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All-
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I have an Amp Supply Company LK800A amplifier that puts out full power.? However, I noticed recently that it shows no grid current reading when transmitting on multiple bands.? This is odd behavior, as the grid current normally runs ca. 20-50 mA from my past experience.? I know the meter is fine, because when I turn the meter switch to measure plate voltage, I get the expected reading.? I looked at the meter/ALO board and found that R29 was somewhat charred and had a reading of 180 K ohms.? No other parts look visibly damaged.
?
The LK-800 series manual does not have a schematic for this board.? I was able to find one at .? While the manual is for the LK-400 / LK-500 series, it does have a description of the ALO/Meter board.? The resistor R29 is in the grid current metering circuit and is claimed to have a value of 18 ohms (p. 27 and 29).? I suspect this is the problem.? The other parts on my board seem to match what is listed on p. 29, and the parts list on p. 29 suggests the board works in the LK-800 series amps because it references the heavy resistor R30 as being unique to the LK-800 (and is present on my board).
?
My question - can someone verify that R29 should indeed be 18 ohms?? I would hate for there to be a misprint in the manual and find my grid current meter to be blown when I try this out, as I suspect they are very difficult to obtain.? Also, do you have any insights as to what would blow this resistor?? A current of 120 mA through that resistor would deliver 0.25 watts...? I have always kept the grid current low, but I did loan the amplifier out a few years ago and don't know if the other user experienced an issue.
?
Many thanks,
?
-Mark
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?
I have an Amp Supply Company LK800A amplifier that puts out full power.? However, I noticed recently that it shows no grid current reading when transmitting on multiple bands.? This is odd behavior, as the grid current normally runs ca. 20-50 mA from my past experience.? I know the meter is fine, because when I turn the meter switch to measure plate voltage, I get the expected reading.? I looked at the meter/ALO board and found that R29 was somewhat charred and had a reading of 180 K ohms.? No other parts look visibly damaged.
?
The LK-800 series manual does not have a schematic for this board.? I was able to find one at .? While the manual is for the LK-400 / LK-500 series, it does have a description of the ALO/Meter board.? The resistor R29 is in the grid current metering circuit and is claimed to have a value of 18 ohms (p. 27 and 29).? I suspect this is the problem.? The other parts on my board seem to match what is listed on p. 29, and the parts list on p. 29 suggests the board works in the LK-800 series amps because it references the heavy resistor R30 as being unique to the LK-800 (and is present on my board).
?
My question - can someone verify that R29 should indeed be 18 ohms?? I would hate for there to be a misprint in the manual and find my grid current meter to be blown when I try this out, as I suspect they are very difficult to obtain.? Also, do you have any insights as to what would blow this resistor?? A current of 120 mA through that resistor would deliver 0.25 watts...? I have always kept the grid current low, but I did loan the amplifier out a few years ago and don't know if the other user experienced an issue.
?
Many thanks,
?
-Mark
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Mark- The link to the LK800 manual didn't work here, error says page no longer exists. Can you check to make sure it's displayed correctly in your post- some of us would like to? obtain that manual. Thanks!
Tom K0SN
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I have an Amp Supply Company LK800A amplifier that puts out full power.? However, I noticed recently that it shows no grid current reading when transmitting on multiple bands.? This is odd behavior, as the grid current normally runs ca. 20-50 mA from my past experience.? I know the meter is fine, because when I turn the meter switch to measure plate voltage, I get the expected reading.? I looked at the meter/ALO board and found that R29 was somewhat charred and had a reading of 180 K ohms.? No other parts look visibly damaged.
?
The LK-800 series manual does not have a schematic for this board.? I was able to find one at .? While the manual is for the LK-400 / LK-500 series, it does have a description of the ALO/Meter board.? The resistor R29 is in the grid current metering circuit and is claimed to have a value of 18 ohms (p. 27 and 29).? I suspect this is the problem.? The other parts on my board seem to match what is listed on p. 29, and the parts list on p. 29 suggests the board works in the LK-800 series amps because it references the heavy resistor R30 as being unique to the LK-800 (and is present on my board).
?
