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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sun Feb 21, 2016 3:01 am Post subject: |
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| redfox001 wrote: | In this thread you have been cought several times. Perhaps we are not as stupid as your average type of customer  |
Lol... yeah, I really need to figure out how to modify a CRT projector. But until I'm able to reach that plateau with the rest of y'all. I'll leave a shot for you that's 1920X1080P, but would like to bring to your attention that it's 1080P bandwidth is not -3db. I just want to say that my goal is a flat bandwidth, so to some degree I still have a ways to go..
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redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
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| Posted: Sun Feb 21, 2016 6:51 am Post subject: |
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Can't believe that we can not report this spam to a moderator.
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701s->runco933->8500ultra->cinemax->9500mp->919 splitpack + cinemax
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Sun Feb 21, 2016 8:54 am Post subject: |
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| mp20748 wrote: | | gjaky wrote: | | It'really not a mystery it's all in the datasheet: those transistors are "emitter ballasted" ones. Power RF transistors are usualy made of multiple lower power transistor tied in parallel on the same die, with emitter ballasting the emitters are tied to the terminal through a small resistor, that is very common with parallel transistors. This, however only helps to distribute the power between the transistors inside the die, especially with impedance mismatched networks. A spark still can destroy the transistor if it exceeds the maximal breakdown voltage of the transistor, and not meet the spark gap's ignition voltage, the diode sure helps then steering the currents to the supply or ground. |
Yes it is, but you still missed it....oh, and I also remove the exact same diode from the Input of the first stage on the neck boards, and never had one fail..
Now when I mentioned this to certain engineers and what/why I was doing it, they were amazed. And they also agreed with me that I shouldn't need to worry about arc failure, and as time went by, they along with myself were right about this..
And that's only one of the many tihngs that I've been able to prove the theory wrong on. But why is it, that these devices did not need that diode....I'm not asking a question here, because it's still a mystery.. |
I did not say I wouldn't remove any diode, in fact I also removed the input diode from the VNB I build for the XG too, but in this case I use two of those diodes in series by halving their capacitance and still retaining their protection purpose. Also as already stated LUGs and the other "modern" tubes have less tube capacitance anyway so the diode's added capacitance mean less problem too.
_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sun Feb 21, 2016 11:36 am Post subject: |
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| gjaky wrote: | | mp20748 wrote: | | gjaky wrote: | | It'really not a mystery it's all in the datasheet: those transistors are "emitter ballasted" ones. Power RF transistors are usualy made of multiple lower power transistor tied in parallel on the same die, with emitter ballasting the emitters are tied to the terminal through a small resistor, that is very common with parallel transistors. This, however only helps to distribute the power between the transistors inside the die, especially with impedance mismatched networks. A spark still can destroy the transistor if it exceeds the maximal breakdown voltage of the transistor, and not meet the spark gap's ignition voltage, the diode sure helps then steering the currents to the supply or ground. |
Yes it is, but you still missed it....oh, and I also remove the exact same diode from the Input of the first stage on the neck boards, and never had one fail..
Now when I mentioned this to certain engineers and what/why I was doing it, they were amazed. And they also agreed with me that I shouldn't need to worry about arc failure, and as time went by, they along with myself were right about this..
And that's only one of the many tihngs that I've been able to prove the theory wrong on. But why is it, that these devices did not need that diode....I'm not asking a question here, because it's still a mystery.. |
I did not say I wouldn't remove any diode, in fact I also removed the input diode from the VNB I build for the XG too, but in this case I use two of those diodes in series by halving their capacitance and still retaining their protection purpose. Also as already stated LUGs and the other "modern" tubes have less tube capacitance anyway so the diode's added capacitance mean less problem too. |
Ok, I'll give you a peep into my logic on this, since you somewhat agree with what I've been doing and have also done similar. But in your response did not attack or come across as telling me I'm wrong about this. So let's see if you agree, because after all, how can you dispute someone why has sound and proven end results.
Let's start with the first stage (input) of the neck board, that is directly coupled to the first stage input IC. I'll borrow a word you used "modern" -- Here's why I remove those diodes there... The modern chips have the diodes built into the chip already. So adding an additional diode to the input also increases capacitance there... This may be fine for lower scan rates and lower bandwidth expectation, but if your goal is SPEED and Bandwidth performance. Leaving or putting that diode there goes against the goal. And to add, something else happens when you double up on diodes on the input, but for the sake of time and writing I'll skip that one.
