Re: Need Help with Amp Supply LK500ZC
Here's the photo of the relays that I tried to attach to my last post.
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Re: Need Help with Amp Supply LK500ZC
Steve, Dave, Lou, and allOne of my problems is that I'm doubtful that I have a complete schematic for this amplifier.?? Best I've been able to find is from a 1988 users manual I found? . The previous owner who refurbished the amp replaced what I believe is the relay you refer to with what I was told are high-end vacuum relays, which if so, I wouldn't expect to be the problem and if it is, I wouldn't think burnishing contacts would be feasible. I'm also not understanding on how a bad relay would relate to the overheating when the amp was idling??
I have on my to-do list the task of reconciling the schematic with the existing circuitry, which is not something I feel I'm very good at.? I was told the QSK circuitry was bypassed (removed?) ("They're nothing but trouble")? and I've never seen the ALO light come on so not sure it hasn't also been disabled.? Other questions I have about the amp are whether it is good on the WARC bands and how to tell if it has a soft-start circuit which I read somewhere were factory installed on later models but I don't recognize in the schematic I have.
And to clarify my earlier post, the tubes were refitted not replaced.? Thanks Adrian.
Cheers for now.
/John
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Re: Need Help with Amp Supply LK500ZC
Very often, all that is necessary is to run a bizness card
between the contacts. A card with a particularly-rough finish is
great, but don't use a card with an epoxied smooth or glossy
finish on one side. If you do, then try to stick a sheet of
ordinary notebook paper to that side of the card so it doesn't
contact the relay contacts. The epoxy or gloss may rub off onto
the relay contact and make the problem even worse.
When you run a bizness card thruogh the contacts and examine it,
you will notice gray or black residue is left on the card.
However, the card will not clean up a burned or pitted contact
very well.
73,
Steve K0XP
On 11/30/2023 3:46 PM, Dave w6de wrote:
There
are burnishing tools for exactly this purpose.?
Using finger nail files and files for this purpose is
risky, as the potential damage of removing too much contact
material is high.
?
I
have one of these:
Here
are two more:
?
?
Burnishing
tools have very fine almost invisible teeth.?
Using a burnishing tool is a safe method for cleaning
relay contacts.?
Every radio amateur that works on equipment with open
frame relays should have one in his tool kit.
?
73,
Dave,
w6de
?
?
John,
you just might have a worn out contact that switches bias on
the antenna relay. ?If the contacts are severely pitted they
might not make up too good sometimes and other times ok.
?You need to inspect the that set of contacts in particular.
?If you carefully remove the rear spring on the relay you
can lift the armature off and inspect all the contacts. ?The
contacts that switch the RF can be cleaned gently, the
contacts on the bias may be in bad shape, there may be a
tiny point on the armature contact and a tiny depression on
the body contact. A gentle filing to remove the ¡°pit¡± and a
cleaning should restore reliable contact. ?It¡¯s not unusual
at all to see the bias contact hood bad with the age of thst
amp especially being used on CW a lot. ?Seen it quit often
and by doctoring up the bias?contact that problem went away.
?Lou
?
On Thursday, November
30, 2023, 3:58 PM, John Roland <johnroland51@...> wrote:
--
See my QRZ.com page at
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Re: Need Help with Amp Supply LK500ZC
There are burnishing tools for exactly this purpose.?
Using finger nail files and files for this purpose is risky, as the potential damage of removing too much contact material is high.
?
I have one of these:
Here are two more:
?
?
Burnishing tools have very fine almost invisible teeth.?
Using a burnishing tool is a safe method for cleaning relay contacts.?
Every radio amateur that works on equipment with open frame relays should have one in his tool kit.
?
73,
Dave, w6de
?
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From: [email protected] <[email protected]>
On Behalf Of Louis Parascondola via groups.io
Sent: 30 November, 2023 22:56
To: [email protected]
Subject: Re: [ham-amplifiers] Need Help with Amp Supply LK500ZC
?
