Kleos - Dipole Line Array

[Johnloudb]

I keep wondering about a board defect causing this problem. I mean I have found shorts to ground around pads, and whose knows what stray capacitances or resistances there are on the board that aren't quite a short?

I'll measure the resistances again and see if they check out. the crossover frequency is on the dot, but maybe a resistance path that shouldn't be there is causing problems? Just just on part of the positive half cycle?

This is so weard!

[wkhanna]

You had the boards custom made to your specs, IIRC, right?

[Johnloudb]

It is only apparent near the crossover frequency too, which is a pretty low frequency. So, could a board defect really cause a problem that low a frequency? Micro diodes?

Well, look at the board again later today and maybe find something.

[Johnloudb]

You had the boards custom made to your specs, IIRC, right?

Just saw your comment. Yeah I had the boards made by expressPCB using their layout software. The board had some pads where the copper wasn't completely etched through, and caused shorts that I blew up like a fuse, after given sone helpful advice on the forum here.

Sorry, what does IIRC mean?

[wkhanna]

what does IIRC mean?

If I Recall Correctly

Just saw your comment. Yeah I had the boards made by expressPCB using their layout software. The board had some pads where the copper wasn't completely etched through, and caused shorts that I blew up like a fuse, after given sone helpful advice on the forum here.

So was the board defective?

[Johnloudb]

Yeah, I was really surprised. It shouldn't have pads shorted to the ground plane, except where I put pads connected to ground. You couldn't see the short, just a really very thin layer of metal, that didn't get etched through. I had to put some current through to blow it, and open the circuit.

[wkhanna]

Did you 'High Current' all the circuit paths on the boards?

Did you ask the supplier for a refund or replacements?

Your information is making me V suspicious of these boards.

[Hank]

I'm thinking that also. Perhaps dirty baths or insufficient tank time. I've seen lots of not-obvious-at-first PCB defects pointed out in incoming QC back in the day. Icicles, whiskers, shorts that were just like lint - so tiny. But John is not doing high freq stuff here. He has signal, so this doesn't sound like more blatant shorts. Maybe a signal trace too close to ground plane at the wrong spot, creating a tad of capacitance. Where is Sherlock when ya need him?

[Johnloudb]

Well, I think the circuit design is Okay, just because spice worked fine and my prototype worked fine. I agree with you guys that a problem with the PCB board may be causing this issue, but I can't say for sure how. My only other thought is that the caps could be damaged, but I have not solved any problems to date by replacing caps. So I have another board here, the one that had the short at the regulator output. And I'll get that ready, and test it, see if it has the same issue.

I'm going to contact express PCB as well, and see about replacement boards. It's been some time, so I'll just have to see.

[Hank]

Just send 'em photos of the defects, with an explanation of the hours you've invested in troubleshooting. Maybe send them a board and ask them to look at it under a microscope or x-ray it. Their defects have certainly caused you a big delay and wasted time.

[Johnloudb]

Just send 'em photos of the defects, with an explanation of the hours you've invested in troubleshooting. Maybe send them a board and ask them to look at it under a microscope or x-ray it. Their defects have certainly caused you a big delay and wasted time.

I've four unused boards and have found shorted pads on every one! I'm circling then with a marker and I'll send a photo. They cannot deny the problem!

[Hank]

sic 'em!

[Johnloudb]

sic 'em!

I'm on it time will tell.

School is has started today ... Impressed with my teachers. School has improved since I was their 17 years ago! Very teaching oriented and knowledgeable professors who communicate well, and care. More professional instead of amateur. Before the EE department was mostly a research oriented program ... Teaching was an afterthought. There were some very good ones but some real losers too! Systems sucked eggs!

I will do my best to stay focused and spend time on speaker as well!

[Johnloudb]

sic 'em!

New boards are on the way! Took them awhile but very thankful they are replacing them. I'm think I'm going to test the other board I have completed and see if it has the same problem with the high pass filter circuits.

[wkhanna]

Nice that they stand behind their products.

Not so nice you lost so much time.

But trouble shooting is one of the best ways to learn your craft, if not a V pleasant exercise.
.

[Johnloudb]

Nice that they stand behind their products.

Not so nice you lost so much time.

But trouble shooting is one of the best ways to learn your craft, if not a V pleasant exercise.
.

Absolutely! learned quite a bit about trouble shooting ... been a real learning experience. Though, let's have no more learning experiences with this project, please!!! Not quite there yet, but hope it goes more smoothly.

I just got to spend time on this ... that's the trick. Got the new boards but first want to find out the issue I'm having with the Low Pass filter. I've almost got the other board ready to test, I checked it out good with multi-meter and the connections look okay.

[Johnloudb]

Think I should update. I have looked at this some more and talked to my analog IC design professor about this problem awhile back. I showed him a waveform around 400Hz that looked pretty noisy, and he suggested that there was ringing and that it could oscillating and that the circuit may be unstable. Said that either the trace capacitances or my change in component values for this circuit vs. my prototype could have caused this. Changing values (scaling the values for lower impedance) does affect the the loop gain since the resistance and cap values inherent in the devices don't change as well.

