The AM Forum
July 23, 2024, 01:18:24 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Lysco 600 as a VFO for my BC-610E  (Read 13126 times)
0 Members and 1 Guest are viewing this topic.
N6YW
Contributing
Member
*
Offline Offline

Posts: 458


WWW
« on: May 25, 2014, 03:08:08 PM »

Greetings
Finally getting things in order to bring the BC-160E on the air. After a couple of months of having other priorities going on, I am getting back to the 610 mindset. My good friend Brian NI6Q suggested and provided, a Lysco 600 Transmaster to be used as a powerful yet stable VFO. He had used one with his BC-610E with excellent results. So, begs the question: Is 6.5 volts RMS too much signal for the 610 crystal input? If so, a simple resistor network attenuator should work to reduce this output level. What would you do? I measured this voltage on the two binding post outputs, which are isolated from ground. I measured 410 vdc from either post to ground. Yikes! Here is the schematic of the unit attached.
Thanks!

* LY-500-600.pdf (576.91 KB - downloaded 339 times.)
Logged

"Life is too short for QRP"
W3GMS
Contributing
Member
*
Offline Offline

Posts: 3047



« Reply #1 on: May 25, 2014, 04:39:35 PM »

That RF drive level sounds fine. 

My Heathkit HG-10 puts somewhere around that drive level out and its never been a problem.  A lot of standalone VFO's do not have a low impedance output so when they are loaded the signal drops down considerable.

I also have a Lysco and its a nice transmitter.     

Joe, W3GMS
Logged

Simplicity is the Elegance of Design---W3GMS
Ralph W3GL
Contributing
Member
*
Offline Offline

Posts: 748



« Reply #2 on: May 25, 2014, 06:18:44 PM »


You should not have that kind of HV on so called "isolated"
contacts.   The schematic you show for that rig shows an
unbalanced output thru a low pass filter.  A quick scan of the
schematic does not show any isolated output from the final
807 stage...

It's time for some trouble shooting.  If, in fact, there is HV at
the center pin connection of the coax connecter, the plate
coupling cap is shorted! 
Logged

73,  Ralph  W3GL 

"Just because the microphone in front of you amplifies your voice around the world is no reason to think we have any more wisdom than we had when our voices could reach from one end of the bar to the other"     Ed Morrow
N6YW
Contributing
Member
*
Offline Offline

Posts: 458


WWW
« Reply #3 on: May 25, 2014, 06:21:47 PM »


You should not have that kind of HV on so called "isolated"
contacts.   The schematic you show for that rig shows an
unbalanced output thru a low pass filter.  A quick scan of the
schematic does not show any isolated output from the final
807 stage...

It's time for some trouble shooting.  If, in fact, there is HV at
the center pin connection of the coax connecter, the plate
coupling cap is shorted! 

Actually, there are two binding posts on the back of the chassis. You add a strap across those terminals and the output goes through the low pass filter. Otherwise, use the binding posts with balanced line. The manual does not really treat this at all which I find very strange. Not a lot of documentation on this rig.
Logged

"Life is too short for QRP"
WQ9E
Member

Offline Offline

Posts: 3287



« Reply #4 on: May 25, 2014, 06:42:42 PM »

No matter how it is configured you shouldn't have any DC on the output because there is a DC blocking capacitor that couples the anode to the output network.  What is even more strange is that you are measuring DC from both binding posts to ground.  Either there is a measurement error or you have a modified 600 and you need to figure out what was done (and I would suggest undoing it back to stock).

I have a Lysco 600 I bought from the original owner that also save the original railway crate it was shipped inside.  It is a very nice little rig.
Logged

Rodger WQ9E
N6YW
Contributing
Member
*
Offline Offline

Posts: 458


WWW
« Reply #5 on: May 25, 2014, 06:52:39 PM »

No matter how it is configured you shouldn't have any DC on the output because there is a DC blocking capacitor that couples the anode to the output network.  What is even more strange is that you are measuring DC from both binding posts to ground.  Either there is a measurement error or you have a modified 600 and you need to figure out what was done (and I would suggest undoing it back to stock).