John, you just might have a worn out contact that switches bias on the antenna relay. ?If the contacts are severely pitted they might not make up too good
sometimes and other times ok. ?You need to inspect the that set of contacts in particular. ?If you carefully remove the rear spring on the relay you can lift the armature off and inspect all the contacts. ?The contacts that switch the RF can be cleaned gently,
the contacts on the bias may be in bad shape, there may be a tiny point on the armature contact and a tiny depression on the body contact. A gentle filing to remove the ¡°pit¡± and a cleaning should restore reliable contact. ?It¡¯s not unusual at all to see the
bias contact hood bad with the age of thst amp especially being used on CW a lot. ?Seen it quit often and by doctoring up the bias?contact that problem went away. ?Lou
?
On Thursday, November 30, 2023, 3:58 PM, John Roland <johnroland51@...>
wrote:
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Re: Need Help with Amp Supply LK500ZC
John, you just might have a worn out contact that switches bias on the antenna relay. ?If the contacts are severely pitted they might not make up too good sometimes and other times ok. ?You need to inspect the that set of contacts in particular. ?If you carefully remove the rear spring on the relay you can lift the armature off and inspect all the contacts. ?The contacts that switch the RF can be cleaned gently, the contacts on the bias may be in bad shape, there may be a tiny point on the armature contact and a tiny depression on the body contact. A gentle filing to remove the ¡°pit¡± and a cleaning should restore reliable contact. ?It¡¯s not unusual at all to see the bias contact hood bad with the age of thst amp especially being used on CW a lot. ?Seen it quit often and by doctoring up the bias? contact that problem went away. ?Lou
On Thursday, November 30, 2023, 3:58 PM, John Roland <johnroland51@...> wrote: Lou, Mike, Jim, Adrian and all, I removed the tubes one at a time.? I let the amp idle (no drive) for 10 minutes with each tube in place individually.?? No signs of anything overheating.? I then replaced both tubes and let it set another 10 minutes, still no sign of overheating.?? I then applied about 20 watts of drive in RTTY mode and was getting around 200 watts out.? (I'm still using my Heathkit watt meter circa 1978)? Attached is a photo of my grid and plate current with that 20 watt drive.? The meter shows 2900 volts when idling and drops to about 2600 when transmitting.?? (I'm operating 240 volts on about a 20 foot length of 12 AWG from the panel.)? The pictures below are 1.? the front tube at 10 minutes.? 2. the rear tube at 10 minutes? 3. Both tubes back in place after 10 minutes.? 4.? A picture from yesterday of both tubes just after switching off the power (light) which looks to me like both tubes are overheated. 5.? A picture of my meters with 20 watts RTTY drive applied.? The Plate volt meter does return to 0 when switched off. So it now looks like I may have some kind of an intermittent ?? Thanks again /John? W7SWB     
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Re: Need Help with Amp Supply LK500ZC
Lou, Mike, Jim, Adrian and all, I removed the tubes one at a time.? I let the amp idle (no drive) for 10 minutes with each tube in place individually.?? No signs of anything overheating.? I then replaced both tubes and let it set another 10 minutes, still no sign of overheating.?? I then applied about 20 watts of drive in RTTY mode and was getting around 200 watts out.? (I'm still using my Heathkit watt meter circa 1978)? Attached is a photo of my grid and plate current with that 20 watt drive.? The meter shows 2900 volts when idling and drops to about 2600 when transmitting.?? (I'm operating 240 volts on about a 20 foot length of 12 AWG from the panel.)? The pictures below are 1.? the front tube at 10 minutes.? 2. the rear tube at 10 minutes? 3. Both tubes back in place after 10 minutes.? 4.? A picture from yesterday of both tubes just after switching off the power (light) which looks to me like both tubes are overheated. 5.? A picture of my meters with 20 watts RTTY drive applied.? The Plate volt meter does return to 0 when switched off. So it now looks like I may have some kind of an intermittent ?? Thanks again /John? W7SWB     
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Re: Alpha Amp Group Still Active??
