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Re: LK 5xx Variable Cap Plates with pix attached

 

开云体育

Sorry. they must have changed part numbers again. I just searched for that part number and it is no good already.

Happy hunting!

Joe WB9SBD


A Contest 40 Years in The Making!

MAIDENHEAD MAYHEM
On 1/22/2024 12:51 PM, Joe wrote:

?The ameritron? tune cap from the? AL-1500/1200/82? amp.??? Rated for 4.5 kv? and is ameritron part # 204-2570.
It's a 190 pf cap....with real low min C, like < 20 pf.

Joe WB9SBD
On 1/22/2024 12:46 PM, Rich k0zx wrote:
which caps were you referring to Joe?


Re: LK 5xx Variable Cap Plates with pix attached

 

开云体育

?The ameritron? tune cap from the? AL-1500/1200/82? amp.??? Rated for 4.5 kv? and is ameritron part # 204-2570.
It's a 190 pf cap....with real low min C, like < 20 pf.

Joe WB9SBD
On 1/22/2024 12:46 PM, Rich k0zx wrote:

which caps were you referring to Joe?

Re: LK 5xx Variable Cap Plates with pix attached

 
Edited

could you pass me a link to that page, mike... i'm on??with no results. Also tried there 2023 catalog and 204-2112
Re: LK 5xx Variable Cap Plates with pix attached

 

which caps were you referring to Joe?
Re: LK 5xx Variable Cap Plates with pix attached

 

Tnx Peter, i'll check that out!
rich
Re: LK 5xx Variable Cap Plates with pix attached

 

开云体育

The Caps are Great! Especially for the price! But unless you know the exact part number, finding them is near impossible.

I went through the same issue a few years ago.

Once found and ordered. in less than a week it was in the amp.

Joe WB9SBD


A Contest 40 Years in The Making!

MAIDENHEAD MAYHEM
On 1/22/2024 11:38 AM, Amp Guy Llc wrote:

Spec in one pic , current part number in the second pic?

Same value as what you need?


image0.jpegimage1.png

Amp guy llc
Amprepairguy.com
YouTube Amp repair guy
203-892-4119

On Jan 22, 2024, at 12:31 PM, Amp Guy Llc <kb1sel@...> wrote:

?
<image0.png>


Amp guy llc
Amprepairguy.com
YouTube Amp repair guy
203-892-4119

On Jan 22, 2024, at 12:07 PM, Rich k0zx <k0zx.co@...> wrote:

?Not seeing anything at Ameritron that matches this thing, needing 75-250pf 3.5kv min

Re: LK 5xx Variable Cap Plates with pix attached

 

开云体育

Spec in one pic , current part number in the second pic?

Same value as what you need?


image0.jpegimage1.png

Amp guy llc
Amprepairguy.com
YouTube Amp repair guy
203-892-4119

On Jan 22, 2024, at 12:31 PM, Amp Guy Llc <kb1sel@...> wrote:

?
<image0.png>


Amp guy llc
Amprepairguy.com
YouTube Amp repair guy
203-892-4119

On Jan 22, 2024, at 12:07 PM, Rich k0zx <k0zx.co@...> wrote:

?Not seeing anything at Ameritron that matches this thing, needing 75-250pf 3.5kv min

Re: Tuned input

 

开云体育

I cant imagine what could be wrong.? I went through it front to back and made sure its all timed correctly.? I think it must be a measurement error.? I need to try to confirm that today.?

Side note. I am not using a two tone. I have a generator but did not use it for this test. I just transmitted an RTTY carrier, Varied tuning, loading and drive power at about 1 KW out into a bird dummy load.

I cant find any IMD data for the 3cx3000A7. The data sheets do not seem to be as in depth as other Eimac tubes for some reason.? ?I am really surprised you suggested its a clean tube. It has a reputation of being really bad on IMD and that seems to be what I am seeing here.?

The amp is rated at 32DB in manual but it does not say how they measured that. Two tone or carrier.??

