Re: TL-922 47pF Capacitor
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On 28 Aug 2023, at 7:35 am, Alek Petkovic via groups.io <vk6apk@...> wrote:
?
Yes. A silly activity.?
Alek. VK6APK
On 28/08/2023 7:08 am, HaL Mandel
wrote:
Dear Alek,
?
My thoughts on seeing the word “bypassed”
lead me to believe
“running barefoot.”
?
?
Hal Mandel
W4HBM
|
Re: TL-922 47pF Capacitor
Yes. A silly activity.?
Alek. VK6APK
On 28/08/2023 7:08 am, HaL Mandel
wrote:
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Show quoted text
Dear Alek,
?
My thoughts on seeing the word “bypassed”
lead me to believe
“running barefoot.”
?
?
Hal Mandel
W4HBM
|
Re: TL-922 47pF Capacitor
Dear Alek,
?
My thoughts on seeing the word “bypassed” lead me to believe
“running barefoot.”
?
?
Hal Mandel
W4HBM
|
Re: TL-922 47pF Capacitor
Yes. That was my observation too. Maybe VC2-1 was marginal on 40m
and the 47pF was selected so that it provided that little bit of
extra capacitance without messing up 10m with too much
capacitance.
73, Alek.
On 27/08/2023 5:41 am, Louis
Parascondola via groups.io wrote:
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That 47 pf cap basically would add 47pf to the total of the entire
value of the load cap. ?Usually load padding is switched in and
out rather than hung on there forever. ?That’s a relatively small
amount compared to the value to the cap.
On Saturday, August
26, 2023, 4:48 PM, HaL Mandel <hmandel@...> wrote:
?
{SNIP}
I have a question regarding what appears to be an added
47pF/3kV blue ceramic capacitor in the output tank
circuit. It goes from the output contact of the
bandswitch to ground, as seen below.
{SNIP}
?
Dear Alek,
There is a veritable “no-nonsense” test for your
question.
You should do either an “S11,” or an “S21” test with a
Vector Network Analyzer, like the ever-popular
NanoVNA as seen on Ebay or Amazon, etc.
?
Dialing-in the Start Frequency (more than likely 1.0
MHz),
and the Stop Frequency, (again, more than likely
30.0MHz),
look at the graph displaying the Reflected Power curve,
and when you have it in front of you, clip the blue cap
and see what it does, For Your Amp.
?
Of course, no power in the amp needed. A test clip on
the input
and on the output of the tank will suffice.
?
My friend AB2NI uses his Nano’ on all the various
amplifiers
he’s attempting to renovate, and has uncovered
mistunings because
of incorrect padding, incorrect choking, incorrect
input tuning, etc.,
and has become astute with the small instrument enough
to now
use it as easily as a DMM.
?
I am still training for operating knowledge on my VNA.
It came
with clips and a small PCB with bits so I could set the
machine up
and duplicate the various curves the I/M sez it should.
?
I hope this suggestion helps!
?
Hal Mandel
W4HBM
?
?
?
?
|
Re: TL-922 47pF Capacitor
Thanks Hal.
That would be an interesting exercise. I use my nano vna all the
time too but I don't think I'll bother in this case, as it seems
to work fine with the cap in place. I'll let sleeping dogs lie.
I'm just finishing off some mods for a local ham, which were
started many years ago and the guy doing them got ill and sadly
passed away.
I saw a reference where Rich Measures mentioned the addition of a
small cap around this size from the normally closed I/O relay to
ground, to improve the through SWR on 10m when the amp is
bypassed. Why anyone would ever operate with the amp bypassed is
beyond me.???
73, Alek, VK6APK
On 27/08/2023 4:48 am, HaL Mandel
wrote:
toggle quoted message
Show quoted text
?
{SNIP}
I have a question regarding what appears to be an added
47pF/3kV blue ceramic capacitor in the output tank circuit. It
goes from the output contact of the bandswitch to ground, as
seen below.
{SNIP}
?
Dear Alek,
There is a veritable “no-nonsense” test for your question.