On 11/30/2023 5:17 AM, Adrian Fewster wrote: On 30/11/23 22:51, Floyd - K8AC wrote:
I believe that the AE9K monitor program works only with the 8410 amplifier.? I have an 8100 and tried the program with it but was unable to establish communications. ?
I've already installed, and have been running, the program. But mine is running some 3 or 4 MINUTES behind the amplifier, and since I've seen nothing complaining about that, I'm wondering whether that's normal. That's almost like reading a book about the amp... "3 minutes 36.25 seconds ago, Alpha 8410 bandswitch=40 meters, 0 faults, Ip=2.453 amperes, Ig=0, Ep=340 volts ... "etc. etc.. TNX, Steve K0XP
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Re: Alpha Amp Group Still Active??
On 11/30/2023 4:51 AM, Floyd - K8AC wrote: There are a couple of specialized Alpha groups here on groups.io. There is one for the 87A and there was one other but don't recall which it was.? I usually use the Amplifier group on eHam and Glenn, AE0Q, responds to Alpha questions there.? Which Alpha(s) do you have? Mine is the 8410. TNX, Steve K0XP
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Re: Need Help with Amp Supply LK500ZC
Jim, it could be ?reflection. The OP didn¡¯t give much information like if the amp works, reads hi voltage, gives idle current if keyed up, etc etc. ?I?agree with you but I¡¯m just trying to get the OP to do something to obtain more data. ?Yup you are correct I have hi pot brand new Chinese tubes right out the box and some will conduct at just over 400volrs. ?I like to see around 1500. ?I¡¯ve test some old ?Eimacs G-F to almost the P-G amount. ?Rare but I have seen it. ?Chinese are mostly ok P-G upwards of 7kv. ?If you didn¡¯t accept just above 500v G-F you¡¯ll be rejecting lots of tubes!
On Thursday, November 30, 2023, 7:08 AM, Jim VE7RF <jim.thom@...> wrote: Lou, on the 2nd pix, it looks like BOTH tubes are going red.? My guess is.... it's a grid to cathode short on one or both tubes.?
The baffling part is..... his grid and plate current meters are still reading zero.?
More baffling is..... it takes 5 mins for the problem to manifest itself.?
Typ with a grid to cathode short on just one tube.....? BOTH tubes will go red asap, as soon as you turn on the amp.
?
On a related note, on Eimac 3-500Z's, they typ hi-pot test 5 kv? from grid to cathode ( good tube).? ?On all the chinese ( good tube)? 3-500Z's.... they all only hi-pot test 1 kv from grid to cathode.?
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Re: Alpha Amp Group Still Active??
I believe that the AE9K monitor program works only with the 8410 amplifier.? I have an 8100 and tried the program with it but was unable to establish communications.? I do have experience with using a terminal program such as Tera Term to talk to the 8100 over the USB connection to the amp, which creates a virtual serial port.? That's how you change the grid bias when you change tubes and it's how Alpha sets up the amp during manufacturing.
There are a couple of specialized Alpha groups here on groups.io.? There is one for the 87A and there was one other but don't recall which it was.? I usually use the Amplifier group on eHam and Glenn, AE0Q, responds to Alpha questions there.? Which Alpha(s) do you have?
73, Floyd - K8AC
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Re: Need Help with Amp Supply LK500ZC
Lou, on the 2nd pix, it looks like BOTH tubes are going red.? My guess is.... it's a grid to cathode short on one or both tubes.?
The baffling part is..... his grid and plate current meters are still reading zero.?
More baffling is..... it takes 5 mins for the problem to manifest itself.?
Typ with a grid to cathode short on just one tube.....? BOTH tubes will go red asap, as soon as you turn on the amp.
?
