DIY T4B, matching EL Panels and Cells
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dmp
Well-known member
Quoting Electro-Joe from another thread:
Agreed, good point. I had 3 seconds between the light pulses, and they do not seem to be completely returning to full dark resistance. I was interested in the max Gain reduction characteristics in this test since I wanted to match a second cell for the meter, but selecting a cell for proper release time is mentioned in the UA manual:
dmp
Well-known member
Quoting Joe-electro:
The cells I recently purchased from Allied were gray.
The cells I recently purchased from Allied were gray.
I've had to fundamentally change my testing procedures to accommodate the gray cells. I now test 48 cells per batch and import the data into an Excel workbook that has 54 separate spreadsheets in it. The spreadsheets calculate the match of each cell with every other cell and sort the results according to closest match. There are over 11,000 calculations per spreadsheet, so over 500,000 calculations in the workbook. It took me 2-1/2 days to put the workbook together, but now it only takes a few minutes to import the data and view the resullts. Lots of work to make a simple unit with two photocells and a light source.
Joe
Joe
dmp
Well-known member
The cost to get two matched cells is pretty high if you need to buy 20 @ $3 a piece! I'd much prefer to just be able to buy a pair of the 'rust' version!
mitsos
Well-known member
- Joined
- May 4, 2007
- Messages
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No offense but I wonder about your sanity! 11000 calculations! but then I'm clueless as to how this thing works. That said, I think it would be super nice if someone (hint, hint, joe!) would sell matched pairs for $15-20 and put this thing to rest. That along with the EL group buy in the BM would be very cool indeed.
Okay, let's get this out of way right now, I'm a jerk. Matching the photocells to my specs takes so much time I have to reserve them for my T4B customers. That, coupled with my special EL panel are my "secret recipe". The Colonel doesn't give it away and neither do I. That's what sets my T4B's apart from the crowd. I know, I'm an asshole. But look at it this way, it would take all the DIY fun out of it if I did.
However, I would DEFINITELY love participate as a part of this group in finding another supplier for photocells. One that can supply more consistent cells. That would benefit everybody!
Thanks!!!
Joe
However, I would DEFINITELY love participate as a part of this group in finding another supplier for photocells. One that can supply more consistent cells. That would benefit everybody!
Thanks!!!
Joe
mitsos said:
No problem with that, nobody wants to see you without food. Or much worse, new gear 
.
But what would already be a big step in the right direction would be to know which specs are
really desirable. Is that a trade secret as well? Not sure if I understood you right. Or is it even
common knowledge? I don't know. I remember CJ had described his selection process in detail
on his unfortunately long gone page. He also had listed what exactly to look for spec wise.
Really a loss that it's not online anymore.
.But what would already be a big step in the right direction would be to know which specs are
really desirable. Is that a trade secret as well? Not sure if I understood you right. Or is it even
common knowledge? I don't know. I remember CJ had described his selection process in detail
on his unfortunately long gone page. He also had listed what exactly to look for spec wise.
Really a loss that it's not online anymore.
Biasrocks
Well-known member
I posted the Urei T4 test procedure in the gdiy gmail account, a few months back. Look there to start.
Mark
Mark
dmp
Well-known member
And those that haven't seen it, Joe is sharing a lot of info on his website:
http://www.kenetek.com/T4AT4BUnits/TestingPhotocells/tabid/206/Default.aspx
http://www.kenetek.com/T4AT4BUnits/TestingPhotocells/tabid/206/Default.aspx
And much more to come in the very near future!
Joe
Joe
dmp said:
kato
Well-known member
If it takes 20 cells to make a match, and 11,000 calculations, you're entitled to be an "asshole." Matchmaking isn't cheap, and many of us are unaware of how much work is involved. (myself included.)
I too have poured over the information on your site, hoping to crack the code. So I appreciate you sharing what knowledge you are willing to.
It sounds like the cells are more effort than the panel. Is there anything you can tell us about the suitability of the panels that are readily available? I remember you mentioning that your closer to the original panels have a shorter lifespan than the LSI panels. Did you find something readily available, have a batch made to spec, or burned in something with a thousand hours? Am i asking too much?
I bought some of these on ebay. Even if they don't work, it's worth the fun of experimenting / learning.
Matchmaking isn't cheap, and many of us are unaware of how much work is involved. (myself included.)I too have poured over the information on your site, hoping to crack the code. So I appreciate you sharing what knowledge you are willing to.
It sounds like the cells are more effort than the panel. Is there anything you can tell us about the suitability of the panels that are readily available? I remember you mentioning that your closer to the original panels have a shorter lifespan than the LSI panels. Did you find something readily available, have a batch made to spec, or burned in something with a thousand hours? Am i asking too much?