From: [email protected] <[email protected]> on behalf of Peter Voelpel via groups.io <dj7ww@...>
Sent: Monday, January 22, 2024 10:25 AM
To: [email protected] <[email protected]>
Subject: Re: [ham-amplifiers] Tuned input
?

?

There might be something wrong.with the output tuning.

At DR1A we use (d) 7? modified Henry 3000D amplifiers without tuned input.

No problem at all with harmonics with just stub filters on the antennas and standard Pi not Pi-L.

DR1A is a Multi/Multi station.

The 3CX3000A 7 is a very clean tube.

?

73

Peter

?

?

?

?

-----Original-Nachricht-----

Betreff: Re: [ham-amplifiers] Tuned input

Datum: 2024-01-22T16:02:22+0100

Von: "W7WRX" <clark@...>

An: "[email protected]" <[email protected]>

?

?

?

The board is now complete.
?
I went through and tuned the board for 50 ohms.? Actually, my Cantenna has been beaten badly over the years and is more like 60 ohms.?
?
I then added a 40 PF cap across the tube side of the board to simulate the tube. That through off 10, 15,20 and 40 big time.? I had to go back and retune those bands.
?
80 and 160 are not effected by the tube PF.
?
I then added a .01 coupling cap and saw no difference.? I read an article showing the .01 will change it slightly. I did not see this on bench.
?
I then hooked the board to the 8K using coax.? ?
?
10M now 1.2 to 1 from 3 to 1.
15M flat from 2 to 1
20M flat from 2.5 to 1
40M Flat from 1.8 to 1
80M flat from 2 to 1
160M Flat from 1.5 to 1
?
So the matching DOES WORK.
?
I then switched the board ON and OFF while testing harmonics on the Spec AN.? The 8K is a very dirty amplifier.? Even if I use an ICOM 7800 which shows the second harmonic way down in the noise Like 50 to 60 down At low drive levels or an FT2000D in Class A mode. The harmonics are only 10 to 20 DB down on most bands.
?
With the board I noticed I can actually tune the second harmonic live and further reduce it by 10 DB.? This makes the match very slightly higher at 1.1 to 1.2.
?
With the board most bands are 30 to 40 DB down now.? So this is a HUGE improvement.
?
I do notice something very odd on 20 and 40 meters with the 8K. It shows the SECOND harmonic STRONGER than the primary.? This is with the board off. With it on, the problem is fixed and the second is 30 to 40 db down.
?
How is it possible that the second harmonic be 5 DB stronger than the primary???? Is this a measurement error?
?
Keep in mind, this is with COAX and the henry UNUN input mess is still in line!? So all this will change when that is removed, I am sure.
?
Just wanted to check board operation.
?
IT WORKS!! ?
?
C
?
?
?
?
?
?
?
?
From: [email protected] <[email protected]> on behalf of Jim VE7RF via groups.io <jim.thom@...>
Sent: Saturday, January 20, 2024 5:19 PM
To: [email protected] <[email protected]>
Subject: Re: [ham-amplifiers] Tuned input
?
On Sat, Jan 20, 2024 at 07:47 PM, W7WRX wrote:
The RF flows into the center common pins in and out.? The coils are across the common pins when keyed.? These relays are labeled DPDT but the common pins are tied together!!!!!!!!!!!!!!!!!!!!!? ??

I checked the NO and NC operation and it passed. I did not think to check ACROSS the two center poles to each other!

I got the new relays from mouser. I have 10, 15, 20 and 40 working now!? ?The cut off is very sharp. On 40, at 8MHZ its brick wall steep cut off.? Flat in the band.

I am going to work on 80 and 160 today.
## excellent. Once all done....and installed, the trick will be trying to adjust each band, with drive applied.? ?Document it really good.? It will? come in handy? for 8k and 3k owners.?
?

