New 4-1000A modulated by 4-1000As AM Project - Fabio II Reborn

[W2NBC]

Great on the used timers.. I am sure there are more elegant ways to do the sequencing digitally .. BUT this gives you sequencing and individual timing on ALL
keyed events..
Get that schematic to you soon.. more tornado coverage OM ..

A toast to FABIO #2 ( and to this LONG thread)..

[K1JJ]

Jessie,

Yeah, this seems like the way to go... to be able to set the delay between individual steps to any value - and have the unkey sequence different from the key-up. Well tailored to the rig.  I remember Bruce describing this system before, but it really didn't sink in to the versatility it held. That's until I needed more flexibility and was locked into the 4-step standard sequencer. Now I see.

Among other things, this will allow me to key the HV immediately and the contactor step start clack-clack will be over by the time the audio comes up. Then I can turn the HV off first and give it the whole unkey cycle to bleed off as much as possible, using a long step. No way to do this with the old sequencer.

BTW, I was checking out your AM audio recordings in the link of the various guys.
http://www.dealamerica.com
Good editing and samples of their shticks.


Yep, this thread is long and if like similar ones (Fabio I, Rico Suave, etc) will probably go semi-viral over the next few years from Google people searching for info we have discussed.  It's amazing how many times I've searched for ham technical info on Google and got pointed to this website.  

OK on the tornado coverage. As a senior-anchor, I'm sure you are doing a  hi hi FB ham job at it.

T

** Update - Found the remaining relays I needed on eBay.  Should all be here by the end of the week.  

[KA2DZT]

Tom,

Main thing to do is raise up the idle current (no drive) to some amount (100-200ma).  I'm nearly positive this will eliminate the arcing.  I'll have to eat my hat if it doesn't (good thing I don't have any hats).  

You should be able to test this without the HV damping resistor.  It'll be good to know that the rig is not producing arcs and then add in the damping resistor for secondary backup.

You can run the test at 2KV, then if it looks OK try the 3KV.  If it's going to work, it will work with the sequencer you're using.

OK on the 5 step sequencer, I see you're trying to get rid of the HV relay noise out of the audio.  I guess the noise is still ringing a bit when the audio comes on.

You probably could have used some smaller less noisy relays, although I'm not sure how big your plate xfmr is.  The relay that shorts out the 10ohm resistor doesn't have to be as big as the main relay.

Fred

[K1JJ]

Fred,

I may be able to run some tests when I install the new zener - which should arrive tmw.

Just got the new vacuum relay today, but don't expect to risk it until I get a good working sequencer.

I actually DID try the higher idling current using a lower fixed bias back a few weeks ago. This was when I was still keying the CTs, etc.  It did not stop the arcing, but it may be a different situation now.  

With Fabio I, the higher idle solved the arcing problem, so that's what was confusing.

Anyway, with all the new additions going in soon, that back-EMF will have nowhere to hide.

The contactor clack-clack was in the key up audio simply cuz I was forced to turn it on late.  Then on unkey, it would turn off early as desired.  The new sequencer will allow me to have it fully completed by the time the audio comes on. I built a "sound-proof" enclosure for it, but it can still be heard, though less. With the new system, there will be complete silence on key-up and unkey going out over the air.


Jeff:  I see they shipped most of the relays for the sequencer. I'm having trouble visualizing the circuit that controls the un-key,  the delay on break timers and relays. Hopefully your schematic will clear it up.

T

[KA2DZT]

Fred,


I actually DID try the higher idling current using a lower fixed bias back a few weeks ago. This was when I was still keying the CTs, etc.  It did not stop the arcing, but it may be a different situation now.  

With Fabio I, the higher idle solved the arcing problem, so that's what was confusing.


T

Not confusing at all.  You raised the idle current but that didn't help simple because you were still opening the CT which instantly cut off all current, resulting in the same arcing.

Now you're no longer opening CTs which allows the finals to continue conducting current.  So, when you drop the drive the finals will still continue conducting the idle current which will finish decaying away the last bit of current.  If the idle current is very close to the plate current (with drive) at the instant the drive drops there would be nearly no sudden change in current (up or down).  It would be difficult to hit that target.  Not exactly sure how close it has to be, but 100-200ma is a good starting point.

As for Fabio I,  I didn't follow that threat so not sure how it was set up to operate.  If you were using the CT opening method and you raised the idle current to eliminate arcing, well hard to say why it may have worked.  There may have been some other conditions existing in that rig that are not in Fabio II.

