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Valiant Restoration K3MSB




 
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k3msb
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« Reply #75 on: February 01, 2018, 10:24:09 PM »

The original power cord has been replaced with a three wire grounded power cord, with a single fuse in the hot side (8A) -- that would correspond to F3 on the schematics. 

F1 is the 2A fuse, thought it's shown as 1.8A on the schematics.   I have no idea where to get 1.8A fuses around here.

The high voltage rectifers have been solid-stated.
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73 Mark K3MSB
York, PA
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« Reply #76 on: February 01, 2018, 10:30:42 PM »

Started blowing fuses as soon as I turn on the MAN/PTT switch;  don't even need to key down.

This sounds like classic J8 shorts. Specifically, either a disk bypass cap has shorted or one of the pesky TVI coils whose insulation has rubbed through. Kevin, WZ8J, another Valiant restoration jockey, experienced a bypass cap failure at J8, and this reminds me of what he went through.

1) Unplug and discharge.

2) Put an Ohmmeter between the + lead of one of the filter caps and chassis.

3) Start wiggling components near J8. If that doesn't do it, unsolder a lead somewhere to start isolating the HV circuitry.

You're earning your doctorate degree in Valiantology!
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KA2DZT
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« Reply #77 on: February 01, 2018, 11:43:30 PM »

The original power cord has been replaced with a three wire grounded power cord, with a single fuse in the hot side (8A) -- that would correspond to F3 on the schematics.  

F1 is the 2A fuse, thought it's shown as 1.8A on the schematics.   I have no idea where to get 1.8A fuses around here.

The high voltage rectifers have been solid-stated.

Most likely a 2amp fuse is a little light for that xmtr.  OK FB on the 3 wire cord and the single 8amp fuse in the hot leg, that's all correct.

The 2amp fuse should be a slow blow type.  If it is not a slow blow type, that could be the reason they are blowing.  When you hit the PTT, the relay puts power to the HV xfmr.  If that is when you blow the fuse,  check the all those stupid and unnecessary .005 bypass caps on the AC line. check the plug jack for the antenna relay.

Also make sure there isn't a wiring mistake where the 2amp fuse is in series with HV xfmr primary instead of just the LV xfmr primary.

Looked at the schematic again.  You mentioned that you moved the 2amp fuse holder to the top of the chassis.  Make sure that when you did that, that you didn't make a wiring mistake and you have the current for the HV xfmr also passing through the 2amp fuse.

Fred
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k3msb
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« Reply #78 on: February 02, 2018, 08:46:59 AM »

Are those bypass caps and coils really necessary?   I've had the urge to just rip them all out;  It's not like I'm going to interfere with Channel 2 anymore.....

I get what fuses I can;  slow blow fuses aren't stocked too much around here.   If it's not a Home-Depot, Lowes, or an auto-parts store,  that's pretty much it around here.   I'm pretty sure the fuses I exhausted last night were slow-blow.    At any rate, I haven't replaced one all through the shunt resistor "ordeal",  so whatever I had was working.

I will start tracing tonight.

I found a VFO issue.   Turning the VFO does not necessarily change the frequency;  I may have to turn it an eigth of a turn for it to actually change frequency;  that seems to depend where on the dial it is.    I looked into the VFO cage and the cap is turning and moves throughout it's range.   Not sure what's going on with that.    I was pretty careful about the coupler,  never resting the radio on it's front panel.     I was looking into that when the fuse blowing started.......
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73 Mark K3MSB
York, PA
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« Reply #79 on: February 02, 2018, 11:06:25 AM »

Those TVI coils and caps would have been the first thing I would have ripped out.  They are just a possible cause of problems.

The 2amp fuse is only suppose to be on the LV xfmr primary.  Should have nothing to do with the HV xfmr or the HV circuits.

I've built many power supplies (I have more than 1000 xfmrs and chokes) over the past 55+ years.  Without measuring the primary current I think a 2amp fuse is a little too light for that xmtr.  I would use at least a 3amp slow blow, ,maybe even a 4amp fuse.  There is a 8amp fuse on the main AC line.

A little rough figuring,  700VDC x 500ma = 350 watts for the HV supply.  Add 20% for xfmr loses. that's about 420 watts.  420 watts/120vac = about 3.5 amps primary current for the HV xfmr.  

