On Mar 20, 2024, at 8:20?PM, Paul Kraemer <elespe@...> wrote:

The L7 I recently had instability problems and tune capacitor arc has been REPAIRED. I managed with time and a jeweler file to clean the burn from the capacitor plate without removing it. I gingerly tried the amp again and although it didn't arc the same spot it started in other spots on the tune capacitor. Inspecting closely I found the tubes looked like Eimac but they were imports from RF Parts. I changed those out for some OLD Eimac and very pleased to report PROBLEM SOLVED. Everything behaved and tuning / loading adjust is now smooth as glass with NO instability. It is as it should be on all bands!

Not to imply the RF Parts tubes are not good but the subtle differences between Eimac and those particular import ARE significant. Now to find good tubes for the next time

Paul K0UYA

Well, aside from marginal vacuum, the RF Parts tubes are good. They just have more gain than the originals, and this makes them more susceptible to instability.

There are parasitic choke upgrades available and they work pretty well.

Gary

W0DVN

On Mar 20, 2024, at 8:20?PM, Paul Kraemer <elespe@...> wrote:

The L7 I recently had instability problems and tune capacitor arc has been REPAIRED. I managed with time and a jeweler file to clean the burn from the capacitor plate without removing it. I gingerly tried the amp again and although it didn't arc the same spot it started in other spots on the tune capacitor. Inspecting closely I found the tubes looked like Eimac but they were imports from RF Parts. I changed those out for some OLD Eimac and very pleased to report PROBLEM SOLVED. Everything behaved and tuning / loading adjust is now smooth as glass with NO instability. It is as it should be on all bands!

Not to imply the RF Parts tubes are not good but the subtle differences between Eimac and those particular import ARE significant. Now to find good tubes for the next time

Paul K0UYA

On Mar 20, 2024, at 8:39?PM, Paul Kraemer <elespe@...> wrote:

Please enlighten me Gary.? With the imports installed the tune and load just didn't "feel" right and it was interesting to me that there was a faint orange glow for nominal power output(same in both cases)while the Eimac exhibited none of that.? Neither set could be classified as nearly new but that is what I observed. What is sold today may be totally different than what was sold then.

Paul

On 3/20/2024 8:22 PM, Gary Follett wrote:

Well, aside from marginal vacuum, the RF Parts tubes are good. They just have more gain than the originals, and this makes them more susceptible to instability.

There are parasitic choke upgrades available and they work pretty well.

Gary

W0DVN

On Mar 20, 2024, at 8:20?PM, Paul Kraemer <elespe@...> wrote:

The L7 I recently had instability problems and tune capacitor arc has been REPAIRED. ?I managed with time and a jeweler file to clean the burn from the capacitor plate without removing it. ?I gingerly tried the amp again and although it didn't arc the same spot it started in other spots on the tune capacitor. ?Inspecting closely I found the tubes looked like Eimac but they were imports from RF Parts. ?I changed those out for some OLD Eimac and very pleased to report PROBLEM SOLVED. ?Everything behaved and tuning / loading adjust is now smooth as glass with NO instability. ?It is as it should be on all bands!

Not to imply the RF Parts tubes are not good but the subtle differences between Eimac and those particular import ARE significant. ?Now to find good tubes for the next time

Paul K0UYA

Paul, I assume you have the grids directly bonded to the chassis ?? ? That alone will improve stability.? I would leave the suppressors alone.?

Do you have a hi-pot tester ?? ?One / both tubes could have lost some of their vacuum.? ?But if it arced from anode to grid, it shoulda just taken out a fuse... and not the tune cap.?

Did it arc in the CW (1900v) position..... or in the SSB ( 2650 v ) position ??

Ok, this is where my hb adjustable spark gap pays off.? ?One across the tune cap...protects the tune cap and the bandswitch.? ?2nd one is across the load cap.?

Usually what happens is when plates arc, they are a bitch to get cleaned up, depending on damage.??

On Mar 21, 2024, at 12:07?PM, Paul Kraemer <elespe@...> wrote:

Jim

I have two L7, one bonded grids and other stock.? The bonded grids makes more power than stock.? It is the stock one I need to have OK as it is sold waiting to be picked up.? I just want it right, stock condition,? and not another project.

I have a 2kv hipot tester so not really high @ only 2kv

All testing done in SSB mode, 89 watts drive from TT OMNI VI+, L7 output a KW more or less depending on band

As earlier comment the import tubes? showed orange plates and not the typical faint orange like all do under normal conditions but I mean LOTS OF ORANGE and the Eimac don't do that.? Baffles my simple mind as it was working perfectly for years and then I sold it and was just going to tweak the meter adjustments before it left and before I even got to that it started it's bad behavior.

