Re: Need Help with Amp Supply LK500ZC
Lou, Mike and all,
I turned it on and watched it with no drive.听 At around 5 minutes the plates began turning red. See hopefully attached pictures.听 I got no reading (0) on the plate and grid current meters.听 I haven't yet tried removing the tubes.
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Re: Need Help with Amp Supply LK500ZC
Turn amp on and observe two things, as soon as听you turn it on look for your grid meter going negative and or the plate meter reading positive. 听Look for you tubes starting to gest up in a minute or two. 听If any of these happen report what you see. 听You may have developed a tube short or a loss of cut of bias. 听Report the findings here when you have them. Lou
On Tuesday, November 28, 2023, 11:43 PM, John Roland <johnroland51@...> wrote: Hi Everone,
I've owned this amp about 5 years but used very little. The amp was refurbished (new tubes, and relays) by a guy in north Idaho about 2017, just before I bought it. I have tried to contact him but get no response.
A couple weeks ago in the middle of a QSO I sensed some unusual heat from the amp and noticed the tubes were both cherry red. I shut it down immediately.听 I have tuned it up a couple times since and the symptoms reoccur. 听 I am (obviously) not an amp guy or much of a technician so I have 2 questions.听 1.听 Is this a symptom of something that might be easily confirmed and repaired by me, 听 and if not 听 2.听听 Is there anyone in the Portland-Seattle-Vancouver BC area I might take it to for repair?
Thanks for any help or ideas
John
W7SWB
Does
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Re: Need Help with Amp Supply LK500ZC
Sounds like one of the 3-500s has a grid to cathode short. Remove them one at a time to find the bad one be VERY CAREFUL the plate meter is at zero before you touch anything. HV KILLS! 听 73 Mike N2LYM 听 听 听
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From: [email protected] [mailto:[email protected]] On Behalf Of John Roland
Sent: Tuesday, November 28, 2023 5:44 PM
To: [email protected]
Subject: [ham-amplifiers] Need Help with Amp Supply LK500ZC 听 Hi Everone,
I've owned this amp about 5 years but used very little. The amp was refurbished (new tubes, and relays) by a guy in north Idaho about 2017, just before I bought it. I have tried to contact him but get no response.
A couple weeks ago in the middle of a QSO I sensed some unusual heat from the amp and noticed the tubes were both cherry red. I shut it down immediately.听 I have tuned it up a couple times since and the symptoms reoccur. 听 I am (obviously) not an amp guy or much of a technician so I have 2 questions.听 1.听 Is this a symptom of something that might be easily confirmed and repaired by me, 听 and if not 听 2.听听 Is there anyone in the Portland-Seattle-Vancouver BC area I might take it to for repair?
Thanks for any help or ideas
John
W7SWB
Does
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Need Help with Amp Supply LK500ZC
Hi Everone,
I've owned this amp about 5 years but used very little. The amp was refurbished (new tubes, and relays) by a guy in north Idaho about 2017, just before I bought it. I have tried to contact him but get no response.
A couple weeks ago in the middle of a QSO I sensed some unusual heat from the amp and noticed the tubes were both cherry red. I shut it down immediately.听 I have tuned it up a couple times since and the symptoms reoccur. 听 I am (obviously) not an amp guy or much of a technician so I have 2 questions.听 1.听 Is this a symptom of something that might be easily confirmed and repaired by me, 听 and if not 听 2.听听 Is there anyone in the Portland-Seattle-Vancouver BC area I might take it to for repair?
Thanks for any help or ideas
John
W7SWB
Does
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I have a 4cx1500B with 350 screen, 3500 volts plate. It does 3kw peak on SSB.听 Its been run at 1500 with 2500 volts on plate for
4 years now.听 Very important to have a negative and positive going screen meter so you can tune it properly.
The 4cx1500A is a completely different tube. Its directly heated, Has a huge Filament current of 40 amps, Tons of emission and is
flat out a beast of a tube.听 Probably one of the most over looked.听
There is also a 5CX1500A that is pretty much the same as the 4cx1500 but has a suppressor grid that gets grounded.听 Those tubes where
used in industrial generators and are fairly cheap.听 A friend built an amp with this tube and it is incredibly clean. He has IMD down very low.
I have 6 of them with several sockets.听 I plan to build a dual 5cx1500 amp for HF in the next year or so.听 The cabinet, Roller and
other parts are all in the garage.听
C
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Hi guys. I found this on another site 鈥� interesting !
听
Regards,
听
John VK6JX
听
听
听
听
You had a weak 1500B.听 Its a far better tube and for sure will make more power.听 I have swapped these many times.
