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My Drake TR4cw/rit is going in tomorrow to a very experienced tech for a bit of servicing.? If needed, he'll be doing
an alignment for me.? All three of the 6JB6's presently in the rig are the green label Sylvania possibly originals, or at least were replaced
with the manual's recommended Sylvania tubes at one time?? All three are fairly close to 90% or a bit over on my Jackson 658-1 tube tester. I have a selection of 6JB6 tubes, which include anything from Raytheon, RCA, GE, Marconi, Westinghouse, but not another "matched" set of three of any specific brand.? I can match two, but not three.? I do have some that test at 107% +or- and would be able to put three tubes together that test around this 107%.
Do the three 90% green label Sylvania's stay in place or would three of the "stronger" non matching brand tubes, but are heathier at 107% +or- be better, or is it completely unacceptable to install different brand tubes for this purpose.
I was planning on bringing these extra 6JB6's with me tomorrow and asking the tech what he think about it, but
would love to hear what you think of this.? My take on it is you don't mix and match here and therefore leave the Sylvania's in.
Thanks,
Peter
VE9KX
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With no data to support my suggestion, I would stick with the three Sylvania tubes if the RF output is reasonable. ?Rob, NC0B?
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On Mar 24, 2024, at 7:45 AM, Peter A <christinepeterarsenault@...> wrote:
?My Drake TR4cw/rit is going in tomorrow to a very experienced tech for a bit of servicing.? If needed, he'll be doing
an alignment for me.? All three of the 6JB6's presently in the rig are the green label Sylvania possibly originals, or at least were replaced
with the manual's recommended Sylvania tubes at one time?? All three are fairly close to 90% or a bit over on my Jackson 658-1 tube tester. I have a selection of 6JB6 tubes, which include anything from Raytheon, RCA, GE, Marconi, Westinghouse, but not another
"matched" set of three of any specific brand.? I can match two, but not three.? I do have some that test at 107% +or- and would be able to put three tubes together that test around this 107%.
Do the three 90% green label Sylvania's stay in place or would three of the "stronger" non matching brand tubes, but are heathier at 107% +or- be better, or is it completely unacceptable to install different brand tubes for this purpose.
I was planning on bringing these extra 6JB6's with me tomorrow and asking the tech what he think about it, but
would love to hear what you think of this.? My take on it is you don't mix and match here and therefore leave the Sylvania's in.
Thanks,
Peter
VE9KX
?
|
On Sun, Mar 24, 2024 at 12:43 PM, Rob Sherwood wrote:
With no data to support my suggestion, I would stick with the three Sylvania tubes if the RF output is reasonable. ?Rob, NC0B?
Thank you for your input Rob.? Output is between 165 and 185 watt SSB on my Array Solutions Powermaster II.
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Peter, as Rob mentioned: if you are getting adequate output, I would leave the tubes you have in the rig.? Keep others for spares.
IMO, the concept of having "matched" 6JB6's is overrated.? Given tolerances for other parts in the circuits, you can have one tube doing more "work" than the others, regardless of their DC characteristics.? The important thing to remember is not to overdrive them to try and eke out every last milliwatt from the set. (You'd be surprised how many people do this!).
A TR3/4 is capable of 200W output on 80 and 40 and new tubes can also do this on 20 but you're starting to push them.? 150W out on 15 and 10 is absolutely grand.??
Yes, I've been able to get 200W out on 15m with a fresh set but I throttle back on mine to about 140-150 on 10, going to about 180-200W on 80.? By keeping them below their absolute max, it doesn't matter if one tube is pulling more than the others because they're all within their plate dissipation ratings.? Those are 17.5W per tube in CCS -- you can run more than that in ordinary CW or SSB.
Having said all of the above, it's wise to use tubes that are the same brand or at least of the same mechanical design (it's easy to discern the two types from looking at the top of the frame inside) and within 20% of each other.
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Sunday, March 24th, 2024 at 9:43 AM, Peter A <christinepeterarsenault@...> wrote:
My Drake TR4cw/rit is going in tomorrow to a very experienced tech for a bit of servicing.? If needed, he'll be doing
an alignment for me.? All three of the 6JB6's presently in the rig are the green label Sylvania possibly originals, or at least were replaced
with the manual's recommended Sylvania tubes at one time?? All three are fairly close to 90% or a bit over on my Jackson 658-1 tube tester. I have a selection of 6JB6 tubes, which include anything from Raytheon, RCA, GE, Marconi, Westinghouse, but not another "matched" set of three of any specific brand.? I can match two, but not three.? I do have some that test at 107% +or- and would be able to put three tubes together that test around this 107%.
