Dave K6XYZ
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« on: March 07, 2010, 08:16:59 PM » |
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Howdy! I've had this Valiant about 19 years and have not used it much. It is a very nice factory assembled unit...I think it is anyway...has riveted tube sockets.
Before turning it on I replaced the bias, LV and HV lytics with new...not NOS parts. Replaced the 866A's with 3B28. Tested all tubes and in general spiffied it up a bit for the next round. I replaced the Chernobyl resistor. Other than that, it is un-modified...so far.
Here's the problem.... If I remember correctly...I never used it other than 80mtrs...and not much of that. Cut to last week..... It works on 160 and 80 and I made a few contacts and sounds ok.
There is no grid drive on 40 through 11mtrs.
I removed the 160 VFO trimmer phenolic trimmer adjuster and inserted a RF sniffer probe into the VFO box and I get 1.8xx reading on the counter when the b/s knob is on 160/80.
I change the b/s to 40mtrs and the VFO sniffs 7.xx (same freq as VFO pointer) To me, this means the VFO is generating the correct frequencies. So far....so good.
The 7.xx signal should go straight through the 6CL6 and 5763...there is no need to double or triple on 40mtrs....but it dosen't....no drive.
The meter works fine with the expected current readings....and I measured the shunts too....they are reasonably close.
Same thing on the rest of the band positions....the VFO is on 7.xx and the b/s can be on any other band and there is no multiplication...and no drive of cuss.
I DID find that the L6A coil tap for 20mtrs was missing....never installed. And....the 15mtr tap was installed but on the wrong (clip 4) SW3A (rear) clip. I moved the 15mtr tap to the correct location (clip 5) and installed the missing tap (clip 4) and fired it up. (per assy manual page 7 steps H4, 5, 6.) Of cuss....it still don't woik!
Next....even though the VFO seems to be working correctly I plugged in a 7.150 xtal just to eliminate the VFO and it's b/s. Same thing....no drive 40 through 11mtrs.
I replaced the 6CL6 and 5763 and no change.
I replaced C29 50pf coupling off 6CL6.6....nada.
I grid dipped L6A & L6B and I see a decent dip for 160 and 80mtrs that responds when I turn C7. C7 is close to the expected position per the manual.
The rest of the bands show no dip or very little dip.
Right now....I'm dipped....skunked...done.
Somebody rescue me!!
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WA1GFZ
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« Reply #1 on: March 07, 2010, 09:49:07 PM » |
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Dirty contacts on the band switch?
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ke7trp
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« Reply #2 on: March 07, 2010, 11:12:32 PM » |
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Yes.. Take a tooth brush and Deoxit and SCRUB the band switches. ALL of them. Turn them to a no contact position and slightly bend them down. It takes 5 minutes and might solve your issue. Mine was missing two bands. This fixed it.
Good luck!
c
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Dave K6XYZ
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« Reply #3 on: March 07, 2010, 11:29:40 PM » |
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Nope....dirty band switches was the first thing I thought of....I forgot to add that to the original rant.
On sw3A (rear) contact 4 & 5 there is an 11T coil that is not shown on the schematic. I removed it and there was no change...still didnt work on 40>11mtrs. If anyone can take a picture of the front and back of SW3A I would appreciate it....or look and see if that coil is there. There is a second 11T coil (L16) on contact 11 & 12 and is shown on the schiz.
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w3jn
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« Reply #4 on: March 07, 2010, 11:30:29 PM » |
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Love your avatar, Dave A little Deoxit goes a long way. Don't douche it down; rather, apply a bit of deoxit to a Q-tip and use that to apply it to the switch rotors. You don't want to saturate the insulation on the switch wafers, be they bakelite or ceramic.
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FCC: "The record is devoid of a demonstrated nexus between Morse code proficiency and on-the-air conduct."
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ke7trp
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« Reply #5 on: March 08, 2010, 12:11:57 AM » |
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You must scrub the Johnson switches and wafers. Pretty damn hard with a brush. If you dont, You will have them arc. Carbon builds up at the rivets. You will see the carbon tracks if you look close. Enough scrubbing and enough deoxit will get them spotless and white again.
