CurtPalme.com Home Theater Forum

[cmjohnson]

Mike has made so many different versions of his mods that you can't say exactly what's going on with his mods in any specific terms
unless you address a specific modded board.

But in general he's upgrading ampliifier stages and improving the quality of the power supply voltages to those stages, and enhancing bandwidth thru a combination of replacing amplifier ICs and related components with higher quality components.
Component values are also adjusted to increase bandwidth.

On some boards, it's obvious he's adding more DC power filtering.

That's not black paint, it's black epoxy. On some chips that he replaces, he even removes the manufacturer's markings so
you'd have to guess what chip he ended up using.

[greg9518lc]

[cmjohnson]

Could you possibly just be a LITTLE bit more precise, please?

Let me cite an example:


"I have found by testing many boards that all of my best performing boards with LUG tubes came from the 50-2038-01P Issue 1 board type. Not every board of this type is that great. No top performing boards with other part numbers have been found."

Something like that. Something very clear, very specific, and tells people which boards to START looking at. Some real actual
searchable data. THAT is what is needed.


Just off the top of my head, I know that there are boards in type series 2000, 2005, 2013, 2038, 2039, and the newer 2040 and 21771 types. I'm fairly sure the OLD boards, the 2013 and below series boards with the two metal can transistors, are out of the running. But the other types are the ones most likely to be found today and we need to know which ones are most promising
and are at least candidates for repair and rebuilding if not modification.

[gjaky]

[jbltecnicspro]

Honestly - a Spring 2017 meet I would be down for. I've never done a CRT meet before and would love to get in on it.

[greg9518lc]

Preferred lug boards stock[img][/img]

[greg9518lc]

[Curt Palme]

Greg, what do you mean the other boards are 'sh*t'? While I've worked on dozens of Marquee neck boards and repaired them, I haven't seen quality or performance vary between boards as radically as you say they do. I'm happy to spin this off into a different thread if you want, we're sort of off topic here.
First off, I can't see neck boards affecting focus. Do you mean sharpness? I can see some of the older Motorola transistors causing issues, in fact they were a root cause of the significant streaking in many cases, but some better precision as to the issues as CM says would really help here..

[Curt Palme]

Greg, what do you mean the other boards are 'sh*t'? While I've worked on dozens of Marquee neck boards and repaired them, I haven't seen quality or performance vary between boards as radically as you say they do. I'm happy to spin this off into a different thread if you want, we're sort of off topic here.
First off, I can't see neck boards affecting focus. Do you mean sharpness? I can see some of the older Motorola transistors causing issues, in fact they were a root cause of the significant streaking in many cases, but some better precision as to the issues as CM says would really help here..

[cmjohnson]

See what I'm talking about, regarding a lack of information?

So there's an unlabelled photograph of PART of a circuit board to look at. Who here knows what they're seeing?

I just so happen to have ONE matching board, a VDC made 50-270340-01 board here, also identified by VDC's part number 65518-01, so I can tell that's what it is, but my board doesn't have that added resistor. Since the photo isn't even of the WHOLE board, I can't TELL if there are any other changes made referenced to my board.


Now, the idea that a Tse (Scott Edwards) designed 0340 type neck board has superior video bandwidth to a 2038/2039 card
is absolutely ludicrous, and that's what Scott himself has said, both here on this forum and to me personally. These "new" cards were made strictly because the Motorola MRF548 and MRF549 power transistors became UNAVIALABLE. They are NOT better bandwidth video amp cards, in fact as per Scott's own comments he says they're "good enough for our simulation customers" but in no way are they better, or even equal to, the 2038 and 2039 type cards. The power transistors used on these newer cards do not have the bandwidth or power delivery capacity and Scott told me that at high IRE levels (much above 60 contrast in a normal setting) you can expect them to stop tracking correctly.


I'm going to go with the considered opinion of a very experienced professional electronic engineer who DESIGNS CRT video projector circuits including these cards.

Now, Curt, please do note, focus potential is very much affected by how all the electron gun elements are connected and controlled, and as is evident, they ALL are connected thru the neck card, so it IS possible that in fact these newer cards could be accidentally very sharp in terms of being able to resolve a small spot size and scan line as they may simply have support circuitry connecting to all electron gun elements including G1, G2, and G3 in the case of LUG tubes, which, whether by accident or design, is more optimal for best focus than what is present on the older cards.

That being POSSIBLE, I also specifically asked Scott if he made any design change to tailor the "new" (remember, these were designed about 10 years ago) cards for more optimal control of the grids. He replied to me that he did not have any such intent in mind when he designed these cards. He pretty much just copied the existing circuitry as it pertains to control of G1, G2, and G3 for LUGs.