My question - can someone verify that R29 should indeed be 18 ohms?? I would hate for there to be a misprint in the manual and find my grid current meter to be blown when I try this out, as I suspect they are very difficult to obtain.? Also, do you have any insights as to what would blow this resistor?? A current of 120 mA through that resistor would deliver 0.25 watts...? I have always kept the grid current low, but I did loan the amplifier out a few years ago and don't know if the other user experienced an issue.
?
Many thanks,
?
-Mark
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All-
The PDF file here works for me.? I have seen this manual before.? It has no information on the ALO/metering board.? Yes, there are two meters in the schematic, but my LK800a does not have the same wiring of those meters.
Many thanks,
-Mark
All-
?
I have an Amp Supply Company LK800A amplifier that puts out full power.? However, I noticed recently that it shows no grid current reading when transmitting on multiple bands.? This is odd behavior, as the grid current normally runs ca. 20-50 mA from my past experience.? I know the meter is fine, because when I turn the meter switch to measure plate voltage, I get the expected reading.? I looked at the meter/ALO board and found that R29 was somewhat charred and had a reading of 180 K ohms.? No other parts look visibly damaged.
?
The LK-800 series manual does not have a schematic for this board.? I was able to find one at .? While the manual is for the LK-400 / LK-500 series, it does have a description of the ALO/Meter board.? The resistor R29 is in the grid current metering circuit and is claimed to have a value of 18 ohms (p. 27 and 29).? I suspect this is the problem.? The other parts on my board seem to match what is listed on p. 29, and the parts list on p. 29 suggests the board works in the LK-800 series amps because it references the heavy resistor R30 as being unique to the LK-800 (and is present on my board).
?
My question - can someone verify that R29 should indeed be 18 ohms?? I would hate for there to be a misprint in the manual and find my grid current meter to be blown when I try this out, as I suspect they are very difficult to obtain.? Also, do you have any insights as to what would blow this resistor?? A current of 120 mA through that resistor would deliver 0.25 watts...? I have always kept the grid current low, but I did loan the amplifier out a few years ago and don't know if the other user experienced an issue.
?
Many thanks,
?
-Mark
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All-
I gave the amplifier a try tonight at very low drive, slowly working my way up to legal limit to ensure the meter did not peg to the right due to an incorrect resistor value.? Everything seems normal (grid current of ca. 30 mA when tuned, and turning the load control clockwise reduces it), so that resistor R29 is indeed 18 ohms.? If anyone knows why that might have?blown, I would?be interested in your thoughts.
Many thanks,
-Mark
All-
The PDF file here works for me.? I have seen this manual before.? It has no information on the ALO/metering board.? Yes, there are two meters in the schematic, but my LK800a does not have the same wiring of those meters.
Many thanks,
-Mark
All-
?
I have an Amp Supply Company LK800A amplifier that puts out full power.? However, I noticed recently that it shows no grid current reading when transmitting on multiple bands.? This is odd behavior, as the grid current normally runs ca. 20-50 mA from my past experience.? I know the meter is fine, because when I turn the meter switch to measure plate voltage, I get the expected reading.? I looked at the meter/ALO board and found that R29 was somewhat charred and had a reading of 180 K ohms.? No other parts look visibly damaged.
?
The LK-800 series manual does not have a schematic for this board.? I was able to find one at .? While the manual is for the LK-400 / LK-500 series, it does have a description of the ALO/Meter board.? The resistor R29 is in the grid current metering circuit and is claimed to have a value of 18 ohms (p. 27 and 29).? I suspect this is the problem.? The other parts on my board seem to match what is listed on p. 29, and the parts list on p. 29 suggests the board works in the LK-800 series amps because it references the heavy resistor R30 as being unique to the LK-800 (and is present on my board).
?
My question - can someone verify that R29 should indeed be 18 ohms?? I would hate for there to be a misprint in the manual and find my grid current meter to be blown when I try this out, as I suspect they are very difficult to obtain.? Also, do you have any insights as to what would blow this resistor?? A current of 120 mA through that resistor would deliver 0.25 watts...? I have always kept the grid current low, but I did loan the amplifier out a few years ago and don't know if the other user experienced an issue.
?
Many thanks,
?
-Mark
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Plate/Grid flash over.?
With a manual tune amplifier, a likely suspect is a band change and failure to tune the plate and load at low power.?