You should do either an “S11,” or an “S21” test with a
Vector Network Analyzer, like the ever-popular
NanoVNA as seen on Ebay or Amazon, etc.
?
Dialing-in the Start Frequency (more than likely 1.0 MHz),
and the Stop Frequency, (again, more than likely 30.0MHz),
look at the graph displaying the Reflected Power curve,
and when you have it in front of you, clip the blue cap
and see what it does, For Your Amp.
?
Of course, no power in the amp needed. A test clip on the
input
and on the output of the tank will suffice.
?
My friend AB2NI uses his Nano’ on all the various amplifiers
he’s attempting to renovate, and has uncovered mistunings
because
of incorrect padding, incorrect choking, incorrect input
tuning, etc.,
and has become astute with the small instrument enough to now
use it as easily as a DMM.
?
I am still training for operating knowledge on my VNA. It
came
with clips and a small PCB with bits so I could set the
machine up
and duplicate the various curves the I/M sez it should.
?
I hope this suggestion helps!
?
Hal Mandel
W4HBM
?
?
?
?
|
Re: TL-922 47pF Capacitor
That 47 pf cap basically would add 47pf to the total of the entire value of the load cap. ?Usually load padding is switched in and out rather than hung on there forever. ?That’s a relatively small amount compared to the value to the cap.
On Saturday, August 26, 2023, 4:48 PM, HaL Mandel <hmandel@...> wrote:
?
{SNIP}
I have a question regarding what appears to be an added 47pF/3kV blue ceramic capacitor in the output tank circuit. It goes from the output contact of the bandswitch to ground, as seen below.
{SNIP}
?
Dear Alek,
There is a veritable “no-nonsense” test for your question.
You should do either an “S11,” or an “S21” test with a
Vector Network Analyzer, like the ever-popular
NanoVNA as seen on Ebay or Amazon, etc.
?
Dialing-in the Start Frequency (more than likely 1.0 MHz),
and the Stop Frequency, (again, more than likely 30.0MHz),
look at the graph displaying the Reflected Power curve,
and when you have it in front of you, clip the blue cap
and see what it does, For Your Amp.
?
Of course, no power in the amp needed. A test clip on the input
and on the output of the tank will suffice.
?
My friend AB2NI uses his Nano’ on all the various amplifiers
he’s attempting to renovate, and has uncovered mistunings because
of incorrect padding, incorrect choking, incorrect input tuning, etc.,
and has become astute with the small instrument enough to now
use it as easily as a DMM.
?
I am still training for operating knowledge on my VNA. It came
with clips and a small PCB with bits so I could set the machine up
and duplicate the various curves the I/M sez it should.
?
I hope this suggestion helps!
?
Hal Mandel
W4HBM
?
?
?
?
|
Re: TL-922 47pF Capacitor
?
{SNIP}
I have a question regarding what appears to be an added 47pF/3kV blue ceramic capacitor in the output tank circuit. It goes from the output contact of the bandswitch to ground, as seen below.
{SNIP}
?
Dear Alek,
There is a veritable “no-nonsense” test for your question.
You should do either an “S11,” or an “S21” test with a
Vector Network Analyzer, like the ever-popular
NanoVNA as seen on Ebay or Amazon, etc.
?
Dialing-in the Start Frequency (more than likely 1.0 MHz),
and the Stop Frequency, (again, more than likely 30.0MHz),
look at the graph displaying the Reflected Power curve,
and when you have it in front of you, clip the blue cap
and see what it does, For Your Amp.
?
Of course, no power in the amp needed. A test clip on the input
and on the output of the tank will suffice.
?
My friend AB2NI uses his Nano’ on all the various amplifiers
he’s attempting to renovate, and has uncovered mistunings because
of incorrect padding, incorrect choking, incorrect input tuning, etc.,
and has become astute with the small instrument enough to now
use it as easily as a DMM.
?
I am still training for operating knowledge on my VNA. It came
with clips and a small PCB with bits so I could set the machine up
and duplicate the various curves the I/M sez it should.