Re: LK 5xx Variable Cap Plates with pix attached

 

开云体育

image0.png

Amp guy llc
Amprepairguy.com
YouTube Amp repair guy
203-892-4119

On Jan 22, 2024, at 12:07 PM, Rich k0zx <k0zx.co@...> wrote:

?Not seeing anything at Ameritron that matches this thing, needing 75-250pf 3.5kv min

Re: LK 5xx Variable Cap Plates with pix attached

 

开云体育

Might be a Johnson capacitor.

?

?

73

Peter

?

?

?

-----Original-Nachricht-----

Betreff: [ham-amplifiers] LK 5xx Variable Cap Plates with pix attached

Datum: 2024-01-22T17:51:25+0100

Von: "Rich k0zx" <k0zx.co@...>

An: "[email protected]" <[email protected]>

?

?

?

Repost added pix:
Rebuilding another LK cap here and another Plate Tuning cap with nasty pits and therefore....arcing. Any info to secure those rotor and stator plates appreciated.
Rich k0zx
?
Re: Tuned input

 

开云体育

?

There might be something wrong.with the output tuning.

At DR1A we use (d) 7? modified Henry 3000D amplifiers without tuned input.

No problem at all with harmonics with just stub filters on the antennas and standard Pi not Pi-L.

DR1A is a Multi/Multi station.

The 3CX3000A 7 is a very clean tube.

?

73

Peter

?

?

?

?

-----Original-Nachricht-----

Betreff: Re: [ham-amplifiers] Tuned input

Datum: 2024-01-22T16:02:22+0100

Von: "W7WRX" <clark@...>

An: "[email protected]" <[email protected]>

?

?

?

The board is now complete.
?
I went through and tuned the board for 50 ohms.? Actually, my Cantenna has been beaten badly over the years and is more like 60 ohms.?
?
I then added a 40 PF cap across the tube side of the board to simulate the tube. That through off 10, 15,20 and 40 big time.? I had to go back and retune those bands.
?
80 and 160 are not effected by the tube PF.
?
I then added a .01 coupling cap and saw no difference.? I read an article showing the .01 will change it slightly. I did not see this on bench.
?
I then hooked the board to the 8K using coax.? ?
?
10M now 1.2 to 1 from 3 to 1.
15M flat from 2 to 1
20M flat from 2.5 to 1
40M Flat from 1.8 to 1
80M flat from 2 to 1
160M Flat from 1.5 to 1
?
So the matching DOES WORK.
?
I then switched the board ON and OFF while testing harmonics on the Spec AN.? The 8K is a very dirty amplifier.? Even if I use an ICOM 7800 which shows the second harmonic way down in the noise Like 50 to 60 down At low drive levels or an FT2000D in Class A mode. The harmonics are only 10 to 20 DB down on most bands.
?
With the board I noticed I can actually tune the second harmonic live and further reduce it by 10 DB.? This makes the match very slightly higher at 1.1 to 1.2.
?
With the board most bands are 30 to 40 DB down now.? So this is a HUGE improvement.
?
I do notice something very odd on 20 and 40 meters with the 8K. It shows the SECOND harmonic STRONGER than the primary.? This is with the board off. With it on, the problem is fixed and the second is 30 to 40 db down.
?
How is it possible that the second harmonic be 5 DB stronger than the primary???? Is this a measurement error?
?
Keep in mind, this is with COAX and the henry UNUN input mess is still in line!? So all this will change when that is removed, I am sure.
?
Just wanted to check board operation.
?
IT WORKS!! ?
?
C
?
?
?
?
?
?
?
?

From: [email protected] <[email protected]> on behalf of Jim VE7RF via groups.io <jim.thom@...>
Sent: Saturday, January 20, 2024 5:19 PM
To: [email protected] <[email protected]>
Subject: Re: [ham-amplifiers] Tuned input
?
On Sat, Jan 20, 2024 at 07:47 PM, W7WRX wrote:
The RF flows into the center common pins in and out.? The coils are across the common pins when keyed.? These relays are labeled DPDT but the common pins are tied together!!!!!!!!!!!!!!!!!!!!!? ??