Mine has the two Coils...
C
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Dave K6XYZ
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« Reply #6 on: March 08, 2010, 12:53:29 AM » |
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Ok guys....thanks for all that. I didnt check the clips for tension so that's next. Thanks for the bit about the 2 coils..... I'll post the outcome.
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Dave K6XYZ
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« Reply #7 on: March 08, 2010, 11:19:48 AM » |
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I re-cleaned the band switches and mode switches, scrubbed the hell out of them until the Deoxit started to foam. I looked at every, single contact and rotated the wafer through...each of them has good contact follow...meaning that the clip expands nicely as the tang rotates through......it still won't work on any band but 160 and 80mtrs. If anyone else has any suggestions.....I'm listening.
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ke7trp
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« Reply #8 on: March 08, 2010, 11:28:33 AM » |
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Damn.. Sorry. Now at least you have good band switches..
Acc plug in back have good tight connections?
Clamper tube adjustment set correctly?
Screen resistor ok on final? Sometimes they go.
Check the plate choke and the caps at the bottom. Mine burned one up once.
Make sure the Doorknob is ok Someone put a low voltage one in on one valiant and it was dead. I use 5k or 10kv 1000puf.
C
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ka3zlr
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« Reply #9 on: March 08, 2010, 11:42:16 AM » |
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Howdy,
Check yer Grounds OM, Solder Joints all connection points with a Magnifier Glass sounds Crazy but it Sounds like a connection issue to me...somewhere in there, If all Active Devices are operating no Sig getting through.
73 Jack.
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Dave K6XYZ
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« Reply #10 on: March 08, 2010, 12:13:01 PM » |
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Thanks again for the suggestions guys.....
The entire rig operates normally on 160 & 80mtrs so I wouldnt think the acc plug, screens or anything else in the PA would have a problem....at least at this point. The rig won't make any drive on 40>11mtrs. The 5763 does not double or triple.
The clamper is set to 10ma.
The doorknob is the original 500pf 20kv unit on the 'early' units......and the rig has the bias pots mod as well. I dont have any way to identify when it was built but this thing is so clean that I'm sure it was a closet classic for decades before I got it. Little wonder that it wasn't used.....it probably wouldnt work for anyone else either! There is no evidence of anyone else troubleshooting it either....it's never been hacked.
I located a local source of 2000pf 20kv doorknobs and I'll put one of em' on there....that is if I can get it fixed......summer is coming so I better hurry up before the fishing season is here.....I don't wanna foul up the lakes with oversized weights.
I re-soldered all connections on SW3A front and rear and a few others here and there.
I guess the damn thing is was a kit after all because the decal on the back does not have a -2 after the model number. Congrats to whoever assembled it even though he is likely dead for years.....he did a great job but made a mistake or two....mebby more!
There is still some question in my mind if SW3A is assembled correctly....I'll post some pix soon. I have a the .pdf assy manual but it dosen't have the drawings showing orientation etc of the componants.
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ke7trp
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« Reply #11 on: March 08, 2010, 12:18:13 PM » |
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Boy. I wish I could help you further.. Time to trace it down step by step with the manual
C
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w3jn
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« Reply #12 on: March 08, 2010, 12:22:09 PM » |
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Time to break out the scope and see where you're losing the signal.
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FCC: "The record is devoid of a demonstrated nexus between Morse code proficiency and on-the-air conduct."
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Pete, WA2CWA
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« Reply #13 on: March 08, 2010, 12:24:23 PM » |
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With the VFO connected, bandswitch on 80M, put a scope probe on pin 9 (grid input) of the 6CL6. Verify signal appears there. Now switch to 40 M and verify signal is at the grid. (Yes) then, put the scope probe on output side of C29 (6CL6 plate coupling cap). Verify signal is there. (Yes) move on to the 5763 stage and repeat the same process. You should also verify tube voltages of the 6CL6 and the 5763. First in the 80 or 160 position (ones that work), and then repeat checking tube voltages in a bandswitch position that doesn't work. Random part or tube replacements generally doesn't always solve a problem.
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Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
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Dave K6XYZ
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« Reply #14 on: March 08, 2010, 01:33:07 PM » |
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Ok....but first.....here's a couple of pix of SW3A front and rear.