I bought some of these on ebay. Even if they don't work, it's worth the fun of experimenting / learning.
I don't think I ever said that. Maybe somebody else? I warranty my T4B's for three years - longer than anybody. As far as I can tell these EL panels will last at least as long as the originals - maybe longer - from the tests I've done so far.
This is what happened. I, like everybody else, called the "OEM" for these panels and was insulted by the price they quoted me. So, like everybody else, I tried every alternative panel I could find. During that hunt I found a panel that had a smoother curve to it, and sounded more like the original T4A's and T4B's I have from the sixties and seventies. I traced the manufacturer of that panel and had them make a run of them for me to my specs. The secret recipe is the phosphor used in the panels.
Looks like the panels you bought will work okay, but they put out white light, not blue-green, which happens to correspond better with the natural response of the photocells. Give them a try and let us know how they work out.
Thanks,
Joe
This is what happened. I, like everybody else, called the "OEM" for these panels and was insulted by the price they quoted me. So, like everybody else, I tried every alternative panel I could find. During that hunt I found a panel that had a smoother curve to it, and sounded more like the original T4A's and T4B's I have from the sixties and seventies. I traced the manufacturer of that panel and had them make a run of them for me to my specs. The secret recipe is the phosphor used in the panels.
Looks like the panels you bought will work okay, but they put out white light, not blue-green, which happens to correspond better with the natural response of the photocells. Give them a try and let us know how they work out.
Thanks,
Joe
kato said:
Biasrocks
Well-known member
joe-electro said:
The more I hear you talk about this Joe, the more I want to buy one of your T4's and call it a day.
It doesn't sound like DIY one of these is gonna be that cost effective, considering how many parts need to be gone through and the quality of the parts being in question.
It just makes sense to me.
Mark
Let's put it this way. I've built hundreds of these things and I'm still waiting to break even
It's like any other DIY endeavor. You don't do it for the money, you do it as an expression of your art and curiosity. But it reeeaaaallly makes me respect the guys who came up with these in the early sixties when computerized testers and spreadsheets didn't exist. I'm still trying to achieve the perfection they were able to. I'm finally getting pretty close!
Joe
It's like any other DIY endeavor. You don't do it for the money, you do it as an expression of your art and curiosity. But it reeeaaaallly makes me respect the guys who came up with these in the early sixties when computerized testers and spreadsheets didn't exist. I'm still trying to achieve the perfection they were able to. I'm finally getting pretty close!
Joe
Biasrocks said:
Some of what I say now is going to be unpopular but I guess still needs to be said.
I bought 10 Allied cells and used CJ's method to find matching pairs, I got several matches but chose the best pair for the LA-2A I made from scratch.
What I found more trouble than the matching was the original meter circuit which didn't correlate with degree of GR until I tweeked the bridge resistors around it.
As I have made electroluminescent powders in my career (I'm head of R&D at a UK phosphor Company) I can tell you that they are a flawed product. Normal phosphors last indefinitely, but electroluminescent phosphors work on the migration of copper ions within the crystals (imagine a transistor that gradually lost its holes) so their life is limited. They were designed for use at 50/60 Hz but the LA2/3 use them for audio which accelerates their decline (more cycles/second).
The only good point about EL panels is that they are very fast, almost as fast as a green LED in fact, which lasts indefinitely. I bought a high brightness green led which closely matched the response spectrum of the Allied photocell and fitted them into an aluminum tube and sealed them tight with black mastic, they work very well indeed.
For anyone else who wants to try this approach, the circuit mods are shown below.
best
DaveP
I bought 10 Allied cells and used CJ's method to find matching pairs, I got several matches but chose the best pair for the LA-2A I made from scratch.
What I found more trouble than the matching was the original meter circuit which didn't correlate with degree of GR until I tweeked the bridge resistors around it.
As I have made electroluminescent powders in my career (I'm head of R&D at a UK phosphor Company) I can tell you that they are a flawed product. Normal phosphors last indefinitely, but electroluminescent phosphors work on the migration of copper ions within the crystals (imagine a transistor that gradually lost its holes) so their life is limited. They were designed for use at 50/60 Hz but the LA2/3 use them for audio which accelerates their decline (more cycles/second).
The only good point about EL panels is that they are very fast, almost as fast as a green LED in fact, which lasts indefinitely. I bought a high brightness green led which closely matched the response spectrum of the Allied photocell and fitted them into an aluminum tube and sealed them tight with black mastic, they work very well indeed.
For anyone else who wants to try this approach, the circuit mods are shown below.
best
DaveP
radardoug
Well-known member
Dave, you show the leds coupled straight to the transformer without current limiting resistors. Is this how you did it? What about the different thresholds of the two leds? Wouldn't series-ing the leds have been better?