Rudi was clever. He had the socket centre pin modified to take the Eimac tubes and put a 6V tap on the transformer in the DX-2SP amplifier. I have tried both the 4CX1500B and the 4CX1000A in a friend's amp and the 4CX1000A is the much better choice. The
output with the 4CX1500B installed was quite a bit lower.
73, Alek VK6APK
On 26/11/2023 8:00 pm, Louis Parascondola via groups.io wrote:
If an amp uses FU728 by design and has an actual 728 socket stem, a 4cx1000 will not just fit in. The center shaft is too wide in diameter. 听It may be possible to enlarge the center hole on the 4cx1000 with
the right size drill bit to make it fit. 听The FU728 with a larger hole will fit a real 4cx1000 socket without an issue. 听Change filament voltage of course either way..
听
On Sunday, November 26, 2023, 6:49 AM, Adrian Fewster
<vk4tux@...> wrote:
Alek, see听
Can dropin for a FU-728 with filament voltage changed to 6v ..
73
vk4tux
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Hi guys. I found this on another site 鈥� interesting ! 听 
Regards, 听 John VK6JX 听 听 听
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From: [email protected] <[email protected]> On Behalf Of W7WRX
Sent: Tuesday, November 28, 2023 1:24 AM
To: [email protected]
Subject: Re: [ham-amplifiers] CX1500听 You had a weak 1500B.听 Its a far better tube and for sure will make more power.听 I have swapped these many times.
Rudi was clever. He had the socket centre pin modified to take the Eimac tubes and put a 6V tap on the transformer in the DX-2SP amplifier. I have tried both the 4CX1500B and the 4CX1000A in a friend's amp and the 4CX1000A is the much better choice. The output with the 4CX1500B installed was quite a bit lower. 73, Alek VK6APK On 26/11/2023 8:00 pm, Louis Parascondola via groups.io wrote: If an amp uses FU728 by design and has an actual 728 socket stem, a 4cx1000 will not just fit in. The center shaft is too wide in diameter. 听It may be possible to enlarge the center hole on the 4cx1000 with the right size drill bit to make it fit. 听The FU728 with a larger hole will fit a real 4cx1000 socket without an issue. 听Change filament voltage of course either way..
听 On Sunday, November 26, 2023, 6:49 AM, Adrian Fewster <vk4tux@...> wrote: Alek, see听
Can dropin for a FU-728 with filament voltage changed to 6v ..
73
vk4tux
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OK. That's very encouraging. You could be right, as we had no
other 1500B tubes to compare it with.
Thanks, Alek.
On 28/11/2023 1:24 am, W7WRX wrote:
toggle quoted message
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You had a weak 1500B.听 Its a far better tube and for sure will
make more power.听 I have swapped these many times.
C
Rudi was clever. He had the socket centre pin modified to
take the Eimac tubes and put a 6V tap on the transformer in
the DX-2SP amplifier. I have tried both the 4CX1500B and the
4CX1000A in a friend's amp and the 4CX1000A is the much better
choice. The output with the 4CX1500B installed was quite a bit
lower.
73, Alek VK6APK
On 26/11/2023 8:00 pm, Louis
Parascondola via groups.io wrote:
If an amp uses FU728 by design and has
an actual 728 socket stem, a 4cx1000 will not just fit in. The
center shaft is too wide in diameter. 听It may be possible to
enlarge the center hole on the 4cx1000 with the right size
drill bit to make it fit. 听The FU728 with a larger hole will
fit a real 4cx1000 socket without an issue. 听Change filament
voltage of course either way..
On Sunday, November 26, 2023, 6:49 AM, Adrian Fewster
<vk4tux@...> wrote:
Alek, see听
Can dropin for a FU-728 with filament voltage changed to
6v ..
73
vk4tux
|
If you run a drill bit into the base of a 4x1k or 4x1.5k to
enlarge the hole slightly, you'll also wind up grinding out that
dimpled keyway that aligns the tube with the notched socket shaft.
Of course, for a tube that's otherwise unusable, that's
mostly-inconsequential.
Steve, K0XP
On 11/26/2023 4:00 AM, Louis
Parascondola via groups.io wrote:
If an amp uses FU728 by design and has an actual 728 socket stem,
a 4cx1000 will not just fit in. The center shaft is too wide in
diameter. 听It may be possible to enlarge the center hole on the
4cx1000 with the right size drill bit to make it fit. 听The FU728
with a larger hole will fit a real 4cx1000 socket without an
issue. 听Change filament voltage of course either way..