Now for the RF Power transistors. I had just so happened to remember what they taught us when I ws in Radio School in the military. Both Tube RF power final stages and transistor RF final stages were exposed to danger from the final stage antenna. That antenna put all kinds of static and other electrical charges directly into the final RF stage. This was not a bigger problem for the tube transmitters as it was for the transistor designs. So a true RF final transistor would have already protection from this.... and following the general on the shelf rule for this transistor was not necessary, though some of the later RF modules require series diodes be added after the module. I can explain that further, but hands getting tired.
The Motorola's are RF transistors being used as video finals (Brilliant), but there is an added benefit if you respect that they are built to protect themselves, therefore adding diodes there would GREATLY increase capacitance.
For the standard transistor, there is a way to both protect and keep the capacitance low, and that is what I'm doing on my newer VDC neck boards..
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Sun Feb 21, 2016 11:51 am Post subject: |
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| mp20748 wrote: |
Now for the RF Power transistors. I had just so happened to remember what they taught us when I ws in Radio School in the military. Both Tube RF power final stages and transistor RF final stages were exposed to danger from the final stage antenna. That antenna put all kinds of static and other electrical charges directly into the final RF stage. This was not a bigger problem for the tube transmitters as it was for the transistor designs. So a true RF final transistor would have already protection from this.... and following the general on the shelf rule for this transistor was not necessary, though some of the later RF modules require series diodes be added after the module. I can explain that further, but hands getting tired.
The Motorola's are RF transistors being used as video finals (Brilliant), but there is an added benefit if you respect that they are built to protect themselves, therefore adding diodes there would GREATLY increase capacitance.
For the standard transistor, there is a way to both protect and keep the capacitance low, and that is what I'm doing on my newer VDC neck boards.. |
I have no knowledge about these details of Motorola RF transistors, so I really can't comment if this is a valid point or not.
On the other hand the "protection" diodes themselves aren't making miracles either, in NEC projectors they trip time-to time, but since the diode itself sometimes get shorted from the spark then it has little effect in protecting the end stage, since it either ties it to ground or vcc depending on which diode got shorted. So the output transistor will fail eventually from simple overload...
_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sun Feb 21, 2016 11:51 am Post subject: |
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.. ..Lol
Doing your usual again, shooting first then later finding that the target was behind you..
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sun Feb 21, 2016 11:56 am Post subject: |
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| gjaky wrote: | | so the diode's added capacitance mean less problem too. |
Let me address this one separately: This may be true at lower scan rates and low-speed requirements, which has been the case with the LUG tubes in every one of the known applications because they did not have an HIGH BANDWIDTH obligation all up until recently.
But for any bandwidth requirement above 1280X1024, the lowest capacitance is critical for best SPEED. And that makes sense why the LUG has the capacitance pin (HK).
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the dude
Joined: 11 Sep 2013
Posts: 179
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| Posted: Sun Feb 21, 2016 11:57 am Post subject: |
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| Quote: | | And to add, something else happens when you double up on diodes on the input, but for the sake of time and writing I'll skip that one. |
As usual something vague... What should happen? 0.7V extra forward voltage per diode? This will give protection anyway.
BTW, we are talking about the output of the video amp where arcing can take place. I agree that you might remove the diodes from the input stages. Op Amps are cheap to replace and overvoltage in the internal video chain is nothing to really worry about. I removed almost any diodes from the switcher. I don't need input switching and due to short cable and only the fury connected input protection is also not required.
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redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
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| Posted: Sun Feb 21, 2016 11:57 am Post subject: |
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Look this is said in the clc449 documentation. Yes there are diodes but still protection needed. In the equivalent cirquit of the el5166 that mike uses only those same diodes as in the clc449 are shown.
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Input ESD diodes are present on all connected pins for protection from static voltage damage. For a signal that may exceed the supply voltages, we recommend using diode clamps at the amplifier’s input to limit the signals to less than the supply voltages.
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sun Feb 21, 2016 12:01 pm Post subject: |
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| the dude wrote: | | As usual something vague... What should happen? 0.7V extra forward voltage per diode? This will give protection anyway |
You're not ready for the explanation there and it's proven here:
| Quote: | | BTW, we are talking about the output of the video amp where arcing can take place |
Did you actually read what I said about the output?
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sun Feb 21, 2016 12:03 pm Post subject: |
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| redfox001 wrote: | Look this is said in the clc449 documentation. Yes there are diodes but still protection needed. In the equivalent cirquit of the el5166 that mike uses only those same diodes as in the clc449 are shown.