In the future if I needed more tubes I WOULD without hesitation try what RF Parts offers today.? Their reputation and good service has earned that but I'd just like to know what went off the rails with the pair in a working amp.

Paul K0UYA

On 3/21/2024 5:26 AM, Jim VE7RF wrote:

Paul, I assume you have the grids directly bonded to the chassis ?? ? That alone will improve stability.? I would leave the suppressors alone.?

Do you have a hi-pot tester ?? ?One / both tubes could have lost some of their vacuum.? ?But if it arced from anode to grid, it shoulda just taken out a fuse... and not the tune cap.?

Did it arc in the CW (1900v) position..... or in the SSB ( 2650 v ) position ??

Ok, this is where my hb adjustable spark gap pays off.? ?One across the tune cap...protects the tune cap and the bandswitch.? ?2nd one is across the load cap.?

Usually what happens is when plates arc, they are a bitch to get cleaned up, depending on damage.??

Do both tubes show the same degree of orange? Is this when keyed but with no drive?

What is the idle plate current, with the Eimac tubes, then the other tubes?

Gary

W0DVN

On Mar 21, 2024, at 12:07?PM, Paul Kraemer <elespe@...> wrote:

Jim

I have two L7, one bonded grids and other stock.? The bonded grids makes more power than stock.? It is the stock one I need to have OK as it is sold waiting to be picked up.? I just want it right, stock condition,? and not another project.

I have a 2kv hipot tester so not really high @ only 2kv

All testing done in SSB mode, 89 watts drive from TT OMNI VI+, L7 output a KW more or less depending on band

As earlier comment the import tubes? showed orange plates and not the typical faint orange like all do under normal conditions but I mean LOTS OF ORANGE and the Eimac don't do that.? Baffles my simple mind as it was working perfectly for years and then I sold it and was just going to tweak the meter adjustments before it left and before I even got to that it started it's bad behavior.

In the future if I needed more tubes I WOULD without hesitation try what RF Parts offers today.? Their reputation and good service has earned that but I'd just like to know what went off the rails with the pair in a working amp.

Paul K0UYA

On 3/21/2024 5:26 AM, Jim VE7RF wrote:

Paul, I assume you have the grids directly bonded to the chassis ?? ? That alone will improve stability.? I would leave the suppressors alone.?

Do you have a hi-pot tester ?? ?One / both tubes could have lost some of their vacuum.? ?But if it arced from anode to grid, it shoulda just taken out a fuse... and not the tune cap.?

Did it arc in the CW (1900v) position..... or in the SSB ( 2650 v ) position ??

Ok, this is where my hb adjustable spark gap pays off.? ?One across the tune cap...protects the tune cap and the bandswitch.? ?2nd one is across the load cap.?

Usually what happens is when plates arc, they are a bitch to get cleaned up, depending on damage.??

On Mar 21, 2024, at 2:18?PM, Paul Kraemer <elespe@...> wrote:

Both import tubes look same color orange

This is keyed and 89w drive applied on all bands

Idle current approx 100ma total either tube type with hv 2650v

Paul K0UYA

On 3/21/2024 12:21 PM, Gary Follett wrote:

Do both tubes show the same degree of orange? Is this when keyed but with no drive?

What is the idle plate current, with the Eimac tubes, then the other tubes?

Gary

W0DVN

On Mar 21, 2024, at 12:07?PM, Paul Kraemer <elespe@...> wrote:

Jim

I have two L7, one bonded grids and other stock.? The bonded grids makes more power than stock.? It is the stock one I need to have OK as it is sold waiting to be picked up.? I just want it right, stock condition,? and not another project.

I have a 2kv hipot tester so not really high @ only 2kv

All testing done in SSB mode, 89 watts drive from TT OMNI VI+, L7 output a KW more or less depending on band

As earlier comment the import tubes? showed orange plates and not the typical faint orange like all do under normal conditions but I mean LOTS OF ORANGE and the Eimac don't do that.? Baffles my simple mind as it was working perfectly for years and then I sold it and was just going to tweak the meter adjustments before it left and before I even got to that it started it's bad behavior.

In the future if I needed more tubes I WOULD without hesitation try what RF Parts offers today.? Their reputation and good service has earned that but I'd just like to know what went off the rails with the pair in a working amp.

Paul K0UYA

On 3/21/2024 5:26 AM, Jim VE7RF wrote:

Paul, I assume you have the grids directly bonded to the chassis ?? ? That alone will improve stability.? I would leave the suppressors alone.?