On
Sunday, November 26, 2023, 6:49 AM, Adrian Fewster
<vk4tux@...> wrote:
Alek, see听
Can dropin for a FU-728 with filament voltage changed to 6v ..
73
vk4tux
--
See my QRZ.com page at
|
You had a weak 1500B.听 Its a far better tube and for sure will make more power.听 I have swapped these many times.
C
toggle quoted message
Show quoted text
Rudi was clever. He had the socket centre pin modified to take the Eimac tubes and put a 6V tap on the transformer in the DX-2SP amplifier. I have tried both the 4CX1500B and the 4CX1000A in a friend's amp and the 4CX1000A is the much better choice. The
output with the 4CX1500B installed was quite a bit lower.
73, Alek VK6APK
On 26/11/2023 8:00 pm, Louis Parascondola via groups.io wrote:
If an amp uses FU728 by design and has an actual 728 socket stem, a 4cx1000 will not just fit in. The center shaft is too wide in diameter. 听It may be possible to enlarge the center hole on the 4cx1000 with the right size drill bit to
make it fit. 听The FU728 with a larger hole will fit a real 4cx1000 socket without an issue. 听Change filament voltage of course either way..
On Sunday, November 26, 2023, 6:49 AM, Adrian Fewster
<vk4tux@...> wrote:
Alek, see听
Can dropin for a FU-728 with filament voltage changed to 6v ..
73
vk4tux
|
Rudi was clever. He had the socket centre pin modified to take
the Eimac tubes and put a 6V tap on the transformer in the DX-2SP
amplifier. I have tried both the 4CX1500B and the 4CX1000A in a
friend's amp and the 4CX1000A is the much better choice. The
output with the 4CX1500B installed was quite a bit lower.
73, Alek VK6APK
On 26/11/2023 8:00 pm, Louis
Parascondola via groups.io wrote:
toggle quoted message
Show quoted text
If an amp uses FU728 by design and has an actual 728 socket stem,
a 4cx1000 will not just fit in. The center shaft is too wide in
diameter. 听It may be possible to enlarge the center hole on the
4cx1000 with the right size drill bit to make it fit. 听The FU728
with a larger hole will fit a real 4cx1000 socket without an
issue. 听Change filament voltage of course either way..
On
Sunday, November 26, 2023, 6:49 AM, Adrian Fewster
<vk4tux@...> wrote:
Alek, see听
Can dropin for a FU-728 with filament voltage changed to 6v ..
73
vk4tux
|
If an amp uses FU728 by design and has an actual 728 socket stem, a 4cx1000 will not just fit in. The center shaft is too wide in diameter. 听It may be possible to enlarge the center hole on the 4cx1000 with the right size drill bit to make it fit. 听The FU728 with a larger hole will fit a real 4cx1000 socket without an issue. 听Change filament voltage of course either way..
On Sunday, November 26, 2023, 6:49 AM, Adrian Fewster <vk4tux@...> wrote: Alek, see听
Can dropin for a FU-728 with filament voltage changed to 6v ..
73
vk4tux
|
WTB: AL80,AL80A, SB1000 transformer
Looking for a good working transformer. 听Any one of the three. 听Send email direct to me , gudguyham@.... 听Thank you.
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Re: Coax to connect between exciter and SB-200
I'm wondering if a CM choke, right at he input of the xcvr might help ?听 听I have 2 x spare CM chokes....so听 could put one at output of xcvr.... and 2nd one at input of amp.听
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Re: Coax to connect between exciter and SB-200
Jim,
听
They are engraved plastic labels.
听
Hal
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Re: Coax to connect between exciter and SB-200
Hi Mike,听 Again, SWR does not change along a coax unless the coax has loss.听 If you put the SWR meter anywhere in the coax between the rig and the amp, the SWR should read the same.听 Sometimes, there are strange SWR readings when the RF travels both inside the coax and on the outer conductor as common mode currents.听 This has lead to some incorrect understanding about SWR.听 Putting a SWR meter at the input of an amp would be interesting.听 I have a SWR meter between my rig and my SB-220.听 I use the meter to check my antenna SWR before turning the amp on.听 It also shows the SWR at the input of the amp.听 I am happy with anything less than 1.75:1 going into the amp.听 I get all the power output that I need.听 GL with your amp.听听 ....Bill K3HZP
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Re: Coax to connect between exciter and SB-200
What is the name for those labels used on that tuner ??听 听I have seen em white on black,听 white on blue, and white on red.听 听Used in industrial commercial applications.听
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Re: Coax to connect between exciter and SB-200
On Wed, Nov 1, 2023 at 10:48 PM, mfle2001 wrote:
Thats interesting Bill, I guess VSWR read by an SWR meter varies along the length of coax because of the changing impedance / voltage ratio, but the actual SWR does not. I am currently building a GG amp and wondering about having a VSWR meter coupler directly at the input.