The schematic shows less than a 2amp fuse for the LV xfmr.  If you add up all the loads on the LV xfmr and do the same rough figuring you will probably find that the primary current on the LV xfmr primary is at or near 2 amps.  You would need a fuse greater than 2amps.

Another thing,  with today's higher AC line voltages the primary current on these old xfmrs can increase do to core saturation increasing the xfmr loses.

Another thing,  if you replaced the PS filter caps with caps that have more capacitance. that will increase the start-up in-rush current causing fuses to blow.

Fred
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k3msb
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« Reply #80 on: February 02, 2018, 12:49:08 PM »

Fred --

I posted incorrectly (which I just corrected in a previous)......    I posted

"Turn on the HV and blowing plate fuses like candy"

That should have been

Turn on the HV and blowing fuse F1 to the LV transformer T2 like candy.

I will check my wiring in that area tonight.   I may "harvest" those coils and caps too......

Interesting if I have a wiring error in that section and it's worked so far without incident.   Will let you know.
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73 Mark K3MSB
York, PA
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« Reply #81 on: February 02, 2018, 01:50:10 PM »

Well this is a new one...

So, activating the HV supply is overloading the LV supply. Here are my guesses...

1) There's a short causing the HV to feed into the LV supply - Check the 6146 plate voltage when the LV is on but the HV is off. Could occur at J8 where the supply wiring converges.

2) If the diodes that replaced the 866 high voltage regulators are wired to plugs, perhaps they are wired to pin 4 instead of pin 1 on the 5 pin plug. This would put the heater wiring (derived from the LV power transformer) in series with the HV supply. Turning it on would induce a pulse of current back into the LV transformer as the HV caps charge. While the heater winding is only 2.5V, a solid surge of current would be transformer up in voltage, causing momentary saturation.

Okay, okay, long shot, but it had to me mentioned. Why it's happening now and not before kinda defuses (pardon the pun) the theory.

I plan on being on for the AM Rally this weekend...

The AM Rally starts in 5 hours. No pressure, though, just sayin'.
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KA2DZT
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« Reply #82 on: February 02, 2018, 03:30:23 PM »

I was checking the filament wiring on the schematic.  All the audio tube filaments are returned to "Y" on the LV xfmr.  All the RF and other tube filaments are returned to "H" but I can not find the feed for "H" anywhere on the schematic.  Is there another filament xfmr somewhere??

Have to take another look maybe I missed something.

Fred
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KA2DZT
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« Reply #83 on: February 02, 2018, 03:38:55 PM »

Not seeing anything for the "H" filaments
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N1BCG
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« Reply #84 on: February 02, 2018, 03:49:09 PM »

Not seeing anything for the "H" filaments

"H" connects to terminal 8 of J8 via a small coil and the circuit is completed to the power transformer from there. This allows the RF heaters to be disabled if the unit is used solely as an audio amplifier.
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DMOD
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« Reply #85 on: February 02, 2018, 03:50:26 PM »

Dupe

What Clark said.

See J8.

Phil - AC0OB


* Johnson_Viking_Valiant Later schematic.jpg (735.03 KB, 1944x1476 - viewed 46 times.)
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KA2DZT
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« Reply #86 on: February 02, 2018, 03:58:08 PM »

Ok now I see it,  looked at everything except the jumper on the octal plug and I looked close at the socket just not the plug.
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k3msb
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« Reply #87 on: February 02, 2018, 07:55:50 PM »

Well,  the old girl is up and running and putting out RF!!

There were three issues.    First,  when I moved the LV fuse holder F1 to a rear chassis mount fuse holder,  I did not wire up the new fuse holder correctly.   Second,  I incorrectly labeled the fuse holders on the inside when I was soldering the connections.

After fixing that, I turned on the HV and no fuses blew;  repeated a few times.

I then removed power from the unit and remounted the HV bulb I3 assembly.   Applied power and blew the 8A fuse the second time the HV switch was thrown.    To make a long story short (pun intended  Grin)  one of the lugs from the bulb mount was shorting to ground.

So,  will continue to test tonight and see.

