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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Thu Feb 25, 2016 4:57 pm Post subject: |
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| cmjohnson wrote: | I wouldn't really expect anyone to read my previous wall of text. It's mostly there to remind ME of what may be possible with these tubes.
The usage of expensive wet tantalum capacitors will be limited to replacement or augmentation of electrolytic capacitors in critical circuit areas where they directly affect the slew rate of the related amplifiers and of the power supply. Basically, the electrolytics in the non-potted section of the HVPS and directly down the video amplifier chain. The two 100V electrolytics on a neck card would be replaced with wet tants, to give an important example. |
I read it. It's a good tech head read.
What's the cost of Wet caps vs Dry?
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cmjohnson
Joined: 03 Apr 2006
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Location: Buried under G90s
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| Posted: Thu Feb 25, 2016 5:07 pm Post subject: |
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I need EIGHT 20 uf 100v rated wet tants for the HVPS mod.
Typical cost of these caps is about 125 dollars EACH.
If I do that mod it's going to cost me a grand.
The rest isn't so alarmingly expensive.
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cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
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| Posted: Thu Feb 25, 2016 5:19 pm Post subject: |
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I have purchased a set of Cine 9 focus yokes. They will be trialled in the monster in the making.
I have made inquiries about getting the Barco deflection and convergence coils as well. Reason: The full stack off the Barco tube
is guaranteed to place the focus yoke right where it should be. I BELIEVE that the combination of the Barco deflection yoke and convergence yoke is shorter than the Marquee deflection and convergence yokes.
If they're sufficiently electrically compatible, and I don't see why they wouldn't be, as tube requirements dictate magnetics design,
then I may be running a complete Cine 9 magnetic stack on these tubes.
I will then have to call the projector a Barquee. Cine 9500LCHR.
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Thu Feb 25, 2016 6:32 pm Post subject: |
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| cmjohnson wrote: | I need EIGHT 20 uf 100v rated wet tants for the HVPS mod.
Typical cost of these caps is about 125 dollars EACH.
If I do that mod it's going to cost me a grand.
The rest isn't so alarmingly expensive. |
I am curious how much better a wet tant capacitor is compared to film capacitor, which are much cheaper
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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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cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
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| Posted: Thu Feb 25, 2016 6:39 pm Post subject: |
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It comes down to ESR ratings. What is the actual ESR value of two capacitors being evaluated for the application?
In this case, imagine a black raster with a single full brightness pixel in the middle of it. Now consider this: The ENTIRE purpose of the projector is to direct the energy of the power supply to the screen in the form of visible light.
The power supply, and the whole video chain, have to go from zero to 100 and back to zero in the space of a single pixel.
Without streaking, smearing, or missing.
THAT requires a massive slew rate and very precise ability to deliver ALL the power, on time and on target, and turn it on and off like a true square wave.
That's why we want the lowest ESR parts we can get, so power delivery is INSTANT, and so is power cutoff.
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Thu Feb 25, 2016 6:46 pm Post subject: |
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I am under the impressiont that film capacitors have lower ESR than any polarized capacitor.
_________________
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: Thu Feb 25, 2016 7:04 pm Post subject: |
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| gjaky wrote: | | cmjohnson wrote: | I need EIGHT 20 uf 100v rated wet tants for the HVPS mod.
Typical cost of these caps is about 125 dollars EACH.
If I do that mod it's going to cost me a grand.
The rest isn't so alarmingly expensive. |
I am curious how much better a wet tant capacitor is compared to film capacitor, which are much cheaper |
Since you asked, I'll try and answer from my perspective and experience on this.
I've been tweaking stuff for a long time, and that also includes audio gear. I've also had a few boards sent to me that had wet tants on them. I have some wet tants in my stash. That also mean I have some experience with them first hand.
Not really sure why there has been so much discussion on them, and how that simply changing caps or adding them to a circuit could really make for the super claims that has been said over the years. My thought on wet tants would be that the only real difference I could imagine them making to any circuit, it would have to be in Audio Circuits, because video is a whole different story when it come to caps. There are some caps that are special to a video circuit and film (high frequency) is one of them among a few others. Tants should never be used in switching power supplies, nor power rails where there is aggressive switching pulses from a SMPS. They are better suited for Pull-up or de-coupling purposes in video circuits (I also use tants). Now this is all from my more than 20 years experience.
However, if the tants work well on the video boards of the Marquee that's fine. I only have two problems with this if the results are really noticeable beyond the same value of a regular cap. Putting a 20 uf cap on a Marquee video board could only offer 20uf of filtering or usefulness. Because of the noise coming out of the LVPS and other boards and circuits in the projector, 20uf is in no way enough capacitance. (2) Considering the real problem area in these video chains, I'm having hard time understanding how simply changing caps have corrected them all.