Another way is returning to from a break in operation then upon return switching bands or switching antennas without retuning the amp¡ªwith Steppir antennas this is an easy mistake to make. Specially when you have automatic antenna selection from your
rig to the antenna switch and/or automatic band selection to the Steppir.
?
The worst thing for a shack is to have a manual operation set-up required in an otherwise fully automatic switching shack from
a modern transceiver.
?
73,
Dave, w6de
toggle quoted message
Show quoted text
From: [email protected] <[email protected]>
On Behalf Of Mark KE1IU via groups.io
Sent: 26 November, 2024 23:24
To: [email protected]
Subject: Re: [ham-amplifiers] Amp Supply LK800 Meter/ALO Board Question
?
All-
I gave the amplifier a try tonight at very low drive, slowly working my way up to legal limit to ensure the meter did not peg to the right due to an incorrect resistor value.? Everything seems normal (grid current of ca. 30 mA when tuned,
and turning the load control clockwise reduces it), so that resistor R29 is indeed 18 ohms.? If anyone knows why that might have?blown, I would?be interested in your thoughts.
?
The PDF file here works for me.? I have seen this manual before.? It has no information on the ALO/metering board.? Yes, there are two meters in the schematic, but my LK800a does not have the same wiring of those meters.
?
?
I have an Amp Supply Company LK800A amplifier that puts out full power.? However, I noticed recently that it shows no grid current reading when transmitting on multiple bands.? This is odd behavior, as the grid current normally runs ca.
20-50 mA from my past experience.? I know the meter is fine, because when I turn the meter switch to measure plate voltage, I get the expected reading.? I looked at the meter/ALO board and found that R29 was somewhat charred and had a reading of 180 K ohms.?
No other parts look visibly damaged.
The LK-800 series manual does not have a schematic for this board.? I was able to find one at
.? While the manual is for the LK-400 / LK-500 series, it does have a description of the ALO/Meter board.? The resistor R29 is in the grid current metering circuit and
is claimed to have a value of 18 ohms (p. 27 and 29).? I suspect this is the problem.? The other parts on my board seem to match what is listed on p. 29, and the parts list on p. 29 suggests the board works in the LK-800 series amps because it references the
heavy resistor R30 as being unique to the LK-800 (and is present on my board).
My question - can someone verify that R29 should indeed be 18 ohms?? I would hate for there to be a misprint in the manual and find my grid current meter to be blown when I try this out, as I suspect they are very difficult to obtain.?
Also, do you have any insights as to what would blow this resistor?? A current of 120 mA through that resistor would deliver 0.25 watts...? I have always kept the grid current low, but I did loan the amplifier out a few years ago and don't know if the other
user experienced an issue.
|
FWIW, I have changed those series resistors on those amps quite a few times before. ?They are rather small resistors and are probably sacrificial to save the meter in a fault.? ??
On Tuesday, November 26, 2024, 7:51 PM, Dave w6de <w6de@...> wrote:
Plate/Grid flash over.?
With a manual tune amplifier, a likely suspect is a band change and failure to tune the plate and load at low power.?
Another way is returning to from a break in operation then upon return switching bands or switching antennas without retuning the amp¡ªwith Steppir antennas this is an easy mistake to make. Specially when you have automatic antenna selection from your
rig to the antenna switch and/or automatic band selection to the Steppir.
?
The worst thing for a shack is to have a manual operation set-up required in an otherwise fully automatic switching shack from
a modern transceiver.
?
73,
Dave, w6de
?
All-
I gave the amplifier a try tonight at very low drive, slowly working my way up to legal limit to ensure the meter did not peg to the right due to an incorrect resistor value.? Everything seems normal (grid current of ca. 30 mA when tuned,
and turning the load control clockwise reduces it), so that resistor R29 is indeed 18 ohms.? If anyone knows why that might have?blown, I would?be interested in your thoughts.
?
The PDF file here works for me.? I have seen this manual before.? It has no information on the ALO/metering board.? Yes, there are two meters in the schematic, but my LK800a does not have the same wiring of those meters.
?
?
I have an Amp Supply Company LK800A amplifier that puts out full power.? However, I noticed recently that it shows no grid current reading when transmitting on multiple bands.? This is odd behavior, as the grid current normally runs ca.