I need to get to the VFO Shaft Coupler inside the VFO housing through a hole in the chassis bottom.....

I'm still going to try and get the Valiant in the AM Rally for at least one QSO.....

By the way, at least one end of the filament lines to the LV and Bias rectifiers are physically disconnected.   For the HV circuit, the filament lines are as they normally are,  but I do not use those tube sockets pins with the SS replacements.

News as it develops.....

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73 Mark K3MSB
York, PA
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« Reply #88 on: February 02, 2018, 08:37:56 PM »

Good making progress,  I suspected something wasn't wired right with those fuse holders.

Good thing you're not working on my HB xmtr.  It has about 15 power supplies and I think about 30 fuses along with about 35 relays.  Don't ask it's a long story.  Built in stages, it took about 8-10 years to design and build.

Fred
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k3msb
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« Reply #89 on: February 02, 2018, 09:10:35 PM »

I found out how to tighten the VFO coupler.   It was challenging, but once I found the two setscrew through that tiny hole,  it wasn't too bad.

If I put the VFO at either extreme and rotate to the other extreme there's no slipping as verified by watching the tuning capacitor.   If I stop anywhere in between,  more than likely there's slipping – several inches on the dial -- especially if I change direction.

When the dial is slipping I can visually see the setscrews rotating,  but the tuning cap is not turning.

I tried loosening and re-tightening the coupler screws and that has no effect.   I was going to loosen them, rotate the shaft (or tuning cap), then re-tighten.    That shouldn't cause any harm (as I need to realign the dial pointer anyway), but thought I'd ask first.
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73 Mark K3MSB
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« Reply #90 on: February 02, 2018, 10:09:51 PM »

Maybe the tuning cap needs a little WD-40.
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W4DNR
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« Reply #91 on: February 03, 2018, 11:51:35 AM »

Mark,

Thank You  ( and the other contributors on this thread ) for detailing your Valiant rebuild .

Your details will be valuable when I start working on my Valiant.

I purchased a good looking Valiant at a hamfest , but I haven't had the time to even open the case for a visual inspection.   

I'm guessing that it still has the *low-fidelity* interstage audio transformer that could be replaced with a tube phase splitter if necessary.

I see mention ( Timtron ? ) that the 6146s don't make good modulators and that triodes like  807s would be a better match for the three RF 6146s, but I haven't found any schematics for this modification.

Anyway............ Thanks again to everyone who is helping to keep the Vals
active on the bands.

Don W4DNR

   
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k3msb
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« Reply #92 on: February 03, 2018, 04:10:41 PM »

1st QSO with the Valiant !!!

W1TS on 80M in the AM Rally!!

The modulator current meter is really sensitive to the audio gain, and I'm not thrilled with what the scope is showing -- not getting near 100% modulation.   

73 Mark K3MSB
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73 Mark K3MSB
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« Reply #93 on: February 03, 2018, 05:52:51 PM »

Sounded great! Nice to hear the rig on the air (finally, lol) but seriously, the effort has paid off. Keep the plate current modest on AM and you'll have no trouble reaching full mod and use the clipper to keep the current peaks in check.

Looking forward to the next contact!
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k3msb
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« Reply #94 on: February 09, 2018, 08:23:22 AM »

Greetings!

I’ve been busy with non-radio stuff this week but I look forward to getting back to the Valiant tomorrow.

I had a great time in the AM Rally even though I was only able to get on 75 M.    I was going to go to 160 Saturday evening but realized the SX-101A didn’t have 160 capability (duh...) and I was too lazy to haul the R-390A over.   The Valiant’s VFO is way off on 40M – full CW deflection is 7280 – so 75M it was.

I participated in the AWA Net on Sunday afternoon and ran into Jim WA2MER that I haven’t talked to in ages.   I found the comments from the net members to be rather diverse and I wish I had time to hang around for “Round 2” to comment on the comments, but was unable to do so.   

Back to Mark’s Valiant saga.