Anyway. I've tried to stay away from this, but thought I would only give an opinion based on my experience. I would however think if the cap does have any special powers the real test would be the +/- 14 volt rail in the Marquee. I've tried everything to lower that aggressive noise on those rails, and I also use inductors. So far I've yet to find a cap or inductor that really lowers the noise to the level I've been hoping for. If there is such a thing as a magic cap, it should have worked there. So far only a regulator IC has gotten good results.
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Thu Feb 25, 2016 8:11 pm Post subject: |
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Hi,
Have You ever tried OS-CONs?
Regards,
barclay66
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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: Thu Feb 25, 2016 8:59 pm Post subject: |
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| barclay66 wrote: | Hi,
Have You ever tried OS-CONs?
Regards,
barclay66 |
That was one of the other caps I was thinking of when I mentioned the film. It is
without doubt the best of them all. An 100uf Oscon works as well as an 470uf in comparison. I like them bunch, and used to use them a lot. They're not cheap, but they are the best stop gap measure when trying to lower switching frequencies. I never wanted to leave them on the 14 volt rail, where they did help best, but for the ranges they come in, they would not be the best solution. I've made a hobby out of running down noise and lowering iti
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cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
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| Posted: Thu Feb 25, 2016 10:18 pm Post subject: |
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My (tentative) decision to experiment with tantalum capacitor modifications is based on Chris Stephens' modifications and results, with the Reference Imaging CinePro 9x Elite which was his baby.
That doesn't mean that it's the ultimate mod package but it's certainly a proven starting point. Albeit an expensive one.
I'll consider other options before spending a thousand bucks to mod a single power supply, though!
Near as I can tell, all the mods that make the most difference concern just two things: Reducing noise in the system and boosting end-to-end video bandwidth as needed.
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cmjohnson
Joined: 03 Apr 2006
Posts: 5180
Location: Buried under G90s
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| Posted: Fri Feb 26, 2016 2:20 pm Post subject: |
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I like the idea of using os-cons, I mean, why wouldn't I like caps with an ESR measured in milliohms, but they seem to not offer an axial lead style or a 100 volt rating. Which means stacking up even more caps. Actually making a daughter board for the caps instead, at least for the HVPS mod.
Still it's cost effective and well worth considering. For 55 bucks I could buy a bag of a hundred oscons (22 uF, 35v rated) and breadboard up an effective equivalent for the wet tant mod and still have spent less than half the cost of one wet tant.
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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: Fri Feb 26, 2016 4:17 pm Post subject: |
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| cmjohnson wrote: | I like the idea of using os-cons, I mean, why wouldn't I like caps with an ESR measured in milliohms, but they seem to not offer an axial lead style or a 100 volt rating. Which means stacking up even more caps. Actually making a daughter board for the caps instead, at least for the HVPS mod.
Still it's cost effective and well worth considering. For 55 bucks I could buy a bag of a hundred oscons (22 uF, 35v rated) and breadboard up an effective equivalent for the wet tant mod and still have spent less than half the cost of one wet tant. |
I understand what you're saying. But try and understand that for myself and some others who have put thousands of hours into this, you'll have to show a need for such special cap, at least in comparison that they actually do offer better end results.
I was saying that I wasn't able to find a difference when comparing. But that does not mean that a normal $0.05 tant would yield the same results. There has to be a difference, and that is why they cost so much. But again you're going to have taught time convincing me that they would work wonders in video circuits.
Here is why. Large caps needed in video would be the power supply or rail only, and they're still not really large. The problem area in video stages always seems to be frequency related (not ripple). So of course, with that large tants or even electrolytes would not apply here, because large usually means more or higher capacitance. Meaning larger values could be important on the power rails only... But the main and real performance improvements are usually related to the smaller caps in the decoupling and circuits like that. Because the beyond basic filtering is to tame oscillation and lower noise in the video chain (high frequencies). That within itself is almost an art. My most used scope on this has both frequency counter and PP meter built in at the press of a botton it uses the same probe for the scope. So when I'm done with a stage or circuit, you'll see my work as the addition of both caps and inductors. Sometime the caps are a group of various small values all in parrelel. And sometimes you'll see inductors where pull-up resistors use to be. And I can go one to even putting Low pass series filters after a stage to chop off the higher not necessary junk. These of course are a few of the Techniques I've developed over the years. I'm saying all this, to say that from my experience, you'll need to go beyond caps only most of the time. And I use a lot of stuff to figure this all out.
So if the wet tants work for you fine. But with all the smaller things I've had to do that';s not only cap related, I'm not easy to convince on them. I would say for the 85volt rails in the Marquee they could be a hit. But I seriously doubt anywhere else.
if ever up this was stop in and let me show you how and what I do to make things happen..