Do the three 90% green label Sylvania's stay in place or would three of the "stronger" non matching brand tubes, but are heathier at 107% +or- be better, or is it completely unacceptable to install different brand tubes for this purpose.
I was planning on bringing these extra 6JB6's with me tomorrow and asking the tech what he think about it, but
would love to hear what you think of this.? My take on it is you don't mix and match here and therefore leave the Sylvania's in.
Thanks,
Peter
VE9KX
?
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If you are getting this now, your tubes are ok.
David Assaf III
W5XU??? VP8RXU
On Sun, Mar 24, 2024 at 12:43 PM, Rob Sherwood wrote:
With no data to support my suggestion, I would stick with the three Sylvania tubes if the RF output is reasonable.? Rob, NC0B?
Thank you for your input Rob.? Output is between 165 and 185 watt SSB on my Array Solutions Powermaster II.
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I agree with using the Sylvania¡¯s. They have already earned their position by their performance. Keep the others as backups.
We must consider that any given tube type can vary by 20% or so from the specification and still be 100% good FOR THAT PARTICULAR TUBE.?
It is quite common for different brand new tubes to vary even more than that from brand to brand, which is why it is not a rare occurrence that a given tube can test 135% or more of rating. That is why tube testers have expected values in the data tables as the minimum acceptable value. Almost always you will get test readings greater than the specified reading, regardless which parameter you are testing, unless the tube is truly bad.
Also, emission tests can vary a lot from mutual conductance tests. While mutual conductance has some relationship with emission, it is not a 1:1 relationship.
Emission generally dictates idle plate current draw, pretty important as plate current can vary a lot as emission current varies. Two widely mismatched tubes in a parallel tube amplifier can result in one tube¡¯s drawing excess idle current while the other draws significantly less than rating, causing premature failure of the hot-running tube.
Mutual conductance is the variation in plate current versus the grid voltage, whether that variation is DC, AC or RF. Tube design and condition, as well as circuit factors can cause differences in mutual conductance when measured with DC, AC and RF excitation, though I have found that DC step-and-measure tests produce the same values that I obtain using 5 KHz AC test values from my Triplett 3444 tester.?
Mismatch in mutual conductance does not have too much impact in performance in radio transmitters because the tubes are in generally operated in parallel so their operating currents (and subsequent operating power) are additive, as opposed to the condition seen in a push-pull design, wherein this imbalance can cause amplitude distortion.?
Two types can have the same emission reading and significantly different mutual conductance measurements.
All of the above is the reason that the best tube tester is the properly tuned radio operating into a stable test load.
Gary
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On Mar 24, 2024, at 11:07?AM, Peter A <christinepeterarsenault@...> wrote:
On Sun, Mar 24, 2024 at 12:43 PM, Rob Sherwood wrote:
With no data to support my suggestion, I would stick with the three Sylvania tubes if the RF output is reasonable. ?Rob, NC0B?
Thank you for your input Rob.? Output is between 165 and 185 watt SSB on my Array Solutions Powermaster II.
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Sage advice.? While the manual says use a brand not all brands are the same..? remember these tubes started life in TV sets..? there are several 6jb6 tubes that are taller than will fit in the set. On the receiving end there is little difference in max vrs sensible power ? At + $30 a tube you will want to save them soo do not tune for max,? tune for longevity.
David Assaf III
W5XU??? VP8RXU
On Sun, Mar 24, 2024, 11:08 AM Steve Wedge, W1ES/4 via <w1es= [email protected]> wrote: Peter, as Rob mentioned: if you are getting adequate output, I would leave the tubes you have in the rig.? Keep others for spares.
IMO, the concept of having "matched" 6JB6's is overrated.? Given tolerances for other parts in the circuits, you can have one tube doing more "work" than the others, regardless of their DC characteristics.? The important thing to remember is not to overdrive them to try and eke out every last milliwatt from the set. (You'd be surprised how many people do this!).
A TR3/4 is capable of 200W output on 80 and 40 and new tubes can also do this on 20 but you're starting to push them.? 150W out on 15 and 10 is absolutely grand.??