?
I hope this suggestion helps!
?
Hal Mandel
W4HBM
?
?
?
?
|
Re: TL-922 47pF Capacitor
Alek, FWIW, mine has it as well. Attached picture is my 922. That extra circuit board you see is the "Kessler" electronic bias board. 73, Bob? W4JFA
G'day all.
I am currently working on a couple of TL-922 amplifiers and I
have a question regarding what appears to be an added 47pF/3kV
blue ceramic capacitor in the output tank circuit. It goes from
the output contact of the bandswitch to ground, as seen below.
Both amplifiers have this capacitor and the above picture was
from Google.
Does anybody know what the purppose of this capacitor might be?
It definitely looks like an addition.
I'm happy to leave it in place but I'm wondering what it does.
Thanks and 73, Ale, VK6APK.
|
G'day all.
I am currently working on a couple of TL-922 amplifiers and I
have a question regarding what appears to be an added 47pF/3kV
blue ceramic capacitor in the output tank circuit. It goes from
the output contact of the bandswitch to ground, as seen below.
Both amplifiers have this capacitor and the above picture was
from Google.
Does anybody know what the purppose of this capacitor might be?
It definitely looks like an addition.
I'm happy to leave it in place but I'm wondering what it does.
Thanks and 73, Ale, VK6APK.
|
Re: 17 x pix of the 10 kw 6M amp...using the new Pentalab 3CX-6000A7 tube.
Very impressive workmanship!?? Thanks for sharing this accomplishment.
Mike Peace
|
Re: 17 x pix of the 10 kw 6M amp...using the new Pentalab 3CX-6000A7 tube.
?
{SNIP}
... pix of the 10 kw 6M amp...using the new Pentalab 3CX-6000A7 tube...
{SNIP}
?
Yuss!
?
Here’s what chassismongery is all about.
No greezy kid stuff, no tell-tale fingerprints.
And plenty of P/Sup horsepower, laddies!
?
Hal Mandel
W4HBM
?
|
17 x pix of the 10 kw 6M amp...using the new Pentalab 3CX-6000A7 tube.
17 x pix of the 10 kw 6M amp...using the new Pentalab 3CX-6000A7 tube. If you want to see pix of both top + bottom of the RF deck, + pix of the HV supply, here is the link.
The next amp is the 80-15m bandswitched unit, using the same 3CX-6000A7 tube. I have finalized the design for the RF deck. Components of course are a lot bigger. 1/2" silver plated tubing used for the 20-17-15m coil (and also the L coil before the main PI-net). The 80-40-30 coil will be hand wound, using 3/8" tubing.
500 pf ceramic vacuum tune cap, and a 3000 pf vacuum load cap. Same setup for the TR relays. RJ1A for the cutoff bias, and a 2nd RJ1A for the input. 2 x paralleled RJ2B's for the output. 7-16 DIN connector for the output. 4 x 200pf HT-57 plate blockers used. I have also finalized the design for the 160-80-40-20-17-15m version. It uses a 4000 pf vac load cap, and one extra coil.... for 160m (silver plated 1/4" tubing used). 8-9 x 200pf HT-57 plate blockers used.
The HV supply will use a lot more B+ (7500 vdc)...and will use 2 x identical plate xfmrs in parallel. Both designs employ a bandswitched PI tuned input. (C1 + C2 are padded on 160m)
Stay tuned.
Jim VE7RF
|
Re: Plate modulated GG triodes
We build this kind of thing out of junk we have laying around.? It's out there is you ask and look for it.??
?
Dear Clark,
?
Thanks for posting the reply to a previous post regarding the power supplies
for plate modulation.
?
The schematic you included shows a grid reactor with a value of 20 henries.
?
Wow.
?
In this day and age finding the bits and pieces to put together a set
will probably require much time and investment. Gone are the days
of surplus treasures, I’m afraid.
?
Even approaching the fabrication of a viable transformer to run a couple of
gallons on HF is not so easy as it once was. PWD, then Hammond, then
Harbach... They may have the specs on file, but who can come up with a
tape-wound Hypersil and vacuum seal it like they used to in Texas?