Fred

[K1JJ]

Fred,

Fabio I used CT keying - that's why it's confusing that the higher idle worked.  But it added a  plate current surge upwards and dropped off before the RF drive dropped, thus the success of more bleed-off.   Seems last week I tried higher idle with the CT always on and the arc was still bad, so who knows until I get the complete system working together the way it should.


Jeff:  I drew out the circuit and  got an idea how it shud work. However, I wonder what will happen at initial power up?  Do I need to turn the sequencer on first, let it set itself and then activate the rig T/R system?  Hopefully it needs just one  initialization.

Also, Bruce mentioned in his old post that he used some of the relay contacts to make sure that each relay turned on before the next relay. Kind of a fail-safe.  Maybe we can add  that to the design.  There are two sets of  SPDT contacts for each relay available.

T

[W2NBC]

T,

One shot is all it should take.. when you switch in 120 though all 5 key-up timers to --->5 key-up relays it all happens at the zoo.. You will use the poles on those key-up relays in a sequence to trigger all events.. Just to clarify the second set of 5 timers (un-key) and 5 relays (all poles in parallel with the other 5) are there to keep closure on un-key for a different sequence..

To daisy-chain a fail-safe would be an exercise.. 
at work again.. later

[K1JJ]

J,

Gots it pretty well figgered out now, tnx.

I just built up a chassis, front/back panels and drilled all the holes for the sequencer.  When the parts arrive we will be in business again.


Note to readers:    Jeff and I will take the new sequencer discussion off-board for a while.  I will post back with pictures of a completed and working unit - and a schematic for those interested.  The Fabio II project will continue from there.

Tnx for the help, guys.

T

[K1JJ]

It may not be done, but it sure is fun!

This is the new sequencer using delay timers to control both interval length and forward and backwards order. Full versatility to sequence the various relays in Fabio II. Five steps forward, five steps back, any order, any length.

Each LED will light up (1 of 10) to indicate which relay is activated. I left some extra jacks for expansion.

Everything found on eBay, cheap.

Lots of wiring to do before operational.  This and the four overload trip Hall effect sensor boards is all that's needed to get Fabio II on the air.  (When will it end?)


T

[Opcom]

Tom,

My HV is 5500v under load

What kind of modulation transformer do you use that can take such voltages reliably?

[Opcom]

It may not be done, but it sure is fun!

This is the new sequencer using delay timers to control both interval length and forward and back order. Full versatility to sequence the various relays in Fabio II. Five steps forward, five steps back, any order, any length.

Have you ever had issues with RF getting to the solid state relays and making them act crazy? Or is it as simple as a closed box and maybe bypass caps on each relay?

[K1JJ]

Have you ever had issues with RF getting to the solid state relays and making them act crazy? Or is it as simple as a closed box and maybe bypass caps on each relay?

I haven't wired it up yet.

Though I know that Bruce / W2XR uses the same timers and circuit, but have never seen a schematic of it to know how it's bypassed, if at all.

It would be smart to use bypassing for sure - and place it all in a sealed RF-proof box.

It certainly is a big project just for a sequencer, but I had no other choice to get a variable ordered sequence.

Jeff/ W2NBC did the design on this one. Not sure if he is using one or not. We will post his schematic once it is tested.

T

[K1JJ]

An update:

I haven't forgotten this thread - just ploughing through modifications and testing.

The 5-step W2NBC sequencer works very FB now. The sequencer has gotten very complex with hundreds of internal connections, but the 4X1 rig now is as silent as a mouse. No arcing and it bleeds off the grid, screen and plate energy nicely.

At this point I have not bypassed anything in the sequencer for RF. It is running out of the cabinet exposed to the final. No signs of the solid state timers and associated circuits being affected.  The only thang that may need more bypassing is the solid state MOSFET driver.

Been working on optimizing the plate tanks for 160, 75 and 40M.  Had to add another coil and some C2 load padding for 160M. Now full output on these bands with a good Q.