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Input ESD diodes are present on all connected pins for protection from static voltage damage. For a signal that may exceed the supply voltages, we recommend using diode clamps at the amplifier’s input to limit the signals to less than the supply voltages.
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Oh I see you found the target..
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redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
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| Posted: Sun Feb 21, 2016 12:14 pm Post subject: |
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I just show that the el5166 is build the same as the clc449 so your suggestion that the modern opamp does not need them is false. It is still a risk to take them away that is all.
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the dude
Joined: 11 Sep 2013
Posts: 179
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| Posted: Sun Feb 21, 2016 12:15 pm Post subject: |
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| Quote: | | Did you actually read what I said about the output? |
Yes, you said the RF transistors are arc proof. I didn't comment that, just to be kind. The MRF 548 has no internal protection, at least it is not mentioned in the datasheet. These devices are not avalance rated, so you can expect them to be destroyed when exceeding the breakdown voltage.
And internal protection diodes or avalance ratings are ALWAYS mentioned in datasheets.
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sun Feb 21, 2016 12:17 pm Post subject: |
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| redfox001 wrote: | | I just show that the el5166 is build the same as the clc449 so your suggestion that the modern opamp does not need them is false. It is still a risk to take them away that is all. |
Why do you ALWAYS speak on something without knowing first what you're talking about. At some point you need to realize you're over your head here...
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redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
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| Posted: Sun Feb 21, 2016 12:20 pm Post subject: |
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Why do you always play on the person when you are caught on a lie?
I estimate you add 10% truth to 90% lies. And those are educated estimates
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sun Feb 21, 2016 12:24 pm Post subject: |
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| the dude wrote: | | Quote: | | Did you actually read what I said about the output? |
Yes, you said the RF transistors are arc proof. I didn't comment that, just to be kind. The MRF 548 has no internal protection, at least it is not mentioned in the datasheet. These devices are not avalance rated, so you can expect them to be destroyed when exceeding the breakdown voltage.
And internal protection diodes or avalance ratings are ALWAYS mentioned in datasheets. |
So with you knowing how aggressive the ARC voltages would be on any solid state device there, can you tell me WHY none of these transistors have failed from ARC damage?
Actually, and based on one of the engineers, those transistors would be subject to failure during the tubes initial turn-on and all during operation. Yet, I've been running them in a many boards for more than ten years, and the only failures have been Q13, which would fail from heat damage.
Again, we are arguing Theory against 1o years of facts
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Sun Feb 21, 2016 12:24 pm Post subject: |
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| the dude wrote: | | And internal protection diodes or avalance ratings are ALWAYS mentioned in datasheets. |
2N2369 is a commonly used avalance transistor yet it was not designed in that way, therefore there is no mention about this in its datasheets.
I think we all can can settle down with that Mike is allowed to remove the diodes on his own will, and leave him at that, no one else is forced to follow him with this. if he ever experience a defective transistor due to arc it will be his problem. All happy? 
_________________
projectors in the past : NEC 6-9PG xtra, Electrohome Marquee 6-7500, NEC XG 1351 LC ( with super modified Electrohome VNB neckboard !!!)
current: VDC Marquee 9500LC
The MOD: VNB-DB, VIM-DB
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redfox001
Joined: 16 Mar 2009
Posts: 2257
Location: The Netherlands
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| Posted: Sun Feb 21, 2016 12:26 pm Post subject: |
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Yes it is boring to say the least.
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mp20748
Joined: 12 Sep 2006
Posts: 5689
Location: Maryland
TV/Projector: 9500LC Ultra / Super 02 and 03 VIM
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| Posted: Sun Feb 21, 2016 12:27 pm Post subject: |
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| redfox001 wrote: | Why do you always play on the person when you are caught on a lie?
I estimate you add 10% truth to 90% lies. And those are educated estimates |
Where is the lies..
You of all people are challenging me on things you have consistently proven you know absolutely nothing about, and you are adamant in your pursuit to be wrong consistently because you have contradicted yourself many times.
So who has been presenting lies here?
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the dude
Joined: 11 Sep 2013
Posts: 179
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| Posted: Sun Feb 21, 2016 12:31 pm Post subject: |
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| Quote: | | can you tell me WHY none of these transistors have failed from ARC damage? |
Maybe they did... these devices are made of several smaller transistors with the emitters tied together with resistors. Maybe the transistor is still functional to some degree if one of them is dead.
Yes!
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