IF these are in fact sharper in terms of focus, then the two most likely reasons for that is (A) these cards are not less than 10 years newer and thus have that much less component ageing and drifting to work against them, and (B), it's just a happy accident of the design. Something in the layout of the card may optimize circuit constants, as a supposition.

So let us establish, for certain, that there is a difference between sharpness of focus (electron beam spot size) and resolution capacity (ability of the electron beam to be modulated at a high rate and achieve a target MTF value over a time constant, expressed as a length of scan line on the screen.) and one is NOT the same as the other.

Breaking it down to the essentials, ultimately there are just THREE essential factors at play: Intrinsic sharpness/focus of the system, video system bandwidth, and modulation. (Greyscale tracking.) Intrinsic sharpness is a SEPARATE issue of its own,
while bandwidth and greyscale tracking are inseparably related.

To properly evaluate any video card, you must independently evaluate focus apart from bandwidth and greyscale tracking. They are completely different, and UNRELATED, systems, aside from the fact that they can all be affected by different portions of the same video neck board.


So, YES, it is possible that the newer cards may yield a sharper beam spot. But that does not mean they'll RESOLVE better.

And in fact, it may simply be that your older 2038/2039 cards are the victims of component ageing and can be refreshed if the aged components can be identified and replaced.

In fact I have a pretty good idea of how to do that. Replace all the yellow surface mounted tantalum capacitors with fresh ones of the same values, and replace the reservoir electrolytics, which everybody sort of knows about, but don't go crazy on making them bigger or raising their rated voltage. They only run on 85 volt rails and if you use 105c rated capacitors rated for 100 volts at the original 22 µF values then the caps will last for their rated lifespan. While going to a 150 or 160 volt rating is considered desirable by some people, no responsible electrical engineer will tell you that this is necessary or that it is by itself going to improve performance of the circuit.

Tantalum capacitors do age. Their value changes as they age. Same applies, of course, to aluminum electrolytics. But while changing the electrolytics is commonplace, who bothers to change out the tants? Do it, and I predict the circuit will run a bit better. And of course, check for ring cracks and evidence of overheating at the solder connections of the two big power resistors.


Techno-diatribe completed.

[greg9518lc]

Insults on poor quality control in the fact these boards were designed to work for
lugs not be used in Hometheater and any type of picture quality. So when it takes
many lug neck boards to make 1 good set am I hurting VDC feelings?

[Curt Palme]

See Greg, you're throwing insults again, both at VDC and myself.

[Curt Palme]

See Greg, you're throwing insults again, both at VDC and myself.

[jbmeyer13]

[greg9518lc]

Voldermort who can't be mentioned has around 75 neckcards and I have 36 and have been matching sets up
for Gijaky's mods so they are uniform and the same every time everytime. Here is a pic of a few more.[img][/img]So we believe the sets must match and have excellent focus and
linearity before the boards are modded. I think Voldermort has a pretty good idea to fine tune a set of neck cards.

Curt sorry if I ranted and a little sore but still waiting on my refund and parts from MP and sparking interest that
there are other options out there hence this new title change.

[cmjohnson]

Incidentally, I think that anyone who cares to investigate deeply will find that the largest variance between neck cards of the same type
will be due to the fact that the power transistors were NEVER matched to each other. So there is a significant variance from one card to the next.

I'm sure several people have seen this. If you replace a neck card you almost always will have a noticeable color imbalance and will have to recalibrate because of it.


Now, if this was 1997, you could buy trays full of new transistors and match up sets of them and when you have nine matched pairs that all are matched to the same values, you could be assured of having the best base to start from. But that is impractical and even if you have boxes full
of spare cards with good transistors, it'd be a huge amount of work and there's always a chance of breaking the leads off the transistors during
removal. They are rather delicate.

[draganm]

[mp20748]

[mp20748]

Oh, I forgot to mention that they changed the small electrolytics on them. Some boards have the shorter size (mini0 caps. with the others having the more standard taller caps

[cmjohnson]

I just want to add here that I am always willing to purchase ANY....ANY....surplus Marquee neck boards as long as they have usable Motorola power transistors on them. If it has even ONE of the MRF 548 transistors on it and it's not apparently damaged, I can use it.

I have a pile of 2038 and 2039 neck cards that are perfect working cards other than the fact that some of them were previously robbed of those transistors before I got them.

So if you have spare Marquee neck cards, I'm buying. ANY version that has the Motorola transistors.

[greg9518lc]

[draganm]