Do you have a hi-pot tester ?? ?One / both tubes could have lost some of their vacuum.? ?But if it arced from anode to grid, it shoulda just taken out a fuse... and not the tune cap.?

Did it arc in the CW (1900v) position..... or in the SSB ( 2650 v ) position ??

Ok, this is where my hb adjustable spark gap pays off.? ?One across the tune cap...protects the tune cap and the bandswitch.? ?2nd one is across the load cap.?

Usually what happens is when plates arc, they are a bitch to get cleaned up, depending on damage.??

Then you see almost no orange with the Eimac tubes when driven with 89 watts?

What plate current readings do you get with each set of tubes driven with 50 watts and output power? (I picked a lower value for the sake of the tubes). I’m trying to get at how efficiently the amp is running with different tubes. The brighter glow on the plates simply means the newer tubes are dissipating more heat than the Eimac tubes (due to poorer efficiency) or the newer tube design itself is less efficient at disposing of plate heat than the old Eimac tubes.

It is quite possible that the emissivity of the newer plates is less than the iMac’s, and this would make them run hotter than the Eimac’s.?

Gary

W0DVN

On Mar 21, 2024, at 2:18?PM, Paul Kraemer <elespe@...> wrote:

Both import tubes look same color orange

This is keyed and 89w drive applied on all bands

Idle current approx 100ma total either tube type with hv 2650v

Paul K0UYA

On 3/21/2024 12:21 PM, Gary Follett wrote:

Do both tubes show the same degree of orange? Is this when keyed but with no drive?

What is the idle plate current, with the Eimac tubes, then the other tubes?

Gary

W0DVN

On Mar 21, 2024, at 12:07?PM, Paul Kraemer <elespe@...> wrote:

Jim

I have two L7, one bonded grids and other stock.? The bonded grids makes more power than stock.? It is the stock one I need to have OK as it is sold waiting to be picked up.? I just want it right, stock condition,? and not another project.

I have a 2kv hipot tester so not really high @ only 2kv

All testing done in SSB mode, 89 watts drive from TT OMNI VI+, L7 output a KW more or less depending on band

As earlier comment the import tubes? showed orange plates and not the typical faint orange like all do under normal conditions but I mean LOTS OF ORANGE and the Eimac don't do that.? Baffles my simple mind as it was working perfectly for years and then I sold it and was just going to tweak the meter adjustments before it left and before I even got to that it started it's bad behavior.

In the future if I needed more tubes I WOULD without hesitation try what RF Parts offers today.? Their reputation and good service has earned that but I'd just like to know what went off the rails with the pair in a working amp.

Paul K0UYA

On 3/21/2024 5:26 AM, Jim VE7RF wrote:

Paul, I assume you have the grids directly bonded to the chassis ?? ? That alone will improve stability.? I would leave the suppressors alone.?

Do you have a hi-pot tester ?? ?One / both tubes could have lost some of their vacuum.? ?But if it arced from anode to grid, it shoulda just taken out a fuse... and not the tune cap.?

Did it arc in the CW (1900v) position..... or in the SSB ( 2650 v ) position ??

Ok, this is where my hb adjustable spark gap pays off.? ?One across the tune cap...protects the tune cap and the bandswitch.? ?2nd one is across the load cap.?

Usually what happens is when plates arc, they are a bitch to get cleaned up, depending on damage.??

On Mar 21, 2024, at 3:49?PM, Paul Kraemer <elespe@...> wrote:

That is correct.? Eimac almost no orange with same drive and output as the RFP

I had to put it aside for bench space for more pressing matters.? I'll try to fill in all the blanks next week

Paul

On 3/21/2024 2:47 PM, Gary Follett wrote:

Then you see almost no orange with the Eimac tubes when driven with 89 watts?

What plate current readings do you get with each set of tubes driven with 50 watts and output power? (I picked a lower value for the sake of the tubes). I’m trying to get at how efficiently the amp is running with different tubes. The brighter glow on the plates simply means the newer tubes are dissipating more heat than the Eimac tubes (due to poorer efficiency) or the newer tube design itself is less efficient at disposing of plate heat than the old Eimac tubes.

It is quite possible that the emissivity of the newer plates is less than the iMac’s, and this would make them run hotter than the Eimac’s.?

Gary

W0DVN

On Mar 21, 2024, at 2:18?PM, Paul Kraemer <elespe@...> wrote:

Both import tubes look same color orange

This is keyed and 89w drive applied on all bands

Idle current approx 100ma total either tube type with hv 2650v

Paul K0UYA

On 3/21/2024 12:21 PM, Gary Follett wrote:

Do both tubes show the same degree of orange? Is this when keyed but with no drive?