Last edited by mp20748 on Fri Feb 26, 2016 4:31 pm; edited 1 time in total
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cmjohnson
Joined: 03 Apr 2006
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| Posted: Fri Feb 26, 2016 4:29 pm Post subject: |
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Thanks, Mike.
I realize that noise control will involve filtering on several (maybe all) DC rails, and if I'm not mistaken the 02P modded VIM in my projector (your work) has added filtration right on it.
That sort of thing is certainly on the "to do" list but it's not the top item on the list.
I want to START with the Chris Stephens mod and go from there, one board at a time.
Actually, I'll start with (once the Barco magnetics arrive) adapting the Barco magnetics to work in the Marquee chassis
on the Lexel tubes, set up the tube assemblies, drop them into the test projector, and establish a baseline for performance.
With a little luck I will be able to do MTF measurements and get some real hard data for comparison's sake.
Incidentally, Scott (Tse) says that the MTF value that rates as "pass" for a CRT projector is 15 percent, as per VDC's specs.
So if you can get an MTF of 15 percent on a given resolution, then you can say that it RESOLVES that image.
I will use that 15 percent value as my minimum performance criteria. Start out at lower resolutions and work my way up
until I run out of the ability to generate higher resolution test patterns, or drop below 15 percent.
There's a fair chance that I'll run out of displayable resolutions FIRST. 2048x1536, qxga, is currently my top end limit but
I'm seriously thinking about picking up a generator that goes past that. Another Sencore. They're cheap these days.
Maybe somethign else.
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Fri Feb 26, 2016 4:33 pm Post subject: |
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| mp20748 wrote: | | cmjohnson wrote: | I like the idea of using os-cons, I mean, why wouldn't I like caps with an ESR measured in milliohms, but they seem to not offer an axial lead style or a 100 volt rating. Which means stacking up even more caps. Actually making a daughter board for the caps instead, at least for the HVPS mod.
Still it's cost effective and well worth considering. For 55 bucks I could buy a bag of a hundred oscons (22 uF, 35v rated) and breadboard up an effective equivalent for the wet tant mod and still have spent less than half the cost of one wet tant. |
I understand what you're saying. But try and understand that for myself and some others who have put thousands of hours into this, you'll have to show a need for such special cap, at least in comparison that they actually do offer better end results.
I was saying that I wasn't able to find a difference when comparing. But that does not mean that a normal $0.05 tant would yield the same results. There has to be a difference, and that is why they cost so much. But again you're going to have taught time convincing me that they would work wonders in video circuits.
Here is why. Large caps in video be it supply or stages, the problem area also seems to be frequency related. So of course, with that large tants or even electrolytes would not apply here, because large usually means more or hgigher capacitance. And larger value could be important on the power rails only. But the main and real performance improvements are usually related to the smaller caps in the decoupling and circuit like that. Because the beyond basic filtering is to tame oscillation and lower noise in the video chain. That within itself is almost an art. My most used scope on this has both frequency counter and PP meter built in at the press of a botton it uses the same probe for the scope. So when I'n done with a stage or circuit, you'll see my work as the addition of both caps and inductors. Sometime the caps are a group of various small values all in parrelel. And sometimes you'll see inductor where pull-up resistors use to be. And I can go one to even putting Low pass series filters after a stage to chop off the higher not necessary junk. These of course are Techniques I've developed ove the years. I'm saying all this, to say that from my experience, you'll need to go beyond caps only most of the time. And I use a lot of stuff to figure this all out.
So if the wet tants work for you fine. But with all the smaller things I've had to do that';s not only cap related, I'm not easy to convince on them. I would say for the 85volt rails in the Marquee they could be a hit. But I seriously doubt anywhere else.
if ever up this was stop in and let me show you how and what I do to make things happen.. |
For me the Chris Stevens HVPS mod is which is somewhat contradictionary.
You buy a bounch of crazy expensive LOW ESR wet tant caps, and what you do? Put seven of them in series... that will yeld seven times of ESR (compared to the single capacitor) for the capacitor bank, seventh of capacitance at the of seven times money. Great deal!
Think about this:
A 20uF 60V wet tant has an ESR of ~4 Ohm (for $50), a 10uF 63V film cap has 0.1 Ohm ESR (for $2)
_________________
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: Fri Feb 26, 2016 4:42 pm Post subject: |
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| gjaky wrote: |
For me the Chris Stevens HVPS mod is which is somewhat contradictionary.
You buy a bounch of crazy expensive LOW ESR wet tant caps, and what you do? Put seven of them in series... that will yeld seven times of ESR (compared to the single capacitor) for the capacitor bank, seventh of capacitance at the of seven times money. Great deal!