The issue with the dial slipping was the rear screws on flexible shaft coupler.  The front screws can be reached fairly easily, but I could not reach those rear screws.  After pondering options, I drilled a second one-half inch hole just behind the existing chassis hole, slightly offset so as to be under the tuning shaft.  I then snipped the “bridge” between these holes to make a larger oval opening.   It is now very easy to access the fore and aft set screws and the new opening is big enough so you can shine some light inside while working.    Drilling holes goes against my mantra of not doing irreversible mods, but the hole is inside the VFO cage and will not be seen.   

So the radio is basically squirting RF and the plate current seems well behaved now that I redid the solder connections for the meter shunt.    Things to be done:

Dial tracking / VFO alignment on 40 and higher is off.    I have the alignment procedure for that.    Dial tracking / VFO alignment on 80 and 160 is almost spot on.

The modulator resting current is about 25 mA too high with the adjustment pot at its limit.   I plan to add a dropping resistor in series with the adjustment pot.    I added a dropping resistor in series with the RF adjustment pot and that worked nicely.

Add the new inductor to increase drive as Clark N1BCG suggested.

Perform the mods to the two VR tubes so the modulator current reads correctly.

Add a new plate current shunt resistor – the “real” one came in from Mouser this week…..

Will keep y’all posted!
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73 Mark K3MSB
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« Reply #95 on: February 09, 2018, 08:46:09 AM »

The modulator resting current is about 25 mA too high with the adjustment pot at its limit.   I plan to add a dropping resistor in series with the adjustment pot.    I added a dropping resistor in series with the RF adjustment pot and that worked nicely.

What's the bias voltage on the output of the supply? The manual calls for -265 but you should see a bit more. I had an issue like this and it turned out to be C93 having gone bad.

I'm leery of adding components to fix issues. There's some problem getting masked...
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k3msb
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« Reply #96 on: February 13, 2018, 12:05:20 PM »

Not a lot of radio time this weekend.

What time I did have I built a signal "pick off box" -- which may not be the correct name.    Basically an aluminum box with 3 SO-239 connectors -- input, output, and "pick-off".   The pick-off is coupled to the input/output wire by being about 1/4 inch from the other wire.    Very simple, and I think it was K1JJ that had the original idea.    I have it going into my frequency counter as I was told a few times during the AM Rally that I was a bit off frequency.

Last night I got the VFO working correctly on 40 and higher.  I need to squirt RF to be sure all's OK.

Clark,  OK on your comments.   I will recheck my voltages after the SS replacements.

All the electrolytics are new,  and the HV ones are bit more stout.
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73 Mark K3MSB
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« Reply #97 on: February 13, 2018, 12:39:18 PM »

If you want to monitor your frequency, the pick off point needs to be pre-modulation. Sideband energy from sampling the RF output will confuse your counter.

You could use the SSB adapter input jack, an SO-239 connector on the rear of the chassis, if you don't plan to use the Valiant as a linear amplifier. Just unsolder the connection that's there, and run shielded wire to the 6146 RF tube area.

The connection would be to the grid circuit through a D.C. blocking cap and a resistor divider (there's way more PtoP voltage there than you need). A 0.001uF cap would work. The divider values would depend on the voltage your counter needs but it's a good idea to use a high value resistor in series with the cap and a low (50-100 Ohm) resistor for the shunt at the input of the shielded wire.
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k3msb
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« Reply #98 on: February 13, 2018, 02:27:32 PM »

If you want to monitor your frequency, the pick off point needs to be pre-modulation. Sideband energy from sampling the RF output will confuse your counter.

Yep.   I have to use an unmodulated carrier or else the frequency counter doesn't stabilize.   I wanted a solution that is transmitter non-specific.   Also, I do a lot more CW than I do AM.
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73 Mark K3MSB
York, PA
k3msb
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« Reply #99 on: February 14, 2018, 08:29:42 PM »

Is the -265V bias voltage on the schematics correct (possibly from model run to model run) ?

With a 170 ohm dropping resistor,  I measure -225V at the downstream end of R50,  and -261 volts right at the end of the diode stack.   Current is 32 mA.

With no dropping resistor, I measure -241V  at the downstream end of R50,  and -272V right at the end of the diode stack.   Current is 34 mA.

I did not replace R50, so it had to be in tolerance.  C93 and C98 are new.   Line Voltage is 115V.    Measurement made key up,  HV off.
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73 Mark K3MSB
York, PA
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