or very low RF outpoot.

So, if there actually was a pool set up, please forward funds for the upkeep of AMFone.

 ;D

FEELEEP

And now its working yet again. No reason determined, but narrowed it down to one of the rotary switches since the plate cap is ok....Intermittent. Life is good, I guess???