20-50 mA from my past experience.? I know the meter is fine, because when I turn the meter switch to measure plate voltage, I get the expected reading.? I looked at the meter/ALO board and found that R29 was somewhat charred and had a reading of 180 K ohms.?
No other parts look visibly damaged.
The LK-800 series manual does not have a schematic for this board.? I was able to find one at
.? While the manual is for the LK-400 / LK-500 series, it does have a description of the ALO/Meter board.? The resistor R29 is in the grid current metering circuit and
is claimed to have a value of 18 ohms (p. 27 and 29).? I suspect this is the problem.? The other parts on my board seem to match what is listed on p. 29, and the parts list on p. 29 suggests the board works in the LK-800 series amps because it references the
heavy resistor R30 as being unique to the LK-800 (and is present on my board).
My question - can someone verify that R29 should indeed be 18 ohms?? I would hate for there to be a misprint in the manual and find my grid current meter to be blown when I try this out, as I suspect they are very difficult to obtain.?
Also, do you have any insights as to what would blow this resistor?? A current of 120 mA through that resistor would deliver 0.25 watts...? I have always kept the grid current low, but I did loan the amplifier out a few years ago and don't know if the other
user experienced an issue.
|
All-
Thank you for the information.? I do not recall having a spectacular failure like that, but perhaps the person I loaned the amp to did.? Regardless, it still appears to be working.? Thank you for your help!
Regarding manually tuned gear in an automatic station, I fully agree.? My main amp is an Alpha 9500 for that reason, as the antennas and rig are interfaced, and all switching is done whenever I change band on the radio.? This amplifier is being driven by a Swan 350B, which is manual everything - my first radio?that my father bought me when I was a kid.? That brings me to my next question: The?Swan puts out 50-100W, and I need to detune the driver as the only method?for bringing the power down.? Is there a simple mod that will allow this amplifier to accept more power?? If not, then I will buy a 3 dB attenuator to put between the radio and the amplifier (rated for at least 100 W - they're pretty inexpensive).
Many thanks,
-Mark
Many thanks,
-Mark
On Wed, Nov 27, 2024 at 8:02?AM Louis Parascondola via <Gudguyham= [email protected]> wrote:
FWIW, I have changed those series resistors on those amps quite a few times before.? They are rather small resistors and are probably sacrificial to save the meter in a fault.? ??
On Tuesday, November 26, 2024, 7:51 PM, Dave w6de <w6de@...> wrote:
Plate/Grid flash over.?
With a manual tune amplifier, a likely suspect is a band change and failure to tune the plate and load at low power.?
Another way is returning to from a break in operation then upon return switching bands or switching antennas without retuning the amp¡ªwith Steppir antennas this is an easy mistake to make. Specially when you have automatic antenna selection from your
rig to the antenna switch and/or automatic band selection to the Steppir.
?
The worst thing for a shack is to have a manual operation set-up required in an otherwise fully automatic switching shack from
a modern transceiver.
?
73,
Dave, w6de
?
All-
I gave the amplifier a try tonight at very low drive, slowly working my way up to legal limit to ensure the meter did not peg to the right due to an incorrect resistor value.? Everything seems normal (grid current of ca. 30 mA when tuned,
and turning the load control clockwise reduces it), so that resistor R29 is indeed 18 ohms.? If anyone knows why that might have?blown, I would?be interested in your thoughts.
?
The PDF file here works for me.? I have seen this manual before.? It has no information on the ALO/metering board.? Yes, there are two meters in the schematic, but my LK800a does not have the same wiring of those meters.
?
?
I have an Amp Supply Company LK800A amplifier that puts out full power.? However, I noticed recently that it shows no grid current reading when transmitting on multiple bands.? This is odd behavior, as the grid current normally runs ca.
20-50 mA from my past experience.? I know the meter is fine, because when I turn the meter switch to measure plate voltage, I get the expected reading.? I looked at the meter/ALO board and found that R29 was somewhat charred and had a reading of 180 K ohms.?
No other parts look visibly damaged.
The LK-800 series manual does not have a schematic for this board.? I was able to find one at
.? While the manual is for the LK-400 / LK-500 series, it does have a description of the ALO/Meter board.? The resistor R29 is in the grid current metering circuit and
is claimed to have a value of 18 ohms (p. 27 and 29).? I suspect this is the problem.? The other parts on my board seem to match what is listed on p. 29, and the parts list on p. 29 suggests the board works in the LK-800 series amps because it references the
heavy resistor R30 as being unique to the LK-800 (and is present on my board).