Added a tiny 30 pF  17KV  vacuum variable neutralizing capacitor. The neutralization works FB and the feed thru signal sucked right out.  Very stable  on all bands of interest. (160 - 40)

Working on six optical-isolator sensors for overload shut-down  -  grid, screen and plate current of the RF deck and modulator. If any circuit exceeds a pre-set point, the PTT will toggle off and the sequencer will shut everything down orderly. (not counting smoke and fire)

Due to circuit losses, etc., the 4X1s need about 40 watts of drive total.  I am running them deep into class C which makes them even harder to drive, but more efficient.  I'm working on putting in a one MOSFET pre-driver that will take a few watts from the ricebox to drive the 4X1.

With the new sequencer installed, I brought the HV up to 3200V with no problems. This is the minimum voltage Eimac recommends in their datasheet, and that will be my high-tap.

The PTT key-up and unkey is dead quiet on the air due to the audio coming on last for  key-up  - and audio dropping off first on unkey. We hear just a carrier with no pops, relay clacks or thumps on PTT.

W2NBC did a recording the other night and it's getting there. Needs some more work.  Have a slight problem with low freq oscillation in the SS driver, but working on it.

The THD tests are encouraging.  At 100% modulation, I see the 2nd AUDIO harmonic down about -25 dB and the 3rd and higher drop off better than -40 DB++ .  Very sharp containment of energy up the band.   This is cleaner than my e-rig by 10-15dB in some cases.  The audio negative feedback made a difference as well as adjusting certain parameters to find their THD sweet spots.

I would love to set up a trapezoid on the scope, but so far have had no success. More later.


T

Here's Fabio II live at 2200 volts - the W2NBC recording last Saturday off his R-390:   The modulators  get somewhat cleaner at 3200 V.  Considering my average voice, I am pleased so far.  Notice the subtle lip smacks and breathing - and other high frequency sounds that require a good high end. Still needs low level processing, but is getting cleaner.

[steve_qix]

Shark Fins    The acid test.  Seriously, it sounded pretty good the one time I heard you on.

I have the new big rig set up at Rattlesnake Island.  Look for you over the weekend if you're on.  I may have a mod monitor set up on the receiver - depends on how much tinkering time I have when I'm up there.  If I get it set up, I'll send you a transcript like I did one other time if you're on.

[KA2DZT]

Tom,

You didn't mention in your update what you did to eliminate the arcing problems.

Are you using the damping resistors??  Did you increase the idle current (no drive) on the finals??

I'm wondering if my idea of increased idle current worked, without the damping resistors, to clear up the arcing issues.  Don't know if you tried it without the resistors.

Fred

[K1JJ]

Steve,

Well, I am seeing what I'd call "semi-shark fins."    The low end falls apart below 25 Hz, so it's not a bad compromise.  The SS driver uses coupling caps that limit it to about 20 Hz as well as the mod xfmr having its own limitations.  So all in all, I'm pleased with what I'm seeing so far.  I'll be interested to see what you think.

I've been hearing you on from Rat Is with the new rig.  Perfect audio, though sig down maybe 10dB from your closer MA QTH. Still rock crushing just the same.


Fred,

I haven't tried the rig with the dampers disconnected. Fear is the big reason... :-)   I did try it some time back with a small idle, using a lower RF fixed bias, and still had arcing.  So, the dampers appear to be making a big difference.

I still have the sequencer set slow,  at  3/4 second keyup and 3/4 second unkey.  The HV and screen supplies die off about 80% before releasing. This is a good thang until I speed up the sequencer and take a chance later on.

Today I had a BIG bang. The vac cap for neutralization was mounted 1" from the chassis and it arced over to chassis big time. Sustained blue flash. Took out the HV wire fuses and toasted the cap Plexiglas mount.  I re-mounted it 3" away from the chassis and it worked FB.

Had it on 160M using 3200V and everything hung in there very well.  I think the shakedown testing and perfection phase is going to take TWICE as long as it took to build the rig in the first place.  I keep finding new things to add or modify as it goes on.  

Gonna mount up a solid state RF driver tmw for 1 watt in, 50 watts out as an IPA. I'll be able to drive Fabio II directly with the one watt hi-tech SDR rig.


Itching to start on a new linear project - maybe a posse of convection-cooled 813's in tetrode config - not sure yet.  I need a quiet amp for those hot summer nights when Fabio II is just too hot to handle.


T

[KA2DZT]

T

OK FB,  at 3200V, no sense not using the dampers for a fail safe.  You'll be able to tell how much the dampers are doing by the amount heat being dissipated by them.

