K3ZRF Valiant II

[W3GMS]

The other option is to find a local ham and the two of you can work together on it.  In fact, when working around HV that is a good thing to do anyway.   Good on the lower level stages working.  Don't forget to look at the screen voltage on the driver tube. I believe it was done the same way on the valiant as the rangers and if that's the case, those WW pots do go bad.  Just stage by stage and walla,,,,,you will have success.  Methodical analytical approach.

Joe, GMS     

[Tim WA1HnyLR]

Once the ZRF Valiant is operating it would be prudent to change the modulator tubes to triode connected 6DQ5s or other similar types(6CD6-6CB5-6DN6-6EX6) All of these types are interchangeable in pairs as long as the pinout for the 6BG6 is observed when hooking things up. A reverse connected outpoot transformer,probably what's in there already will work OK. About 10 watts of audio is needed. The screens are directly driven.The CT of the driver transformer goes to ground. The grids are tied to ground as well. A string of plain old rectifier diode is wired in series with the cathode return in order to bias the tubes to a range of 50-70Ma. 6146s are not good audio tubes in tetrode configuration . In triode connected mode they will not be able to make full modulation. This has been tried before( PW Fallon valiant,1976) I gave him a pair of 6CD6s. End of low modulation problem. Next step would be a real modulation transformer. You could turbo connect (Auto transformer)the stock transformer which has a split secondary. Parallel up the two secondary windings and wire one end in series with the primary in the correct phase. The impedance match will be about a 1-1/2 :1 step down. Being that the existing transformer has all it can do to handle the unbalanced DC in the secondary a 10Hy 300Ma filter reactor makes a suitable heising reactor. A 8 MFD 200VDC plastic film capacitor will work well to couple the audio from the topside of the secondary of the mod transformer to the junction of the 10Hy reactor and the modulated PA stage. Being that there is very little DC voltage that appears across the coupling capacitor a 200 volt rating is sufficient. This will allow the Valiant to be modulated in excess of 100% positive. Good luck,
Tim WA1HnyLR

[flintstone mop]

The Tron has spoken. And many wise mods!!. There is an article from the old AM Window (button above) in tech write-ups that Tim explains clearly how to make sure the power transformer is wired properly to become a fabulous mod transformer. And checking the phasing in the transformer is important and also clearly explained.
I did  a turbo job on an Elmac AF-67 and it had 6550's as modulators. Backwards transformer to drive the mod tubes. Plenty of audio and soooo smooth.
But take your steps, one at a time, and get the beast working again, and then do the magic part.
Fred

[W3GMS]

But take your steps, one at a time, and get the beast working again, and then do the magic part.
Fred

Very wise words especially if one is a little rusty! 

Please get it working the way Dave had it first.  BTW....It sounded excellent on the air with his external audio amp driving it. 

Joe, W3GMS 

[WA4JK]

I'm hoping to find a loose connection in the grid circuit from the travels. We will see and thanks Tim for the Turbo recount. That may have to wait for a while. I want to get her back on her feet first and then gather some quality parts. I've read the TECH posting on how to, but I'll think on it first.
Thanks for the help.

[WA4JK]

Well friends I'm going to have to ask for some help if I can, I need someone in or around the florence Huntsville alabama area who would not mind giving me a hand on figuring out this Valiant.
Anybody up for it??
Thanks

[W2INR]

I have that amp Dave used if you need it. It was a Crown DC300 he modified.

G

[WA4JK]

Thanks for the offer... First I have to get the rig running.. I never heard of a DC300.. I'll look it up.

[WA4JK]

Well after had tracing the curcits I have discovered that the Final and Mod. Bias curcuits have been disconnected and a replacement Mod,. Bias pot installed with added fixed resistors placed across the windings. None of this is complete nor connected to the ground side. This rig in it's current configuration could have worked, so this must of been a work in progress or is a dead carcus. The things some people will tell you just to sell something.
I've been looking for a replacement R61&62 pots for a month in the used market with no luck, the cheep $17-20 pots don't look like they would last under rag chew operations and unless I want to spend over $65 plus unbelivible shipping it looks like I'm going to have to do something else.
I've got an old Al-811 I'm thinking of converting to a modulator and feeding the that back into the finals.
I'm not sure but I susspect the Mod. trany. could not handle the 811's.
I know Tron has done this but I can't find a drawing of how he hooked it up and the component line up.
Anyone have such a document??

[W3GMS]

Well after had tracing the curcits I have discovered that the Final and Mod. Bias curcuits have been disconnected and a replacement Mod,. Bias pot installed with added fixed resistors placed across the windings. None of this is complete nor connected to the ground side. This rig in it's current configuration could have worked, so this must of been a work in progress or is a dead carcus. The things some people will tell you just to sell something.
I've been looking for a replacement R61&62 pots for a month in the used market with no luck, the cheep $17-20 pots don't look like they would last under rag chew operations and unless I want to spend over $65 plus unbelivible shipping it looks like I'm going to have to do something else.
I've got an old Al-811 I'm thinking of converting to a modulator and feeding the that back into the finals.
I'm not sure but I susspect the Mod. trany. could not handle the 811's.
I know Tron has done this but I can't find a drawing of how he hooked it up and the component line up.
Anyone have such a document??