I checked the NO and NC operation and it passed. I did not think to check ACROSS the two center poles to each other!

I got the new relays from mouser. I have 10, 15, 20 and 40 working now!? ?The cut off is very sharp. On 40, at 8MHZ its brick wall steep cut off.? Flat in the band.

I am going to work on 80 and 160 today.
## excellent. Once all done....and installed, the trick will be trying to adjust each band, with drive applied.? ?Document it really good.? It will? come in handy? for 8k and 3k owners.?
?
Re: LK 5xx Variable Cap Plates with pix attached

 

Not seeing anything at Ameritron that matches this thing, needing 75-250pf 3.5kv min
Re: LK 5xx Variable Cap Plates with pix attached

 

开云体育

Fyi a used cap will cost the same or more then a new one from Ameritron .?



Amp guy llc
Amprepairguy.com
YouTube Amp repair guy
203-892-4119

On Jan 22, 2024, at 11:26 AM, Rich k0zx <k0zx.co@...> wrote:

?ok, tnx Mike, appreciate the lead
rich

Re: LK 5xx Variable Cap Plates with pix attached

 
Edited

ok, tnx Mike, appreciate the lead. No it is from an Amp Supply LK-500, 2 3-500s
rich
Re: LK 5xx Variable Cap Plates

 

开云体育

Here’s a video showing the mod?



Amp guy llc
Amprepairguy.com
YouTube Amp repair guy
203-892-4119

On Jan 22, 2024, at 11:04 AM, Amp Guy Llc <kb1sel@...> wrote:

?Can you just obtain a new capacitor from Ameritron and modify the shaft to fit.

I use the plate side air variable capacitor out of the al80b, which is also used in a couple other models. I remove the plastic phenolic shaft and cut off the now exposed spline . I then use a shaft coupler to extend the 1/4 shaft extending out of the capacitor.?

New capacitor is under 40 bucks?

I used to rebuild the capacitors years ago, set plate gaps and hi pot. Not worth it when a new one is so cheap. Even after replacing plates , you still could end up having an intermittent connection issue between the plate shaft and end plates.

I would add a nice 50 ohm series glitch in series with the plate b+ . I like the Kanthal type resistors. And a spark gap for the Newley replaced capacitor .?

73 Scott Kb1sel?

Amp guy llc
Amprepairguy.com
YouTube Amp repair guy
203-892-4119

On Jan 22, 2024, at 10:36 AM, Rich k0zx <k0zx.co@...> wrote:

?Now that's a very adventuresome solution there, well done....unfortunately space is available only for this cap, so probably not the best for this 500. Tnx for the idea tho
rich?

Re: LK 5xx Variable Cap Plates

 

开云体育

Can you just obtain a new capacitor from Ameritron and modify the shaft to fit.

I use the plate side air variable capacitor out of the al80b, which is also used in a couple other models. I remove the plastic phenolic shaft and cut off the now exposed spline . I then use a shaft coupler to extend the 1/4 shaft extending out of the capacitor.?

New capacitor is under 40 bucks?

I used to rebuild the capacitors years ago, set plate gaps and hi pot. Not worth it when a new one is so cheap. Even after replacing plates , you still could end up having an intermittent connection issue between the plate shaft and end plates.

I would add a nice 50 ohm series glitch in series with the plate b+ . I like the Kanthal type resistors. And a spark gap for the Newley replaced capacitor .?

73 Scott Kb1sel?

Amp guy llc
Amprepairguy.com
YouTube Amp repair guy
203-892-4119

On Jan 22, 2024, at 10:36 AM, Rich k0zx <k0zx.co@...> wrote:

?Now that's a very adventuresome solution there, well done....unfortunately space is available only for this cap, so probably not the best for this 500. Tnx for the idea tho
rich?