My question - can someone verify that R29 should indeed be 18 ohms?? I would hate for there to be a misprint in the manual and find my grid current meter to be blown when I try this out, as I suspect they are very difficult to obtain.?
Also, do you have any insights as to what would blow this resistor?? A current of 120 mA through that resistor would deliver 0.25 watts...? I have always kept the grid current low, but I did loan the amplifier out a few years ago and don't know if the other
user experienced an issue.
|
If you do use an attenuator, which I do here for one of my amps, you will have to find a way to bypass it in receive or you will have 3dB attenuation of the receive signal. ?
toggle quoted message
Show quoted text
From: [email protected] < [email protected]> On Behalf Of Mark KE1IU via groups.io Sent: Wednesday, November 27, 2024 9:23 AM To: [email protected]Subject: Re: [ham-amplifiers] Amp Supply LK800 Meter/ALO Board Question ? All- Thank you for the information.? I do not recall having a spectacular failure like that, but perhaps the person I loaned the amp to did.? Regardless, it still appears to be working.? Thank you for your help! Regarding manually tuned gear in an automatic station, I fully agree.? My main amp is an Alpha 9500 for that reason, as the antennas and rig are interfaced, and all switching is done whenever I change band on the radio.? This amplifier is being driven by a Swan 350B, which is manual everything - my first radio?that my father bought me when I was a kid.? That brings me to my next question: The?Swan puts out 50-100W, and I need to detune the driver as the only method?for bringing the power down.? Is there a simple mod that will allow this amplifier to accept more power?? If not, then I will buy a 3 dB attenuator to put between the radio and the amplifier (rated for at least 100 W - they're pretty inexpensive).
|
All-
I'm willing to accept the 3 dB on receive, although it is not great.? I have a separate question?on the Swan forum to see if there?is an easy way to put an RF output adjustment on the radio.? I suspect that will be the easier of the mods to make.
-Mark
If you do use an attenuator, which I do here for one of my amps, you will have to find a way to bypass it in receive or you will have 3dB attenuation of the receive signal. ? ? All- Thank you for the information.? I do not recall having a spectacular failure like that, but perhaps the person I loaned the amp to did.? Regardless, it still appears to be working.? Thank you for your help! Regarding manually tuned gear in an automatic station, I fully agree.? My main amp is an Alpha 9500 for that reason, as the antennas and rig are interfaced, and all switching is done whenever I change band on the radio.? This amplifier is being driven by a Swan 350B, which is manual everything - my first radio?that my father bought me when I was a kid.? That brings me to my next question: The?Swan puts out 50-100W, and I need to detune the driver as the only method?for bringing the power down.? Is there a simple mod that will allow this amplifier to accept more power?? If not, then I will buy a 3 dB attenuator to put between the radio and the amplifier (rated for at least 100 W - they're pretty inexpensive).
|
Any chance you could lower the screen voltage? Assuming it's a tetrode or pentode. A string of zeners?
If you do use an attenuator, which I do here for one of my amps, you will have to find a way to bypass it in receive or you will have 3dB attenuation of the receive signal. ?
From: [email protected] < [email protected]> On Behalf Of Mark KE1IU via groups.io Sent: Wednesday, November 27, 2024 9:23 AM To: [email protected]Subject: Re: [ham-amplifiers] Amp Supply LK800 Meter/ALO Board Question ? All- Thank you for the information.? I do not recall having a spectacular failure like that, but perhaps the person I loaned the amp to did.? Regardless, it still appears to be working.? Thank you for your help! Regarding manually tuned gear in an automatic station, I fully agree.? My main amp is an Alpha 9500 for that reason, as the antennas and rig are interfaced, and all switching is done whenever I change band on the radio.? This amplifier is being driven by a Swan 350B, which is manual everything - my first radio?that my father bought me when I was a kid.? That brings me to my next question: The?Swan puts out 50-100W, and I need to detune the driver as the only method?for bringing the power down.? Is there a simple mod that will allow this amplifier to accept more power?? If not, then I will buy a 3 dB attenuator to put between the radio and the amplifier (rated for at least 100 W - they're pretty inexpensive).
|
All-
It's a grounded grid triode amplifier - three 3CX800A7s.