I knew Dave, K3ZRF(sk) most of my adult life and I worked him many times very close to his  passing with that rig.  I hear what your saying but it just makes no sense to me.  I  also know  the seller very well and he is an extremely honest man with lots of integrity.  My suggestion is if you have a bone to pick call him on the phone and discuss the issue rather than posting rants on this site. 
73,
Joe, W3GMS 

[WA4JK]

It was not a rant just a fact.. there were two of the Valiant II's and the one you most likely work him on belongs to another.

[W3GMS]

It was not a rant just a fact.. there were two of the Valiant II's and the one you most likely work him on belongs to another.

Sorry to say, but that was not the case.  The Valiant you have now was modulated with the Phase Linear amplifier so nothing inside the Valiant audio system was used including the bias pot.  Dave was a very competent engineer and really knew his stuff.  In the last year or so he commonly switched from your Valiant to a FT-1000D driving an external amplifier.  When the estate came up  everyone involved were Dave's good friends including who you purchased the Valiant from.  The other Valiant was more of a parts rig.  I saw them both and would of purchased them myself if I had not had several Valiants.   

Joe, W3GMS       

[WA4JK]

Alright we'll have it your way. At some point both bias pots were diconnected by cutting the return wire to the ground side of the circuit and seporated from a common connection. This leaves no bais voltage to either the modulators nor finals. I'm not accusing anyone of any intent. Just stating a fact as I do a hand over hand tracing of the circuits. The Mod bias pot has been replaced with a higher wattage pot of lower Resistance vlaue with added 2W resistors strapped across the ends to raise the value yet restrict the variance.
Thanks for your input..it's been so helpful

[WA4JK]

Joe, if no bias was used for the 6146's either the modulators or RF bias how did the 6146's function. I'm totally stumped on this. If the Fianl and Mod bias pots are not connected to ground on one end of the pots how in the world did Gary get this to function. I'm concerned to hook this back up the way the Valiant manual shows for fear of causing issue with what may very well be a perfectly fine design, I just don't know what it is.
Since W2VW has Gary's other Valiant II maybe he has some idea if the bias pots are connected and if he gets Grid Current.?

I have Dave's other Valiant II which was modified extensively.

We took photos of your transmitter and I probably would have taken detailed photos of any obvious mods. I do not remember that rig having what looked like typical modifications.

There's a good sized folder here of Valiant II docs which came from Dave's stuff. I would be glad to help you figure out any missing information. Can you let me know what you are looking for? Is the transmitter working normally for you?

Dave W2VW

 
 
What I need is what is in the valiant folder he holds. It most likely would tell me the design.

[W2VW]

The other Valiant reads grid current but I do not believe the reading to be accurate. The one here is only RF components. The modulator was totally external.

I've carefully checked the paperwork for anything that might help you.

The bias pot would not necessarily need to have one end connected to ground. A mod well known to many who strive for a good trap pattern is combine fixed and grid leak bias. The fixed bias should be just enough for cutoff. The rest of the bias is provided by grid leak and tracks plate voltage swing.

Not sure how this would function properly with a modulator though. 

[WA4JK]

I just can't figure out why a wire would be hanging out in space from the return ground on the RF Bias pot? I also do not know why it would not have grid current indicated. It does have fixed bais based on what you are saying due to the fixed resistance across the mod. bias pot. Not knowing what mods are done makes it hard to look for the missing grid current path. Or at least it does for this Amature. If anyone has any ideas where to look based on what mods are perceived to be in place let me know. My method of probing is not working.

[WA4JK]

I have Dave's valiant II working 100%. Finally got time to chase every wire down and connect everything the way I believe he intended it to work. Everything is solid into the dummy load no sagging current in either the Plate or grid on a 10min. shakedown. Audio works with plenty of swing.
It will go on the air tomorrow night as soon as I get the desk cleaned up and everything back in order. Then the fun begins setting the audio up for the ear on the other end.
P.S. It will remain out of the case...

[W3GMS]

I have Dave's valiant II working 100%. Finally got time to chase every wire down and connect everything the way I believe he intended it to work. Everything is solid into the dummy load no sagging current in either the Plate or grid on a 10min. shakedown. Audio works with plenty of swing.
It will go on the air tomorrow night as soon as I get the desk cleaned up and everything back in order. Then the fun begins setting the audio up for the ear on the other end.
P.S. It will remain out of the case...

Congratulations!!  Glad you stuck with tracing things out and getting the beast on the air.  Now its time to enjoy all your hard work.

73,
Joe, W3GMS

[ka4koe]

Congratulations!

Philip

[Jim, W5JO]

I heard Jerry on the air yesterday morning and the transmitter sounded very good.  The audio was smooth and understandable even though the QRM was pretty bad.  Good work Jerry