Re: LK 5xx Variable Cap Plates with pix attached

 

That looks like the tune cap from a SB-220 amp? They show up on Ebay from time to time. Look for one from a 221 with the wider spacing.

On Monday, January 22, 2024 at 10:49:41 AM EST, Rich k0zx <k0zx.co@...> wrote:


Repost added pix:
Rebuilding another LK cap here and another Plate Tuning cap with nasty pits and therefore....arcing. Any info to secure those rotor and stator plates appreciated.
Rich k0zx

LK 5xx Variable Cap Plates with pix attached

 

Repost added pix:
Rebuilding another LK cap here and another Plate Tuning cap with nasty pits and therefore....arcing. Any info to secure those rotor and stator plates appreciated.
Rich k0zx

PXL_20240113_182813310.PORTRAIT.jpg
PXL_20240113_184055922.PORTRAIT.ORIGINAL.jpg
PXL_20240113_224945743.MP.jpg

Re: LK 5xx Variable Cap Plates

 

Now that's a very adventuresome solution there, well done....unfortunately space is available only for this cap, so probably not the best for this 500. Tnx for the idea tho
rich?

Re: Tuned input

 

开云体育

The board is now complete.

I went through and tuned the board for 50 ohms.? Actually, my Cantenna has been beaten badly over the years and is more like 60 ohms.?

I then added a 40 PF cap across the tube side of the board to simulate the tube. That through off 10, 15,20 and 40 big time.? I had to go back and retune those bands.

80 and 160 are not effected by the tube PF.

I then added a .01 coupling cap and saw no difference.? I read an article showing the .01 will change it slightly. I did not see this on bench.

I then hooked the board to the 8K using coax.? ?

10M now 1.2 to 1 from 3 to 1.
15M flat from 2 to 1
20M flat from 2.5 to 1
40M Flat from 1.8 to 1
80M flat from 2 to 1
160M Flat from 1.5 to 1

So the matching DOES WORK.

I then switched the board ON and OFF while testing harmonics on the Spec AN.? The 8K is a very dirty amplifier.? Even if I use an ICOM 7800 which shows the second harmonic way down in the noise Like 50 to 60 down At low drive levels or an FT2000D in Class A mode. The harmonics are only 10 to 20 DB down on most bands.

With the board I noticed I can actually tune the second harmonic live and further reduce it by 10 DB.? This makes the match very slightly higher at 1.1 to 1.2.

With the board most bands are 30 to 40 DB down now.? So this is a HUGE improvement.

I do notice something very odd on 20 and 40 meters with the 8K. It shows the SECOND harmonic STRONGER than the primary.? This is with the board off. With it on, the problem is fixed and the second is 30 to 40 db down.

How is it possible that the second harmonic be 5 DB stronger than the primary???? Is this a measurement error?

Keep in mind, this is with COAX and the henry UNUN input mess is still in line!? So all this will change when that is removed, I am sure.

Just wanted to check board operation.

IT WORKS!! ?

C







From: [email protected] <[email protected]> on behalf of Jim VE7RF via groups.io <jim.thom@...>
Sent: Saturday, January 20, 2024 5:19 PM
To: [email protected] <[email protected]>
Subject: Re: [ham-amplifiers] Tuned input
?
On Sat, Jan 20, 2024 at 07:47 PM, W7WRX wrote:
The RF flows into the center common pins in and out.? The coils are across the common pins when keyed.? These relays are labeled DPDT but the common pins are tied together!!!!!!!!!!!!!!!!!!!!!? ??

I checked the NO and NC operation and it passed. I did not think to check ACROSS the two center poles to each other!

I got the new relays from mouser. I have 10, 15, 20 and 40 working now!? ?The cut off is very sharp. On 40, at 8MHZ its brick wall steep cut off.? Flat in the band.

I am going to work on 80 and 160 today.
## excellent. Once all done....and installed, the trick will be trying to adjust each band, with drive applied.? ?Document it really good.? It will? come in handy? for 8k and 3k owners.?

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