Many thanks,
-Mark
On Wed, Nov 27, 2024 at 11:22?AM mike repinski via <mikflathead= [email protected]> wrote:
Any chance you could lower the screen voltage? Assuming it's a tetrode or pentode. A string of zeners?
On Wednesday, November 27, 2024 at 09:45:32 AM EST, Omni < selcor@...> wrote:
If you do use an attenuator, which I do here for one of my amps, you will have to find a way to bypass it in receive or you will have 3dB attenuation of the receive signal. ? ? All- Thank you for the information.? I do not recall having a spectacular failure like that, but perhaps the person I loaned the amp to did.? Regardless, it still appears to be working.? Thank you for your help! Regarding manually tuned gear in an automatic station, I fully agree.? My main amp is an Alpha 9500 for that reason, as the antennas and rig are interfaced, and all switching is done whenever I change band on the radio.? This amplifier is being driven by a Swan 350B, which is manual everything - my first radio?that my father bought me when I was a kid.? That brings me to my next question: The?Swan puts out 50-100W, and I need to detune the driver as the only method?for bringing the power down.? Is there a simple mod that will allow this amplifier to accept more power?? If not, then I will buy a 3 dB attenuator to put between the radio and the amplifier (rated for at least 100 W - they're pretty inexpensive).
|
Pad the input to the final tube? Lot's of ways. Good luck. Listening on 10 on my 50 year old Siltronics 1011C. Memories from High school.?
All-
I'm willing to accept the 3 dB on receive, although it is not great.? I have a separate question?on the Swan forum to see if there?is an easy way to put an RF output adjustment on the radio.? I suspect that will be the easier of the mods to make.
-Mark
If you do use an attenuator, which I do here for one of my amps, you will have to find a way to bypass it in receive or you will have 3dB attenuation of the receive signal. ? ? All- Thank you for the information.? I do not recall having a spectacular failure like that, but perhaps the person I loaned the amp to did.? Regardless, it still appears to be working.? Thank you for your help! Regarding manually tuned gear in an automatic station, I fully agree.? My main amp is an Alpha 9500 for that reason, as the antennas and rig are interfaced, and all switching is done whenever I change band on the radio.? This amplifier is being driven by a Swan 350B, which is manual everything - my first radio?that my father bought me when I was a kid.? That brings me to my next question: The?Swan puts out 50-100W, and I need to detune the driver as the only method?for bringing the power down.? Is there a simple mod that will allow this amplifier to accept more power?? If not, then I will buy a 3 dB attenuator to put between the radio and the amplifier (rated for at least 100 W - they're pretty inexpensive).
|
Lower the screen voltage on the radio not the amp to lower the drive to the amp.
All-
It's a grounded grid triode amplifier - three 3CX800A7s.
Many thanks,
-Mark
On Wed, Nov 27, 2024 at 11:22?AM mike repinski via <mikflathead= [email protected]> wrote:
Any chance you could lower the screen voltage? Assuming it's a tetrode or pentode. A string of zeners?
On Wednesday, November 27, 2024 at 09:45:32 AM EST, Omni < selcor@...> wrote:
If you do use an attenuator, which I do here for one of my amps, you will have to find a way to bypass it in receive or you will have 3dB attenuation of the receive signal. ? ? All- Thank you for the information.? I do not recall having a spectacular failure like that, but perhaps the person I loaned the amp to did.? Regardless, it still appears to be working.? Thank you for your help! Regarding manually tuned gear in an automatic station, I fully agree.? My main amp is an Alpha 9500 for that reason, as the antennas and rig are interfaced, and all switching is done whenever I change band on the radio.? This amplifier is being driven by a Swan 350B, which is manual everything - my first radio?that my father bought me when I was a kid.? That brings me to my next question: The?Swan puts out 50-100W, and I need to detune the driver as the only method?for bringing the power down.? Is there a simple mod that will allow this amplifier to accept more power?? If not, then I will buy a 3 dB attenuator to put between the radio and the amplifier (rated for at least 100 W - they're pretty inexpensive).
|
Bob