On a related note, on Eimac 3-500Z's, they typ hi-pot test 5 kv? from grid to cathode ( good tube).? ?On all the chinese ( good tube)? 3-500Z's.... they all only hi-pot test 1 kv from grid to cathode.?
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Re: Alpha Amp Group Still Active??
Get a hold of glen, AE0Q.? He's active on both the QRZ amp group...and also the E-ham amp group....as well as other alpha experts.?
Glen answers all alpha e-mail issues everyday.
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Re: Need Help with Amp Supply LK500ZC
Especially the PLATE VOLTAGE meter it must measure 2400 to 3000 and decay to zero with the AC line power switched off.? Do NOT touch anything if it doesn¡¯t work this way! ? One more thing ¨C when you get to the part when you want to remove a tube be sure the plate cap off the tube you removed doesn¡¯t touch the chassis and completely UNPLUG the AC power cord before opening it up. ? Mike N2LYM ? ? ?
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From: [email protected] [mailto:[email protected]] On Behalf Of Bob
Sent: Wednesday, November 29, 2023 9:16 PM
To: [email protected]
Subject: Re: [ham-amplifiers] Need Help with Amp Supply LK500ZC ? Verify that your meters are working correctly. ? Lou, Mike and all,
I turned it on and watched it with no drive.? At around 5 minutes the plates began turning red. See hopefully attached pictures.? I got no reading (0) on the plate and grid current meters.? I haven't yet tried removing the tubes.
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Re: Need Help with Amp Supply LK500ZC
Verify that your meters are working correctly. Bob W4JFA?
Lou, Mike and all,
I turned it on and watched it with no drive.? At around 5 minutes the plates began turning red. See hopefully attached pictures.? I got no reading (0) on the plate and grid current meters.? I haven't yet tried removing the tubes.
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Re: Need Help with Amp Supply LK500ZC
That tube is bad. Remove that tube and just try the other tube by itself to see what it does.
On Wednesday, November 29, 2023, 7:12 PM, John Roland <johnroland51@...> wrote: FWIW? Here are the pictures I intended to attach to my previous post.?? The top is after about 1 minute and bottom is at about 5 minutes.? No drive.? No meter readings.? Adrian I got your note and will try to work through your suggestions I am able to in the next few days.??? Thanks everyone.?? /John? W7SWB 
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Alpha Amp Group Still Active??
Anybody know whether there is an active Alpha amplifier group anywhere? I have a cupla questions about the AE9K monitor program for Alpha amps.
TNX,
Steve K0XP
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Re: Need Help with Amp Supply LK500ZC
FWIW? Here are the pictures I intended to attach to my previous post.?? The top is after about 1 minute and bottom is at about 5 minutes.? No drive.? No meter readings.? Adrian I got your note and will try to work through your suggestions I am able to in the next few days.??? Thanks everyone.?? /John? W7SWB 
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Re: Need Help with Amp Supply LK500ZC
Lou, Mike and all,
I turned it on and watched it with no drive.? At around 5 minutes the plates began turning red. See hopefully attached pictures.? I got no reading (0) on the plate and grid current meters.? 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?you turn it on look for your grid meter going negative and or the plate meter reading positive. ?Look for you tubes starting to gest up in a minute or two. ?If any of these happen report what you see. ?You may have developed a tube short or a loss of cut of bias. ?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.? I have tuned it up a couple times since and the symptoms reoccur. ? I am (obviously) not an amp guy or much of a technician so I have 2 questions.? 1.? Is this a symptom of something that might be easily confirmed and repaired by me, ? and if not ? 2.?? 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! ? 73 Mike N2LYM ? ? ?
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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 ? 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.? I have tuned it up a couple times since and the symptoms reoccur. ? I am (obviously) not an amp guy or much of a technician so I have 2 questions.? 1.? Is this a symptom of something that might be easily confirmed and repaired by me, ? and if not ? 2.?? 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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Floyd - K8AC
Bob