What is the idle plate current, with the Eimac tubes, then the other tubes?

Gary

W0DVN

On Mar 21, 2024, at 12:07?PM, Paul Kraemer <elespe@...> wrote:

Jim

I have two L7, one bonded grids and other stock.? The bonded grids makes more power than stock.? It is the stock one I need to have OK as it is sold waiting to be picked up.? I just want it right, stock condition,? and not another project.

I have a 2kv hipot tester so not really high @ only 2kv

All testing done in SSB mode, 89 watts drive from TT OMNI VI+, L7 output a KW more or less depending on band

As earlier comment the import tubes? showed orange plates and not the typical faint orange like all do under normal conditions but I mean LOTS OF ORANGE and the Eimac don't do that.? Baffles my simple mind as it was working perfectly for years and then I sold it and was just going to tweak the meter adjustments before it left and before I even got to that it started it's bad behavior.

In the future if I needed more tubes I WOULD without hesitation try what RF Parts offers today.? Their reputation and good service has earned that but I'd just like to know what went off the rails with the pair in a working amp.

Paul K0UYA

On 3/21/2024 5:26 AM, Jim VE7RF wrote:

Paul, I assume you have the grids directly bonded to the chassis ?? ? That alone will improve stability.? I would leave the suppressors alone.?

Do you have a hi-pot tester ?? ?One / both tubes could have lost some of their vacuum.? ?But if it arced from anode to grid, it shoulda just taken out a fuse... and not the tune cap.?

Did it arc in the CW (1900v) position..... or in the SSB ( 2650 v ) position ??

Ok, this is where my hb adjustable spark gap pays off.? ?One across the tune cap...protects the tune cap and the bandswitch.? ?2nd one is across the load cap.?

Usually what happens is when plates arc, they are a bitch to get cleaned up, depending on damage.??

It will be really interesting to see the plate current comparison.

Gary

W0DVN

On Mar 21, 2024, at 3:49?PM, Paul Kraemer <elespe@...> wrote:

That is correct.? Eimac almost no orange with same drive and output as the RFP

I had to put it aside for bench space for more pressing matters.? I'll try to fill in all the blanks next week

Paul

On 3/21/2024 2:47 PM, Gary Follett wrote:

Then you see almost no orange with the Eimac tubes when driven with 89 watts?

What plate current readings do you get with each set of tubes driven with 50 watts and output power? (I picked a lower value for the sake of the tubes). I’m trying to get at how efficiently the amp is running with different tubes. The brighter glow on the plates simply means the newer tubes are dissipating more heat than the Eimac tubes (due to poorer efficiency) or the newer tube design itself is less efficient at disposing of plate heat than the old Eimac tubes.

It is quite possible that the emissivity of the newer plates is less than the iMac’s, and this would make them run hotter than the Eimac’s.?

Gary

W0DVN

On Mar 21, 2024, at 2:18?PM, Paul Kraemer <elespe@...> wrote:

Both import tubes look same color orange

This is keyed and 89w drive applied on all bands

Idle current approx 100ma total either tube type with hv 2650v

Paul K0UYA

On 3/21/2024 12:21 PM, Gary Follett wrote:

Do both tubes show the same degree of orange? Is this when keyed but with no drive?

What is the idle plate current, with the Eimac tubes, then the other tubes?

Gary

W0DVN

On Mar 21, 2024, at 12:07?PM, Paul Kraemer <elespe@...> wrote:

Jim

I have two L7, one bonded grids and other stock.? The bonded grids makes more power than stock.? It is the stock one I need to have OK as it is sold waiting to be picked up.? I just want it right, stock condition,? and not another project.

I have a 2kv hipot tester so not really high @ only 2kv

All testing done in SSB mode, 89 watts drive from TT OMNI VI+, L7 output a KW more or less depending on band

As earlier comment the import tubes? showed orange plates and not the typical faint orange like all do under normal conditions but I mean LOTS OF ORANGE and the Eimac don't do that.? Baffles my simple mind as it was working perfectly for years and then I sold it and was just going to tweak the meter adjustments before it left and before I even got to that it started it's bad behavior.

In the future if I needed more tubes I WOULD without hesitation try what RF Parts offers today.? Their reputation and good service has earned that but I'd just like to know what went off the rails with the pair in a working amp.

Paul K0UYA

On 3/21/2024 5:26 AM, Jim VE7RF wrote:

Paul, I assume you have the grids directly bonded to the chassis ?? ? That alone will improve stability.? I would leave the suppressors alone.?