Yes, I've been able to get 200W out on 15m with a fresh set but I throttle back on mine to about 140-150 on 10, going to about 180-200W on 80.? By keeping them below their absolute max, it doesn't matter if one tube is pulling more than the others because they're all within their plate dissipation ratings.? Those are 17.5W per tube in CCS -- you can run more than that in ordinary CW or SSB.
Having said all of the above, it's wise to use tubes that are the same brand or at least of the same mechanical design (it's easy to discern the two types from looking at the top of the frame inside) and within 20% of each other.
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Sunday, March 24th, 2024 at 9:43 AM, Peter A < christinepeterarsenault@...> wrote:
My Drake TR4cw/rit is going in tomorrow to a very experienced tech for a bit of servicing.? If needed, he'll be doing
an alignment for me.? All three of the 6JB6's presently in the rig are the green label Sylvania possibly originals, or at least were replaced
with the manual's recommended Sylvania tubes at one time?? All three are fairly close to 90% or a bit over on my Jackson 658-1 tube tester. I have a selection of 6JB6 tubes, which include anything from Raytheon, RCA, GE, Marconi, Westinghouse, but not another "matched" set of three of any specific brand.? I can match two, but not three.? I do have some that test at 107% +or- and would be able to put three tubes together that test around this 107%.
Do the three 90% green label Sylvania's stay in place or would three of the "stronger" non matching brand tubes, but are heathier at 107% +or- be better, or is it completely unacceptable to install different brand tubes for this purpose.
I was planning on bringing these extra 6JB6's with me tomorrow and asking the tech what he think about it, but
would love to hear what you think of this.? My take on it is you don't mix and match here and therefore leave the Sylvania's in.
Thanks,
Peter
VE9KX
?
|
I agree with using the Sylvania¡¯s. They have already earned their position by their performance. Keep the others as backups.
Steve, Gary, David, Rob, I agree 100 percent and the Sylvania's will indeed remain.? I did a quick search on the subject earlier and wasn't able to find much info on mixing and matching tube finals so I thought the question was worth asking, and this is the place to do it.
Thanks for your willingness to share your experience/knowledge and valuable time.
73
Peter
VE9KX
|
A good move, Peter.
Side note: I remember seeing an article (sadly, I didn't save it) that advised padding the neutralisation cap by a few pF if using RCA finals.? This is not to say that the RCA tubes aren't as good but they are different.? Sylvanias and GE's are the go-to tubes.? They also have identical frames, so it's not surprising.
If you look at the tube from the top, there are some that have cut-outs that are rounded and others that are angular.? If you have a pile of these, you can quickly see the difference.
Steve Wedge, W1ES/4
Time flies like an arrow.? Fruit flies like a banana.
Sent with secure email.
On Sunday, March 24th, 2024 at 3:47 PM, Peter A <christinepeterarsenault@...> wrote:
I agree with using the Sylvania¡¯s. They have already earned their position by their performance. Keep the others as backups.
Steve, Gary, David, Rob, I agree 100 percent and the Sylvania's will indeed remain.? I did a quick search on the subject earlier and wasn't able to find much info on mixing and matching tube finals so I thought the question was worth asking, and this is the place to do it.
Thanks for your willingness to share your experience/knowledge and valuable time.
73
Peter
VE9KX
|
I had the good fortune to spend a good part of my working years as an RF Engineer at RFCOM and Scientific Radio Systems, and designed and supported commercial SSB gear with both "transmitting tubes" (6146, 8122, 3-400Z, 3-100Z, etc) and sweep tubes.? One of the things you have to do in a commercial manufacturing environment is evaluate and approve vendor changes, including tubes.? One of the first things you learn is that the name stenciled on the tube is not always the actual manufacturer, and there were rude surprises when major manufacturers decided not to run a give type (permanent or temporary) and instead bought unmarked tubes from a competitor and mark them as theirs.? We learned to discern details of internal and external construction as a clue to this sort of substitution.
So since we can't really count on the brand name, how would a commercial PA designer approach this: 1.? First match tubes by internal construction details that give away the actual factory:? mica shapes, plate contours, grid leads and welding. 2.? Among the most similar I would want to first match by transconductance using a mutual conductance tester.? If the anode current change for a given grid change matches they will share the load on a large signal basis. 3.? Last I would match by idle current, so they start at similar currents and hence will track each other for best load sharing and linearity.