Mike
VK2AMF
I don't buy that for one second.听 听SWR won't change at all with different line lengths.听 Only the R / X听 will change, but swr remains the same.听 听Having said that, with real long lines to ants, like say 200-300'听 on upper HF,听 swr at the shack end will decrease, simply cuz of line loss.听 IE: say 3 db of line loss.听 Reflected power (after line loss to the ant,听 听gets attenuated by the same 3 db).听 IE: joe ham puts put 200 watts frwd power.... but only 100 w gets to the ant.听 With a 3:1 swr ( measured at the ant), he has 25% reflected power...( 25 watts reflected).听 听That same 25 watts gets attenuated by 3db, and only 12.5 watts is shown as reflected power at shack end.听
听
200 frwd and 12.5 watts reflected is the same as听 100w frwd and 6.25 watts听 reflected = 1.4:1 swr.听 听Meanwhile his real swr is 3:1听 at the ant, and he only has听 75 watts radiated.听
听
In the case of coax to the amp, we are only talking abt real short lengths, like 3' to 10'...and coax loss is dick.听 听 The input Z of the amp didn't change... and the stray C, between cathode听 and chassis听 (via the grnded grid)听 didn't change, it's constant....and it's also directly in parallel with the C2 cap of the tuned input for each band.听 On the L4B, a single .01uf @ 2 kv disc coupling cap,听 directly between the tuned input...and the cathode.听 There is NO coax听 between the output of the tuned inputs...and cathode of tube....just the single coupling cap.听 听
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Re: Coax to connect between exciter and SB-200
Interesting, not familiar with those tuners, thanks for the info
Hal.
Actually thinking further about it, whilst reflected voltage would change
along the line not sure if the ratio to forward would alter, but I have
experienced different readings depending on the length.
Mike.
VK2AMF
At 09:05 AM 2/11/2023, you wrote:
Dear Mike,
听
The ETO/Alpha AC-77 antenna tuner has a Bird
wattmeter right in the chassis, with a front panel
slug socket.
![[]](/g/ham-amplifiers/attachment/39630/)
John Bliss adopted that idea into his Bliss Z-Matchmaster
tuners.
听
I know W9AC has one of John抯 tuners and that came with two separate
wattmeters.
听
听
听
Hal Mandel
W4HBM
Mike Fleetwood
Canberra Australia and Sidcup UK.
Worldwide email address
is:听听听听听
mfleetwood@...
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Re: Coax to connect between exciter and SB-200
Dear Mike,
听
The ETO/Alpha AC-77 antenna tuner has a Bird
wattmeter right in the chassis, with a front panel
slug socket.
John Bliss adopted that idea into his Bliss Z-Matchmaster tuners.
听
I know W9AC has one of John鈥檚 tuners and that came with two separate wattmeters.
听
听
听
Hal Mandel
W4HBM
|
Re: Coax to connect between exciter and SB-200
Thats interesting Bill, I guess VSWR read by an SWR meter varies along
the length of coax because of the changing impedance / voltage ratio, but
the actual SWR does not. I am currently building a GG amp and wondering
about having a VSWR meter coupler directly at the input.
Mike
VK2AMF
At 01:28 AM 2/11/2023, you wrote:
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Show quoted text
The best way to view the
mismatch at the amp input is to look at a point on the Smith chart.听
If the amp input impedance is not 50+j0, the point will NOT be at the
center of the Smith chart.听 It will be on a SWR circle going around
the center.听 This circle is centered on the center location of the
Smith chart.听 The distance the point moves on the circle is a
function of its electrical length of the coax.听 The SWR does NOT
change along the coax unless there ls loss in the coax.听 What does
change is the reactance and resistance combination.听 Assume the amp
input impedance is on a 2:1 SWR circle.听 Then the impedance could be
100+j0 ohms at a certain coax length or could be 25+j0 at another coax
length.听 In other words the real and imaginary combination change a
lot but the point stays on the 2:1 SWR circle.听 The SWR does not
change.听 ...Bill K3HZP
Mike Fleetwood
Canberra Australia and Sidcup UK.
Worldwide email address
is:听听听听听
mfleetwood@...
|
HaL Mandel
Bill K3HZP