Don't put your finger on them while the HV is on   Not sure if you know enough not to do that

Fred

[K1JJ]

Don't put your finger on them while the HV is on  Not sure if you know enough not to do that

Fred

After years of developing calluses on my tongue testing 9 volt batteries, why use my fingers?

T

[K1JJ]

Here's two pics of the finished 5-step sequencer.  All lights are on and all relays keyed.

It uses ten NCC timers and twelve DPDT relays. It will step forward and backwards in any order and also vary the delay between any step.

Works very FB now with Fabio II. There is no arcing or problems on key-up or key-down.

It's a lot of effort for a sequencing system, but the standard 4-step fixed step and interval did not do the job.

I left a few holes for expansion.  Still needs panel labels.

T

[K1JJ]

Here's the 2 watt in, 100 watt out  solid state amplifier used for a dead carrier - to drive Fabio II in class C.  It uses a CCI kit board using four MRF-150s.   It is rated at 600 watts out, so will be running conservatively.

It has a small fan blowing air thru the heatsink as well as across the copper spreader.  Seems pretty stable. There is a missing MRF-150 due to a previous mishap. Just ordered one from China for $26, free shipping.

It runs silently and will keep the load off my ricebox driver, needing only a few watts.   There is a 10A meter on the front for monitoring. The unit is rated at 50V - I am using just 24V.

There are no LP filters required since it will be driving a tuned grid and plate circuit in class C that will greatly reduce any harmonics.

Picture 2 shows a 3 dB resistor input pad towards the rear of the board.  I plan to add a shutdown overload circuit to the RF input in case of errors.

Still needs painting and labels.

This module goes after the antenna relay and feeds into a 50 ohm to 50 ohm unbalanced tuner which feeds the 4X1 grid circuit. Thus, this solid state IPA will always have a perfect 1:1 match to work into on the various bands.

As you can see, I take a modular approach to most all of my building. This is convenient when changes, additions or modifications are made.  Sub-systems can be reused without re-building all over again.

T

[W2NBC]

 Dang!.. there be some WIRES in there.. anyway, it works and that's a good thang OM.. Next time maybe a ribbon cable or 5 would make it " look" less complicated.. 
..and the amp looks great! A toast to Fabio and his offspring..

[K1JJ]

Dang!.. there be some WIRES in there.. anyway, it works and that's a good thang OM.. Next time maybe a ribbon cable or 5 would make it " look" less complicated..  
..and the amp looks great! A toast to Fabio and his offspring..

A neat ribbon cable?   Just wait til you see the rents I charge the local rats to live in there!


Yep, the NBC design worked FB.  The only problem I had is that the Q3T unkey timers did NOT want to be tied together and signalled with one set of contacts. I needed a separate pole for each timer.  (see the extra 4 pole relay glued to the top on the right?) The Q3T triggers are solid state based and did not like associating wid each other, caw mawn.   Otherwise, smooth sailing and I'm moving on to the next trial by fire.


T

[K1JJ]

Here's the finished panels for the W2NBC sequencer and the new 4X1 shutdown overload unit.

Notice the power resistors in the shutdown unit that sample the RF screen, RF plate, modulator screen and modulator plate currents.  Works like a charm! The series resistors are in the negative lead of the supply or fil CT - and about 1-3 ohms. Each feeds an optical-isolator board. This in turn feeds the relays and latching circuits. If any current exceeds a pre-determined level, the 4X1 PTT sequencer methodically unkeys the rig.  The iso boards and relays worked out FB and I may add these to other rigs.

The four holes are for fine-tune trip sensitivity pots to be added later.

I am using another method to shut down the RF grid and Mod grid circuits in case of overload. They involve shutting down the SS IPA.

I realize the wiring is not dressed off, but on certain units I sometimes leave it loose to make troubleshooting and servicing easy in the future. It is very difficult to trace out wires that are bound together.  This way I can usually fix something quickly without the schematic.

Now down to final testing and optimization of  Fabio II since all the safety devices are finally in place.

T

[K1JJ]

And the IPA. No name for it yet...

[K1JJ]

Fabio testing resumes.  More gadgets added. Everything still out-of-cabinet.  Black lettering on white, caw mawn.

It's really too hot to test, so I'm starting a new pair of grounded grid 4-1000As linear amp in the cool cellar workshop. Regulated screen and grid.  Check the QSO section for the next thread.


***  Here's the new 4-1000As linear project:

http://amfone.net/Amforum/index.php?topic=34543.0

T