?
Anyway, thanks. Good luck on your build.
?
Hal
W4HBM
?
|
Re: Plate modulated GG triodes
?
Dear Clark,
?
Thanks for posting the reply to a previous post regarding the power supplies
for plate modulation.
?
The schematic you included shows a grid reactor with a value of 20 henries.
?
Wow.
?
In this day and age finding the bits and pieces to put together a set
will probably require much time and investment. Gone are the days
of surplus treasures, I’m afraid.
?
Even approaching the fabrication of a viable transformer to run a couple of
gallons on HF is not so easy as it once was. PWD, then Hammond, then
Harbach... They may have the specs on file, but who can come up with a
tape-wound Hypersil and vacuum seal it like they used to in Texas?
?
Anyway, thanks. Good luck on your build.
?
Hal
W4HBM
?
|
Re: Plate modulated GG triodes
It is best to run a separate Power supply for the modulators.? You can run the RF deck and Modulator deck off the same supply of course.? The reason is that you can run higher voltage on the modulator and get more ratio to modulate the final.? Example, The Modulator is at 3000 volts and the RF final is at 2500 volts.? You wont need as much ratio on the modulation transformer. This way higher positive peaks can be had.
You just need a standard Filiment transformer.? You do need a strong filiment choke on the final Tho.? A standard 15 amp will get warm.
Attached is a schematic.
|
Re: Plate modulated GG triodes
?
Gents,
?
For those experimenting with Plate Modulation I need to ask
about the power supplies and the modulation transformer(s).
?
Especially with 3-400’s as modulators.
?
The filament supply must be stout, there as well.
?
Please describe?
?
Hal Mandel
W4HBM
?
|
Plate modulated GG triodes
Recently a friend and I have been playing around with plate modulating GG Triodes in class C.? ?Just for fun.? ?My rig is a 450TH modulated by a pair of 100TH tubes.? His rig is a single 3-400Z modulated by a pair of 3-400Z tubes.? He is getting 600 watts carrier fully modulated.??
This is a tricky thing to get to work correctly but can be done. The trick was to place a choke and resistor in the grid line to self-modulate the grid. bingo. 100 percent modulated carrier.?
We noticed the 8877 3cx1500 actually has this mode listed on the PDF.? They specify grounded Grid Class C plate modulated, cathode driven configuration.??
It also states that you must modulate the Driver to 83 percent and plate modulate the rig to the rest required.? ?This is because the Drive power is never modulated.
Anyone ever try this?? I might try it for fun.? Probably wont use an 8877.?
I wonder what the purpose of this config was.? What was the advantage? They could get 1000 watts AM carrier fully modulated from a single 8877 in this config which is amazing. Maybe it never caught on?
I am simply going use my ranger to modulate the Cathode to 83 percent. Then tap off the ranger's modulators to drive the outboard modulates in phase through a transformer.? I will need to adjust the audio to the outboard modulators to get it working.??
C
|
Re: Kenwood TL-922-Need a plate current meter.
Ok Jim. You'll be happy. Let us know how you do. Bob W4JFA?
On Mon, Aug 21, 2023, 1:13 PM Jim McPhee < jmcphee@...> wrote: Hi Bob,
Lou sent me a photo, and I am ordering a meter from him. It looks just great. No need for you to go to the trouble of taking a picture.
Jim McPhee
Placitas, NM
W5ABA
|
Re: Kenwood TL-922-Need a plate current meter.
Hi Bob,
Lou sent me a photo, and I am ordering a meter from him. It looks just great. No need for you to go to the trouble of taking a picture.
Jim McPhee
Placitas, NM
W5ABA
|
Re: Kenwood TL-922-Need a plate current meter.
Hi Bob,
Thanks for the offer of a picture. I would like to see one. Would you post it here or send it to me? My email is jmcphee at comcast dot net.
Jim McPhee
Placitas, NM
W5ABA
|
HaL Mandel
Bob
Mike Peace