Note that the index mark on the center of the wafer is 180 degrees from the other wafer on the same b/s shaft. The rear wafer switches the PA coil taps. I've never seen a rig of any kind where this is so....
Anyone see anything wrong here?? Wiring...etc....
Urrrgg....I made a mistake labeling the pix....this is the FRONT view....not the rear.
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Dave K6XYZ
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« Reply #15 on: March 08, 2010, 01:36:03 PM » |
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Here's the REAR view of SW3A. I labeled the pix incorrectly.
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ke7trp
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« Reply #16 on: March 08, 2010, 01:40:51 PM » |
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If you really need me too.. I will lug my working Valiant out of the storage room, Pull the case and take close ups.. A friend is comming over at some point today to help me lug some stuff around anyways.
C
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Dave K6XYZ
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« Reply #17 on: March 08, 2010, 01:53:19 PM » |
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Thanks Clark....that would be great....break out the chain hoist and let the rough side drag!! If you could try to get the same view on your pix it would make for easier stare and compare considering that I dont have the pictorial of this area. The b/s is in the 160mtr position.
Note that the black wire on lug 4 in the rear view (20mtr tap) is supposed to be red. This is the missing tap I added.....I didnt have any red wire.
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ke7trp
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« Reply #18 on: March 08, 2010, 01:57:24 PM » |
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Does your valiant have the SIDE adjustment Bias pots? I have three valients here.. One old factory made one with the NO side mounted pots. One that has the side mounted pots and one new in the box valiant that has the side pots.
i want to take pictures of the one that matches yours. Give me the serial, I will take pics of the one that is close.
C
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Dave K6XYZ
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« Reply #19 on: March 08, 2010, 02:07:18 PM » |
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Well....it seems like this unit was a kit after all because the model number does not have the -2 of the factory assd units. It has the side mounted bias adjust pots but are obviously added as a mod later...plus it has the 500pf doorknob of the earlier units. The s/n is...as near as I can tell on the ancient decal is 20794.
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ke7trp
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« Reply #20 on: March 08, 2010, 02:10:18 PM » |
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Alright.. I will see what I can do.. I have to wait until my friend gets here.. to help me lug the thing to the table top. I will yank the case and take the photos for you. I know how frusterating it is to deal with these things. I am going to make T shirts that say "it takes a valiant effort, to keep a johnson running" ...
C
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w3jn
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« Reply #21 on: March 08, 2010, 02:28:45 PM » |
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Mine has the side bias pots obviously added later. Someone (not me) labeled 'em in magic marker "Bi-ASS"
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Pete, WA2CWA
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« Reply #22 on: March 08, 2010, 02:42:35 PM » |
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Did you check the voltages? Use a scope to check the signal at the grid of the 6CL6 and 5763?
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Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
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Dave K6XYZ
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« Reply #23 on: March 08, 2010, 02:52:58 PM » |
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Clark.....that would make a cool T-shirt for sure.....or mebby a pix on the shirt of a Valiant with Johnny's logo saying 'Set your biASS'....HEH
My avitar is me wondering what to do next while working on a thrashed Collins KWM-2A that I rescued. It turned out to be a very nice operating unit and is in service today in Cincinatti. So much for self portraits.
The voltages and resistances are ok....I havent scoped it yet....but, I have traced it and I don't see any errors other than the 20mtr tap that I fixed. If Clark's rig compares to this one then I'll start scoping with a counter attached to determine the freq of the signal. The 5763 works ok as long as it dosen't have to multiply....it might have a mis-marked part or dead part....who knows. That is the reason for the emphasis on the driver b/s assy..
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ke7trp
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« Reply #24 on: March 08, 2010, 02:57:37 PM » |
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Ok.. My friend is still not here... LOL. I wanted to make the T shirts for a while.. I am going to have them in HAM sizes. 2XL tall and 3X.. I want to use the old Ef johnson logo with a pic of an old Valiant on the back. Great for Swap and swindles.. Nobody in there right mind would choose a valiant over other transmitters. They constantly crap out and have troubles. But something keeps me from getting rid of them C
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