My opinion, but based on actual experience with many thousands of tubes, YMMV.
______________________________________________________________ Clyde Washburn, K2UE
"It is better to light one candle than to curse the darkness"
------ Original Message ------
Date 3/24/2024 3:47:57 PM
Subject Re: [DRAKE-RADIO] 6JB6 question.
I agree with using the Sylvania¡¯s. They have already earned their position by their performance. Keep the others as backups.
Steve, Gary, David, Rob, I agree 100 percent and the Sylvania's will indeed remain.? I did a quick search on the subject earlier and wasn't able to find much info on mixing and matching tube finals so I thought the question was worth asking, and this is the place to do it.
Thanks for your willingness to share your experience/knowledge and valuable time.
73
Peter
VE9KX
|
It seems to me that the Tube Collector's group may have information on how to distinguish the actual manufacturer, done by means of construction, as you point out, and sometimes by markings. Some of the markings may be subtle. I am not sure if this stuff is on their web site or is available to non-members.
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On 3/24/2024 1:56 PM, Clyde K2UE wrote: I had the good fortune to spend a good part of my working years as an RF Engineer at RFCOM and Scientific Radio Systems, and designed and supported commercial SSB gear with both "transmitting tubes" (6146, 8122, 3-400Z, 3-100Z, etc) and sweep tubes.? One of the things you have to do in a commercial manufacturing environment is evaluate and approve vendor changes, including tubes.? One of the first things you learn is that the name stenciled on the tube is not always the actual manufacturer, and there were rude surprises when major manufacturers decided not to run a give type (permanent or temporary) and instead bought unmarked tubes from a competitor and mark them as theirs.? We learned to discern details of internal and external construction as a clue to this sort of substitution.
So since we can't really count on the brand name, how would a commercial PA designer approach this:
1.? First match tubes by internal construction details that give away the actual factory:? mica shapes, plate contours, grid leads and welding.
2.? Among the most similar I would want to first match by transconductance using a mutual conductance tester.? If the anode current change for a given grid change matches they will share the load on a large signal basis.
3.? Last I would match by idle current, so they start at similar currents and hence will track each other for best load sharing and linearity.
My opinion, but based on actual experience with many thousands of tubes, YMMV.
______________________________________________________________
Clyde Washburn, K2UE
ClydeWashburn1@... <mailto:ClydeWashburn1@...>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
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On Sun, Mar 24, 2024 at 7:56?PM Richard Knoppow < 1oldlens1@...> wrote: ? ? It seems to me that the Tube Collector's group may have information
on how to distinguish the actual manufacturer, done by means of
construction, as you point out, and sometimes by markings. Some of the
markings may be subtle. I am not sure if this stuff is on their web site
or is available to non-members.
On 3/24/2024 1:56 PM, Clyde K2UE wrote:
> I had the good fortune to spend a good part of my working years as an RF
> Engineer at RFCOM and Scientific Radio Systems, and designed and
> supported commercial SSB gear with both "transmitting tubes" (6146,
> 8122, 3-400Z, 3-100Z, etc) and sweep tubes.? One of the things you have
> to do in a commercial manufacturing environment is evaluate and approve
> vendor changes, including tubes.? One of the first things you learn is
> that the name stenciled on the tube is not always the actual
> manufacturer, and there were rude surprises when major manufacturers
> decided not to run a give type (permanent or temporary) and instead
> bought unmarked tubes from a competitor and mark them as theirs.? We
> learned to discern details of internal and external construction as a
> clue to this sort of substitution.
>
> So since we can't really count on the brand name, how would a commercial
> PA designer approach this:
> 1.? First match tubes by internal construction details that give away
> the actual factory:? mica shapes, plate contours, grid leads and welding.
> 2.? Among the most similar I would want to first match by
> transconductance using a mutual conductance tester.? If the anode
> current change for a given grid change matches they will share the load
> on a large signal basis.
> 3.? Last I would match by idle current, so they start at similar
> currents and hence will track each other for best load sharing and
> linearity.
>
> My opinion, but based on actual experience with many thousands of tubes,
> YMMV.
>
> ______________________________________________________________
> Clyde Washburn, K2UE
> ClydeWashburn1@... <mailto:ClydeWashburn1@...>
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
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Rob Sherwood
David