I have a Lysco 600 I bought from the original owner that also save the original railway crate it was shipped inside.  It is a very nice little rig.
Exactly what I was thinking. No DC at all. I just fired the thing up the morning, so the learning about this rig grows by the minute. I'll keep you informed and THANKS!!!!!  Smiley
Logged

"Life is too short for QRP"
AB2EZ
Member

Offline Offline

Posts: 1711


"Season's Greetings" looks okay to me...


« Reply #6 on: May 25, 2014, 06:53:54 PM »

The documentation you posted says that the plate voltage is around 400V, and that the plate current (properly tuned and loaded) is around 100mA. Therefore the input power is around 40W. The corresponding RF output power would be 20W or more.

A 20W sine wave into a 50 ohm load corresponds to more than 30V rms. This suggests that the transmitter was not tuned and loaded into a 50 ohm load when you measured 6.5V rms across the output binding posts... or these binding posts do not correspond to the RF output. For example, they could be connected to the opposite sides of a shunt resistor used to measure the plate current.

Stu

Logged

Stewart ("Stu") Personick. Pictured: (from The New Yorker) "Season's Greetings" looks OK to me. Let's run it by the legal department
Ralph W3GL
Contributing
Member
*
Offline Offline

Posts: 748



« Reply #7 on: May 25, 2014, 06:54:46 PM »


You should not have that kind of HV on so called "isolated"
contacts.   The schematic you show for that rig shows an
unbalanced output thru a low pass filter.  A quick scan of the
schematic does not show any isolated output from the final
807 stage...
However close examination of the schematic shows what might
be a shorted jumper above the plate/screen feed of the 807 stage
that might come out of the rig to binding posts allowing connection
to a high level modulator...  This would allow the rig to be powered
up with final disabled with the jumper (if this actually exists)
removed...  With it in place you would measure HV on both
terminals...
It's time for some trouble shooting.  If, in fact, there is HV at
the center pin connection of the coax connecter, the plate
coupling cap is shorted!  

Logged

73,  Ralph  W3GL 

"Just because the microphone in front of you amplifies your voice around the world is no reason to think we have any more wisdom than we had when our voices could reach from one end of the bar to the other"     Ed Morrow
AB2EZ
Member

Offline Offline

Posts: 1711


"Season's Greetings" looks okay to me...


« Reply #8 on: May 25, 2014, 07:05:52 PM »

Ralph

Yes... and if the jumper is in place, you would not only measure the DC plate voltage between either binding post and ground... you would also have an additional sinusoidal voltage, between either binding post and ground, with a frequency equal to that of the RF output of the transmitter. This could correspond to the portion of the plate voltage waveform that passes through the voltage divider formed by the plate choke and the plate choke input bypass capacitor(s)... if the plate choke is acting like a capacitor at the frequency of operation. More likely, it is inductive coupling (pickup) between the transmitter's output circuitry and the wires that lead to the binding posts.


Stu
Logged

Stewart ("Stu") Personick. Pictured: (from The New Yorker) "Season's Greetings" looks OK to me. Let's run it by the legal department
N6YW
Contributing
Member
*
Offline Offline

Posts: 458


WWW
« Reply #9 on: May 25, 2014, 08:10:23 PM »

I had the transmitter connected to a Drake 300 watt dummy load. I tuned for a dip on the plate meter, and it produced about 15 watts of carrier. From either binding post, I read approximately 6.5 volts RMS with a Fluke 87-IV DVM. I also checked DC potential from both posts to ground, and I read 415 vdc. On my scope, the sine wave looked decent with a good note. A little ripple is audible. Someone had recently replaced the electrolytics. This transmitter shows signs of being very hot with the possibility of a major flashover in the power supply compartment. Something went poof sometime in it's existence. The plate choke blocking capacitor is a molded mica affair that may be suspect. I'll sub it out tonight to see if things
are happier. It seems to me safety wise, that no DC at all should appear on those terminals.
Logged

"Life is too short for QRP"
N6YW
Contributing
Member
*
Offline Offline

Posts: 458


WWW
« Reply #10 on: May 25, 2014, 08:21:04 PM »

BTW...
Both plate bypass and plate blocking capacitors are .002 @ 1200 vdc. In this circuit, is the actual
capacitance critical?
Logged

"Life is too short for QRP"
WQ9E
Member

Offline Offline

Posts: 3287



« Reply #11 on: May 25, 2014, 08:22:02 PM »

Were you trying to measure DC with the transmitter producing output?  That wouldn't be a valid measurement.