But I'm more inclined to blame the PCB because the distorted waveforms of each buffer are different, the second stage always being the worst and this didn't change with me changing out JFET devices.

Okay, so still need to hook up the other board and see how that looks. I'll really try to give it a go after I finish this homework assignment due Thursday.

I want this to get done! Just wish it could finish itself oh, I'm a bad engineer, to be ...

[Hank]

Hi Jon - hang in there, man. You've got a sticky problem. I've wondered about trace capacitances on that PCB. Is there an internal ground layer, or is it just a two-sided board?

[Johnloudb]

Hi Jon - hang in there, man. You've got a sticky problem. I've wondered about trace capacitances on that PCB. Is there an internal ground layer, or is it just a two-sided board?

It's a two sided board, ground plane on top. I hate to keep this dragging, really hate it ... Hopefully can test that other board out this weekend. it is the one that had the power supply short and is still missing a PS cap I removed. Hard to get a replacement soldered in there but will get one in. If it works okay, then I think I'll just buy new parts and stuff the new boards, with the same value filter caps.

If it has the same problems I'll go back to the values I had in the prototype filter that worked. Also stuffing new boards.

Sorry for late reply ... Didn't get around to checking the message board ... Had an assignment due.

[Johnloudb]

Feels like years since I've posted here ... Been around 10 months. Glad to still see familiar people still here. Just been so focused on other life stuff!

I found that the problem with my Circuit was a stability issue, not a PCB problem. So have gone back to higher impedance values that worked in my prototype crossover ...

I'll post more in a bit, I've got to get this done for myself ...

[JonMarsh]

OK- glad to see you're working on this and seem to have a handle on the issues- keep us informed of progress! 2016 is the year of progress- should be for you, too! :B :T

[Hank]

Hi John - glad to see you back and determined to finish your project. I did something in December that I'd thought about for months: I built a 134" diagonal projection screen for a used JVC RS25 projector I won on ebay. What beautiful PQ that JVC produces! Projectors suffer incredible price depreciation - worse than cars. That PJ was $7,995 when introduced 6 years ago and I bought it for $747:E Anyway, I look forward to your speaker project completion.

[JonMarsh]

That's a stone cold deal, Hank- even if you need to replace the bulb soon!

Man, I just took a look at their current offerings- hoo boy, that DLA RS56 is one heck of a piece for $8K, and the RS4810 is pretty amazing at $5K.

But at $747 you've got the value proposition down cold!

[Johnloudb]

Hank, wow ... What a great project! And great deal! Awesome

Jon, I sure hope I have a good handle on this. I have tested two boards with same result ... Get that wild distortion at and below crossover frequency for the high pass.

Glad to be back you guys ... Going to order some correct value caps tomorrow, I have the resistors ... Updates to come!

[Hank]

Couldn't help it, Jon - I negotiate Sourcing contracts. BTW, the owner had a spare new lamp and included it:W
Yes, I actually broke my procrastination and built something! Maybe I'll post photos on the appropriate HT area on HTGUIDE.
I've built so many speakers that I just can't get motivated to do any more, especially since I acquired a pair of Acoustat Model 3's last year.
Of course, I've applied a bit of my procrastination to that - a few months ago I bought upgrade parts for the interfaces: resistors, caps, wire.
Also high voltage diodes and caps to replace those on the HV ladder PCB's.
Speaking of PQ, the John Wayne movies directed by John Ford - wow! There's a reason directors didn't shoot movies in Monument Valley after Ford did his - he OWNED Monument Valley!
Spectacular direction and cinematography:T

It appears Johnloudb and I are conquering our procrastination, year by year.

[JonMarsh]

I was going to ask if you had a new lamp for it, but geez, you're covered! Way to score....

But now I'm starting to daydream about that RS56- have always like the JVC DILA projectors and technology. I might even have a viable plan for sneaking it in here past the GF- :W :B

[Hank]

I might even have a viable plan for sneaking it in here past the GF-

Yeah, right. The JVC's are huge projectors - you can't sneak it in your backpack. Just be prepped to answer the question: "That looks like it cost more than any speaker components - didn't it?:uhoh:

[JonMarsh]

Well, she knows those diamond tweeters were kind of pricey, and if you've gotten something similar looking for less than half what I paid for them, maybe I have a chance, if I can convince her they're used....

Oh heck, I just discovered the JVC RS57 - the 56 is out of production. Native contrast ratio of 120K:1. Data up to 4096x2160 (like my LG monitors) Oh my...

Of course, these aren't really native 4K panels; they use the eShift technology to move the chip to an alternate position and scan the other pixels from HD, but reviews say it is pretty close to the native panels on that high end Sony. I wonder what pretty close actually looks like... something to ponder when I have more time.

=====================

well, the somewhat more expensive Sony VPLVW365 has it's achilles heel; contrast ratio and black levels. That's it's main performance weakness, along with overall brightness (i.e., not so bright, even compared with just slightly higher rated other Sony projectors). And mind you, the Sony goes for for about $2K more.

Just be advised... early adopters may experience some pain!

[wkhanna]

Feels like years since I've posted here ... Been around 10 months.....I found that the problem with my Circuit ...

Well done, John!

Glad to hear from you.