Think about this:
A 20uF 60V wet tant has an ESR of ~4 Ohm (for $50), a 10uF 63V film cap has 0.1 Ohm ESR (for $2) |
Good point there gjaky. I've always wondered how the projector even turned on with all those caps in it. If you put higher value caps in the LVPS, it shuts down or won't fire up - that has been my experience, so it told me a long time ago, it's Smart
Last edited by mp20748 on Fri Feb 26, 2016 5:30 pm; edited 1 time in total
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cmjohnson
Joined: 03 Apr 2006
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| Posted: Fri Feb 26, 2016 5:29 pm Post subject: |
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Actually it's 4 caps in series, going over each of two different capacitors.
The reason for running them in series is because the voltage requirement is too high for one wet tant to handle.
I've never seen one rated higher than 150 volts and that part of the circuit needs a 600 volt rated part.
This implies that if it creates a worthwhile improvement, then the ESR on the stock cap is not very good at all.
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gjaky
Joined: 05 Jun 2010
Posts: 2802
Location: Budapest, Hungary
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| Posted: Fri Feb 26, 2016 5:58 pm Post subject: |
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| cmjohnson wrote: | Actually it's 4 caps in series, going over each of two different capacitors.
The reason for running them in series is because the voltage requirement is too high for one wet tant to handle.
I've never seen one rated higher than 150 volts and that part of the circuit needs a 600 volt rated part.
This implies that if it creates a worthwhile improvement, then the ESR on the stock cap is not very good at all. |
I have to disagree here, I think the only advantage there is the extra capacitance. I can't imagine four caps in series overperform this ESR...
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_________________
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: Fri Feb 26, 2016 6:13 pm Post subject: |
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| cmjohnson wrote: | Actually it's 4 caps in series, going over each of two different capacitors.
The reason for running them in series is because the voltage requirement is too high for one wet tant to handle.
I've never seen one rated higher than 150 volts and that part of the circuit needs a 600 volt rated part.
This implies that if it creates a worthwhile improvement, then the ESR on the stock cap is not very good at all. |
I think he made some good points in what he posted. But I'll go further, because you mentioned previously that you needed 8 each for the HVPS alone. You list the cost of each of those 20uf 100 vdc wet tants to be $125.00 each. for a total of $1000.00
Going back on what I had said previously, what would be the reason for putting those caps in there, and what would be the end result from this upgrade? I know where you want to put them. The two 0.47 uf 600vdc capacitors that filter the 390vdc supply for the HVPS. I like to first add that whenever you see that small of a value capacitance as the filters for a device or circuit, higher capacitance filtering is not needed or necessary there. That and include the dual inductors in both negative and positive, also indicates a filter network. As such, its goal is for a specific frequency window or range of filtering. If more would be needed, it would be based on my experience either similar value caps both above and below that listed value.
Something like this:
In parrelel to each cap, one each or any combination of the following: 0.1, 0.27, 0.68, 1uf of same class of cap
Adding capacitance to far out of that range would normally not be necessary.
The magic in working with caps is finding out the right values necessary to better filter the device or stage. And that usually would have an end result of finding the right GROUP of caps to add. I know you see and read about it a lot, but in these circuits, the improvements are not made when higher cap values are used. It's usually made when similar of smaller values are made to target the frequencies of concern. We're so used to shot-gun cap upgrades, when simply adding more capacitance make things appear better. But I had learned over the years to develope a technique that would deal more with the un-wanted frequencies involved.
The HVPS is fine from my testing. The only problem area I've found was the G2 feeds to the neck boards. I have a fix for that one I can share with you and should be able to do it for less than $15.00 - and the end results would be quite noticeable.
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Fri Feb 26, 2016 9:21 pm Post subject: |
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| cmjohnson wrote: | | For 55 bucks I could buy a bag of a hundred oscons (22 uF, 35v rated) and breadboard up an effective equivalent for the wet tant mod and still have spent less than half the cost of one wet tant. |
Search for 262305636729 on eBay. There You can get hundreds of 47µF/25V for a fraction of this price. Reliable seller (I've ordered several times over there)...
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barclay66
Joined: 27 Jun 2011
Posts: 1304
Location: Germany
TV/Projector: Marquee 9500 Ultra
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| Posted: Fri Feb 26, 2016 9:27 pm Post subject: |
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| mp20748 wrote: | | The only problem area I've found was the G2 feeds to the neck boards. I have a fix for that one I can share with you and should be able to do it for less than $15.00 - and the end results would be quite noticeable. |
Hi,
That would be interesting. Please share!
Regards,
barclay66
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