Put your scope into the DC coupled position with a sensitivity of 5V per division (or .5V if your probe is a 10X low cap type) and if it really has 400 volts DC at the terminals the trace will deflect off screen.

In general, scope measurements are made in the DC coupled position unless you are knowingly trying to make AC measurements in the presence of DC.
Logged

Rodger WQ9E
N6YW
Contributing
Member
*
Offline Offline

Posts: 458


WWW
« Reply #12 on: May 25, 2014, 08:47:33 PM »

Were you trying to measure DC with the transmitter producing output?  That wouldn't be a valid measurement.

Put your scope into the DC coupled position with a sensitivity of 5V per division (or .5V if your probe is a 10X low cap type) and if it really has 400 volts DC at the terminals the trace will deflect off screen.

In general, scope measurements are made in the DC coupled position unless you are knowingly trying to make AC measurements in the presence of DC.
Both, made no difference. Keyed or unkeyed, 400 plus volts on those terminals. My scope went off scale. Tektronix 475, .5 volts per division, DC coupling with a standard probe. It's cap fishing time.
Logged

"Life is too short for QRP"
N6YW
Contributing
Member
*
Offline Offline

Posts: 458


WWW
« Reply #13 on: May 25, 2014, 09:24:11 PM »

If you look at the schematic, there are two dots joined by a double arrow, where the screen resistor R-10 and the meter intersect. Those two dots represent the two binding posts, isolated from ground. I am not sure what they are for. The low pass filter is on the cold side of the blocking capacitor, so I guess these are take off points for some other arrangement having nothing to do with the RF output of the transmitter.
Having said that, the blocking capacitor tests fine using an ohm meter. I will test when energized to see if it leaks DC on the cold side. Here are some photos of the interior.


* 20140525_180923_resized.jpg (220.96 KB, 612x816 - viewed 832 times.)

* 20140525_180928_resized.jpg (205.67 KB, 612x816 - viewed 708 times.)

* 20140525_180935_resized.jpg (212.02 KB, 816x612 - viewed 758 times.)
Logged

"Life is too short for QRP"
WQ9E
Member

Offline Offline

Posts: 3287



« Reply #14 on: May 25, 2014, 09:36:47 PM »

Those two binding posts are for connecting an external modulator for AM and are in the B+ feed to the final, you don't want to try to take output from there.  That explains the 400 volts.  They should be shorted (together, NOT to ground) unless you are using an external plate modulator.

Take your RF output from the RF output section (the low pass filter may not be present, it is only included in the "TVI proof" models).
Logged

Rodger WQ9E
N6YW
Contributing
Member
*
Offline Offline

Posts: 458


WWW
« Reply #15 on: May 25, 2014, 10:28:25 PM »

Thanks, I figured that out. I misunderstood what Brian tried telling me about those posts.
Anyway, onward. Caps test fine. Putting out about 15 watts carrier. I'm not sure if this is going to work out for a VFO. It needs to be on for over an hour before it settles down and then it still drifts.
Logged

"Life is too short for QRP"
N6YW
Contributing
Member
*
Offline Offline

Posts: 458


WWW
« Reply #16 on: May 26, 2014, 02:18:28 PM »

Rodger, a question for you...
Using the Lysco as a VFO, the RF power will have to be applied to a 50 ohm load and the signal tapped off of that with enough RMS voltage to drive the BC-610E. What arrangement would you devise to accomplish this task?
Logged

"Life is too short for QRP"
WQ9E
Member

Offline Offline

Posts: 3287



« Reply #17 on: May 26, 2014, 02:51:54 PM »

I would follow the suggestions provided by Meissner in their Signal Shifter manual which discusses how to use it to drive a crystal oscillator stage.  You can grab the manual from edebris here:  http://bama.edebris.com/manuals/meissner/newss

Lysco documentation is pretty minimal as you have already discovered.
Logged

Rodger WQ9E
N6YW
Contributing
Member
*
Offline Offline

Posts: 458


WWW
« Reply #18 on: May 26, 2014, 03:38:21 PM »

Rodger
Thank you, I will read this in it's entirety.
73 de Billy N6YW
Logged

"Life is too short for QRP"
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.084 seconds with 19 queries.