Do you have a hi-pot tester ?? ?One / both tubes could have lost some of their vacuum.? ?But if it arced from anode to grid, it shoulda just taken out a fuse... and not the tune cap.?

Did it arc in the CW (1900v) position..... or in the SSB ( 2650 v ) position ??

Ok, this is where my hb adjustable spark gap pays off.? ?One across the tune cap...protects the tune cap and the bandswitch.? ?2nd one is across the load cap.?

Usually what happens is when plates arc, they are a bitch to get cleaned up, depending on damage.??

I got a chance to get back to this project and with the Eimac tubes installed I read the following with amp keyed but no drive. Bias is set by (10) 1N5408 diodes. HVPS is L4PS with the Harbach board but capacitors are 330mfd instead of 220mfd

Ep=2650v, Ip=100ma

Amp keyed with 50w input drive

Ep = 2480, Ip= 450ma, Ig=130ma, Po= 660w. There is minimal color to the plates even held for minutes at that level.

I substituted the RFP tubes to repeat the tests and shocker there was NO difference on all items! WHAT IS HAPPENING HERE?

I went on up to full drive and the amp remained stable

Ep= 2400v, Ip=650ma, Ig = 220ma, Po= 1020w. There is some color to the plates but only with extended key down and certainly nothing to compare to the orange of the previous day.

Today all I can say is both sets of tubes perform equally across the board??? I looked for loose connections. Sockets are clean and TIGHT. Move along folks nothing to see here?

Paul K0UYA

On 3/21/2024 3:50 PM, Gary Follett wrote:

It will be really interesting to see the plate current comparison.

Gary

W0DVN

On Mar 21, 2024, at 3:49?PM, Paul Kraemer <elespe@...> wrote:

That is correct. Eimac almost no orange with same drive and output as the RFP

I had to put it aside for bench space for more pressing matters. I'll try to fill in all the blanks next week

Paul

On 3/21/2024 2:47 PM, Gary Follett wrote:

Then you see almost no orange with the Eimac tubes when driven with 89 watts?

What plate current readings do you get with each set of tubes driven with 50 watts and output power? (I picked a lower value for the sake of the tubes). I’m trying to get at how efficiently the amp is running with different tubes. The brighter glow on the plates simply means the newer tubes are dissipating more heat than the Eimac tubes (due to poorer efficiency) or the newer tube design itself is less efficient at disposing of plate heat than the old Eimac tubes.

It is quite possible that the emissivity of the newer plates is less than the iMac’s, and this would make them run hotter than the Eimac’s.

Gary

W0DVN

On Mar 21, 2024, at 2:18?PM, Paul Kraemer <elespe@...> wrote:

Both import tubes look same color orange

This is keyed and 89w drive applied on all bands

Idle current approx 100ma total either tube type with hv 2650v

Paul K0UYA

On 3/21/2024 12:21 PM, Gary Follett wrote:

Do both tubes show the same degree of orange? Is this when keyed but with no drive?

What is the idle plate current, with the Eimac tubes, then the other tubes?

Gary

W0DVN

On Mar 21, 2024, at 12:07?PM, Paul Kraemer <elespe@...> wrote:

Jim

I have two L7, one bonded grids and other stock. The bonded grids makes more power than stock. It is the stock one I need to have OK as it is sold waiting to be picked up. I just want it right, stock condition, and not another project.

I have a 2kv hipot tester so not really high @ only 2kv

All testing done in SSB mode, 89 watts drive from TT OMNI VI+, L7 output a KW more or less depending on band

As earlier comment the import tubes showed orange plates and not the typical faint orange like all do under normal conditions but I mean LOTS OF ORANGE and the Eimac don't do that. Baffles my simple mind as it was working perfectly for years and then I sold it and was just going to tweak the meter adjustments before it left and before I even got to that it started it's bad behavior.

In the future if I needed more tubes I WOULD without hesitation try what RF Parts offers today. Their reputation and good service has earned that but I'd just like to know what went off the rails with the pair in a working amp.

Paul K0UYA

On 3/21/2024 5:26 AM, Jim VE7RF wrote:

Paul, I assume you have the grids directly bonded to the chassis ? That alone will improve stability. I would leave the suppressors alone.

Do you have a hi-pot tester ? One / both tubes could have lost some of their vacuum. But if it arced from anode to grid, it shoulda just taken out a fuse... and not the tune cap.

Did it arc in the CW (1900v) position..... or in the SSB ( 2650 v ) position ?

Ok, this is where my hb adjustable spark gap pays off. One across the tune cap...protects the tune cap and the bandswitch. 2nd one is across the load cap.

Usually what happens is when plates arc, they are a bitch to get cleaned up, depending on damage.